[libegg/spread-table-dnd] Enhanced EggSpreadTableDnd

[Tristan Van Berkom <tvb src gnome org>]

commit f9847346f2fa27bc0db2f86209977118921bd816
Author: Tristan Van Berkom <tristan van berkom gmail com>
Date:   Sat Mar 12 19:28:36 2011 +0900

    Enhanced EggSpreadTableDnd
    
     o Added possibility to drag children that have no window by
       setting the spread table itself to be a drag source and
       starting the drags manually.
    
     o Highlight drop targets using gtk_drag_highlight()
    
     o Support drag'n'drop from one spread table to another,
       even if the spread table is embedded in another spread table.
    
    Currently I left all the Drag'n'Drop vfunc there with debug prints as
    that might be useful to anyone picking up this example.

 libegg/spreadtable/eggspreadtablednd.c |  357 ++++++++++++++++++++++++++++----
 1 files changed, 313 insertions(+), 44 deletions(-)
---
diff --git a/libegg/spreadtable/eggspreadtablednd.c b/libegg/spreadtable/eggspreadtablednd.c
index 97c6f8d..edacb44 100644
--- a/libegg/spreadtable/eggspreadtablednd.c
+++ b/libegg/spreadtable/eggspreadtablednd.c
@@ -30,6 +30,41 @@
 
 /* GtkWidgetClass */
 static void          egg_spread_table_dnd_realize            (GtkWidget         *widget);
+static gboolean      egg_spread_table_dnd_motion             (GtkWidget         *widget,
+							      GdkEventMotion    *event);
+static gboolean      egg_spread_table_dnd_button_press       (GtkWidget         *widget,
+							      GdkEventButton    *event);
+static gboolean      egg_spread_table_dnd_button_release     (GtkWidget         *widget,
+							      GdkEventButton    *event);
+
+/* GtkWidgetClass drag-source */
+static void          egg_spread_table_dnd_drag_begin         (GtkWidget         *widget,
+							      GdkDragContext    *context);
+static void          egg_spread_table_dnd_drag_end	     (GtkWidget         *widget,
+							      GdkDragContext    *context);
+static void          egg_spread_table_dnd_drag_data_get      (GtkWidget         *widget,
+							      GdkDragContext    *context,
+							      GtkSelectionData  *selection_data,
+							      guint              info,
+							      guint              time_);
+static void          egg_spread_table_dnd_drag_data_delete   (GtkWidget         *widget,
+							      GdkDragContext    *context);
+
+
+/* GtkWidgetClass drag-dest */
+static void          egg_spread_table_dnd_drag_leave         (GtkWidget         *widget,
+							      GdkDragContext    *context,
+							      guint              time_);
+static gboolean      egg_spread_table_dnd_drag_motion        (GtkWidget	        *widget,
+							      GdkDragContext    *context,
+							      gint               x,
+							      gint               y,
+							      guint              time_);
+static gboolean      egg_spread_table_dnd_drag_drop          (GtkWidget         *widget,
+							      GdkDragContext    *context,
+							      gint               x,
+							      gint               y,
+							      guint              time_);
 static void          egg_spread_table_dnd_drag_data_received (GtkWidget         *widget,
 							      GdkDragContext    *drag_context,
 							      gint               x,
@@ -37,6 +72,9 @@ static void          egg_spread_table_dnd_drag_data_received (GtkWidget
 							      GtkSelectionData  *data,
 							      guint              info,
 							      guint              time);
+static gboolean      egg_spread_table_dnd_drag_failed        (GtkWidget         *widget,
+							      GdkDragContext    *context,
+							      GtkDragResult      result);
 
