chiark / gitweb /
Most of intro section
[disorder] / disobedience / queue-generic.c
index 045b38ab104171fb7f4c02cabce9d4aa34991f04..de86f299894f3a9dfa5b1556dd2f592c08f70b1e 100644 (file)
 #include "disobedience.h"
 #include "popup.h"
 #include "queue-generic.h"
-
-static struct queuelike *const queuelikes[] = {
-  &ql_queue, &ql_recent, &ql_added
-};
-#define NQUEUELIKES (sizeof queuelikes / sizeof *queuelikes)
-
-static const GtkTargetEntry queuelike_targets[] = {
-  {
-    (char *)"text/x-disorder-track-data", /* drag type */
-    GTK_TARGET_SAME_WIDGET,             /* rearrangement only for now */
-    0                                   /* ID value */
-  },
-};
+#include "multidrag.h"
+#include "autoscroll.h"
 
 /* Track detail lookup ----------------------------------------------------- */
 
@@ -253,22 +242,27 @@ static void record_queue_map(hash *h,
     hash_add(h, id, empty, HASH_INSERT);
     nqd = hash_find(h, id);
   }
-  if(old)
+  if(old) {
+#if DEBUG_QUEUE
+    fprintf(stderr, " old: %s\n", id);
+#endif
     nqd->old = old;
-  if(new)
+  }
+  if(new) {
+#if DEBUG_QUEUE
+    fprintf(stderr, " new: %s\n", id);
+#endif
     nqd->new = new;
+  }
 }
 
-#if 0
+#if DEBUG_QUEUE
 static void dump_queue(struct queue_entry *head, struct queue_entry *mark) {
   for(struct queue_entry *q = head; q; q = q->next) {
     if(q == mark)
-      fprintf(stderr, "!");
-    fprintf(stderr, "%s", q->id);
-    if(q->next)
-      fprintf(stderr, " ");
+      fprintf(stderr, " !");
+    fprintf(stderr, " %s\n", q->id);
   }
-  fprintf(stderr, "\n");
 }
 
 static void dump_rows(struct queuelike *ql) {
@@ -278,11 +272,8 @@ static void dump_rows(struct queuelike *ql) {
   while(it) {
     struct queue_entry *q = ql_iter_to_q(GTK_TREE_MODEL(ql->store), iter);
     it = gtk_tree_model_iter_next(GTK_TREE_MODEL(ql->store), iter);
-    fprintf(stderr, "%s", q->id);
-    if(it)
-      fprintf(stderr, " ");
+    fprintf(stderr, " %s\n", q->id);
   }
-  fprintf(stderr, "\n");
 }
 #endif
 
@@ -298,11 +289,15 @@ void ql_new_queue(struct queuelike *ql,
   ++suppress_actions;
 
   /* Tell every queue entry which queue owns it */
-  //fprintf(stderr, "%s: filling in q->ql\n", ql->name);
+#if DEBUG_QUEUE
+  fprintf(stderr, "%s: filling in q->ql\n", ql->name);
+#endif
   for(struct queue_entry *q = newq; q; q = q->next)
     q->ql = ql;
 
-  //fprintf(stderr, "%s: constructing h\n", ql->name);
+#if DEBUG_QUEUE
+  fprintf(stderr, "%s: constructing h\n", ql->name);
+#endif
   /* Construct map from id to new and old structures */
   hash *h = hash_new(sizeof(struct newqueue_data));
   for(struct queue_entry *q = ql->q; q; q = q->next)
@@ -312,7 +307,9 @@ void ql_new_queue(struct queuelike *ql,
 
   /* The easy bit: delete rows not present any more.  In the same pass we
    * update the secret column containing the queue_entry pointer. */
-  //fprintf(stderr, "%s: deleting rows...\n", ql->name);
+#if DEBUG_QUEUE
+  fprintf(stderr, "%s: deleting rows...\n", ql->name);
+#endif
   GtkTreeIter iter[1];
   gboolean it = gtk_tree_model_get_iter_first(GTK_TREE_MODEL(ql->store),
                                               iter);
@@ -329,7 +326,9 @@ void ql_new_queue(struct queuelike *ql,
       ++kept;
     } else {
       /* Delete this row (and move iter to the next one) */
-      //fprintf(stderr, " delete %s", q->id);
+#if DEBUG_QUEUE
+      fprintf(stderr, " delete %s\n", q->id);
+#endif
       it = gtk_list_store_remove(ql->store, iter);
       ++deleted;
     }
@@ -340,7 +339,9 @@ void ql_new_queue(struct queuelike *ql,
 
