loopy.c

   1 /*
   2  * loopy.c: An implementation of the Nikoli game 'Loop the loop'.
   3  * (c) Mike Pinna, 2005
   4  *
   5  * vim: set shiftwidth=4 :set textwidth=80:
   6  */
   7
   8 /*
   9  * TODO:
  10  *
  11  *  - setting very high recursion depth seems to cause memory
  12  *    munching: are we recursing before checking completion, by any
  13  *    chance?
  14  *
  15  *  - there's an interesting deductive technique which makes use of
  16  *    topology rather than just graph theory. Each _square_ in the
  17  *    grid is either inside or outside the loop; you can tell that
  18  *    two squares are on the same side of the loop if they're
  19  *    separated by an x (or, more generally, by a path crossing no
  20  *    LINE_UNKNOWNs and an even number of LINE_YESes), and on the
  21  *    opposite side of the loop if they're separated by a line (or
  22  *    an odd number of LINE_YESes and no LINE_UNKNOWNs). Oh, and
  23  *    any square separated from the outside of the grid by a
  24  *    LINE_YES or a LINE_NO is on the inside or outside
  25  *    respectively. So if you can track this for all squares, you
  26  *    can occasionally spot that two squares are separated by a
  27  *    LINE_UNKNOWN but their relative insideness is known, and
  28  *    therefore deduce the state of the edge between them.
  29  *     + An efficient way to track this would be by augmenting the
  30  *       disjoint set forest data structure. Each element, along
  31  *       with a pointer to a parent member of its equivalence
  32  *       class, would also carry a one-bit field indicating whether
  33  *       it was equal or opposite to its parent. Then you could
  34  *       keep flipping a bit as you ascended the tree during
  35  *       dsf_canonify(), and hence you'd be able to return the
  36  *       relationship of the input value to its ultimate parent
  37  *       (and also you could then get all those bits right when you
  38  *       went back up the tree rewriting). So you'd be able to
  39  *       query whether any two elements were known-equal,
  40  *       known-opposite, or not-known, and you could add new
  41  *       equalities or oppositenesses to increase your knowledge.
  42  *       (Of course the algorithm would have to fail an assertion
  43  *       if you tried to tell it two things it already knew to be
  44  *       opposite were equal, or vice versa!)
  45  *       This data structure would also be useful in the
  46  *       graph-theoretic part of the solver, where it could be used
  47  *       for storing information about which lines are known-identical
  48  *       or known-opposite.  (For example if two lines bordering a 3
  49  *       are known-identical they must both be LINE_YES, and if they
  50  *       are known-opposite, the *other* two lines bordering that clue
  51  *       must be LINE_YES, etc).  This may duplicate some
  52  *       functionality already present in the solver but it is more
  53  *       general and we could remove the old code, so that's no bad
  54  *       thing.
  55  */
  56
  57 #include <stdio.h>
  58 #include <stdlib.h>
  59 #include <string.h>
  60 #include <assert.h>
  61 #include <ctype.h>
  62 #include <math.h>
  63
  64 #include "puzzles.h"
  65 #include "tree234.h"
  66
  67 #define PREFERRED_TILE_SIZE 32
  68 #define TILE_SIZE (ds->tilesize)
  69 #define LINEWIDTH (ds->linewidth)
  70 #define BORDER (TILE_SIZE / 2)
  71
  72 #define FLASH_TIME 0.5F
  73
  74 #define HL_COUNT(state) ((state)->w * ((state)->h + 1))
  75 #define VL_COUNT(state) (((state)->w + 1) * (state)->h)
  76 #define DOT_COUNT(state) (((state)->w + 1) * ((state)->h + 1))
  77 #define SQUARE_COUNT(state) ((state)->w * (state)->h)
  78
  79 #define ABOVE_SQUARE(state, i, j) ((state)->hl[(i) + (state)->w * (j)])
  80 #define BELOW_SQUARE(state, i, j) ABOVE_SQUARE(state, i, (j)+1)
  81
  82 #define LEFTOF_SQUARE(state, i, j)  ((state)->vl[(i) + ((state)->w + 1) * (j)])
  83 #define RIGHTOF_SQUARE(state, i, j) LEFTOF_SQUARE(state, (i)+1, j)
  84
  85 #define LEGAL_DOT(state, i, j) ((i) >= 0 && (j) >= 0 &&                 \
  86                                 (i) <= (state)->w && (j) <= (state)->h)
  87
  88 /*
  89  * These macros return rvalues only, but can cope with being passed
  90  * out-of-range coordinates.
  91  */
  92 #define ABOVE_DOT(state, i, j) ((!LEGAL_DOT(state, i, j) || j <= 0) ?  \
  93                                 LINE_NO : LV_ABOVE_DOT(state, i, j))
  94 #define BELOW_DOT(state, i, j) ((!LEGAL_DOT(state, i, j) || j >= (state)->h) ? \
  95                                 LINE_NO : LV_BELOW_DOT(state, i, j))
  96
  97 #define LEFTOF_DOT(state, i, j)  ((!LEGAL_DOT(state, i, j) || i <= 0) ? \
  98                                   LINE_NO : LV_LEFTOF_DOT(state, i, j))
  99 #define RIGHTOF_DOT(state, i, j) ((!LEGAL_DOT(state, i, j) || i >= (state)->w)?\
 100                                   LINE_NO : LV_RIGHTOF_DOT(state, i, j))
 101
 102 /*
 103  * These macros expect to be passed valid coordinates, and return
 104  * lvalues.
 105  */
 106 #define LV_BELOW_DOT(state, i, j) ((state)->vl[(i) + ((state)->w + 1) * (j)])
 107 #define LV_ABOVE_DOT(state, i, j) LV_BELOW_DOT(state, i, (j)-1)
 108
 109 #define LV_RIGHTOF_DOT(state, i, j) ((state)->hl[(i) + (state)->w * (j)])
 110 #define LV_LEFTOF_DOT(state, i, j)  LV_RIGHTOF_DOT(state, (i)-1, j)
 111
 112 #define CLUE_AT(state, i, j) ((i < 0 || i >= (state)->w || \
 113                                j < 0 || j >= (state)->h) ? \
 114                              ' ' : LV_CLUE_AT(state, i, j))
 115
 116 #define LV_CLUE_AT(state, i, j) ((state)->clues[(i) + (state)->w * (j)])
 117
 118 #define OPP(dir) (dir == LINE_UNKNOWN ? LINE_UNKNOWN : \
 119                   dir == LINE_YES ? LINE_NO : LINE_YES)
 120
 121 #define BIT_SET(field, bit) ((field) & (1<<(bit)))
 122
 123 #define SET_BIT(field, bit)  (BIT_SET(field, bit) ? FALSE : \
 124                               ((field) |= (1<<(bit)), TRUE))
 125
 126 #define CLEAR_BIT(field, bit) (BIT_SET(field, bit) ?        \
 127                                ((field) &= ~(1<<(bit)), TRUE) : FALSE)
 128
 129 static char *game_text_format(game_state *state);
 130
 131 enum {
 132     COL_BACKGROUND,
 133     COL_FOREGROUND,
 134     COL_HIGHLIGHT,
 135     COL_MISTAKE,
 136     NCOLOURS
 137 };
 138
 139 /*
 140  * Difficulty levels. I do some macro ickery here to ensure that my
 141  * enum and the various forms of my name list always match up.
 142  */
 143 #define DIFFLIST(A) \
 144     A(EASY,Easy,e) \
 145     A(NORMAL,Normal,n)
 146 #define ENUM(upper,title,lower) DIFF_ ## upper,
 147 #define TITLE(upper,title,lower) #title,
 148 #define ENCODE(upper,title,lower) #lower
 149 #define CONFIG(upper,title,lower) ":" #title
 150 enum { DIFFLIST(ENUM) DIFFCOUNT };
 151 /* static char const *const loopy_diffnames[] = { DIFFLIST(TITLE) }; */
 152 static char const loopy_diffchars[] = DIFFLIST(ENCODE);
 153 #define DIFFCONFIG DIFFLIST(CONFIG)
 154
 155 /* LINE_YES_ERROR is only used in the drawing routine */
 156 enum line_state { LINE_UNKNOWN, LINE_YES, LINE_NO /*, LINE_YES_ERROR*/ };
 157
 158 enum direction { UP, DOWN, LEFT, RIGHT };
 159
 160 struct game_params {
 161     int w, h, diff, rec;
 162 };
 163
 164 struct game_state {
 165     int w, h;
 166
 167     /* Put ' ' in a square that doesn't get a clue */
 168     char *clues;
 169
 170     /* Arrays of line states, stored left-to-right, top-to-bottom */
 171     char *hl, *vl;
 172
 173     int solved;
 174     int cheated;
 175
 176     int recursion_depth;
 177 };
 178
 179 static game_state *dup_game(game_state *state)
 180 {
 181     game_state *ret = snew(game_state);
 182
 183     ret->h = state->h;
 184     ret->w = state->w;
 185     ret->solved = state->solved;
 186     ret->cheated = state->cheated;
 187
 188     ret->clues   = snewn(SQUARE_COUNT(state), char);
 189     memcpy(ret->clues, state->clues, SQUARE_COUNT(state));
 190
 191     ret->hl      = snewn(HL_COUNT(state), char);
 192     memcpy(ret->hl, state->hl, HL_COUNT(state));
 193
 194     ret->vl      = snewn(VL_COUNT(state), char);
 195     memcpy(ret->vl, state->vl, VL_COUNT(state));
 196
 197     ret->recursion_depth = state->recursion_depth;
 198
 199     return ret;
 200 }
 201
 202 static void free_game(game_state *state)
 203 {
 204     if (state) {
 205         sfree(state->clues);
 206         sfree(state->hl);
 207         sfree(state->vl);
 208         sfree(state);
 209     }
 210 }
 211
 212 enum solver_status {
 213     SOLVER_SOLVED,    /* This is the only solution the solver could find */
 214     SOLVER_MISTAKE,   /* This is definitely not a solution */
 215     SOLVER_AMBIGUOUS, /* This _might_ be an ambiguous solution */
 216     SOLVER_INCOMPLETE /* This may be a partial solution */
 217 };
 218
 219 typedef struct solver_state {
 220   game_state *state;
 221   char *dot_atleastone;
 222   char *dot_atmostone;
 223 /*   char *dline_identical; */
 224   int recursion_remaining;
 225   enum solver_status solver_status;
 226   /* NB looplen is the number of dots that are joined together at a point, ie a
 227    * looplen of 1 means there are no lines to a particular dot */
 228   int *dotdsf, *looplen;
 229 } solver_state;
 230
 231 static solver_state *new_solver_state(game_state *state) {
 232     solver_state *ret = snew(solver_state);
 233     int i;
 234
 235     ret->state = dup_game(state);
 236
 237     ret->dot_atmostone = snewn(DOT_COUNT(state), char);
 238     memset(ret->dot_atmostone, 0, DOT_COUNT(state));
 239     ret->dot_atleastone = snewn(DOT_COUNT(state), char);
 240     memset(ret->dot_atleastone, 0, DOT_COUNT(state));
 241
 242 #if 0
 243     dline_identical = snewn(DOT_COUNT(state), char);
 244     memset(dline_identical, 0, DOT_COUNT(state));
 245 #endif
 246
 247     ret->recursion_remaining = state->recursion_depth;
 248     ret->solver_status = SOLVER_INCOMPLETE;
 249
 250     ret->dotdsf = snewn(DOT_COUNT(state), int);
 251     ret->looplen = snewn(DOT_COUNT(state), int);
 252     for (i = 0; i < DOT_COUNT(state); i++) {
 253         ret->dotdsf[i] = i;
 254         ret->looplen[i] = 1;
 255     }
 256
 257     return ret;
 258 }
 259
 260 static void free_solver_state(solver_state *sstate) {
 261     if (sstate) {
 262         free_game(sstate->state);
 263         sfree(sstate->dot_atleastone);
 264         sfree(sstate->dot_atmostone);
 265         /*    sfree(sstate->dline_identical); */
 266         sfree(sstate->dotdsf);
 267         sfree(sstate->looplen);
 268         sfree(sstate);
 269     }
 270 }
 271
 272 static solver_state *dup_solver_state(solver_state *sstate) {
 273     game_state *state;
 274
 275     solver_state *ret = snew(solver_state);
 276
 277     ret->state = state = dup_game(sstate->state);
 278
 279     ret->dot_atmostone = snewn(DOT_COUNT(state), char);
 280     memcpy(ret->dot_atmostone, sstate->dot_atmostone, DOT_COUNT(state));
 281
 282     ret->dot_atleastone = snewn(DOT_COUNT(state), char);
 283     memcpy(ret->dot_atleastone, sstate->dot_atleastone, DOT_COUNT(state));
 284
 285 #if 0
 286     ret->dline_identical = snewn((state->w + 1) * (state->h + 1), char);
 287     memcpy(ret->dline_identical, state->dot_atmostone,
 288            (state->w + 1) * (state->h + 1));
 289 #endif
 290
 291     ret->recursion_remaining = sstate->recursion_remaining;
 292     ret->solver_status = sstate->solver_status;
 293
 294     ret->dotdsf = snewn(DOT_COUNT(state), int);
 295     ret->looplen = snewn(DOT_COUNT(state), int);
 296     memcpy(ret->dotdsf, sstate->dotdsf, DOT_COUNT(state) * sizeof(int));
 297     memcpy(ret->looplen, sstate->looplen, DOT_COUNT(state) * sizeof(int));
 298
 299     return ret;
 300 }
 301
 302 /*
 303  * Merge two dots due to the existence of an edge between them.
 304  * Updates the dsf tracking equivalence classes, and keeps track of
 305  * the length of path each dot is currently a part of.
 306  * Returns TRUE if the dots were already linked, ie if they are part of a
 307  * closed loop, and false otherwise.