 /* GtkContainerClass */
 static void          egg_spread_table_dnd_remove       (GtkContainer      *container,
@@ -56,13 +94,18 @@ static void          drag_data_get                     (GtkWidget         *widge
 							EggSpreadTableDnd *spread_table);
 static GtkWidget    *get_drag_child                    (EggSpreadTableDnd *spread_table,
 							const GtkSelectionData *selection);
-static gint          get_drop_target_index             (EggSpreadTableDnd *spread_table,
-							GtkWidget         *drag_child,
+static GtkWidget    *get_child_at_position             (EggSpreadTableDnd *spread_table,
 							gint               x,
 							gint               y);
 
 struct _EggSpreadTableDndPrivate {
-  GtkWidget *drag_child;
+  GtkWidget *drop_target;  /* Remember which child widget has the drop highlight */
+
+  GtkWidget *drag_child;   /* The widget that is currently being dragged, if the widget has
+			    * no window and the SpreadTable is the active drag source */
+  gint pressed_button;
+  gint press_start_x;
+  gint press_start_y;
 };
 
 typedef struct {
@@ -75,6 +118,7 @@ static const GtkTargetEntry dnd_targets[] = {
   { "application/x-egg-spread-table-dnd-child", GTK_TARGET_SAME_APP, 0 }
 };
 
+
 G_DEFINE_TYPE (EggSpreadTableDnd, egg_spread_table_dnd, EGG_TYPE_SPREAD_TABLE)
 
 static void
@@ -84,10 +128,25 @@ egg_spread_table_dnd_class_init (EggSpreadTableDndClass *class)
   GtkContainerClass   *container_class = GTK_CONTAINER_CLASS (class);
   EggSpreadTableClass *spread_class    = EGG_SPREAD_TABLE_CLASS (class);
 
-  widget_class->realize            = egg_spread_table_dnd_realize;
+  widget_class->realize              = egg_spread_table_dnd_realize;
+  widget_class->button_press_event   = egg_spread_table_dnd_button_press;
+  widget_class->button_release_event = egg_spread_table_dnd_button_release;
+  widget_class->motion_notify_event  = egg_spread_table_dnd_motion;
+
+  /* Drag source */
+  widget_class->drag_begin         = egg_spread_table_dnd_drag_begin;
+  widget_class->drag_end           = egg_spread_table_dnd_drag_end;
+  widget_class->drag_data_get      = egg_spread_table_dnd_drag_data_get;
+  widget_class->drag_data_delete   = egg_spread_table_dnd_drag_data_delete;
+
+  /* Drag dest */
+  widget_class->drag_leave         = egg_spread_table_dnd_drag_leave;
+  widget_class->drag_motion        = egg_spread_table_dnd_drag_motion;
+  widget_class->drag_drop          = egg_spread_table_dnd_drag_drop;
   widget_class->drag_data_received = egg_spread_table_dnd_drag_data_received;
+  widget_class->drag_failed        = egg_spread_table_dnd_drag_failed;
 
-  container_class->remove    = egg_spread_table_dnd_remove;
+  container_class->remove = egg_spread_table_dnd_remove;
   spread_class->insert_child = egg_spread_table_dnd_insert_child;
 
   dnd_target_atom_child = gdk_atom_intern_static_string (dnd_targets[0].target);
@@ -103,16 +162,28 @@ egg_spread_table_dnd_init (EggSpreadTableDnd *spread_table)
   spread_table->priv = priv =
     G_TYPE_INSTANCE_GET_PRIVATE (spread_table, EGG_TYPE_SPREAD_TABLE_DND, EggSpreadTableDndPrivate);
 
+  priv->pressed_button = -1;
+
   /* Setup the spread table as a drag target for our target type */
-  gtk_drag_dest_set (GTK_WIDGET (spread_table), 
-		     GTK_DEST_DEFAULT_ALL, 
-		     dnd_targets, G_N_ELEMENTS (dnd_targets), 
+  gtk_drag_dest_set (GTK_WIDGET (spread_table),
+		     GTK_DEST_DEFAULT_ALL,
+		     dnd_targets, G_N_ELEMENTS (dnd_targets),
 		     GDK_ACTION_MOVE);
 
+  /* Setup the spread table as a drag source for our target type also 
+   * (to handle no-window widget children) */
+  gtk_drag_source_set (GTK_WIDGET (spread_table),
+		       0, dnd_targets, G_N_ELEMENTS (dnd_targets),
+		       GDK_ACTION_MOVE);
+
   gtk_widget_set_has_window (GTK_WIDGET (spread_table), TRUE);
 }
 