   /* We're going to have to support arbitrary rearrangements, so we might as
    * well add new elements at the end. */
-  //fprintf(stderr, "%s: adding rows...\n", ql->name);
+#if DEBUG_QUEUE
+  fprintf(stderr, "%s: adding rows...\n", ql->name);
+#endif
   struct queue_entry *after = 0;
   for(struct queue_entry *q = newq; q; q = q->next) {
     const struct newqueue_data *nqd = hash_find(h, q->id);
@@ -361,7 +362,9 @@ void ql_new_queue(struct queuelike *ql,
       gtk_list_store_set(ql->store, iter,
                          ql->ncolumns + QUEUEPOINTER_COLUMN, q,
                          -1);
-      //fprintf(stderr, " add %s", q->id);
+#if DEBUG_QUEUE
+      fprintf(stderr, " add %s\n", q->id);
+#endif
       ++inserted;
     }
     after = newq;
@@ -374,132 +377,155 @@ void ql_new_queue(struct queuelike *ql,
    * The current code is simple but amounts to a bubble-sort - we might easily
    * called gtk_tree_model_iter_next a couple of thousand times.
    */
-  //fprintf(stderr, "%s: rearranging rows\n", ql->name);
-  //fprintf(stderr, "%s: queue state: ", ql->name);
-  //dump_queue(newq, 0);
-  //fprintf(stderr, "%s: row state: ", ql->name);
-  //dump_rows(ql);
-  it = gtk_tree_model_get_iter_first(GTK_TREE_MODEL(ql->store),
-                                              iter);
-  struct queue_entry *rq = newq;        /* r for 'right, correct' */
+#if DEBUG_QUEUE
+  fprintf(stderr, "%s: rearranging rows\n", ql->name);
+  fprintf(stderr, "%s: target state:\n", ql->name);
+  dump_queue(newq, 0);
+  fprintf(stderr, "%s: current state:\n", ql->name);
+  dump_rows(ql);
+#endif
+  it = gtk_tree_model_get_iter_first(GTK_TREE_MODEL(ql->store), iter);
+  struct queue_entry *tq = newq;        /* t-for-target */
   int swaps = 0, searches = 0;
+  int row = 0;
   while(it) {
-    struct queue_entry *q = ql_iter_to_q(GTK_TREE_MODEL(ql->store), iter);
-    //fprintf(stderr, " rq = %p, q = %p\n", rq, q);
-    //fprintf(stderr, " rq->id = %s, q->id = %s\n", rq->id, q->id);
-
-    if(q != rq) {
-      //fprintf(stderr, "  mismatch\n");
+    struct queue_entry *cq = ql_iter_to_q(GTK_TREE_MODEL(ql->store), iter);
+    /* c-for-current */
+
+    /* Everything has the right queue pointer (see above) so it's sufficient to
+     * compare pointers to detect mismatches */
+    if(cq != tq) {
+#if DEBUG_QUEUE
+      fprintf(stderr, "  pointer mismatch at row %d\n", row);
+      fprintf(stderr, "   target id %s\n", tq->id);
+      fprintf(stderr, "   actual id %s\n", cq->id);
+#endif
+      /* Start looking for the target row fromn the next row */
       GtkTreeIter next[1] = { *iter };
       gboolean nit = gtk_tree_model_iter_next(GTK_TREE_MODEL(ql->store), next);
       while(nit) {
         struct queue_entry *nq = ql_iter_to_q(GTK_TREE_MODEL(ql->store), next);
-        //fprintf(stderr, "   candidate: %s\n", nq->id);
-        if(nq == rq)
+#if DEBUG_QUEUE
+        fprintf(stderr, "   candidate: %s\n", nq->id);
+#endif
+        if(nq == tq)
           break;
         nit = gtk_tree_model_iter_next(GTK_TREE_MODEL(ql->store), next);
         ++searches;
       }
+      /* Note that this assertion will fail in the face of duplicate IDs.
+       * q->id really does need to be unique. */
       assert(nit);
-      //fprintf(stderr, "  found it\n");
       gtk_list_store_swap(ql->store, iter, next);
       *iter = *next;
-      //fprintf(stderr, "%s: new row state: ", ql->name);
-      //dump_rows(ql);
+#if DEBUG_QUEUE
+      fprintf(stderr, "%s: found it.  new row state:\n", ql->name);
+      dump_rows(ql);
+#endif
       ++swaps;
     }
     /* ...and onto the next one */
     it = gtk_tree_model_iter_next(GTK_TREE_MODEL(ql->store), iter);
-    rq = rq->next;
+    tq = tq->next;
+    ++row;
   }
-#if 0
+#if DEBUG_QUEUE
   fprintf(stderr, "%6s: %3d kept %3d inserted %3d deleted %3d swaps %4d searches\n", ql->name,
           kept, inserted, deleted, swaps, searches);
+  fprintf(stderr, "done\n");
 #endif
-  //fprintf(stderr, "done\n");
   ql->q = newq;
   /* Set the rest of the columns in new rows */
   ql_update_list_store(ql);
   --suppress_actions;
 }
 