 308  */
 309 static int merge_dots(solver_state *sstate, int x1, int y1, int x2, int y2)
 310 {
 311     int i, j, len;
 312
 313     i = y1 * (sstate->state->w + 1) + x1;
 314     j = y2 * (sstate->state->w + 1) + x2;
 315
 316     i = dsf_canonify(sstate->dotdsf, i);
 317     j = dsf_canonify(sstate->dotdsf, j);
 318
 319     if (i == j) {
 320         return TRUE;
 321     } else {
 322         len = sstate->looplen[i] + sstate->looplen[j];
 323         dsf_merge(sstate->dotdsf, i, j);
 324         i = dsf_canonify(sstate->dotdsf, i);
 325         sstate->looplen[i] = len;
 326         return FALSE;
 327     }
 328 }
 329
 330 /* Count the number of lines of a particular type currently going into the
 331  * given dot.  Lines going off the edge of the board are assumed fixed no. */
 332 static int dot_order(const game_state* state, int i, int j, char line_type)
 333 {
 334     int n = 0;
 335
 336     if (i > 0) {
 337         if (LEFTOF_DOT(state, i, j) == line_type)
 338             ++n;
 339     } else {
 340         if (line_type == LINE_NO)
 341             ++n;
 342     }
 343     if (i < state->w) {
 344         if (RIGHTOF_DOT(state, i, j) == line_type)
 345             ++n;
 346     } else {
 347         if (line_type == LINE_NO)
 348             ++n;
 349     }
 350     if (j > 0) {
 351         if (ABOVE_DOT(state, i, j) == line_type)
 352             ++n;
 353     } else {
 354         if (line_type == LINE_NO)
 355             ++n;
 356     }
 357     if (j < state->h) {
 358         if (BELOW_DOT(state, i, j) == line_type)
 359             ++n;
 360     } else {
 361         if (line_type == LINE_NO)
 362             ++n;
 363     }
 364
 365     return n;
 366 }
 367 /* Count the number of lines of a particular type currently surrounding the
 368  * given square */
 369 static int square_order(const game_state* state, int i, int j, char line_type)
 370 {
 371     int n = 0;
 372
 373     if (ABOVE_SQUARE(state, i, j) == line_type)
 374         ++n;
 375     if (BELOW_SQUARE(state, i, j) == line_type)
 376         ++n;
 377     if (LEFTOF_SQUARE(state, i, j) == line_type)
 378         ++n;
 379     if (RIGHTOF_SQUARE(state, i, j) == line_type)
 380         ++n;
 381
 382     return n;
 383 }
 384
 385 /* Set all lines bordering a dot of type old_type to type new_type
 386  * Return value tells caller whether this function actually did anything */
 387 static int dot_setall(game_state *state, int i, int j,
 388                        char old_type, char new_type)
 389 {
 390     int retval = FALSE;
 391     if (old_type == new_type)
 392         return FALSE;
 393
 394     if (i > 0        && LEFTOF_DOT(state, i, j) == old_type) {
 395         LV_LEFTOF_DOT(state, i, j) = new_type;
 396         retval = TRUE;
 397     }
 398
 399     if (i < state->w && RIGHTOF_DOT(state, i, j) == old_type) {
 400         LV_RIGHTOF_DOT(state, i, j) = new_type;
 401         retval = TRUE;
 402     }
 403
 404     if (j > 0        && ABOVE_DOT(state, i, j) == old_type) {
 405         LV_ABOVE_DOT(state, i, j) = new_type;
 406         retval = TRUE;
 407     }
 408
 409     if (j < state->h && BELOW_DOT(state, i, j) == old_type) {
 410         LV_BELOW_DOT(state, i, j) = new_type;
 411         retval = TRUE;
 412     }
 413
 414     return retval;
 415 }
 416 /* Set all lines bordering a square of type old_type to type new_type */
 417 static void square_setall(game_state *state, int i, int j,
 418                           char old_type, char new_type)
 419 {
 420     if (ABOVE_SQUARE(state, i, j) == old_type)
 421         ABOVE_SQUARE(state, i, j) = new_type;
 422     if (BELOW_SQUARE(state, i, j) == old_type)
 423         BELOW_SQUARE(state, i, j) = new_type;
 424     if (LEFTOF_SQUARE(state, i, j) == old_type)
 425         LEFTOF_SQUARE(state, i, j) = new_type;
 426     if (RIGHTOF_SQUARE(state, i, j) == old_type)
 427         RIGHTOF_SQUARE(state, i, j) = new_type;
 428 }
 429
 430 static game_params *default_params(void)
 431 {
 432     game_params *ret = snew(game_params);
 433
 434 #ifdef SLOW_SYSTEM
 435     ret->h = 4;
 436     ret->w = 4;
 437 #else
 438     ret->h = 10;
 439     ret->w = 10;
 440 #endif
 441     ret->diff = DIFF_EASY;
 442     ret->rec = 0;
 443
 444     return ret;
 445 }
 446
 447 static game_params *dup_params(game_params *params)
 448 {
 449     game_params *ret = snew(game_params);
 450     *ret = *params;                       /* structure copy */
 451     return ret;
 452 }
 453
 454 static const struct {
 455     char *desc;
 456     game_params params;
 457 } loopy_presets[] = {
 458     { "4x4 Easy",     {  4,  4, DIFF_EASY, 0 } },
 459     { "4x4 Normal",   {  4,  4, DIFF_NORMAL, 0 } },
 460     { "7x7 Easy",     {  7,  7, DIFF_EASY, 0 } },
 461     { "7x7 Normal",   {  7,  7, DIFF_NORMAL, 0 } },
 462     { "10x10 Easy",   { 10, 10, DIFF_EASY, 0 } },
 463     { "10x10 Normal", { 10, 10, DIFF_NORMAL, 0 } },
 464 #ifndef SLOW_SYSTEM
 465     { "15x15 Easy",   { 15, 15, DIFF_EASY, 0 } },
 466     { "15x15 Normal", { 15, 15, DIFF_NORMAL, 0 } },
 467     { "30x20 Easy",   { 30, 20, DIFF_EASY, 0 } },
 468     { "30x20 Normal", { 30, 20, DIFF_NORMAL, 0 } }
 469 #endif
 470 };
 471
 472 static int game_fetch_preset(int i, char **name, game_params **params)
 473 {
 474     game_params tmppar;
 475
 476     if (i < 0 || i >= lenof(loopy_presets))
 477         return FALSE;
 478
 479     tmppar = loopy_presets[i].params;
 480     *params = dup_params(&tmppar);
 481     *name = dupstr(loopy_presets[i].desc);
 482
 483     return TRUE;
 484 }
 485
 486 static void free_params(game_params *params)
 487 {
 488     sfree(params);
 489 }
 490
 491 static void decode_params(game_params *params, char const *string)
 492 {
 493     params->h = params->w = atoi(string);
 494     params->rec = 0;
 495     params->diff = DIFF_EASY;
 496     while (*string && isdigit((unsigned char)*string)) string++;
 497     if (*string == 'x') {
 498         string++;
 499         params->h = atoi(string);
 500         while (*string && isdigit((unsigned char)*string)) string++;
 501     }
 502     if (*string == 'r') {
 503         string++;
 504         params->rec = atoi(string);
 505         while (*string && isdigit((unsigned char)*string)) string++;
 506     }
 507     if (*string == 'd') {
 508         int i;
 509
 510         string++;
 511         for (i = 0; i < DIFFCOUNT; i++)
 512             if (*string == loopy_diffchars[i])
 513                 params->diff = i;
 514         if (*string) string++;
 515     }
 516 }
 517
 518 static char *encode_params(game_params *params, int full)
 519 {
 520     char str[80];
 521     sprintf(str, "%dx%d", params->w, params->h);
 522     if (full)
 523         sprintf(str + strlen(str), "r%dd%c", params->rec,
 524                 loopy_diffchars[params->diff]);
 525     return dupstr(str);
 526 }
 527
 528 static config_item *game_configure(game_params *params)
 529 {
 530     config_item *ret;
 531     char buf[80];
 532
 533     ret = snewn(4, config_item);
 534
 535     ret[0].name = "Width";
 536     ret[0].type = C_STRING;
 537     sprintf(buf, "%d", params->w);
 538     ret[0].sval = dupstr(buf);
 539     ret[0].ival = 0;
 540
 541     ret[1].name = "Height";
 542     ret[1].type = C_STRING;
 543     sprintf(buf, "%d", params->h);
 544     ret[1].sval = dupstr(buf);
 545     ret[1].ival = 0;
 546
 547     ret[2].name = "Difficulty";
 548     ret[2].type = C_CHOICES;
 549     ret[2].sval = DIFFCONFIG;
 550     ret[2].ival = params->diff;
 551
 552     ret[3].name = NULL;
 553     ret[3].type = C_END;
 554     ret[3].sval = NULL;
 555     ret[3].ival = 0;
 556
 557     return ret;
 558 }
 559
 560 static game_params *custom_params(config_item *cfg)
 561 {
 562     game_params *ret = snew(game_params);
 563
 564     ret->w = atoi(cfg[0].sval);
 565     ret->h = atoi(cfg[1].sval);
 566     ret->rec = 0;
 567     ret->diff = cfg[2].ival;
 568
 569     return ret;
 570 }
 571
 572 static char *validate_params(game_params *params, int full)
 573 {
 574     if (params->w < 4 || params->h < 4)
 575         return "Width and height must both be at least 4";
 576     if (params->rec < 0)
 577         return "Recursion depth can't be negative";
 578
 579     /*
 580      * This shouldn't be able to happen at all, since decode_params
 581      * and custom_params will never generate anything that isn't
 582      * within range.
 583      */
 584     assert(params->diff >= 0 && params->diff < DIFFCOUNT);
 585
 586     return NULL;
 587 }
 588
 589 /* We're going to store a list of current candidate squares for lighting.
 590  * Each square gets a 'score', which tells us how adding that square right
 591  * now would affect the length of the solution loop.  We're trying to
 592  * maximise that quantity so will bias our random selection of squares to
 593  * light towards those with high scores */
 594 struct square {
 595     int score;
 596     unsigned long random;
 597     int x, y;
 598 };
 599
 600 static int get_square_cmpfn(void *v1, void *v2)
 601 {
 602     struct square *s1 = (struct square *)v1;
 603     struct square *s2 = (struct square *)v2;
 604     int r;
 605
 606     r = s1->x - s2->x;
 607     if (r)
 608         return r;
 609
 610     r = s1->y - s2->y;
 611     if (r)
 612         return r;
 613
 614     return 0;
 615 }
 616
 617 static int square_sort_cmpfn(void *v1, void *v2)
 618 {
 619     struct square *s1 = (struct square *)v1;
 620     struct square *s2 = (struct square *)v2;
 621     int r;
 622
 623     r = s2->score - s1->score;
 624     if (r) {
 625         return r;
 626     }
 627
 628     if (s1->random < s2->random)
 629         return -1;
 630     else if (s1->random > s2->random)
 631         return 1;
 632
 633     /*
 634      * It's _just_ possible that two squares might have been given
 635      * the same random value. In that situation, fall back to
 636      * comparing based on the coordinates. This introduces a tiny
 637      * directional bias, but not a significant one.