 /*****************************************************
+ *                  GObectClass                      *
+ *****************************************************/
+
+/*****************************************************
  *                 GtkWidgetClass                    *
  *****************************************************/
 static void
@@ -137,7 +208,7 @@ egg_spread_table_dnd_realize (GtkWidget *widget)
   attributes.event_mask = gtk_widget_get_events (widget)
                          | GDK_VISIBILITY_NOTIFY_MASK | GDK_EXPOSURE_MASK
                          | GDK_BUTTON_PRESS_MASK | GDK_BUTTON_RELEASE_MASK
-                         | GDK_BUTTON_MOTION_MASK;
+                         | GDK_POINTER_MOTION_MASK;
   attributes_mask = GDK_WA_X | GDK_WA_Y | GDK_WA_VISUAL;
 
   window = gdk_window_new (gtk_widget_get_parent_window (widget),
@@ -148,6 +219,177 @@ egg_spread_table_dnd_realize (GtkWidget *widget)
   gtk_style_context_set_background (gtk_widget_get_style_context (widget), window);
 }
 
+static gboolean
+egg_spread_table_dnd_motion (GtkWidget         *widget,
+			     GdkEventMotion    *event)
+{
+  EggSpreadTableDnd *spread_table = EGG_SPREAD_TABLE_DND (widget);
+
+  if (spread_table->priv->pressed_button >= 0 &&
+      gtk_drag_check_threshold (widget,
+				spread_table->priv->press_start_x,
+				spread_table->priv->press_start_y,
+				event->x, event->y))
+    {
+      spread_table->priv->drag_child = 
+	get_child_at_position (spread_table, 
+			       spread_table->priv->press_start_x,
+			       spread_table->priv->press_start_y);
+
+      g_print ("[widget] Pointer motion threshold reached, maybe beginning drag on child %p\n", 
+	       spread_table->priv->drag_child);
+
+
+      if (spread_table->priv->drag_child)
+	{
+	  gtk_drag_begin (widget,
+			  gtk_drag_source_get_target_list (widget),
+			  GDK_ACTION_MOVE,
+			  spread_table->priv->pressed_button,
+			  (GdkEvent*)event);
+	  return TRUE;
+	}
+    }
+  return FALSE;
+}
+
+static gboolean
+egg_spread_table_dnd_button_press (GtkWidget         *widget,
+				   GdkEventButton    *event)
+{
+  EggSpreadTableDnd *spread_table = EGG_SPREAD_TABLE_DND (widget);
+  gboolean           handled = FALSE;
+
+  if (event->button == 1 && event->type == GDK_BUTTON_PRESS)
+    {
+      /* Save press to possibly begin a drag */
+      if (get_child_at_position (spread_table, event->x, event->y) && 
+	  spread_table->priv->pressed_button < 0)
+	{
+	  spread_table->priv->pressed_button = event->button;
+	  spread_table->priv->press_start_x  = event->x;
+	  spread_table->priv->press_start_y  = event->y;
+	}
+    }
+
+  return handled;
+}
+
+static gboolean
+egg_spread_table_dnd_button_release (GtkWidget      *widget,
+				     GdkEventButton *event)
+{
+  EggSpreadTableDnd *spread_table = EGG_SPREAD_TABLE_DND (widget);
+  
+  if (spread_table->priv->pressed_button == event->button)
+    spread_table->priv->pressed_button = -1;
+
+  return TRUE;
+}
+
+/*****************************************************
+ *            GtkWidgetClass drag source             *
+ *****************************************************/
+static void
+egg_spread_table_dnd_drag_begin (GtkWidget         *widget,
+				 GdkDragContext    *context)
+{
+  g_print ("[source] Drag begin\n");
+
+}
+
+static void
+egg_spread_table_dnd_drag_end (GtkWidget         *widget,
+			       GdkDragContext    *context)
+{
+  g_print ("[source] Drag end\n");
+
+}
+
+static void
+egg_spread_table_dnd_drag_data_get (GtkWidget         *widget,
+				    GdkDragContext    *context,
+				    GtkSelectionData  *selection,
+				    guint              info,
+				    guint              time_)
+{