-/** @brief State for ql_drag_begin() and its callbacks */
-struct ql_drag_begin_state {
-  struct queuelike *ql;
-  int rows;
-  int index;
-  GdkPixmap **pixmaps;
-};
+/* Drag and drop ------------------------------------------------------------ */
 
-/** @brief Callback to construct a row pixmap */
-static void ql_drag_make_row_pixmaps(GtkTreeModel attribute((unused)) *model,
-                                     GtkTreePath *path,
-                                     GtkTreeIter attribute((unused)) *iter,
-                                     gpointer data) {
-  struct ql_drag_begin_state *qdbs = data;
-
-  qdbs->pixmaps[qdbs->index++]
-    = gtk_tree_view_create_row_drag_icon(GTK_TREE_VIEW(qdbs->ql->view),
-                                         path);
-}
-
-/** @brief Called when a drag operation from this queuelike begins
- * @param w Source widget (the tree view)
- * @param dc Drag context
- * @param user_data The queuelike
+/** @brief Identify the drop path
+ * @param w Destination tree view widget
+ * @param model Underlying tree model
+ * @param wx X coordinate
+ * @param wy Y coordinate
+ * @param posp Where to store relative position
+ * @return Target path or NULL
+ *
+ * This is used by ql_drag_motion() and ql_drag_data_received() to identify a
+ * drop would or does land.  It's important that they use the same code since
+ * otherwise the visual feedback can be inconsistent with the actual effect!
+ *
+ * Remember to free the returned path.
  */
-static void ql_drag_begin(GtkWidget attribute((unused)) *w,
-                          GdkDragContext attribute((unused)) *dc,
-                          gpointer user_data) {
-  struct queuelike *const ql = user_data;
-  struct ql_drag_begin_state qdbs[1];
-  GdkPixmap *icon;
-
-  //fprintf(stderr, "drag-begin\n");
-  memset(qdbs, 0, sizeof *qdbs);
-  qdbs->ql = ql;
-  /* Find out how many rows there are */
-  if(!(qdbs->rows = gtk_tree_selection_count_selected_rows(ql->selection)))
-    return;                             /* doesn't make sense */
-  /* Generate a pixmap for each row */
-  qdbs->pixmaps = xcalloc(qdbs->rows, sizeof *qdbs->pixmaps);
-  gtk_tree_selection_selected_foreach(ql->selection,
-                                      ql_drag_make_row_pixmaps,
-                                      qdbs);
-  /* Determine the size of the final icon */
-  int height = 0, width = 0;
-  for(int n = 0; n < qdbs->rows; ++n) {
-    int pxw, pxh;
-    gdk_drawable_get_size(qdbs->pixmaps[n], &pxw, &pxh);
-    if(pxw > width)
-      width = pxw;
-    height += pxh;
-  }
-  if(!width || !height)
-    return;                             /* doesn't make sense */
-  /* Construct the icon */
-  icon = gdk_pixmap_new(qdbs->pixmaps[0], width, height, -1);
-  GdkGC *gc = gdk_gc_new(icon);
-  gdk_gc_set_colormap(gc, gtk_widget_get_colormap(ql->view));
-  int y = 0;
-  for(int n = 0; n < qdbs->rows; ++n) {
-    int pxw, pxh;
-    gdk_drawable_get_size(qdbs->pixmaps[n], &pxw, &pxh);