 638      */
 639     return get_square_cmpfn(v1, v2);
 640 }
 641
 642 static void print_tree(tree234 *tree)
 643 {
 644 #if 0
 645     int i = 0;
 646     struct square *s;
 647     printf("Print tree:\n");
 648     while (i < count234(tree)) {
 649         s = (struct square *)index234(tree, i);
 650         assert(s);
 651         printf("  [%d,%d], %d, %d\n", s->x, s->y, s->score, s->random);
 652         ++i;
 653     }
 654 #endif
 655 }
 656
 657 enum { SQUARE_LIT, SQUARE_UNLIT };
 658
 659 #define SQUARE_STATE(i, j)                 \
 660     (((i) < 0 || (i) >= params->w ||       \
 661       (j) < 0 || (j) >= params->h) ?       \
 662      SQUARE_UNLIT :  LV_SQUARE_STATE(i,j))
 663
 664 #define LV_SQUARE_STATE(i, j) board[(i) + params->w * (j)]
 665
 666 static void print_board(const game_params *params, const char *board)
 667 {
 668 #if 0
 669     int i,j;
 670
 671     printf(" ");
 672     for (i = 0; i < params->w; i++) {
 673         printf("%d", i%10);
 674     }
 675     printf("\n");
 676     for (j = 0; j < params->h; j++) {
 677         printf("%d", j%10);
 678         for (i = 0; i < params->w; i++) {
 679             printf("%c", SQUARE_STATE(i, j) ? ' ' : 'O');
 680         }
 681         printf("\n");
 682     }
 683 #endif
 684 }
 685
 686 static char *new_fullyclued_board(game_params *params, random_state *rs)
 687 {
 688     char *clues;
 689     char *board;
 690     int i, j, a, b, c;
 691     game_state s;
 692     game_state *state = &s;
 693     int board_area = SQUARE_COUNT(params);
 694     int t;
 695
 696     struct square *square, *tmpsquare, *sq;
 697     struct square square_pos;
 698
 699     /* These will contain exactly the same information, sorted into different
 700      * orders */
 701     tree234 *lightable_squares_sorted, *lightable_squares_gettable;
 702
 703 #define SQUARE_REACHABLE(i,j)                      \
 704      (t = (SQUARE_STATE(i-1, j) == SQUARE_LIT ||      \
 705            SQUARE_STATE(i+1, j) == SQUARE_LIT ||      \
 706            SQUARE_STATE(i, j-1) == SQUARE_LIT ||      \
 707            SQUARE_STATE(i, j+1) == SQUARE_LIT),       \
 708 /*      printf("SQUARE_REACHABLE(%d,%d) = %d\n", i, j, t), */ \
 709       t)
 710
 711
 712     /* One situation in which we may not light a square is if that'll leave one
 713      * square above/below and one left/right of us unlit, separated by a lit
 714      * square diagnonal from us */
 715 #define SQUARE_DIAGONAL_VIOLATION(i, j, h, v)           \
 716     (t = (SQUARE_STATE((i)+(h), (j))     == SQUARE_UNLIT && \
 717           SQUARE_STATE((i),     (j)+(v)) == SQUARE_UNLIT && \
 718           SQUARE_STATE((i)+(h), (j)+(v)) == SQUARE_LIT),    \
 719 /*     t ? printf("SQUARE_DIAGONAL_VIOLATION(%d, %d, %d, %d)\n",
 720                   i, j, h, v) : 0,*/ \
 721      t)
 722
 723     /* We also may not light a square if it will form a loop of lit squares
 724      * around some unlit squares, as then the game soln won't have a single
 725      * loop */
 726 #define SQUARE_LOOP_VIOLATION(i, j, lit1, lit2) \
 727     (SQUARE_STATE((i)+1, (j)) == lit1    &&     \
 728      SQUARE_STATE((i)-1, (j)) == lit1    &&     \
 729      SQUARE_STATE((i), (j)+1) == lit2    &&     \
 730      SQUARE_STATE((i), (j)-1) == lit2)
 731
 732 #define CAN_LIGHT_SQUARE(i, j)                                 \
 733     (SQUARE_REACHABLE(i, j)                                 && \
 734      !SQUARE_DIAGONAL_VIOLATION(i, j, -1, -1)               && \
 735      !SQUARE_DIAGONAL_VIOLATION(i, j, +1, -1)               && \
 736      !SQUARE_DIAGONAL_VIOLATION(i, j, -1, +1)               && \
 737      !SQUARE_DIAGONAL_VIOLATION(i, j, +1, +1)               && \
 738      !SQUARE_LOOP_VIOLATION(i, j, SQUARE_LIT, SQUARE_UNLIT) && \
 739      !SQUARE_LOOP_VIOLATION(i, j, SQUARE_UNLIT, SQUARE_LIT))
 740
 741 #define IS_LIGHTING_CANDIDATE(i, j)        \
 742     (SQUARE_STATE(i, j) == SQUARE_UNLIT && \
 743      CAN_LIGHT_SQUARE(i,j))
 744
 745     /* The 'score' of a square reflects its current desirability for selection
 746      * as the next square to light.  We want to encourage moving into uncharted
 747      * areas so we give scores according to how many of the square's neighbours
 748      * are currently unlit. */
 749
 750    /* UNLIT    SCORE
 751     *   3        2
 752     *   2        0
 753     *   1       -2
 754     */
 755 #define SQUARE_SCORE(i,j)                  \
 756     (2*((SQUARE_STATE(i-1, j) == SQUARE_UNLIT)  +   \
 757         (SQUARE_STATE(i+1, j) == SQUARE_UNLIT)  +   \
 758         (SQUARE_STATE(i, j-1) == SQUARE_UNLIT)  +   \
 759         (SQUARE_STATE(i, j+1) == SQUARE_UNLIT)) - 4)
 760
 761     /* When a square gets lit, this defines how far away from that square we
 762      * need to go recomputing scores */
 763 #define SCORE_DISTANCE 1
 764
 765     board = snewn(board_area, char);
 766     clues = snewn(board_area, char);
 767
 768     state->h = params->h;
 769     state->w = params->w;
 770     state->clues = clues;
 771
 772     /* Make a board */
 773     memset(board, SQUARE_UNLIT, board_area);
 774
 775     /* Seed the board with a single lit square near the middle */
 776     i = params->w / 2;
 777     j = params->h / 2;
 778     if (params->w & 1 && random_bits(rs, 1))
 779         ++i;
 780     if (params->h & 1 && random_bits(rs, 1))
 781         ++j;
 782
 783     LV_SQUARE_STATE(i, j) = SQUARE_LIT;
 784
 785     /* We need a way of favouring squares that will increase our loopiness.
 786      * We do this by maintaining a list of all candidate squares sorted by
 787      * their score and choose randomly from that with appropriate skew.
 788      * In order to avoid consistently biasing towards particular squares, we
 789      * need the sort order _within_ each group of scores to be completely
 790      * random.  But it would be abusing the hospitality of the tree234 data
 791      * structure if our comparison function were nondeterministic :-).  So with
 792      * each square we associate a random number that does not change during a
 793      * particular run of the generator, and use that as a secondary sort key.
 794      * Yes, this means we will be biased towards particular random squares in
 795      * any one run but that doesn't actually matter. */
 796
 797     lightable_squares_sorted   = newtree234(square_sort_cmpfn);
 798     lightable_squares_gettable = newtree234(get_square_cmpfn);
 799 #define ADD_SQUARE(s)                                          \
 800     do {                                                       \
 801 /*      printf("ADD SQUARE: [%d,%d], %d, %d\n",
 802                s->x, s->y, s->score, s->random);*/ \
 803         sq = add234(lightable_squares_sorted, s);              \
 804         assert(sq == s);                                       \
 805         sq = add234(lightable_squares_gettable, s);            \
 806         assert(sq == s);                                       \
 807     } while (0)
 808
 809 #define REMOVE_SQUARE(s)                                       \
 810     do {                                                       \
 811 /*      printf("DELETE SQUARE: [%d,%d], %d, %d\n",
 812                s->x, s->y, s->score, s->random);*/ \
 813         sq = del234(lightable_squares_sorted, s);              \
 814         assert(sq);                                            \
 815         sq = del234(lightable_squares_gettable, s);            \
 816         assert(sq);                                            \
 817     } while (0)
 818
 819 #define HANDLE_DIR(a, b)                                       \
 820     square = snew(struct square);                              \
 821     square->x = (i)+(a);                                       \
 822     square->y = (j)+(b);                                       \
 823     square->score = 2;                                         \
 824     square->random = random_bits(rs, 31);                      \
 825     ADD_SQUARE(square);
 826     HANDLE_DIR(-1, 0);
 827     HANDLE_DIR( 1, 0);
 828     HANDLE_DIR( 0,-1);
 829     HANDLE_DIR( 0, 1);
 830 #undef HANDLE_DIR
 831
 832     /* Light squares one at a time until the board is interesting enough */
 833     while (TRUE)
 834     {
 835         /* We have count234(lightable_squares) possibilities, and in
 836          * lightable_squares_sorted they are sorted with the most desirable
 837          * first.  */
 838         c = count234(lightable_squares_sorted);
 839         if (c == 0)
 840             break;
 841         assert(c == count234(lightable_squares_gettable));
 842
 843         /* Check that the best square available is any good */
 844         square = (struct square *)index234(lightable_squares_sorted, 0);
 845         assert(square);
 846
 847         /*
 848          * We never want to _decrease_ the loop's perimeter. Making
 849          * moves that leave the perimeter the same is occasionally
 850          * useful: if it were _never_ done then the user would be
 851          * able to deduce illicitly that any degree-zero vertex was
 852          * on the outside of the loop. So we do it sometimes but
 853          * not always.
 854          */
 855         if (square->score < 0 || (square->score == 0 &&
 856                                   random_upto(rs, 2) == 0))
 857             break;
 858
 859         print_tree(lightable_squares_sorted);
 860         assert(square->score == SQUARE_SCORE(square->x, square->y));
 861         assert(SQUARE_STATE(square->x, square->y) == SQUARE_UNLIT);
 862         assert(square->x >= 0 && square->x < params->w);
 863         assert(square->y >= 0 && square->y < params->h);
 864 /*        printf("LIGHT SQUARE: [%d,%d], score = %d\n", square->x, square->y, square->score); */
 865
 866         /* Update data structures */
 867         LV_SQUARE_STATE(square->x, square->y) = SQUARE_LIT;
 868         REMOVE_SQUARE(square);
 869
 870         print_board(params, board);
 871
 872         /* We might have changed the score of any squares up to 2 units away in
 873          * any direction */
 874         for (b = -SCORE_DISTANCE; b <= SCORE_DISTANCE; b++) {
 875             for (a = -SCORE_DISTANCE; a <= SCORE_DISTANCE; a++) {
 876                 if (!a && !b)
 877                     continue;
 878                 square_pos.x = square->x + a;
 879                 square_pos.y = square->y + b;
 880 /*                printf("Refreshing score for [%d,%d]:\n", square_pos.x, square_pos.y); */
 881                 if (square_pos.x < 0 || square_pos.x >= params->w ||
 882                     square_pos.y < 0 || square_pos.y >= params->h) {
 883 /*                    printf("  Out of bounds\n"); */
 884                    continue;
 885                 }
 886                 tmpsquare = find234(lightable_squares_gettable, &square_pos,
 887                                     NULL);
 888                 if (tmpsquare) {
 889 /*                    printf(" Removing\n"); */
 890                     assert(tmpsquare->x == square_pos.x);
 891                     assert(tmpsquare->y == square_pos.y);
 892                     assert(SQUARE_STATE(tmpsquare->x, tmpsquare->y) ==
 893                            SQUARE_UNLIT);
 894                     REMOVE_SQUARE(tmpsquare);
 895                 } else {
 896 /*                    printf(" Creating\n"); */
 897                     tmpsquare = snew(struct square);
 898                     tmpsquare->x = square_pos.x;
 899                     tmpsquare->y = square_pos.y;
 900                     tmpsquare->random = random_bits(rs, 31);
 901                 }
 902                 tmpsquare->score = SQUARE_SCORE(tmpsquare->x, tmpsquare->y);
 903
 904                 if (IS_LIGHTING_CANDIDATE(tmpsquare->x, tmpsquare->y)) {
 905 /*                    printf(" Adding\n"); */
 906                     ADD_SQUARE(tmpsquare);
 907                 } else {
 908 /*                    printf(" Destroying\n"); */
 909                     sfree(tmpsquare);
 910                 }
 911             }
 912         }
 913         sfree(square);
 914 /*        printf("\n\n"); */
 915     }
 916
 917     while ((square = delpos234(lightable_squares_gettable, 0)) != NULL)
 918         sfree(square);
 919     freetree234(lightable_squares_gettable);
 920     freetree234(lightable_squares_sorted);
 921
 922     /* Copy out all the clues */
 923     for (j = 0; j < params->h; ++j) {
 924         for (i = 0; i < params->w; ++i) {
 925             c = SQUARE_STATE(i, j);
 926             LV_CLUE_AT(state, i, j) = '0';
 927             if (SQUARE_STATE(i-1, j) != c) ++LV_CLUE_AT(state, i, j);
 928             if (SQUARE_STATE(i+1, j) != c) ++LV_CLUE_AT(state, i, j);
 929             if (SQUARE_STATE(i, j-1) != c) ++LV_CLUE_AT(state, i, j);
 930             if (SQUARE_STATE(i, j+1) != c) ++LV_CLUE_AT(state, i, j);
 931         }
 932     }
 933
 934     sfree(board);
 935     return clues;
 936 }
 937
 938 static solver_state *solve_game_rec(const solver_state *sstate, int diff);
 939
 940 static int game_has_unique_soln(const game_state *state, int diff)
 941 {
 942     int ret;
 943     solver_state *sstate_new;
 944     solver_state *sstate = new_solver_state((game_state *)state);
 945
 946     sstate_new = solve_game_rec(sstate, diff);
 947
 948     ret = (sstate_new->solver_status == SOLVER_SOLVED);
 949
 950     free_solver_state(sstate_new);
 951     free_solver_state(sstate);
 952
 953     return ret;
 954 }
 955
 956 /* Remove clues one at a time at random. */
 957 static game_state *remove_clues(game_state *state, random_state *rs, int diff)
 958 {
 959     int *square_list, squares;
 960     game_state *ret = dup_game(state), *saved_ret;
 961     int n;
 962
 963     /* We need to remove some clues.  We'll do this by forming a list of all
 964      * available equivalence classes, shuffling it, then going along one at a
 965      * time clearing every member of each equivalence class, where removing a
 966      * class doesn't render the board unsolvable. */
 967     squares = state->w * state->h;
 968     square_list = snewn(squares, int);
 969     for (n = 0; n < squares; ++n) {
 970         square_list[n] = n;
 971     }
 972
 973     shuffle(square_list, squares, sizeof(int), rs);
 974
 975     for (n = 0; n < squares; ++n) {
 976         saved_ret = dup_game(ret);
 977         LV_CLUE_AT(ret, square_list[n] % state->w,
 978                    square_list[n] / state->w) = ' ';
 979         if (game_has_unique_soln(ret, diff)) {
 980             free_game(saved_ret);
 981         } else {
 982             free_game(ret);
 983             ret = saved_ret;
 984         }
 985     }
 986     sfree(square_list);
 987
 988     return ret;
 989 }
 990
 991 static char *validate_desc(game_params *params, char *desc);
 992
 993 static char *new_game_desc(game_params *params, random_state *rs,
 994                            char **aux, int interactive)
 995 {
 996     /* solution and description both use run-length encoding in obvious ways */
 997     char *retval;
 998     char *description = snewn(SQUARE_COUNT(params) + 1, char);
 999     char *dp = description;
1000     int i, j;
1001     int empty_count;
1002     game_state *state = snew(game_state), *state_new;
1003
1004     state->h = params->h;