+  EggSpreadTableDnd        *spread_table = EGG_SPREAD_TABLE_DND (widget);
+  EggSpreadTableDndDragData drag_data    = { spread_table, NULL };
+  GdkAtom target;
+
+  g_print ("[source] Drag data get\n");
+
+  target = gtk_selection_data_get_target (selection);
+
+  if (spread_table->priv->drag_child && 
+      target == dnd_target_atom_child)
+    {
+      drag_data.child = spread_table->priv->drag_child;
+
+      gtk_selection_data_set (selection, target, 8,
+			      (guchar*) &drag_data, sizeof (drag_data));
+    }
+
+}
+
+static void
+egg_spread_table_dnd_drag_data_delete (GtkWidget         *widget,
+				       GdkDragContext    *context)
+{
+  g_print ("[source] Drag data delete\n");
+}
+
+/*****************************************************
+ *            GtkWidgetClass drag dest               *
+ *****************************************************/
+static void
+egg_spread_table_dnd_drag_leave (GtkWidget         *widget,
+				 GdkDragContext    *context,
+				 guint              time_)
+{
+  g_print ("[dest] Drag leave\n");
+}
+
+static gboolean
+egg_spread_table_dnd_drag_motion (GtkWidget         *widget,
+				  GdkDragContext    *context,
+				  gint               x,
+				  gint               y,
+				  guint              time_)
+{
+  EggSpreadTableDnd *spread_table = EGG_SPREAD_TABLE_DND (widget);
+  GtkWidget         *drop_target;
+
+  drop_target = get_child_at_position (spread_table, x, y);
+
+  if (drop_target != spread_table->priv->drop_target)
+    {
+      if (spread_table->priv->drop_target)
+	gtk_drag_unhighlight (spread_table->priv->drop_target);
+
+      spread_table->priv->drop_target = drop_target;
+
+      if (spread_table->priv->drop_target)
+	gtk_drag_highlight (spread_table->priv->drop_target);
+    }
+
+  g_print ("[dest] Drag motion at %d/%d\n", x, y);
+
+  return FALSE;
+}
+
+static gboolean
+egg_spread_table_dnd_drag_drop (GtkWidget         *widget,
+				GdkDragContext    *context,
+				gint               x,
+				gint               y,
+				guint              time_)
+{
+  g_print ("[dest] Drag drop at %d/%d\n", x, y);
+
+  return FALSE;
+}
+
 static void
 egg_spread_table_dnd_drag_data_received (GtkWidget        *widget,
 					 GdkDragContext   *drag_context,
@@ -158,22 +400,57 @@ egg_spread_table_dnd_drag_data_received (GtkWidget        *widget,
 					 guint             time)
 {
   EggSpreadTableDnd *spread_table = EGG_SPREAD_TABLE_DND (widget);
-  GtkWidget         *child;
-  gint               index;
+  GtkWidget         *drag_child;
 
   /* Action time ! now reorder the child to the new position */
-  child = get_drag_child (spread_table, data);
+  drag_child = get_drag_child (spread_table, data);
 
-  if (child)
+  if (drag_child)
     {
-      /* This will return -1 if the drop was not on a widget */
-      index = get_drop_target_index (spread_table, child, x, y);
+      GtkWidget  *drop_widget;
+      gint        index = -1, orig_index;
+      GList      *children;
+
+      drop_widget = get_child_at_position (spread_table, x, y);
+
+      if (drop_widget)
+	{
+	  children   = gtk_container_get_children (GTK_CONTAINER (spread_table));
+	  index      = g_list_index (children, drop_widget);
+	  orig_index = g_list_index (children, drag_child);
+	  g_list_free (children);
+
+	  if (index >= 0 && orig_index >= 0 && orig_index < index)
+	    index--;
+	}
+
+      /* It might have been inside another spread table in the same application */
+      g_object_ref (drag_child);
+      gtk_container_remove (GTK_CONTAINER (gtk_widget_get_parent (drag_child)), drag_child);
+      egg_spread_table_insert_child (EGG_SPREAD_TABLE (spread_table), drag_child, index);
+      g_object_unref (drag_child);
+    }
 