-    gdk_draw_drawable(icon,
-                      gc,
-                      qdbs->pixmaps[n],
-                      0, 0,             /* source coords */
-                      0, y,             /* dest coords */
-                      pxw, pxh);        /* size */
-    y += pxh;
+static GtkTreePath *ql_drop_path(GtkWidget *w,
+                                 GtkTreeModel *model,
+                                 int wx, int wy,
+                                 GtkTreeViewDropPosition *posp) {
+  GtkTreePath *path = NULL;
+  GtkTreeViewDropPosition pos;
+  GtkTreeIter iter[1], last[1];
+  int tx, ty;
+
+  gtk_tree_view_convert_widget_to_tree_coords(GTK_TREE_VIEW(w),
+                                              wx, wy, &tx, &ty);
+  if(gtk_tree_view_get_dest_row_at_pos(GTK_TREE_VIEW(w),
+                                       wx, wy,
+                                       &path,
+                                       &pos)) {
+    //fprintf(stderr, "gtk_tree_view_get_dest_row_at_pos() -> TRUE\n");
+    // Normalize drop position
+    switch(pos) {
+    case GTK_TREE_VIEW_DROP_INTO_OR_BEFORE:
+      pos = GTK_TREE_VIEW_DROP_BEFORE;
+      break;
+    case GTK_TREE_VIEW_DROP_INTO_OR_AFTER:
+      pos = GTK_TREE_VIEW_DROP_AFTER;
+      break;
+    default: break;
+    }
+  } else if(gtk_tree_model_get_iter_first(model, iter)) {
+    /* If the pointer isn't over any particular row then either it's below
+     * the last row, in which case we want the dropzone to be below that row;
+     * or it's above the first row (in the column headings) in which case we
+     * want the dropzone to be above that row. */
+    if(ty >= 0) {
+      /* Find the last row */
+      do {
+        *last = *iter;
+      } while(gtk_tree_model_iter_next(model, iter));
+      /* The drop target is just after it */
+      pos = GTK_TREE_VIEW_DROP_AFTER;
+      *iter = *last;
+    } else {
+      /* The drop target will be just before the first row */
+      pos = GTK_TREE_VIEW_DROP_BEFORE;
+    }
+    path = gtk_tree_model_get_path(model, iter);
   }
-  // TODO scale down a bit, the resulting icons are currently a bit on the
-  // large side.
-  gtk_drag_source_set_icon(ql->view,
-                           gtk_widget_get_colormap(ql->view),
-                           icon,
-                           NULL);
+  *posp = pos;
+  return path;
+}
+
+#if 0
+static const char *act(GdkDragAction action) {
+  struct dynstr d[1];
+
+  dynstr_init(d);
+  if(action & GDK_ACTION_DEFAULT)
+    dynstr_append_string(d, "|DEFAULT");
+  if(action & GDK_ACTION_COPY)
+    dynstr_append_string(d, "|COPY");
+  if(action & GDK_ACTION_MOVE)
+    dynstr_append_string(d, "|MOVE");
+  if(action & GDK_ACTION_LINK)
+    dynstr_append_string(d, "|LINK");
+  if(action & GDK_ACTION_PRIVATE)
+    dynstr_append_string(d, "|PRIVATE");
+  if(action & GDK_ACTION_ASK)
+    dynstr_append_string(d, "|ASK");
+  dynstr_terminate(d);
+  return d->nvec ? d->vec + 1 : "";
 }
+#endif
 