1005     state->w = params->w;
1006
1007     state->hl = snewn(HL_COUNT(params), char);
1008     state->vl = snewn(VL_COUNT(params), char);
1009
1010 newboard_please:
1011     memset(state->hl, LINE_UNKNOWN, HL_COUNT(params));
1012     memset(state->vl, LINE_UNKNOWN, VL_COUNT(params));
1013
1014     state->solved = state->cheated = FALSE;
1015     state->recursion_depth = params->rec;
1016
1017     /* Get a new random solvable board with all its clues filled in.  Yes, this
1018      * can loop for ever if the params are suitably unfavourable, but
1019      * preventing games smaller than 4x4 seems to stop this happening */
1020
1021     do {
1022         state->clues = new_fullyclued_board(params, rs);
1023     } while (!game_has_unique_soln(state, params->diff));
1024
1025     state_new = remove_clues(state, rs, params->diff);
1026     free_game(state);
1027     state = state_new;
1028
1029     if (params->diff > 0 && game_has_unique_soln(state, params->diff-1)) {
1030         /* Board is too easy */
1031         goto newboard_please;
1032     }
1033
1034     empty_count = 0;
1035     for (j = 0; j < params->h; ++j) {
1036         for (i = 0; i < params->w; ++i) {
1037             if (CLUE_AT(state, i, j) == ' ') {
1038                 if (empty_count > 25) {
1039                     dp += sprintf(dp, "%c", (int)(empty_count + 'a' - 1));
1040                     empty_count = 0;
1041                 }
1042                 empty_count++;
1043             } else {
1044                 if (empty_count) {
1045                     dp += sprintf(dp, "%c", (int)(empty_count + 'a' - 1));
1046                     empty_count = 0;
1047                 }
1048                 dp += sprintf(dp, "%c", (int)(CLUE_AT(state, i, j)));
1049             }
1050         }
1051     }
1052     if (empty_count)
1053         dp += sprintf(dp, "%c", (int)(empty_count + 'a' - 1));
1054
1055     free_game(state);
1056     retval = dupstr(description);
1057     sfree(description);
1058
1059     assert(!validate_desc(params, retval));
1060
1061     return retval;
1062 }
1063
1064 /* We require that the params pass the test in validate_params and that the
1065  * description fills the entire game area */
1066 static char *validate_desc(game_params *params, char *desc)
1067 {
1068     int count = 0;
1069
1070     for (; *desc; ++desc) {
1071         if (*desc >= '0' && *desc <= '9') {
1072             count++;
1073             continue;
1074         }
1075         if (*desc >= 'a') {
1076             count += *desc - 'a' + 1;
1077             continue;
1078         }
1079         return "Unknown character in description";
1080     }
1081
1082     if (count < SQUARE_COUNT(params))
1083         return "Description too short for board size";
1084     if (count > SQUARE_COUNT(params))
1085         return "Description too long for board size";
1086
1087     return NULL;
1088 }
1089
1090 static game_state *new_game(midend *me, game_params *params, char *desc)
1091 {
1092     int i,j;
1093     game_state *state = snew(game_state);
1094     int empties_to_make = 0;
1095     int n;
1096     const char *dp = desc;
1097
1098     state->recursion_depth = 0; /* XXX pending removal, probably */
1099
1100     state->h = params->h;
1101     state->w = params->w;
1102
1103     state->clues = snewn(SQUARE_COUNT(params), char);
1104     state->hl    = snewn(HL_COUNT(params), char);
1105     state->vl    = snewn(VL_COUNT(params), char);
1106
1107     state->solved = state->cheated = FALSE;
1108
1109     for (j = 0 ; j < params->h; ++j) {
1110         for (i = 0 ; i < params->w; ++i) {
1111             if (empties_to_make) {
1112                 empties_to_make--;
1113                 LV_CLUE_AT(state, i, j) = ' ';
1114                 continue;
1115             }
1116
1117             assert(*dp);
1118             n = *dp - '0';
1119             if (n >=0 && n < 10) {
1120                 LV_CLUE_AT(state, i, j) = *dp;
1121             } else {
1122                 n = *dp - 'a' + 1;
1123                 assert(n > 0);
1124                 LV_CLUE_AT(state, i, j) = ' ';
1125                 empties_to_make = n - 1;
1126             }
1127             ++dp;
1128         }
1129     }
1130
1131     memset(state->hl, LINE_UNKNOWN, HL_COUNT(params));
1132     memset(state->vl, LINE_UNKNOWN, VL_COUNT(params));
1133
1134     return state;
1135 }
1136
1137 enum { LOOP_NONE=0, LOOP_SOLN, LOOP_NOT_SOLN };
1138
1139 /* Sums the lengths of the numbers in range [0,n) */
1140 /* See equivalent function in solo.c for justification of this. */
1141 static int len_0_to_n(int n)
1142 {
1143     int len = 1; /* Counting 0 as a bit of a special case */
1144     int i;
1145
1146     for (i = 1; i < n; i *= 10) {
1147         len += max(n - i, 0);
1148     }
1149
1150     return len;
1151 }
1152
1153 static char *encode_solve_move(const game_state *state)
1154 {
1155     int len, i, j;
1156     char *ret, *p;
1157     /* This is going to return a string representing the moves needed to set
1158      * every line in a grid to be the same as the ones in 'state'.  The exact
1159      * length of this string is predictable. */
1160
1161     len = 1;  /* Count the 'S' prefix */
1162     /* Numbers in horizontal lines */
1163     /* Horizontal lines, x position */
1164     len += len_0_to_n(state->w) * (state->h + 1);
1165     /* Horizontal lines, y position */
1166     len += len_0_to_n(state->h + 1) * (state->w);
1167     /* Vertical lines, y position */
1168     len += len_0_to_n(state->h) * (state->w + 1);
1169     /* Vertical lines, x position */
1170     len += len_0_to_n(state->w + 1) * (state->h);
1171     /* For each line we also have two letters and a comma */
1172     len += 3 * (HL_COUNT(state) + VL_COUNT(state));
1173
1174     ret = snewn(len + 1, char);
1175     p = ret;
1176
1177     p += sprintf(p, "S");
1178
1179     for (j = 0; j < state->h + 1; ++j) {
1180         for (i = 0; i < state->w; ++i) {
1181             switch (RIGHTOF_DOT(state, i, j)) {
1182                 case LINE_YES:
1183                     p += sprintf(p, "%d,%dhy", i, j);
1184                     break;
1185                 case LINE_NO:
1186                     p += sprintf(p, "%d,%dhn", i, j);
1187                     break;
1188 /*                default: */
1189                     /* I'm going to forgive this because I think the results
1190                      * are cute. */
1191 /*                    assert(!"Solver produced incomplete solution!"); */
1192             }
1193         }
1194     }
1195
1196     for (j = 0; j < state->h; ++j) {
1197         for (i = 0; i < state->w + 1; ++i) {
1198             switch (BELOW_DOT(state, i, j)) {
1199                 case LINE_YES:
1200                     p += sprintf(p, "%d,%dvy", i, j);
1201                     break;
1202                 case LINE_NO:
1203                     p += sprintf(p, "%d,%dvn", i, j);
1204                     break;
1205 /*                default: */
1206                     /* I'm going to forgive this because I think the results
1207                      * are cute. */
1208 /*                    assert(!"Solver produced incomplete solution!"); */
1209             }
1210         }
1211     }
1212
1213     /* No point in doing sums like that if they're going to be wrong */
1214     assert(strlen(ret) == (size_t)len);
1215     return ret;
1216 }
1217
1218 /* BEGIN SOLVER IMPLEMENTATION */
1219
1220    /* For each pair of lines through each dot we store a bit for whether
1221     * exactly one of those lines is ON, and in separate arrays we store whether
1222     * at least one is on and whether at most 1 is on.  (If we know both or
1223     * neither is on that's already stored more directly.)  That's six bits per
1224     * dot.  Bit number n represents the lines shown in dot_type_dirs[n]. */
1225
1226 enum dline {
1227     DLINE_VERT  = 0,
1228     DLINE_HORIZ = 1,
1229     DLINE_UL    = 2,
1230     DLINE_DR    = 3,
1231     DLINE_UR    = 4,
1232     DLINE_DL    = 5
1233 };
1234
1235 #define OPP_DLINE(dline) (dline ^ 1)
1236
1237
1238 #define SQUARE_DLINES                                                          \
1239                    HANDLE_DLINE(DLINE_UL, RIGHTOF_SQUARE, BELOW_SQUARE, 1, 1); \
1240                    HANDLE_DLINE(DLINE_UR, LEFTOF_SQUARE,  BELOW_SQUARE, 0, 1); \
1241                    HANDLE_DLINE(DLINE_DL, RIGHTOF_SQUARE, ABOVE_SQUARE, 1, 0); \
1242                    HANDLE_DLINE(DLINE_DR, LEFTOF_SQUARE,  ABOVE_SQUARE, 0, 0);
1243
1244 #define DOT_DLINES                                                       \
1245                    HANDLE_DLINE(DLINE_VERT,  ABOVE_DOT,  BELOW_DOT);     \
1246                    HANDLE_DLINE(DLINE_HORIZ, LEFTOF_DOT, RIGHTOF_DOT);   \
1247                    HANDLE_DLINE(DLINE_UL,    ABOVE_DOT,  LEFTOF_DOT);    \
1248                    HANDLE_DLINE(DLINE_UR,    ABOVE_DOT,  RIGHTOF_DOT);   \
1249                    HANDLE_DLINE(DLINE_DL,    BELOW_DOT,  LEFTOF_DOT);    \
1250                    HANDLE_DLINE(DLINE_DR,    BELOW_DOT,  RIGHTOF_DOT);
1251
1252 static void array_setall(char *array, char from, char to, int len)
1253 {
1254     char *p = array, *p_old = p;
1255     int len_remaining = len;
1256
1257     while ((p = memchr(p, from, len_remaining))) {
1258         *p = to;
1259         len_remaining -= p - p_old;
1260         p_old = p;
1261     }
1262 }
1263
1264 static int dot_setall_dlines(solver_state *sstate, enum dline dl, int i, int j,
1265                              enum line_state line_old, enum line_state line_new)
1266 {
1267     game_state *state = sstate->state;
1268     int retval = FALSE;
1269
1270     if (line_old == line_new)
1271         return FALSE;
1272
1273     /* First line in dline */
1274     switch (dl) {
1275         case DLINE_UL:
1276         case DLINE_UR:
1277         case DLINE_VERT:
1278             if (j > 0 && ABOVE_DOT(state, i, j) == line_old) {
1279                 LV_ABOVE_DOT(state, i, j) = line_new;
1280                 retval = TRUE;
1281             }
1282             break;
1283         case DLINE_DL:
1284         case DLINE_DR:
1285             if (j <= (state)->h && BELOW_DOT(state, i, j) == line_old) {
1286                 LV_BELOW_DOT(state, i, j) = line_new;
1287                 retval = TRUE;
1288             }
1289             break;
1290         case DLINE_HORIZ:
1291             if (i > 0 && LEFTOF_DOT(state, i, j) == line_old) {
1292                 LV_LEFTOF_DOT(state, i, j) = line_new;
1293                 retval = TRUE;
1294             }
1295             break;
1296     }
1297
1298     /* Second line in dline */
1299     switch (dl) {
1300         case DLINE_UL:
1301         case DLINE_DL:
1302             if (i > 0 && LEFTOF_DOT(state, i, j) == line_old) {
1303                 LV_LEFTOF_DOT(state, i, j) = line_new;
1304                 retval = TRUE;
1305             }
1306             break;
1307         case DLINE_UR:
1308         case DLINE_DR:
1309         case DLINE_HORIZ:
1310             if (i <= (state)->w && RIGHTOF_DOT(state, i, j) == line_old) {
1311                 LV_RIGHTOF_DOT(state, i, j) = line_new;
1312                 retval = TRUE;
1313             }
1314             break;
1315         case DLINE_VERT:
1316             if (j <= (state)->h && BELOW_DOT(state, i, j) == line_old) {
1317                 LV_BELOW_DOT(state, i, j) = line_new;
1318                 retval = TRUE;
1319             }
1320             break;
1321     }
1322
1323     return retval;
1324 }
1325
1326 #if 0
1327 /* This will fail an assertion if {dx,dy} are anything other than {-1,0}, {1,0}
1328  * {0,-1} or {0,1} */
1329 static int line_status_from_point(const game_state *state,
1330                                   int x, int y, int dx, int dy)
1331 {
1332     if (dx == -1 && dy ==  0)
1333         return LEFTOF_DOT(state, x, y);
1334     if (dx ==  1 && dy ==  0)
1335         return RIGHTOF_DOT(state, x, y);
1336     if (dx ==  0 && dy == -1)
1337         return ABOVE_DOT(state, x, y);
1338     if (dx ==  0 && dy ==  1)
1339         return BELOW_DOT(state, x, y);
1340
1341     assert(!"Illegal dx or dy in line_status_from_point");
1342     return 0;
1343 }
1344 #endif
1345
1346 /* This will return a dynamically allocated solver_state containing the (more)
1347  * solved grid */
1348 static solver_state *solve_game_rec(const solver_state *sstate_start, int diff)
1349 {
1350    int i, j, w, h;
1351    int current_yes, current_no, desired;
1352    solver_state *sstate, *sstate_saved, *sstate_tmp;
1353    int t;
1354    solver_state *sstate_rec_solved;
1355    int recursive_soln_count;
1356    char *square_solved;
1357    char *dot_solved;
1358    int solver_progress;
1359
1360    h = sstate_start->state->h;
1361    w = sstate_start->state->w;
1362
1363    dot_solved = snewn(DOT_COUNT(sstate_start->state), char);
1364    square_solved = snewn(SQUARE_COUNT(sstate_start->state), char);
1365    memset(dot_solved, FALSE, DOT_COUNT(sstate_start->state));
1366    memset(square_solved, FALSE, SQUARE_COUNT(sstate_start->state));
1367
1368 #if 0
1369    printf("solve_game_rec: recursion_remaining = %d\n",
1370           sstate_start->recursion_remaining);
1371 #endif
1372
1373    sstate = dup_solver_state((solver_state *)sstate_start);
1374
1375 #define FOUND_MISTAKE                                    \
1376    do {                                                  \
1377        sstate->solver_status = SOLVER_MISTAKE;           \
1378        sfree(dot_solved);  sfree(square_solved);         \
1379        free_solver_state(sstate_saved);                  \
1380        return sstate;                                    \
1381    } while (0)
1382
1383    sstate_saved = NULL;
1384
1385 nonrecursive_solver:
1386
1387    while (1) {
1388        solver_progress = FALSE;
1389
1390        /* First we do the 'easy' work, that might cause concrete results */
1391
1392        /* Per-square deductions */
1393        for (j = 0; j < h; ++j) {
1394            for (i = 0; i < w; ++i) {
1395                /* Begin rules that look at the clue (if there is one) */
1396                if (square_solved[i + j*w])
1397                    continue;
1398
1399                desired = CLUE_AT(sstate->state, i, j);
1400                if (desired == ' ')
1401                    continue;
1402
1403                desired = desired - '0';
1404                current_yes = square_order(sstate->state, i, j, LINE_YES);
1405                current_no  = square_order(sstate->state, i, j, LINE_NO);
1406
1407                if (current_yes + current_no == 4)  {
1408                    square_solved[i + j*w] = TRUE;
1409                    continue;
1410                }
1411
1412                if (desired < current_yes)
1413                    FOUND_MISTAKE;
1414                if (desired == current_yes) {
1415                    square_setall(sstate->state, i, j, LINE_UNKNOWN, LINE_NO);
1416                    square_solved[i + j*w] = TRUE;
1417                    solver_progress = TRUE;
1418                    continue;
1419                }
1420
1421                if (4 - desired < current_no)
1422                    FOUND_MISTAKE;
1423                if (4 - desired == current_no) {
1424                    square_setall(sstate->state, i, j, LINE_UNKNOWN, LINE_YES);
