chiark - git - mdw - disorder/blob - disobedience/multidrag.c

   1 /*
   2  * This file is part of DisOrder
   3  * Copyright (C) 2009 Richard Kettlewell
   4  *
   5  * This program is free software: you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation, either version 3 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17  */
  18 /** @file disobedience/multidrag.c
  19  * @brief Drag multiple rows of a GtkTreeView
  20  *
  21  * Normally when you start a drag, GtkTreeView sets the selection to just row
  22  * you dragged from (because it can't cope with dragging more than one row at a
  23  * time).
  24  *
  25  * Disobedience needs more.
  26  *
  27  * Firstly it intercepts button-press-event and button-release event and for
  28  * clicks that might be the start of drags, suppresses changes to the
  29  * selection.  A consequence of this is that it needs to intercept
  30  * button-release-event too, to restore the effect of the click, if it turns
  31  * out not to be drag after all.
  32  *
  33  * The location of the initial click is stored in object data called @c
  34  * multidrag-where.
  35  *
  36  * Secondly it intercepts drag-begin and constructs an icon from the rows to be
  37  * dragged.
  38  *
  39  * Inspired by similar code in <a
  40  * href="http://code.google.com/p/quodlibet/">Quodlibet</a> (another software
  41  * jukebox, albeit as far as I can see a single-user one).
  42  */
  43 #include <config.h>
  44
  45 #include <string.h>
  46 #include <glib.h>
  47 #include <gtk/gtk.h>
  48
  49 #include "multidrag.h"
  50
  51 static gboolean multidrag_selection_block(GtkTreeSelection attribute((unused)) *selection,
  52                                           GtkTreeModel attribute((unused)) *model,
  53                                           GtkTreePath attribute((unused)) *path,
  54                                           gboolean attribute((unused)) path_currently_selected,
  55                                           gpointer data) {
  56   return *(const gboolean *)data;
  57 }
  58
  59 static void block_selection(GtkWidget *w, gboolean block,
  60                             int x, int y) {
  61   static const gboolean which[] = { FALSE, TRUE };
  62   GtkTreeSelection *s = gtk_tree_view_get_selection(GTK_TREE_VIEW(w));
  63   gtk_tree_selection_set_select_function(s,
  64                                          multidrag_selection_block,
  65                                          (gboolean *)&which[!!block],
  66                                          NULL);
  67   // Remember the pointer location
  68   int *where = g_object_get_data(G_OBJECT(w), "multidrag-where");
  69   if(!where) {
  70     where = g_malloc(2 * sizeof (int));
  71     g_object_set_data(G_OBJECT(w), "multidrag-where", where);
  72   }
  73   where[0] = x;
  74   where[1] = y;
  75   // TODO release 'where' when object is destroyed
  76 }
  77
  78 static gboolean multidrag_button_press_event(GtkWidget *w,
  79                                              GdkEventButton *event,
  80                                              gpointer attribute((unused)) user_data) {
  81   /* By default we assume that anything this button press does should
  82    * act as normal */
  83   block_selection(w, TRUE, -1, -1);
  84   /* We are only interested in left-button behavior */
  85   if(event->button != 1)
  86     return FALSE;
  87   /* We are only interested in unmodified clicks (not SHIFT etc) */
  88   if(event->state & GDK_MODIFIER_MASK)
  89     return FALSE;
  90   /* We are only interested if a well-defined path is clicked */
  91   GtkTreePath *path;
  92   if(!gtk_tree_view_get_path_at_pos(GTK_TREE_VIEW(w),
  93                                     event->x, event->y,
  94                                     &path,
  95                                     NULL,
  96                                     NULL, NULL))
  97     return FALSE;
  98   //gtk_widget_grab_focus(w);    // TODO why??
  99   /* We are only interested if a selected row is clicked */
 100   GtkTreeSelection *s = gtk_tree_view_get_selection(GTK_TREE_VIEW(w));
 101   if(!gtk_tree_selection_path_is_selected(s, path))
 102     return FALSE;
 103   /* We block subsequent selection changes and remember where the
 104    * click was */
 105   block_selection(w, FALSE, event->x, event->y);
 106   return FALSE;                 /* propagate */
 107 }
 108
 109 static gboolean multidrag_button_release_event(GtkWidget *w,
 110                                                GdkEventButton *event,
 111                                                gpointer attribute((unused)) user_data) {
 112   int *where = g_object_get_data(G_OBJECT(w), "multidrag-where");
 113
 114   /* Did button-press-event do anything?  We just check the outcome rather than
 115    * going through all the conditions it tests. */
 116   if(where && where[0] != -1) {
 117     // Remember where the down-click was
 118     const int x = where[0], y = where[1];
 119     // Re-allow selections
 120     block_selection(w, TRUE, -1, -1);
 121     if(x == event->x && y == event->y) {
 122       // If the up-click is at the same location as the down-click,
 123       // it's not a drag.