 /** @brief Called when a drag moves within a candidate destination
  * @param w Destination widget
@@ -509,16 +535,18 @@ static void ql_drag_begin(GtkWidget attribute((unused)) *w,
  * @param time_ Current time
  * @param user_data Pointer to queuelike
  * @return TRUE in a dropzone, otherwise FALSE
+ *
+ * This is the handler for the "drag-motion" signal.
  */
 static gboolean ql_drag_motion(GtkWidget *w,
                                GdkDragContext *dc,
                                gint x,
                                gint y,
                                guint time_,
-                               gpointer attribute((unused)) user_data) {
-  //struct queuelike *const ql = user_data;
+                               gpointer user_data) {
+  struct queuelike *const ql = user_data;
   GdkDragAction action = 0;
-  
+
   // GTK_DEST_DEFAULT_MOTION vets actions as follows:
   // 1) if dc->suggested_action is in the gtk_drag_dest_set actions
   //    then dc->suggested_action is taken as the action.
@@ -526,50 +554,40 @@ static gboolean ql_drag_motion(GtkWidget *w,
   //    then the lowest-numbered member of the intersection is chosen.
   // 3) otherwise no member is chosen and gdk_drag_status() is called
   //    with action=0 to refuse the drop.
-  // Currently we can only accept _MOVE.  But in the future we will
-  // need to accept _COPY in some cases.
   if(dc->suggested_action) {
-    if(dc->suggested_action == GDK_ACTION_MOVE)
+    if(dc->suggested_action & (GDK_ACTION_MOVE|GDK_ACTION_COPY))
       action = dc->suggested_action;
   } else if(dc->actions & GDK_ACTION_MOVE)
-    action = dc->actions;
-  /*fprintf(stderr, "suggested %#x actions %#x result %#x\n",
-    dc->suggested_action, dc->actions, action);*/
+    action = GDK_ACTION_MOVE;
+  else if(dc->actions & GDK_ACTION_COPY)
+    action = GDK_ACTION_COPY;
+  /* TODO this comes up with the wrong answer sometimes.  If we are in the
+   * middle of a rearrange then the suggested action will be COPY, which we'll
+   * take, even though MOVE would actually be appropriate.  The drag still
+   * seems to work, but it _is_ wrong.  The answer is to take the target into
+   * account. */
+  /*fprintf(stderr, "suggested %s actions %s result %s\n",
+          act(dc->suggested_action), act(dc->actions), act(action));*/
   if(action) {
     // If the action is acceptable then we see if this widget is acceptable
-    if(!gtk_drag_dest_find_target(w, dc, NULL))
+    if(gtk_drag_dest_find_target(w, dc, NULL) == GDK_NONE)
       action = 0;
   }
   // Report the status
+  //fprintf(stderr, "drag action: %u\n", action);
   gdk_drag_status(dc, action, time_);
   if(action) {
-    // Highlight the drop area
-    GtkTreePath *path;
     GtkTreeViewDropPosition pos;
 
-    if(gtk_tree_view_get_dest_row_at_pos(GTK_TREE_VIEW(w),
-                                         x, y,
-                                         &path,
-                                         &pos)) {
-      //fprintf(stderr, "gtk_tree_view_get_dest_row_at_pos() -> TRUE\n");
-      // Normalize drop position
-      switch(pos) {
-      case GTK_TREE_VIEW_DROP_INTO_OR_BEFORE:
-        pos = GTK_TREE_VIEW_DROP_BEFORE;
-        break;
-      case GTK_TREE_VIEW_DROP_INTO_OR_AFTER:
-        pos = GTK_TREE_VIEW_DROP_AFTER;
-        break;
-      default: break;
-      }
-      // Highlight drop target
-      gtk_tree_view_set_drag_dest_row(GTK_TREE_VIEW(w), path, pos);
-    } else {
-      //fprintf(stderr, "gtk_tree_view_get_dest_row_at_pos() -> FALSE\n");
-      gtk_tree_view_set_drag_dest_row(GTK_TREE_VIEW(w), NULL, 0);
-    }
+    // Find the drop target
+    GtkTreePath *path = ql_drop_path(w, GTK_TREE_MODEL(ql->store), x, y, &pos);
+    // Highlight drop target
+    gtk_tree_view_set_drag_dest_row(GTK_TREE_VIEW(w), path, pos);
+    if(path)
+      gtk_tree_path_free(path);
   }
-  return TRUE;
+  autoscroll_add(GTK_TREE_VIEW(w));
+  return TRUE;                          /* We are (always) in a drop zone */
 }
 