1425                    square_solved[i + j*w] = TRUE;
1426                    solver_progress = TRUE;
1427                }
1428            }
1429        }
1430
1431        /* Per-dot deductions */
1432        for (j = 0; j < h + 1; ++j) {
1433            for (i = 0; i < w + 1; ++i) {
1434                if (dot_solved[i + j*(w+1)])
1435                    continue;
1436
1437                switch (dot_order(sstate->state, i, j, LINE_YES)) {
1438                case 0:
1439                    switch (dot_order(sstate->state, i, j, LINE_NO)) {
1440                        case 3:
1441                            dot_setall(sstate->state, i, j, LINE_UNKNOWN, LINE_NO);
1442                            solver_progress = TRUE;
1443                            /* fall through */
1444                        case 4:
1445                            dot_solved[i + j*(w+1)] = TRUE;
1446                            break;
1447                    }
1448                    break;
1449                case 1:
1450                    switch (dot_order(sstate->state, i, j, LINE_NO)) {
1451 #define H1(dline, dir1_dot, dir2_dot, dot_howmany)                             \
1452                        if (dir1_dot(sstate->state, i, j) == LINE_UNKNOWN) {    \
1453                            if (dir2_dot(sstate->state, i, j) == LINE_UNKNOWN){ \
1454                                solver_progress |=                              \
1455                                  SET_BIT(sstate->dot_howmany[i + (w + 1) * j], \
1456                                          dline);                               \
1457                            }                                                   \
1458                        }
1459                        case 1:
1460                            if (diff > DIFF_EASY) {
1461 #define HANDLE_DLINE(dline, dir1_dot, dir2_dot)                               \
1462                            H1(dline, dir1_dot, dir2_dot, dot_atleastone)
1463                                /* 1 yes, 1 no, so exactly one of unknowns is
1464                                 * yes */
1465                                DOT_DLINES;
1466 #undef HANDLE_DLINE
1467                            }
1468                            /* fall through */
1469                        case 0:
1470                            if (diff > DIFF_EASY) {
1471 #define HANDLE_DLINE(dline, dir1_dot, dir2_dot)                               \
1472                            H1(dline, dir1_dot, dir2_dot, dot_atmostone)
1473                                /* 1 yes, fewer than 2 no, so at most one of
1474                                 * unknowns is yes */
1475                                DOT_DLINES;
1476 #undef HANDLE_DLINE
1477                            }
1478 #undef H1
1479                            break;
1480                        case 2: /* 1 yes, 2 no */
1481                            dot_setall(sstate->state, i, j,
1482                                       LINE_UNKNOWN, LINE_YES);
1483                            dot_solved[i + j*(w+1)] = TRUE;
1484                            solver_progress = TRUE;
1485                            break;
1486                        case 3: /* 1 yes, 3 no */
1487                            FOUND_MISTAKE;
1488                            break;
1489                    }
1490                    break;
1491                case 2:
1492                    if (dot_setall(sstate->state, i, j, LINE_UNKNOWN, LINE_NO)) {
1493                        solver_progress = TRUE;
1494                    }
1495                    dot_solved[i + j*(w+1)] = TRUE;
1496                    break;
1497                case 3:
1498                case 4:
1499                    FOUND_MISTAKE;
1500                    break;
1501                }
1502                if (diff > DIFF_EASY) {
1503 #define HANDLE_DLINE(dline, dir1_dot, dir2_dot)                               \
1504                if (BIT_SET(sstate->dot_atleastone[i + (w + 1) * j], dline)) { \
1505                    solver_progress |=                                         \
1506                      SET_BIT(sstate->dot_atmostone[i + (w + 1) * j],          \
1507                              OPP_DLINE(dline));                               \
1508                }
1509                    /* If at least one of a dline in a dot is YES, at most one
1510                     * of the opposite dline to that dot must be YES. */
1511                    DOT_DLINES;
1512                }
1513 #undef HANDLE_DLINE
1514
1515 #define H1(dline, dir1_sq, dir2_sq, dot_howmany, line_query, line_set)        \
1516                if (BIT_SET(sstate->dot_howmany[i + (w+1) * j], dline)) {      \
1517                    t = dir1_sq(sstate->state, i, j);                          \
1518                    if (t == line_query) {                                     \
1519                        if (dir2_sq(sstate->state, i, j) != line_set) {        \
1520                            LV_##dir2_sq(sstate->state, i, j) = line_set;      \
1521                            solver_progress = TRUE;                            \
1522                        }                                                      \
1523                    } else {                                                   \
1524                        t = dir2_sq(sstate->state, i, j);                      \
1525                        if (t == line_query) {                                 \
1526                            if (dir1_sq(sstate->state, i, j) != line_set) {    \
1527                                LV_##dir1_sq(sstate->state, i, j) = line_set;  \
1528                                solver_progress = TRUE;                        \
1529                            }                                                  \
1530                        }                                                      \
1531                    }                                                          \
1532                }
1533                if (diff > DIFF_EASY) {
1534 #define HANDLE_DLINE(dline, dir1_sq, dir2_sq)                                 \
1535                H1(dline, dir1_sq, dir2_sq, dot_atmostone, LINE_YES, LINE_NO)
1536                    /* If at most one of the DLINE is on, and one is definitely
1537                     * on, set the other to definitely off */
1538                    DOT_DLINES;
1539 #undef HANDLE_DLINE
1540                }
1541
1542                if (diff > DIFF_EASY) {
1543 #define HANDLE_DLINE(dline, dir1_sq, dir2_sq)                                 \
1544                H1(dline, dir1_sq, dir2_sq, dot_atleastone, LINE_NO, LINE_YES)
1545                    /* If at least one of the DLINE is on, and one is definitely
1546                     * off, set the other to definitely on */
1547                    DOT_DLINES;
1548 #undef HANDLE_DLINE
1549                }
1550 #undef H1
1551
1552            }
1553        }
1554
1555        /* More obscure per-square operations */
1556        for (j = 0; j < h; ++j) {
1557            for (i = 0; i < w; ++i) {
1558                if (square_solved[i + j*w])
1559                    continue;
1560
1561                switch (CLUE_AT(sstate->state, i, j)) {
1562                    case '1':
1563                        if (diff > DIFF_EASY) {
1564 #define HANDLE_DLINE(dline, dir1_sq, dir2_sq, a, b)                          \
1565                        /* At most one of any DLINE can be set */             \
1566                        SET_BIT(sstate->dot_atmostone[i+a + (w + 1) * (j+b)], \
1567                                dline);                                       \
1568                        /* This DLINE provides enough YESes to solve the clue */\
1569                        if (BIT_SET(sstate->dot_atleastone                    \
1570                                       [i+a + (w + 1) * (j+b)],               \
1571                                    dline)) {                                 \
1572                            solver_progress |=                                \
1573                                dot_setall_dlines(sstate, OPP_DLINE(dline),   \
1574                                                  i+(1-a), j+(1-b),           \
1575                                                  LINE_UNKNOWN, LINE_NO);     \
1576                        }
1577                            SQUARE_DLINES;
1578 #undef HANDLE_DLINE
1579                        }
1580                        break;
1581                    case '2':
1582                        if (diff > DIFF_EASY) {
1583 #define H1(dline, dot_at1one, dot_at2one, a, b)                          \
1584                if (BIT_SET(sstate->dot_at1one                            \
1585                              [i+a + (w+1) * (j+b)], dline)) {            \
1586                    solver_progress |=                                    \
1587                      SET_BIT(sstate->dot_at2one                          \
1588                                [i+(1-a) + (w+1) * (j+(1-b))],            \
1589                              OPP_DLINE(dline));                          \
1590                }
1591 #define HANDLE_DLINE(dline, dir1_sq, dir2_sq, a, b)             \
1592             H1(dline, dot_atleastone, dot_atmostone, a, b);     \
1593             H1(dline, dot_atmostone, dot_atleastone, a, b);
1594                            /* If at least one of one DLINE is set, at most one
1595                             * of the opposing one is and vice versa */
1596                            SQUARE_DLINES;
1597                        }
1598 #undef HANDLE_DLINE
1599 #undef H1
1600                        break;
1601                    case '3':
1602                        if (diff > DIFF_EASY) {
1603 #define HANDLE_DLINE(dline, dir1_sq, dir2_sq, a, b)                           \
1604                        /* At least one of any DLINE can be set */             \
1605                        solver_progress |=                                     \
1606                            SET_BIT(sstate->dot_atleastone                     \
1607                                      [i+a + (w + 1) * (j+b)],                 \
1608                                    dline);                                    \
1609                        /* This DLINE provides enough NOs to solve the clue */ \
1610                        if (BIT_SET(sstate->dot_atmostone                      \
1611                                      [i+a + (w + 1) * (j+b)],                 \
1612                                    dline)) {                                  \
1613                            solver_progress |=                                 \
1614                                dot_setall_dlines(sstate, OPP_DLINE(dline),    \
1615                                                  i+(1-a), j+(1-b),            \
1616                                                  LINE_UNKNOWN, LINE_YES);     \
1617                        }
1618                            SQUARE_DLINES;
1619 #undef HANDLE_DLINE
1620                        }
1621                        break;
1622                }
1623            }
1624        }
1625
1626        if (!solver_progress) {
1627            int edgecount = 0, clues = 0, satclues = 0, sm1clues = 0;
1628            int shortest_chainlen = DOT_COUNT(sstate->state);
1629            int loop_found = FALSE;
1630            int d;
1631            int dots_connected;
1632
1633            /*
1634             * Go through the grid and update for all the new edges.
1635             * Since merge_dots() is idempotent, the simplest way to
1636             * do this is just to update for _all_ the edges.
1637             *
1638             * Also, while we're here, we count the edges, count the
1639             * clues, count the satisfied clues, and count the
1640             * satisfied-minus-one clues.
1641             */
1642            for (j = 0; j < h+1; ++j) {
1643                for (i = 0; i < w+1; ++i) {
1644                    if (RIGHTOF_DOT(sstate->state, i, j) == LINE_YES) {
1645                        loop_found |= merge_dots(sstate, i, j, i+1, j);
1646                        edgecount++;
1647                    }
1648                    if (BELOW_DOT(sstate->state, i, j) == LINE_YES) {
1649                        loop_found |= merge_dots(sstate, i, j, i, j+1);
1650                        edgecount++;
1651                    }
1652
1653                    if (CLUE_AT(sstate->state, i, j) != ' ') {
1654                        int c = CLUE_AT(sstate->state, i, j) - '0';
1655                        int o = square_order(sstate->state, i, j, LINE_YES);
1656                        if (o == c)
1657                            satclues++;
1658                        else if (o == c-1)
1659                            sm1clues++;
1660                        clues++;
1661                    }
1662                }
1663            }
1664
1665            for (i = 0; i < DOT_COUNT(sstate->state); ++i) {
1666                dots_connected = sstate->looplen[dsf_canonify(sstate->dotdsf,i)];
1667                if (dots_connected > 1)
1668                    shortest_chainlen = min(shortest_chainlen, dots_connected);
1669            }
1670
1671            assert(sstate->solver_status == SOLVER_INCOMPLETE);
1672
1673            if (satclues == clues && shortest_chainlen == edgecount) {
1674                sstate->solver_status = SOLVER_SOLVED;
1675                /* This discovery clearly counts as progress, even if we haven't
1676                 * just added any lines or anything */
1677                solver_progress = TRUE;
1678                goto finished_loop_checking;
1679            }
1680
1681            /*
1682             * Now go through looking for LINE_UNKNOWN edges which
1683             * connect two dots that are already in the same
1684             * equivalence class. If we find one, test to see if the
1685             * loop it would create is a solution.
1686             */
1687            for (j = 0; j <= h; ++j) {
1688                for (i = 0; i <= w; ++i) {
1689                    for (d = 0; d < 2; d++) {
1690                        int i2, j2, eqclass, val;
1691
1692                        if (d == 0) {
1693                            if (RIGHTOF_DOT(sstate->state, i, j) !=
1694                                LINE_UNKNOWN)
1695                                continue;
1696                            i2 = i+1;
1697                            j2 = j;
1698                        } else {
1699                            if (BELOW_DOT(sstate->state, i, j) !=
1700                                LINE_UNKNOWN)
1701                                continue;
1702                            i2 = i;
1703                            j2 = j+1;
1704                        }
1705
1706                        eqclass = dsf_canonify(sstate->dotdsf, j * (w+1) + i);
1707                        if (eqclass != dsf_canonify(sstate->dotdsf,
1708                                                    j2 * (w+1) + i2))
1709                            continue;
1710
1711                        val = LINE_NO;  /* loop is bad until proven otherwise */
1712
1713                        /*
1714                         * This edge would form a loop. Next
1715                         * question: how long would the loop be?
