droptarget: Redo

This is a huge reorganization of GtkDropTarget. I did not know how to
split this up, so it's unfortunately all one commit.

Highlights:

- Split GtkDropTarget into GtkDropTarget and GtkDropTargetAsync
  GtkDropTarget is the simple one that only works with GTypes and offers
  a synchronous interface.
  GtkDropTargetAsync retains the full old functionality and allows
  handling mime types.

- Drop events are handled differently
  Instead of picking a single drop target and sending all DND events to
  it, every event is sent to every drop target. The first one to handle
  the event gets to call gdk_drop_status(), further handlers do not
  interact with the GdkDrop.
  Of course, for the ultimate GDK_DROP_STARTING event, only the first
  one to accept the drop gets to handle it.
  This allows stacking DND event controllers that aren't necessarily
  interested in handling the event or that might decide later to drop
  it.

- Port all widgets to either of those
  Both have a somewhat changed API due to the new event handling.
  For the ones who should use the sync version, lots of cleanup was
  involved to operate on a sync API.

1 files changed, 92 insertions, 204 deletions

diff --git a/gtk/gtkplacessidebar.c b/gtk/gtkplacessidebar.c
index 925370a6a4..f62569b5f6 100644
--- a/gtk/gtkplacessidebar.c
+++ b/gtk/gtkplacessidebar.c
@@ -50,7 +50,7 @@
 #include "gtklabel.h"
 #include "gtkbutton.h"
 #include "gtklistbox.h"
-#include "gtkdragdest.h"
+#include "gtkdroptarget.h"
 #include "gtkseparator.h"
 #include "gtkentry.h"
 #include "gtkgesturelongpress.h"
@@ -150,8 +150,6 @@ struct _GtkPlacesSidebar {
   GtkWidget *trash_row;
 
   /* DND */
-  GSList    *drag_list; /* list of GFile */
-  gint       drag_data_info;
   gboolean   dragging_over;
   GtkWidget *drag_row;
   gint drag_row_height;
@@ -175,8 +173,6 @@ struct _GtkPlacesSidebar {
   GtkPlacesOpenFlags open_flags;
 
   guint mounting               : 1;
-  guint  drag_data_received    : 1;
-  guint drop_occurred          : 1;
   guint show_recent_set        : 1;
   guint show_recent            : 1;
   guint show_desktop_set       : 1;
@@ -300,13 +296,6 @@ static GMountOperation * get_mount_operation (GtkPlacesSidebar *sidebar);
 static GMountOperation * get_unmount_operation (GtkPlacesSidebar *sidebar);
 
 
-/* Identifiers for target types */
-enum {
-  DND_UNKNOWN,
-  DND_GTK_SIDEBAR_ROW,
-  DND_TEXT_URI_LIST
-};
-
 G_DEFINE_TYPE (GtkPlacesSidebar, gtk_places_sidebar, GTK_TYPE_WIDGET);
 
 static void
@@ -380,18 +369,6 @@ emit_drag_action_requested (GtkPlacesSidebar *sidebar,
   return ret_action;
 }
 
-static GdkDragAction
-emit_drag_action_ask (GtkPlacesSidebar *sidebar,
-                      GdkDragAction     actions)
-{
-  GdkDragAction ret_action = 0;
-
-  g_signal_emit (sidebar, places_sidebar_signals[DRAG_ACTION_ASK], 0,
-                 actions, &ret_action);
-
-  return ret_action;
-}
-
 static void
 emit_drag_perform_drop (GtkPlacesSidebar *sidebar,
                         GFile            *dest_file,
@@ -1513,7 +1490,8 @@ update_places (GtkPlacesSidebar *sidebar)
 
 static gboolean
 check_valid_drop_target (GtkPlacesSidebar *sidebar,
-                         GtkSidebarRow    *row)
+                         GtkSidebarRow    *row,
+                         const GValue     *value)
 {
   GtkPlacesSidebarPlaceType place_type;
   GtkPlacesSidebarSectionType section_type;
@@ -1522,6 +1500,8 @@ check_valid_drop_target (GtkPlacesSidebar *sidebar,
   GFile *dest_file;
   gint drag_action;
 
+  g_return_val_if_fail (value != NULL, TRUE);
+
   if (row == NULL)
     return FALSE;
 
@@ -1560,19 +1540,18 @@ check_valid_drop_target (GtkPlacesSidebar *sidebar,
     }
 