 /** @brief Called when a drag moves leaves a candidate destination
@@ -577,6 +595,13 @@ static gboolean ql_drag_motion(GtkWidget *w,
  * @param dc Drag context
  * @param time_ Current time
  * @param user_data Pointer to queuelike
+ *
+ * This is the handler for the "drag-leave" signal.
+ *
+ * It turns out that we get a drag-leave event when the data is dropped, too
+ * (See _gtk_drag_dest_handle_event).  This seems logically consistent and is
+ * convenient too - for instance it's why autoscroll_remove() gets called at
+ * the end of a drag+drop sequence.
  */
 static void ql_drag_leave(GtkWidget *w,
                           GdkDragContext attribute((unused)) *dc,
@@ -585,6 +610,7 @@ static void ql_drag_leave(GtkWidget *w,
   //struct queuelike *const ql = user_data;
 
   gtk_tree_view_set_drag_dest_row(GTK_TREE_VIEW(w), NULL, 0);
+  autoscroll_remove(GTK_TREE_VIEW(w));
 }
 
 /** @brief Callback to add selected tracks to the selection data
@@ -611,24 +637,31 @@ static void ql_drag_data_get_collect(GtkTreeModel *model,
  * @param info_ Target @c info parameter
  * @param time_ Time data requested (for some reason not a @c time_t)
  * @param user_data The queuelike
+ *
+ * The list of tracks is converted into a single string, consisting of IDs
+ * and track names.  Each is terminated by a newline.  Including both ID and
+ * track name means that the receiver can use whichever happens to be more
+ * convenient.
+ *
+ * If there are no IDs for rows in this widget then the ID half is undefined.
+ *
+ * This is the handler for the "drag-data-get" signal.
  */
 static void ql_drag_data_get(GtkWidget attribute((unused)) *w,
                              GdkDragContext attribute((unused)) *dc,
                              GtkSelectionData *data,
-                             guint attribute((unused)) info_,
+                             guint attribute((unused)) info,
                              guint attribute((unused)) time_,
                              gpointer user_data) {
   struct queuelike *const ql = user_data;
   struct dynstr result[1];
 
-  /* The list of tracks is converted into a single string, consisting of IDs
-   * and track names.  Each is terminated by a newline.  Including both ID and
-   * track name means that the receiver can use whichever happens to be more
-   * convenient. */
+  //fprintf(stderr, "ql_drag_data_get %s info=%d\n", ql->name, info);
   dynstr_init(result);
   gtk_tree_selection_selected_foreach(ql->selection,
                                       ql_drag_data_get_collect,
                                       result);
+  // TODO must not be able to drag playing track!
   //fprintf(stderr, "drag-data-get: %.*s\n",
   //        result->nvec, result->vec);
   /* gtk_selection_data_set_text() insists that data->target is one of a
@@ -648,13 +681,15 @@ static void ql_drag_data_get(GtkWidget attribute((unused)) *w,
  * @param info_ The target type that was chosen
  * @param time_ Time data received (for some reason not a @c time_t)
  * @param user_data The queuelike
+ *
+ * This is the handler for the "drag-data-received" signal.
  */
 static void ql_drag_data_received(GtkWidget attribute((unused)) *w,
                                   GdkDragContext attribute((unused)) *dc,
                                   gint x,
                                   gint y,
                                   GtkSelectionData *data,
-                                  guint attribute((unused)) info_,
+                                  guint info_,
                                   guint attribute((unused)) time_,
                                   gpointer user_data) {
   struct queuelike *const ql = user_data;
@@ -662,7 +697,7 @@ static void ql_drag_data_received(GtkWidget attribute((unused)) *w,
   struct vector ids[1], tracks[1];
   int parity = 0;
 