1716                         * Would it equal the total number of edges
1717                         * (plus the one we'd be adding if we added
1718                         * it)?
1719                         */
1720                        if (sstate->looplen[eqclass] == edgecount + 1) {
1721                            int sm1_nearby;
1722                            int cx, cy;
1723
1724                            /*
1725                             * This edge would form a loop which
1726                             * took in all the edges in the entire
1727                             * grid. So now we need to work out
1728                             * whether it would be a valid solution
1729                             * to the puzzle, which means we have to
1730                             * check if it satisfies all the clues.
1731                             * This means that every clue must be
1732                             * either satisfied or satisfied-minus-
1733                             * 1, and also that the number of
1734                             * satisfied-minus-1 clues must be at
1735                             * most two and they must lie on either
1736                             * side of this edge.
1737                             */
1738                            sm1_nearby = 0;
1739                            cx = i - (j2-j);
1740                            cy = j - (i2-i);
1741                            if (CLUE_AT(sstate->state, cx,cy) != ' ' &&
1742                                square_order(sstate->state, cx,cy, LINE_YES) ==
1743                                CLUE_AT(sstate->state, cx,cy) - '0' - 1)
1744                                sm1_nearby++;
1745                            if (CLUE_AT(sstate->state, i, j) != ' ' &&
1746                                square_order(sstate->state, i, j, LINE_YES) ==
1747                                CLUE_AT(sstate->state, i, j) - '0' - 1)
1748                                sm1_nearby++;
1749                            if (sm1clues == sm1_nearby &&
1750                                sm1clues + satclues == clues)
1751                                val = LINE_YES;  /* loop is good! */
1752                        }
1753
1754                        /*
1755                         * Right. Now we know that adding this edge
1756                         * would form a loop, and we know whether
1757                         * that loop would be a viable solution or
1758                         * not.
1759                         *
1760                         * If adding this edge produces a solution,
1761                         * then we know we've found _a_ solution but
1762                         * we don't know that it's _the_ solution -
1763                         * if it were provably the solution then
1764                         * we'd have deduced this edge some time ago
1765                         * without the need to do loop detection. So
1766                         * in this state we return SOLVER_AMBIGUOUS,
1767                         * which has the effect that hitting Solve
1768                         * on a user-provided puzzle will fill in a
1769                         * solution but using the solver to
1770                         * construct new puzzles won't consider this
1771                         * a reasonable deduction for the user to
1772                         * make.
1773                         */
1774                        if (d == 0) {
1775                            LV_RIGHTOF_DOT(sstate->state, i, j) = val;
1776                            solver_progress = TRUE;
1777                        } else {
1778                            LV_BELOW_DOT(sstate->state, i, j) = val;
1779                            solver_progress = TRUE;
1780                        }
1781                        if (val == LINE_YES) {
1782                            sstate->solver_status = SOLVER_AMBIGUOUS;
1783                            goto finished_loop_checking;
1784                        }
1785                    }
1786                }
1787            }
1788
1789            finished_loop_checking:
1790
1791            if (!solver_progress ||
1792                sstate->solver_status == SOLVER_SOLVED ||
1793                sstate->solver_status == SOLVER_AMBIGUOUS) {
1794                break;
1795            }
1796        }
1797    }
1798
1799    sfree(dot_solved); sfree(square_solved);
1800
1801    if (sstate->solver_status == SOLVER_SOLVED ||
1802        sstate->solver_status == SOLVER_AMBIGUOUS) {
1803        /* s/LINE_UNKNOWN/LINE_NO/g */
1804        array_setall(sstate->state->hl, LINE_UNKNOWN, LINE_NO,
1805                HL_COUNT(sstate->state));
1806        array_setall(sstate->state->vl, LINE_UNKNOWN, LINE_NO,
1807                VL_COUNT(sstate->state));
1808        return sstate;
1809    }
1810
1811    /* Perform recursive calls */
1812    if (sstate->recursion_remaining) {
1813        sstate_saved = dup_solver_state(sstate);
1814
1815        sstate->recursion_remaining--;
1816
1817        recursive_soln_count = 0;
1818        sstate_rec_solved = NULL;
1819
1820        /* Memory management:
1821         * sstate_saved won't be modified but needs to be freed when we have
1822         * finished with it.
1823         * sstate is expected to contain our 'best' solution by the time we
1824         * finish this section of code.  It's the thing we'll try adding lines
1825         * to, seeing if they make it more solvable.
1826         * If sstate_rec_solved is non-NULL, it will supersede sstate
1827         * eventually.  sstate_tmp should not hold a value persistently.
1828         */
1829
1830        /* NB SOLVER_AMBIGUOUS is like SOLVER_SOLVED except the solver is aware
1831         * of the possibility of additional solutions.  So as soon as we have a
1832         * SOLVER_AMBIGUOUS we can safely propagate it back to our caller, but
1833         * if we get a SOLVER_SOLVED we want to keep trying in case we find
1834         * further solutions and have to mark it ambiguous.
1835         */
1836
1837 #define DO_RECURSIVE_CALL(dir_dot)                                         \
1838        if (dir_dot(sstate->state, i, j) == LINE_UNKNOWN) {                 \
1839            debug(("Trying " #dir_dot " at [%d,%d]\n", i, j));               \
1840            LV_##dir_dot(sstate->state, i, j) = LINE_YES;                   \
1841            sstate_tmp = solve_game_rec(sstate, diff);                      \
1842            switch (sstate_tmp->solver_status) {                            \
1843                case SOLVER_AMBIGUOUS:                                      \
1844                    debug(("Solver ambiguous, returning\n"));                \
1845                    sstate_rec_solved = sstate_tmp;                         \
1846                    goto finished_recursion;                                \
1847                case SOLVER_SOLVED:                                         \
1848                    switch (++recursive_soln_count) {                       \
1849                        case 1:                                             \
1850                            debug(("One solution found\n"));                 \
1851                            sstate_rec_solved = sstate_tmp;                 \
1852                            break;                                          \
1853                        case 2:                                             \
1854                            debug(("Ambiguous solutions found\n"));          \
1855                            free_solver_state(sstate_tmp);                  \
1856                            sstate_rec_solved->solver_status = SOLVER_AMBIGUOUS;\
1857                            goto finished_recursion;                        \
1858                        default:                                            \
1859                            assert(!"recursive_soln_count out of range");   \
1860                            break;                                          \
1861                    }                                                       \
1862                    break;                                                  \
1863                case SOLVER_MISTAKE:                                        \
1864                    debug(("Non-solution found\n"));                         \
1865                    free_solver_state(sstate_tmp);                          \
1866                    free_solver_state(sstate_saved);                        \
1867                    LV_##dir_dot(sstate->state, i, j) = LINE_NO;            \
1868                    goto nonrecursive_solver;                               \
1869                case SOLVER_INCOMPLETE:                                     \
1870                    debug(("Recursive step inconclusive\n"));                \
1871                    free_solver_state(sstate_tmp);                          \
1872                    break;                                                  \
1873            }                                                               \
1874            free_solver_state(sstate);                                      \
1875            sstate = dup_solver_state(sstate_saved);                        \
1876        }
1877
1878        for (j = 0; j < h + 1; ++j) {
1879            for (i = 0; i < w + 1; ++i) {
1880                /* Only perform recursive calls on 'loose ends' */
1881                if (dot_order(sstate->state, i, j, LINE_YES) == 1) {
1882                    DO_RECURSIVE_CALL(LEFTOF_DOT);
1883                    DO_RECURSIVE_CALL(RIGHTOF_DOT);
1884                    DO_RECURSIVE_CALL(ABOVE_DOT);
1885                    DO_RECURSIVE_CALL(BELOW_DOT);
1886                }
1887            }
1888        }
1889
1890 finished_recursion:
1891
1892        if (sstate_rec_solved) {
1893            free_solver_state(sstate);
1894            sstate = sstate_rec_solved;
1895        }
1896    }
1897
1898    return sstate;
1899 }
1900
1901 /* XXX bits of solver that may come in handy one day */
1902 #if 0
1903 #define HANDLE_DLINE(dline, dir1_dot, dir2_dot)                         \
1904                    /* dline from this dot that's entirely unknown must have
1905                     * both lines identical */                           \
1906                    if (dir1_dot(sstate->state, i, j) == LINE_UNKNOWN &&       \
1907                        dir2_dot(sstate->state, i, j) == LINE_UNKNOWN) {       \
1908                        sstate->dline_identical[i + (sstate->state->w + 1) * j] |= \
1909                            1<<dline;                                    \
1910                    } else if (sstate->dline_identical[i +
1911                                                       (sstate->state->w + 1) * j] &\
1912                               1<<dline) {                                   \
1913                        /* If they're identical and one is known do the obvious
1914                         * thing */                                      \
1915                        t = dir1_dot(sstate->state, i, j);                     \
1916                        if (t != LINE_UNKNOWN)                           \
1917                            dir2_dot(sstate->state, i, j) = t;                 \
1918                        else {                                           \
1919                            t = dir2_dot(sstate->state, i, j);                 \
1920                            if (t != LINE_UNKNOWN)                       \
1921                                dir1_dot(sstate->state, i, j) = t;             \
1922                        }                                                \
1923                    }                                                    \
1924                    DOT_DLINES;
1925 #undef HANDLE_DLINE
1926 #endif
1927
1928 #if 0
1929 #define HANDLE_DLINE(dline, dir1_sq, dir2_sq, a, b) \
1930                        if (sstate->dline_identical[i+a +                     \
1931                                                    (sstate->state->w + 1) * (j+b)] &\
1932                            1<<dline) {                                       \
1933                            dir1_sq(sstate->state, i, j) = LINE_YES;                \
1934                            dir2_sq(sstate->state, i, j) = LINE_YES;                \
1935                        }
1936                        /* If two lines are the same they must be on */
1937                        SQUARE_DLINES;
1938 #undef HANDLE_DLINE
1939 #endif
1940
1941
1942 #if 0
1943 #define HANDLE_DLINE(dline, dir1_sq, dir2_sq, a, b) \
1944                if (sstate->dot_atmostone[i+a + (sstate->state->w + 1) * (j+b)] &  \
1945                    1<<dline) {                                   \
1946                    if (square_order(sstate->state, i, j,  LINE_UNKNOWN) - 1 ==  \
1947                        CLUE_AT(sstate->state, i, j) - '0') {      \
1948                        square_setall(sstate->state, i, j, LINE_UNKNOWN, LINE_YES); \
1949                            /* XXX the following may overwrite known data! */ \
1950                        dir1_sq(sstate->state, i, j) = LINE_UNKNOWN;  \
1951                        dir2_sq(sstate->state, i, j) = LINE_UNKNOWN;  \
1952                    }                                  \
1953                }
1954                SQUARE_DLINES;
1955 #undef HANDLE_DLINE
1956 #endif
1957
1958 #if 0
1959 #define HANDLE_DLINE(dline, dir1_sq, dir2_sq, a, b) \
1960                        if (sstate->dline_identical[i+a +
1961                                                    (sstate->state->w + 1) * (j+b)] &\
1962                            1<<dline) {                                       \
1963                            dir1_sq(sstate->state, i, j) = LINE_NO;                 \
1964                            dir2_sq(sstate->state, i, j) = LINE_NO;                 \
1965                        }
1966                        /* If two lines are the same they must be off */
1967                        SQUARE_DLINES;
1968 #undef HANDLE_DLINE
1969 #endif
1970
1971 static char *solve_game(game_state *state, game_state *currstate,
1972                         char *aux, char **error)
1973 {
1974     char *soln = NULL;
1975     solver_state *sstate, *new_sstate;
1976
1977     sstate = new_solver_state(state);
1978     new_sstate = solve_game_rec(sstate, DIFFCOUNT);
1979
1980     if (new_sstate->solver_status == SOLVER_SOLVED) {
1981         soln = encode_solve_move(new_sstate->state);
1982     } else if (new_sstate->solver_status == SOLVER_AMBIGUOUS) {