-      g_object_ref (child);
-      gtk_container_remove (GTK_CONTAINER (spread_table), child);
-      egg_spread_table_insert_child (EGG_SPREAD_TABLE (spread_table), child, index);
-      g_object_unref (child);
+  if (spread_table->priv->drop_target)
+    {
+      gtk_drag_unhighlight (spread_table->priv->drop_target);
+      spread_table->priv->drop_target = NULL;
     }
+
+  spread_table->priv->pressed_button = -1;
+
+  g_print ("[dest] Drag data received at %d/%d\n", x, y);
+
+}
+
+static gboolean
+egg_spread_table_dnd_drag_failed (GtkWidget         *widget,
+				  GdkDragContext    *context,
+				  GtkDragResult      result)
+{
+  g_print ("[dest] Drag data failed\n");
+
+  return FALSE;
 }
 
 /*****************************************************
@@ -224,12 +501,16 @@ drag_data_get (GtkWidget         *widget,
   EggSpreadTableDndDragData drag_data = { spread_table, NULL };
   GdkAtom target;
 
+  g_print ("drag_data_get()\n");
+
   target = gtk_selection_data_get_target (selection);
 
   if (target == dnd_target_atom_child)
     {
       drag_data.child = widget;
 
+      g_print ("drag_data_get() setting selection data\n");
+
       gtk_selection_data_set (selection, target, 8,
 			      (guchar*) &drag_data, sizeof (drag_data));
     }
@@ -249,26 +530,29 @@ get_drag_child (EggSpreadTableDnd      *spread_table,
 
   data = (EggSpreadTableDndDragData*) gtk_selection_data_get_data (selection);
 
-  g_return_val_if_fail (data->table == spread_table, NULL);
+  /* Unhighlight it here since we can drag and drop from one spread table
+   * to another */
+  if (data->table->priv->drop_target)
+    {
+      gtk_drag_unhighlight (data->table->priv->drop_target);
+      data->table->priv->drop_target = NULL;
+    }
 
   return data->child;
 }
 
-static gint
-get_drop_target_index (EggSpreadTableDnd *spread_table,
-		       GtkWidget         *drag_child,
+static GtkWidget *
+get_child_at_position (EggSpreadTableDnd *spread_table,
 		       gint               x,
 		       gint               y)
 {
-  GtkWidget    *child;
+  GtkWidget    *child, *ret_child = NULL;
   GList        *children, *l;
   GtkAllocation allocation;
-  gboolean      found = FALSE;
-  gint          i = 0, drag_child_index = -1;
 
   children = gtk_container_get_children (GTK_CONTAINER (spread_table));
 
-  for (i = 0, l = children; l; l = l->next, i++)
+  for (l = children; ret_child == NULL && l != NULL; l = l->next)
     {
       child = l->data;
 
@@ -277,31 +561,16 @@ get_drop_target_index (EggSpreadTableDnd *spread_table,
 
       gtk_widget_get_allocation (child, &allocation);
 
-      if (child == drag_child)
-	drag_child_index = i;
-
       if (x >= allocation.x && x <= allocation.x + allocation.width &&
 	  y >= allocation.y && y <= allocation.y + allocation.height)
-	{
-	  found = TRUE;
-	  break;
-	}
+	ret_child = child;
     }
 
   g_list_free (children);
 
-  if (found)
-    {
-      if (drag_child_index >= 0 && drag_child_index < i)
-	return i - 1;
-      else
-	return i;
-    }
-
-  return -1;
+  return ret_child;
 }
 
-
 /*****************************************************
  *                       API                         *
  *****************************************************/