-  //fprintf(stderr, "drag-data-received: %d,%d\n", x, y);
+  //fprintf(stderr, "drag-data-received: %d,%d info=%u\n", x, y, info_);
   /* Get the selection string */
   p = result = (char *)gtk_selection_data_get_text(data);
   if(!result) {
@@ -690,41 +725,58 @@ static void ql_drag_data_received(GtkWidget attribute((unused)) *w,
   vector_terminate(ids);
   vector_terminate(tracks);
   /* Figure out which row the drop precedes (if any) */
-  GtkTreePath *path;
   GtkTreeViewDropPosition pos;
   struct queue_entry *q;
-  if(!gtk_tree_view_get_dest_row_at_pos(GTK_TREE_VIEW(ql->view), x, y,
-                                        &path, &pos)) {
-    //fprintf(stderr, "gtk_tree_view_get_dest_row_at_pos returned FALSE\n");
+  GtkTreePath *path = ql_drop_path(w, GTK_TREE_MODEL(ql->store), x, y, &pos);
+  if(path) {
+    q = ql_path_to_q(GTK_TREE_MODEL(ql->store), path);
+    //fprintf(stderr, "  drop path: %s q=%p pos=%d\n",
+    //        gtk_tree_path_to_string(path), q, pos);
+  } else {
     /* This generally means a drop past the end of the queue.  We find the last
      * element in the queue and ask to move after that. */
     for(q = ql->q; q && q->next; q = q->next)
       ;
-  } else {
-    /* Convert the path to a queue entry pointer. */
-    q = ql_path_to_q(GTK_TREE_MODEL(ql->store), path);
-    //fprintf(stderr, "  tree view likes to drop near %s\n",
-    //        q->id ? q->id : "NULL");
-    /* TODO interpretation of q=NULL */
-    /* Q should point to the entry just before the insertion point, so that
-     * moveafter works, or NULL to insert right at the start.  We don't support
-     * dropping into a row, since that doesn't make sense for us. */
-    switch(pos) {
-    case GTK_TREE_VIEW_DROP_BEFORE:
-    case GTK_TREE_VIEW_DROP_INTO_OR_BEFORE:
-      if(q) {
-        q = q->prev;
-        //fprintf(stderr, "  ...but we like to drop near %s\n",
-        //        q ? q->id : "NULL");
-      }
-      break;
-    default:
-      break;
+    //fprintf(stderr, "  after end.  q=%p.  pos=%d\n", q, pos);
+  }
+  switch(pos) {
+  case GTK_TREE_VIEW_DROP_BEFORE:
+  case GTK_TREE_VIEW_DROP_INTO_OR_BEFORE:
+    if(q) {
+      q = q->prev;
+      //fprintf(stderr, "  but we like to drop near %s\n",
+      //        q ? q->id : "NULL");
     }
+    break;
+  default:
+    break;
   }
+  /* Guarantee we never drop an empty list */
+  if(!tracks->nvec)
+    return;
   /* Note that q->id can match one of ids[].  This doesn't matter for
    * moveafter but TODO may matter for playlist support. */
-  ql->drop(ql, tracks->nvec, tracks->vec, ids->vec, q);
+  switch(info_) {
+  case QUEUED_TRACKS_ID:
+  case PLAYLIST_TRACKS_ID:
+    /* Rearrangement within some widget.  Send ID and track data. */
+    ql->drop(ql, tracks->nvec, tracks->vec, ids->vec, q);
+    break;
+  case PLAYABLE_TRACKS_ID:
+    /* Copying between widgets.  IDs mean nothing so don't send them. */
+    ql->drop(ql, tracks->nvec, tracks->vec, NULL, q);
+    break;
+  }
+  if(path)
+    gtk_tree_path_free(path);
+}
+
+static int count_drag_targets(const GtkTargetEntry *targets) {
+  const GtkTargetEntry *t = targets;
+
+  while(t->target)
+    ++t;
+  return t - targets;
 }
 