1983         soln = encode_solve_move(new_sstate->state);
1984         /**error = "Solver found ambiguous solutions"; */
1985     } else {
1986         soln = encode_solve_move(new_sstate->state);
1987         /**error = "Solver failed"; */
1988     }
1989
1990     free_solver_state(new_sstate);
1991     free_solver_state(sstate);
1992
1993     return soln;
1994 }
1995
1996 static char *game_text_format(game_state *state)
1997 {
1998     int i, j;
1999     int len;
2000     char *ret, *rp;
2001
2002     len = (2 * state->w + 2) * (2 * state->h + 1);
2003     rp = ret = snewn(len + 1, char);
2004
2005 #define DRAW_HL                          \
2006     switch (ABOVE_SQUARE(state, i, j)) { \
2007         case LINE_YES:                   \
2008             rp += sprintf(rp, " -");     \
2009             break;                       \
2010         case LINE_NO:                    \
2011             rp += sprintf(rp, " x");     \
2012             break;                       \
2013         case LINE_UNKNOWN:               \
2014             rp += sprintf(rp, "  ");     \
2015             break;                       \
2016         default:                         \
2017             assert(!"Illegal line state for HL");\
2018     }
2019
2020 #define DRAW_VL                          \
2021     switch (LEFTOF_SQUARE(state, i, j)) {\
2022         case LINE_YES:                   \
2023             rp += sprintf(rp, "|");      \
2024             break;                       \
2025         case LINE_NO:                    \
2026             rp += sprintf(rp, "x");      \
2027             break;                       \
2028         case LINE_UNKNOWN:               \
2029             rp += sprintf(rp, " ");      \
2030             break;                       \
2031         default:                         \
2032             assert(!"Illegal line state for VL");\
2033     }
2034
2035     for (j = 0; j < state->h; ++j) {
2036         for (i = 0; i < state->w; ++i) {
2037             DRAW_HL;
2038         }
2039         rp += sprintf(rp, " \n");
2040         for (i = 0; i < state->w; ++i) {
2041             DRAW_VL;
2042             rp += sprintf(rp, "%c", (int)(CLUE_AT(state, i, j)));
2043         }
2044         DRAW_VL;
2045         rp += sprintf(rp, "\n");
2046     }
2047     for (i = 0; i < state->w; ++i) {
2048         DRAW_HL;
2049     }
2050     rp += sprintf(rp, " \n");
2051
2052     assert(strlen(ret) == len);
2053     return ret;
2054 }
2055
2056 static game_ui *new_ui(game_state *state)
2057 {
2058     return NULL;
2059 }
2060
2061 static void free_ui(game_ui *ui)
2062 {
2063 }
2064
2065 static char *encode_ui(game_ui *ui)
2066 {
2067     return NULL;
2068 }
2069
2070 static void decode_ui(game_ui *ui, char *encoding)
2071 {
2072 }
2073
2074 static void game_changed_state(game_ui *ui, game_state *oldstate,
2075                                game_state *newstate)
2076 {
2077 }
2078
2079 struct game_drawstate {
2080     int started;
2081     int tilesize, linewidth;
2082     int flashing;
2083     char *hl, *vl;
2084     char *clue_error;
2085 };
2086
2087 static char *interpret_move(game_state *state, game_ui *ui, game_drawstate *ds,
2088                             int x, int y, int button)
2089 {
2090     int hl_selected;
2091     int i, j, p, q;
2092     char *ret, buf[80];
2093     char button_char = ' ';
2094     enum line_state old_state;
2095
2096     button &= ~MOD_MASK;
2097
2098     /* Around each line is a diamond-shaped region where points within that
2099      * region are closer to this line than any other.  We assume any click
2100      * within a line's diamond was meant for that line.  It would all be a lot
2101      * simpler if the / and % operators respected modulo arithmetic properly
2102      * for negative numbers. */
2103
2104     x -= BORDER;
2105     y -= BORDER;
2106
2107     /* Get the coordinates of the square the click was in */
2108     i = (x + TILE_SIZE) / TILE_SIZE - 1;
2109     j = (y + TILE_SIZE) / TILE_SIZE - 1;
2110
2111     /* Get the precise position inside square [i,j] */
2112     p = (x + TILE_SIZE) % TILE_SIZE;
2113     q = (y + TILE_SIZE) % TILE_SIZE;
2114
2115     /* After this bit of magic [i,j] will correspond to the point either above
2116      * or to the left of the line selected */
2117     if (p > q) {
2118         if (TILE_SIZE - p > q) {
2119             hl_selected = TRUE;
2120         } else {
2121             hl_selected = FALSE;
2122             ++i;
2123         }
2124     } else {
2125         if (TILE_SIZE - q > p) {
2126             hl_selected = FALSE;
2127         } else {
2128             hl_selected = TRUE;
2129             ++j;
2130         }
2131     }
2132
2133     if (i < 0 || j < 0)
2134         return NULL;
2135
2136     if (hl_selected) {
2137         if (i >= state->w || j >= state->h + 1)
2138             return NULL;
2139     } else {
2140         if (i >= state->w + 1 || j >= state->h)
2141             return NULL;
2142     }
2143
2144     /* I think it's only possible to play this game with mouse clicks, sorry */
2145     /* Maybe will add mouse drag support some time */
2146     if (hl_selected)
2147         old_state = RIGHTOF_DOT(state, i, j);
2148     else
2149         old_state = BELOW_DOT(state, i, j);
2150
2151     switch (button) {
2152         case LEFT_BUTTON:
2153             switch (old_state) {
2154                 case LINE_UNKNOWN:
2155                     button_char = 'y';
2156                     break;
2157                 case LINE_YES:
2158                 case LINE_NO:
2159                     button_char = 'u';
2160                     break;
2161             }
2162             break;
2163         case MIDDLE_BUTTON:
2164             button_char = 'u';
2165             break;
2166         case RIGHT_BUTTON:
2167             switch (old_state) {
2168                 case LINE_UNKNOWN:
2169                     button_char = 'n';
2170                     break;
2171                 case LINE_NO:
2172                 case LINE_YES:
2173                     button_char = 'u';
2174                     break;
2175             }
2176             break;
2177         default:
2178             return NULL;
2179     }
2180
2181
2182     sprintf(buf, "%d,%d%c%c", i, j, (int)(hl_selected ? 'h' : 'v'), (int)button_char);
2183     ret = dupstr(buf);
2184
2185     return ret;
2186 }
2187
2188 static game_state *execute_move(game_state *state, char *move)
2189 {
2190     int i, j;
2191     game_state *newstate = dup_game(state);
2192
2193     if (move[0] == 'S') {
2194         move++;
2195         newstate->cheated = TRUE;
2196     }
2197
2198     while (*move) {
2199         i = atoi(move);
2200         move = strchr(move, ',');
2201         if (!move)
2202             goto fail;
2203         j = atoi(++move);
2204         move += strspn(move, "1234567890");
2205         switch (*(move++)) {
2206             case 'h':
2207                 if (i >= newstate->w || j > newstate->h)
2208                     goto fail;
2209                 switch (*(move++)) {
2210                     case 'y':
2211                         LV_RIGHTOF_DOT(newstate, i, j) = LINE_YES;
2212                         break;
2213                     case 'n':
2214                         LV_RIGHTOF_DOT(newstate, i, j) = LINE_NO;
2215                         break;
2216                     case 'u':
2217                         LV_RIGHTOF_DOT(newstate, i, j) = LINE_UNKNOWN;
2218                         break;
2219                     default:
2220                         goto fail;
2221                 }
2222                 break;
2223             case 'v':
2224                 if (i > newstate->w || j >= newstate->h)
2225                     goto fail;
2226                 switch (*(move++)) {
2227                     case 'y':
2228                         LV_BELOW_DOT(newstate, i, j) = LINE_YES;
2229                         break;
2230                     case 'n':
2231                         LV_BELOW_DOT(newstate, i, j) = LINE_NO;
2232                         break;
2233                     case 'u':
2234                         LV_BELOW_DOT(newstate, i, j) = LINE_UNKNOWN;
2235                         break;
2236                     default:
2237                         goto fail;
2238                 }
2239                 break;
2240             default:
2241                 goto fail;
2242         }
2243     }
2244
2245     /*
2246      * Check for completion.
2247      */
2248     i = 0;                             /* placate optimiser */
2249     for (j = 0; j <= newstate->h; j++) {
2250         for (i = 0; i < newstate->w; i++)
2251             if (LV_RIGHTOF_DOT(newstate, i, j) == LINE_YES)
2252                 break;
2253         if (i < newstate->w)
2254             break;
2255     }
2256     if (j <= newstate->h) {
2257         int prevdir = 'R';
2258         int x = i, y = j;
2259         int looplen, count;
2260
2261         /*
2262          * We've found a horizontal edge at (i,j). Follow it round
2263          * to see if it's part of a loop.
2264          */
2265         looplen = 0;
2266         while (1) {
2267             int order = dot_order(newstate, x, y, LINE_YES);
2268             if (order != 2)
2269                 goto completion_check_done;
2270
2271             if (LEFTOF_DOT(newstate, x, y) == LINE_YES && prevdir != 'L') {
2272                 x--;
2273                 prevdir = 'R';
2274             } else if (RIGHTOF_DOT(newstate, x, y) == LINE_YES &&
2275                        prevdir != 'R') {
2276                 x++;
2277                 prevdir = 'L';
2278             } else if (ABOVE_DOT(newstate, x, y) == LINE_YES &&
2279                        prevdir != 'U') {
2280                 y--;
2281                 prevdir = 'D';
2282             } else if (BELOW_DOT(newstate, x, y) == LINE_YES &&
2283                        prevdir != 'D') {
2284                 y++;
2285                 prevdir = 'U';
2286             } else {
2287                 assert(!"Can't happen");   /* dot_order guarantees success */
2288             }
2289
2290             looplen++;
2291
2292             if (x == i && y == j)
2293                 break;
2294         }
2295
2296         if (x != i || y != j || looplen == 0)
2297             goto completion_check_done;
2298
2299         /*
2300          * We've traced our way round a loop, and we know how many
2301          * line segments were involved. Count _all_ the line
2302          * segments in the grid, to see if the loop includes them
2303          * all.
2304          */
2305         count = 0;
2306         for (j = 0; j <= newstate->h; j++)
2307             for (i = 0; i <= newstate->w; i++)
2308                 count += ((RIGHTOF_DOT(newstate, i, j) == LINE_YES) +
2309                           (BELOW_DOT(newstate, i, j) == LINE_YES));
2310         assert(count >= looplen);
2311         if (count != looplen)
2312             goto completion_check_done;
2313
2314         /*
2315          * The grid contains one closed loop and nothing else.
2316          * Check that all the clues are satisfied.
2317          */
2318         for (j = 0; j < newstate->h; ++j) {
2319             for (i = 0; i < newstate->w; ++i) {
2320                 int n = CLUE_AT(newstate, i, j);
2321                 if (n != ' ') {
2322                     if (square_order(newstate, i, j, LINE_YES) != n - '0') {
2323                         goto completion_check_done;
2324                     }
2325                 }
2326             }
2327         }
2328
2329         /*
2330          * Completed!
2331          */
2332         newstate->solved = TRUE;
2333     }
2334
2335 completion_check_done:
2336     return newstate;
2337
2338 fail:
2339     free_game(newstate);
2340     return NULL;
2341 }
2342
2343 /* ----------------------------------------------------------------------
2344  * Drawing routines.
2345  */
2346
2347 #define SIZE(d) ((d) * TILE_SIZE + 2 * BORDER + 1)
2348
2349 static void game_compute_size(game_params *params, int tilesize,
2350                               int *x, int *y)
2351 {
2352     struct { int tilesize; } ads, *ds = &ads;
2353     ads.tilesize = tilesize;
2354
2355     *x = SIZE(params->w);
2356     *y = SIZE(params->h);
2357 }
2358
2359 static void game_set_size(drawing *dr, game_drawstate *ds,
2360                           game_params *params, int tilesize)
2361 {
2362     ds->tilesize = tilesize;
2363     ds->linewidth = max(1,tilesize/16);
2364 }
2365
2366 static float *game_colours(frontend *fe, game_state *state, int *ncolours)
2367 {
2368     float *ret = snewn(4 * NCOLOURS, float);
2369
2370     frontend_default_colour(fe, &ret[COL_BACKGROUND * 3]);
2371
2372     ret[COL_FOREGROUND * 3 + 0] = 0.0F;
2373     ret[COL_FOREGROUND * 3 + 1] = 0.0F;
2374     ret[COL_FOREGROUND * 3 + 2] = 0.0F;
2375
2376     ret[COL_HIGHLIGHT * 3 + 0] = 1.0F;
2377     ret[COL_HIGHLIGHT * 3 + 1] = 1.0F;
2378     ret[COL_HIGHLIGHT * 3 + 2] = 1.0F;
2379
2380     ret[COL_MISTAKE * 3 + 0] = 1.0F;
2381     ret[COL_MISTAKE * 3 + 1] = 0.0F;
2382     ret[COL_MISTAKE * 3 + 2] = 0.0F;
2383
2384     *ncolours = NCOLOURS;
2385     return ret;
2386 }
2387
2388 static game_drawstate *game_new_drawstate(drawing *dr, game_state *state)
2389 {
2390     struct game_drawstate *ds = snew(struct game_drawstate);
2391
2392     ds->tilesize = ds->linewidth = 0;
2393     ds->started = 0;
2394     ds->hl = snewn(HL_COUNT(state), char);
2395     ds->vl = snewn(VL_COUNT(state), char);
2396     ds->clue_error = snewn(SQUARE_COUNT(state), char);
2397     ds->flashing = 0;
2398
2399     memset(ds->hl, LINE_UNKNOWN, HL_COUNT(state));
2400     memset(ds->vl, LINE_UNKNOWN, VL_COUNT(state));
2401     memset(ds->clue_error, 0, SQUARE_COUNT(state));
2402
2403     return ds;
2404 }
2405
2406 static void game_free_drawstate(drawing *dr, game_drawstate *ds)
2407 {
2408     sfree(ds->clue_error);
2409     sfree(ds->hl);
2410     sfree(ds->vl);
2411     sfree(ds);
2412 }
2413
2414 static void game_redraw(drawing *dr, game_drawstate *ds, game_state *oldstate,
2415                         game_state *state, int dir, game_ui *ui,
2416                         float animtime, float flashtime)
2417 {
2418     int i, j, n;
2419     int w = state->w, h = state->h;
2420     char c[2];
2421     int line_colour, flash_changed;
2422     int clue_mistake;
2423
2424     if (!ds->started) {
2425         /*
2426          * The initial contents of the window are not guaranteed and
2427          * can vary with front ends. To be on the safe side, all games
2428          * should start by drawing a big background-colour rectangle
2429          * covering the whole window.