 124       GtkTreePath *path;
 125       GtkTreeViewColumn *col;
 126       if(gtk_tree_view_get_path_at_pos(GTK_TREE_VIEW(w),
 127                                        event->x, event->y,
 128                                        &path,
 129                                        &col,
 130                                        NULL, NULL)) {
 131         gtk_tree_view_set_cursor(GTK_TREE_VIEW(w), path, col, FALSE);
 132       }
 133     }
 134   }
 135   return FALSE;                 /* propagate */
 136 }
 137
 138 /** @brief State for multidrag_begin() and its callbacks */
 139 struct multidrag_begin_state {
 140   GtkTreeView *view;
 141   int rows;
 142   int index;
 143   GdkPixmap **pixmaps;
 144 };
 145
 146 /** @brief Callback to construct a row pixmap */
 147 static void multidrag_make_row_pixmaps(GtkTreeModel attribute((unused)) *model,
 148                                        GtkTreePath *path,
 149                                        GtkTreeIter attribute((unused)) *iter,
 150                                        gpointer data) {
 151   struct multidrag_begin_state *qdbs = data;
 152
 153   qdbs->pixmaps[qdbs->index++]
 154     = gtk_tree_view_create_row_drag_icon(qdbs->view, path);
 155 }
 156
 157 /** @brief Called when a drag operation starts
 158  * @param w Source widget (the tree view)
 159  * @param dc Drag context
 160  * @param user_data Not used
 161  */
 162 static void multidrag_drag_begin(GtkWidget *w,
 163                                  GdkDragContext attribute((unused)) *dc,
 164                                  gpointer attribute((unused)) user_data) {
 165   struct multidrag_begin_state qdbs[1];
 166   GdkPixmap *icon;
 167   GtkTreeSelection *sel;
 168
 169   //fprintf(stderr, "drag-begin\n");
 170   memset(qdbs, 0, sizeof *qdbs);
 171   qdbs->view = GTK_TREE_VIEW(w);
 172   sel = gtk_tree_view_get_selection(qdbs->view);
 173   /* Find out how many rows there are */
 174   if(!(qdbs->rows = gtk_tree_selection_count_selected_rows(sel)))
 175     return;                             /* doesn't make sense */
 176   /* Generate a pixmap for each row */
 177   qdbs->pixmaps = g_new(GdkPixmap *, qdbs->rows);
 178   gtk_tree_selection_selected_foreach(sel,
 179                                       multidrag_make_row_pixmaps,
 180                                       qdbs);
 181   /* Determine the size of the final icon */
 182   int height = 0, width = 0;
 183   for(int n = 0; n < qdbs->rows; ++n) {
 184     int pxw, pxh;
 185     gdk_drawable_get_size(qdbs->pixmaps[n], &pxw, &pxh);
 186     if(pxw > width)
 187       width = pxw;
 188     height += pxh;
 189   }
 190   if(!width || !height)
 191     return;                             /* doesn't make sense */
 192   /* Construct the icon */
 193   icon = gdk_pixmap_new(qdbs->pixmaps[0], width, height, -1);
 194   GdkGC *gc = gdk_gc_new(icon);
 195   gdk_gc_set_colormap(gc, gtk_widget_get_colormap(w));
 196   int y = 0;
 197   for(int n = 0; n < qdbs->rows; ++n) {
 198     int pxw, pxh;
 199     gdk_drawable_get_size(qdbs->pixmaps[n], &pxw, &pxh);
 200     gdk_draw_drawable(icon,
 201                       gc,
 202                       qdbs->pixmaps[n],
 203                       0, 0,             /* source coords */
 204                       0, y,             /* dest coords */
 205                       pxw, pxh);        /* size */
 206     y += pxh;
 207     gdk_drawable_unref(qdbs->pixmaps[n]);
 208     qdbs->pixmaps[n] = NULL;
 209   }
 210   g_free(qdbs->pixmaps);
 211   qdbs->pixmaps = NULL;
 212   // TODO scale down a bit, the resulting icons are currently a bit on the
 213   // large side.
 214   gtk_drag_source_set_icon(w,
 215                            gtk_widget_get_colormap(w),
 216                            icon,
 217                            NULL);
 218 }
 219
 220 /** @brief Allow multi-row drag for @p w
 221  * @param w A GtkTreeView widget
 222  *
 223  * Suppresses the restriction of selections when a drag is started.
 224  */
 225 void make_treeview_multidrag(GtkWidget *w) {
 226   g_signal_connect(w, "button-press-event",
 227                    G_CALLBACK(multidrag_button_press_event), NULL);
 228   g_signal_connect(w, "button-release-event",
 229                    G_CALLBACK(multidrag_button_release_event), NULL);
 230   g_signal_connect(w, "drag-begin",
 231                    G_CALLBACK(multidrag_drag_begin), NULL);
 232 }
 233
 234 /*
 235 Local Variables:
 236 c-basic-offset:2
 237 comment-column:40
 238 fill-column:79
 239 indent-tabs-mode:nil
 240 End:
 241 */