 /** @brief Initialize a @ref queuelike */
@@ -766,6 +818,7 @@ GtkWidget *init_queuelike(struct queuelike *ql) {
 
   /* The selection should support multiple things being selected */
   ql->selection = gtk_tree_view_get_selection(GTK_TREE_VIEW(ql->view));
+  g_object_ref(ql->selection);
   gtk_tree_selection_set_mode(ql->selection, GTK_SELECTION_MULTIPLE);
 
   /* Catch button presses */
@@ -794,17 +847,15 @@ GtkWidget *init_queuelike(struct queuelike *ql) {
     /* This view will act as a drag source */
     gtk_drag_source_set(ql->view,
                         GDK_BUTTON1_MASK,
-                        queuelike_targets,
-                        sizeof queuelike_targets / sizeof *queuelike_targets,
-                        GDK_ACTION_MOVE);
+                        ql->drag_source_targets,
+                        count_drag_targets(ql->drag_source_targets),
+                        ql->drag_dest_actions);
     /* This view will act as a drag destination */
     gtk_drag_dest_set(ql->view,
                       GTK_DEST_DEFAULT_HIGHLIGHT|GTK_DEST_DEFAULT_DROP,
-                      queuelike_targets,
-                      sizeof queuelike_targets / sizeof *queuelike_targets,
-                      GDK_ACTION_MOVE);
-    g_signal_connect(ql->view, "drag-begin",
-                     G_CALLBACK(ql_drag_begin), ql);
+                      ql->drag_dest_targets,
+                      count_drag_targets(ql->drag_dest_targets),
+                      ql->drag_dest_actions);
     g_signal_connect(ql->view, "drag-motion",
                      G_CALLBACK(ql_drag_motion), ql);
     g_signal_connect(ql->view, "drag-leave",
@@ -813,15 +864,24 @@ GtkWidget *init_queuelike(struct queuelike *ql) {
                      G_CALLBACK(ql_drag_data_get), ql);
     g_signal_connect(ql->view, "drag-data-received",
                      G_CALLBACK(ql_drag_data_received), ql);
-    make_treeview_multidrag(ql->view);
+    make_treeview_multidrag(ql->view, NULL);
+    // TODO playing track should be refused by predicate arg
   } else {
-    /* TODO: support copy-dragging out of non-rearrangeable queues.  Will need
-     * to support copy dropping into the rearrangeable ones. */
+    /* For queues that cannot accept a drop we still accept a copy out */
+    gtk_drag_source_set(ql->view,
+                        GDK_BUTTON1_MASK,
+                        ql->drag_source_targets,
+                        count_drag_targets(ql->drag_source_targets),
+                        ql->drag_source_actions);
+    g_signal_connect(ql->view, "drag-data-get",
+                     G_CALLBACK(ql_drag_data_get), ql);
+    make_treeview_multidrag(ql->view, NULL);
   }
   
   /* TODO style? */
 
-  ql->init(ql);
+  if(ql->init)
+    ql->init(ql);
 
   /* Update display text when lookups complete */
   event_register("lookups-completed", queue_lookups_completed, ql);
@@ -831,6 +891,31 @@ GtkWidget *init_queuelike(struct queuelike *ql) {
   return scrolled;
 }
 
+/** @brief Destroy a queuelike
+ * @param ql Queuelike to destroy
+ *
+ * Returns @p ql to its initial state.
+ */
+void destroy_queuelike(struct queuelike *ql) {
+  if(ql->store) {
+    g_object_unref(ql->store);
+    ql->store = NULL;
+  }
+  if(ql->view) {
+    gtk_object_destroy(GTK_OBJECT(ql->view));
+    ql->view = NULL;
+  }
+  if(ql->menu) {
+    gtk_object_destroy(GTK_OBJECT(ql->menu));
+    ql->menu = NULL;
+  }
+  if(ql->selection) {
+    g_object_unref(ql->selection);
+    ql->selection = NULL;
+  }
+  ql->q = NULL;
+}
+
 /*
 Local Variables:
 c-basic-offset:2