2430          */
2431         draw_rect(dr, 0, 0, SIZE(state->w), SIZE(state->h), COL_BACKGROUND);
2432
2433         /* Draw dots */
2434         for (j = 0; j < h + 1; ++j) {
2435             for (i = 0; i < w + 1; ++i) {
2436                 draw_rect(dr,
2437                           BORDER + i * TILE_SIZE - LINEWIDTH/2,
2438                           BORDER + j * TILE_SIZE - LINEWIDTH/2,
2439                           LINEWIDTH, LINEWIDTH, COL_FOREGROUND);
2440             }
2441         }
2442
2443         /* Draw clues */
2444         for (j = 0; j < h; ++j) {
2445             for (i = 0; i < w; ++i) {
2446                 c[0] = CLUE_AT(state, i, j);
2447                 c[1] = '\0';
2448                 draw_text(dr,
2449                           BORDER + i * TILE_SIZE + TILE_SIZE/2,
2450                           BORDER + j * TILE_SIZE + TILE_SIZE/2,
2451                           FONT_VARIABLE, TILE_SIZE/2,
2452                           ALIGN_VCENTRE | ALIGN_HCENTRE, COL_FOREGROUND, c);
2453             }
2454         }
2455         draw_update(dr, 0, 0,
2456                     state->w * TILE_SIZE + 2*BORDER + 1,
2457                     state->h * TILE_SIZE + 2*BORDER + 1);
2458         ds->started = TRUE;
2459     }
2460
2461     if (flashtime > 0 &&
2462         (flashtime <= FLASH_TIME/3 ||
2463          flashtime >= FLASH_TIME*2/3)) {
2464         flash_changed = !ds->flashing;
2465         ds->flashing = TRUE;
2466         line_colour = COL_HIGHLIGHT;
2467     } else {
2468         flash_changed = ds->flashing;
2469         ds->flashing = FALSE;
2470         line_colour = COL_FOREGROUND;
2471     }
2472
2473 #define CROSS_SIZE (3 * LINEWIDTH / 2)
2474
2475     /* Redraw clue colours if necessary */
2476     for (j = 0; j < h; ++j) {
2477         for (i = 0; i < w; ++i) {
2478             c[0] = CLUE_AT(state, i, j);
2479             c[1] = '\0';
2480             if (c[0] == ' ')
2481                 continue;
2482
2483             n = c[0] - '0';
2484             assert(n >= 0 && n <= 4);
2485
2486             clue_mistake = (square_order(state, i, j, LINE_YES) > n     ||
2487                             square_order(state, i, j, LINE_NO ) > (4-n));
2488
2489             if (clue_mistake != ds->clue_error[j * w + i]) {
2490                 draw_rect(dr,
2491                           BORDER + i * TILE_SIZE + CROSS_SIZE,
2492                           BORDER + j * TILE_SIZE + CROSS_SIZE,
2493                           TILE_SIZE - CROSS_SIZE * 2, TILE_SIZE - CROSS_SIZE * 2,
2494                           COL_BACKGROUND);
2495                 draw_text(dr,
2496                           BORDER + i * TILE_SIZE + TILE_SIZE/2,
2497                           BORDER + j * TILE_SIZE + TILE_SIZE/2,
2498                           FONT_VARIABLE, TILE_SIZE/2,
2499                           ALIGN_VCENTRE | ALIGN_HCENTRE,
2500                           clue_mistake ? COL_MISTAKE : COL_FOREGROUND, c);
2501                 draw_update(dr, i * TILE_SIZE + BORDER, j * TILE_SIZE + BORDER,
2502                             TILE_SIZE, TILE_SIZE);
2503
2504                 ds->clue_error[j * w + i] = clue_mistake;
2505             }
2506         }
2507     }
2508
2509     /* I've also had a request to colour lines red if they make a non-solution
2510      * loop, or if more than two lines go into any point.  I think that would
2511      * be good some time. */
2512
2513 #define CLEAR_VL(i, j) do {                                                \
2514                            draw_rect(dr,                                   \
2515                                  BORDER + i * TILE_SIZE - CROSS_SIZE,      \
2516                                  BORDER + j * TILE_SIZE + LINEWIDTH - LINEWIDTH/2,     \
2517                                  CROSS_SIZE * 2,                           \
2518                                  TILE_SIZE - LINEWIDTH,                    \
2519                                  COL_BACKGROUND);                          \
2520                            draw_update(dr,                                 \
2521                                        BORDER + i * TILE_SIZE - CROSS_SIZE, \
2522                                        BORDER + j * TILE_SIZE - CROSS_SIZE, \
2523                                        CROSS_SIZE*2,                       \
2524                                        TILE_SIZE + CROSS_SIZE*2);          \
2525                         } while (0)
2526
2527 #define CLEAR_HL(i, j) do {                                                \
2528                            draw_rect(dr,                                   \
2529                                  BORDER + i * TILE_SIZE + LINEWIDTH - LINEWIDTH/2,     \
2530                                  BORDER + j * TILE_SIZE - CROSS_SIZE,      \
2531                                  TILE_SIZE - LINEWIDTH,                    \
2532                                  CROSS_SIZE * 2,                           \
2533                                  COL_BACKGROUND);                          \
2534                            draw_update(dr,                                 \
2535                                        BORDER + i * TILE_SIZE - CROSS_SIZE, \
2536                                        BORDER + j * TILE_SIZE - CROSS_SIZE, \
2537                                        TILE_SIZE + CROSS_SIZE*2,           \
2538                                        CROSS_SIZE*2);                      \
2539                         } while (0)
2540
2541     /* Vertical lines */
2542     for (j = 0; j < h; ++j) {
2543         for (i = 0; i < w + 1; ++i) {
2544             switch (BELOW_DOT(state, i, j)) {
2545                 case LINE_UNKNOWN:
2546                     if (ds->vl[i + (w + 1) * j] != BELOW_DOT(state, i, j)) {
2547                         CLEAR_VL(i, j);
2548                     }
2549                     break;
2550                 case LINE_YES:
2551                     if (ds->vl[i + (w + 1) * j] != BELOW_DOT(state, i, j) ||
2552                         flash_changed) {
2553                         CLEAR_VL(i, j);
2554                         draw_rect(dr,
2555                                   BORDER + i * TILE_SIZE - LINEWIDTH/2,
2556                                   BORDER + j * TILE_SIZE + LINEWIDTH - LINEWIDTH/2,
2557                                   LINEWIDTH, TILE_SIZE - LINEWIDTH,
2558                                   line_colour);
2559                     }
2560                     break;
2561                 case LINE_NO:
2562                     if (ds->vl[i + (w + 1) * j] != BELOW_DOT(state, i, j)) {
2563                         CLEAR_VL(i, j);
2564                         draw_line(dr,
2565                                  BORDER + i * TILE_SIZE - CROSS_SIZE,
2566                                  BORDER + j * TILE_SIZE + TILE_SIZE/2 - CROSS_SIZE,
2567                                  BORDER + i * TILE_SIZE + CROSS_SIZE - 1,
2568                                  BORDER + j * TILE_SIZE + TILE_SIZE/2 + CROSS_SIZE - 1,
2569                                   COL_FOREGROUND);
2570                         draw_line(dr,
2571                                  BORDER + i * TILE_SIZE + CROSS_SIZE - 1,
2572                                  BORDER + j * TILE_SIZE + TILE_SIZE/2 - CROSS_SIZE,
2573                                  BORDER + i * TILE_SIZE - CROSS_SIZE,
2574                                  BORDER + j * TILE_SIZE + TILE_SIZE/2 + CROSS_SIZE - 1,
2575                                   COL_FOREGROUND);
2576                     }
2577                     break;
2578             }
2579             ds->vl[i + (w + 1) * j] = BELOW_DOT(state, i, j);
2580         }
2581     }
2582
2583     /* Horizontal lines */
2584     for (j = 0; j < h + 1; ++j) {
2585         for (i = 0; i < w; ++i) {
2586             switch (RIGHTOF_DOT(state, i, j)) {
2587                 case LINE_UNKNOWN:
2588                     if (ds->hl[i + w * j] != RIGHTOF_DOT(state, i, j)) {
2589                         CLEAR_HL(i, j);
2590                 }
2591                         break;
2592                 case LINE_YES:
2593                     if (ds->hl[i + w * j] != RIGHTOF_DOT(state, i, j) ||
2594                         flash_changed) {
2595                         CLEAR_HL(i, j);
2596                         draw_rect(dr,
2597                                   BORDER + i * TILE_SIZE + LINEWIDTH - LINEWIDTH/2,
2598                                   BORDER + j * TILE_SIZE - LINEWIDTH/2,
2599                                   TILE_SIZE - LINEWIDTH, LINEWIDTH,
2600                                   line_colour);
2601                         break;
2602                     }
2603                 case LINE_NO:
2604                     if (ds->hl[i + w * j] != RIGHTOF_DOT(state, i, j)) {
2605                         CLEAR_HL(i, j);
2606                         draw_line(dr,
2607                                  BORDER + i * TILE_SIZE + TILE_SIZE/2 - CROSS_SIZE,
2608                                  BORDER + j * TILE_SIZE + CROSS_SIZE - 1,
2609                                  BORDER + i * TILE_SIZE + TILE_SIZE/2 + CROSS_SIZE - 1,
2610                                  BORDER + j * TILE_SIZE - CROSS_SIZE,
2611                                   COL_FOREGROUND);
2612                         draw_line(dr,
2613                                  BORDER + i * TILE_SIZE + TILE_SIZE/2 - CROSS_SIZE,
2614                                  BORDER + j * TILE_SIZE - CROSS_SIZE,
2615                                  BORDER + i * TILE_SIZE + TILE_SIZE/2 + CROSS_SIZE - 1,
2616                                  BORDER + j * TILE_SIZE + CROSS_SIZE - 1,
2617                                   COL_FOREGROUND);
2618                         break;
2619                     }
2620             }
2621             ds->hl[i + w * j] = RIGHTOF_DOT(state, i, j);
2622         }
2623     }
2624 }
2625
2626 static float game_anim_length(game_state *oldstate, game_state *newstate,
2627                               int dir, game_ui *ui)
2628 {
2629     return 0.0F;
2630 }
2631
2632 static float game_flash_length(game_state *oldstate, game_state *newstate,
2633                                int dir, game_ui *ui)
2634 {
2635     if (!oldstate->solved  &&  newstate->solved &&
2636         !oldstate->cheated && !newstate->cheated) {
2637         return FLASH_TIME;
2638     }
2639
2640     return 0.0F;
2641 }
2642
2643 static int game_wants_statusbar(void)
2644 {
2645     return FALSE;
2646 }
2647
2648 static int game_timing_state(game_state *state, game_ui *ui)
2649 {
2650     return TRUE;
2651 }
2652
2653 static void game_print_size(game_params *params, float *x, float *y)
2654 {
2655     int pw, ph;
2656
2657     /*
2658      * I'll use 7mm squares by default.
2659      */
2660     game_compute_size(params, 700, &pw, &ph);
2661     *x = pw / 100.0F;
2662     *y = ph / 100.0F;
2663 }
2664
2665 static void game_print(drawing *dr, game_state *state, int tilesize)
2666 {
2667     int w = state->w, h = state->h;
2668     int ink = print_mono_colour(dr, 0);
2669     int x, y;
2670     game_drawstate ads, *ds = &ads;
2671
2672     game_set_size(dr, ds, NULL, tilesize);
2673
2674     /*
2675      * Dots. I'll deliberately make the dots a bit wider than the
2676      * lines, so you can still see them. (And also because it's
2677      * annoyingly tricky to make them _exactly_ the same size...)
2678      */
2679     for (y = 0; y <= h; y++)
2680         for (x = 0; x <= w; x++)
2681             draw_circle(dr, BORDER + x * TILE_SIZE, BORDER + y * TILE_SIZE,
2682                         LINEWIDTH, ink, ink);
2683
2684     /*
2685      * Clues.
2686      */
2687     for (y = 0; y < h; y++)
2688         for (x = 0; x < w; x++)
2689             if (CLUE_AT(state, x, y) != ' ') {
2690                 char c[2];
2691
2692                 c[0] = CLUE_AT(state, x, y);
2693                 c[1] = '\0';
2694                 draw_text(dr,
2695                           BORDER + x * TILE_SIZE + TILE_SIZE/2,
2696                           BORDER + y * TILE_SIZE + TILE_SIZE/2,
2697                           FONT_VARIABLE, TILE_SIZE/2,
2698                           ALIGN_VCENTRE | ALIGN_HCENTRE, ink, c);
2699             }
2700
2701     /*
2702      * Lines. (At the moment, I'm not bothering with crosses.)
2703      */
2704     for (y = 0; y <= h; y++)
2705         for (x = 0; x < w; x++)
2706             if (RIGHTOF_DOT(state, x, y) == LINE_YES)
2707                 draw_rect(dr, BORDER + x * TILE_SIZE,
2708                           BORDER + y * TILE_SIZE - LINEWIDTH/2,
2709                           TILE_SIZE, (LINEWIDTH/2) * 2 + 1, ink);
2710     for (y = 0; y < h; y++)
2711         for (x = 0; x <= w; x++)
2712             if (BELOW_DOT(state, x, y) == LINE_YES)
2713                 draw_rect(dr, BORDER + x * TILE_SIZE - LINEWIDTH/2,
2714                           BORDER + y * TILE_SIZE,
2715                           (LINEWIDTH/2) * 2 + 1, TILE_SIZE, ink);
2716 }
2717
2718 #ifdef COMBINED
2719 #define thegame loopy
2720 #endif
2721
2722 const struct game thegame = {
2723     "Loopy", "games.loopy",
2724     default_params,
2725     game_fetch_preset,
2726     decode_params,
2727     encode_params,
2728     free_params,
2729     dup_params,
2730     TRUE, game_configure, custom_params,
2731     validate_params,
2732     new_game_desc,
2733     validate_desc,
2734     new_game,
2735     dup_game,
2736     free_game,
2737     1, solve_game,
2738     TRUE, game_text_format,
2739     new_ui,
2740     free_ui,
2741     encode_ui,
2742     decode_ui,
2743     game_changed_state,
2744     interpret_move,
2745     execute_move,
2746     PREFERRED_TILE_SIZE, game_compute_size, game_set_size,
2747     game_colours,
2748     game_new_drawstate,
2749     game_free_drawstate,
2750     game_redraw,
2751     game_anim_length,
2752     game_flash_length,
2753     TRUE, FALSE, game_print_size, game_print,
2754     game_wants_statusbar,
2755     FALSE, game_timing_state,
2756     0,                                       /* mouse_priorities */
2757 };