   /* Dragging a bookmark? */
-  if (sidebar->drag_data_received &&
-      sidebar->drag_data_info == DND_GTK_SIDEBAR_ROW)
+  if (G_VALUE_HOLDS (value, GTK_TYPE_SIDEBAR_ROW))
     {
       /* Don't allow reordering bookmarks into non-bookmark areas */
       valid = section_type == SECTION_BOOKMARKS;
     }
-  else
+  else if (G_VALUE_HOLDS (value, GDK_TYPE_FILE_LIST))
     {
       /* Dragging a file */
       if (uri != NULL)
         {
           dest_file = g_file_new_for_uri (uri);
-          drag_action = emit_drag_action_requested (sidebar, dest_file, sidebar->drag_list);
+          drag_action = emit_drag_action_requested (sidebar, dest_file, g_value_get_boxed (value));
           valid = drag_action > 0;
 
           g_object_unref (dest_file);
@@ -1582,6 +1561,11 @@ check_valid_drop_target (GtkPlacesSidebar *sidebar,
           valid = FALSE;
         }
     }
+  else
+    {
+      g_assert_not_reached ();
+      valid = TRUE;
+    }
 
   g_free (uri);
   return valid;
@@ -1589,7 +1573,7 @@ check_valid_drop_target (GtkPlacesSidebar *sidebar,
 
 static void
 update_possible_drop_targets (GtkPlacesSidebar *sidebar,
-                              gboolean          dragging)
+                              const GValue     *value)
 {
   GList *rows;
   GList *l;
@@ -1599,55 +1583,18 @@ update_possible_drop_targets (GtkPlacesSidebar *sidebar,
 
   for (l = rows; l != NULL; l = l->next)
     {
-      sensitive = !dragging || check_valid_drop_target (sidebar, GTK_SIDEBAR_ROW (l->data));
+      sensitive = value == NULL || check_valid_drop_target (sidebar, GTK_SIDEBAR_ROW (l->data), value);
       gtk_widget_set_sensitive (GTK_WIDGET (l->data), sensitive);
     }
 
   g_list_free (rows);
 }
 
-static void drag_data_received_callback (GObject      *source,
-                                         GAsyncResult *result,
-                                         gpointer      user_data);
-
-static gboolean
-get_drag_data (GtkPlacesSidebar *self,
-               GtkDropTarget    *dest,
-               GdkDrop          *drop,
-               GtkListBoxRow    *row)
-{
-  GdkContentFormats *formats = gdk_drop_get_formats (drop);
-
-  if (row)
-    g_object_set_data_full (G_OBJECT (drop), "places-sidebar-row", g_object_ref (row), g_object_unref);
-
-  gdk_drop_read_value_async (drop,
-                             gdk_content_formats_match_gtype (formats, formats),
-                             G_PRIORITY_DEFAULT,
-                             NULL,
-                             drag_data_received_callback,
-                             self->list_box);
-
-  return TRUE;
-}
-
 static void
-free_drag_data (GtkPlacesSidebar *sidebar)
+start_drop_feedback (GtkPlacesSidebar *sidebar,
+                     const GValue     *value)
 {
-  sidebar->drag_data_received = FALSE;
-
-  if (sidebar->drag_list)
-    {
-      g_slist_free_full (sidebar->drag_list, g_object_unref);
-      sidebar->drag_list = NULL;
-    }
-}
-
-static void
-start_drop_feedback (GtkPlacesSidebar *sidebar)
-{
-  if (sidebar->drag_data_received &&
-      sidebar->drag_data_info != DND_GTK_SIDEBAR_ROW)
+  if (value && !G_VALUE_HOLDS (value, GTK_TYPE_SIDEBAR_ROW))
     {
       gtk_sidebar_row_reveal (GTK_SIDEBAR_ROW (sidebar->new_bookmark_row));
       /* If the state is permanent, don't change it. The application controls it. */
@@ -1655,15 +1602,13 @@ start_drop_feedback (GtkPlacesSidebar *sidebar)
         sidebar->drop_state = DROP_STATE_NEW_BOOKMARK_ARMED;
     }
 
-  update_possible_drop_targets (sidebar, TRUE);
+  update_possible_drop_targets (sidebar, value);
 }
 
 static void
 stop_drop_feedback (GtkPlacesSidebar *sidebar)
 {
-  update_possible_drop_targets (sidebar, FALSE);
-
-  free_drag_data (sidebar);
+  update_possible_drop_targets (sidebar, NULL);
 
   if (sidebar->drop_state != DROP_STATE_NEW_BOOKMARK_ARMED_PERMANENT &&
       sidebar->new_bookmark_row != NULL)
@@ -1686,7 +1631,6 @@ stop_drop_feedback (GtkPlacesSidebar *sidebar)
     }
 
   sidebar->dragging_over = FALSE;
-  sidebar->drag_data_info = DND_UNKNOWN;
 }
 
 static GtkWidget *
@@ -1695,20 +1639,19 @@ create_placeholder_row (GtkPlacesSidebar *sidebar)
   return g_object_new (GTK_TYPE_SIDEBAR_ROW, "placeholder", TRUE, NULL);
 }
 
-static void
-drag_motion_callback (GtkDropTarget *dest,
-                      GdkDrop       *drop,
-                      gint           x,
-                      gint           y,
-                      gpointer       user_data)
+static GdkDragAction
+drag_motion_callback (GtkDropTarget    *target,
+                      double            x,
+                      double            y,
+                      GtkPlacesSidebar *sidebar)
 {
-  GtkPlacesSidebar *sidebar = GTK_PLACES_SIDEBAR (user_data);
-  gint action;
+  GdkDragAction action;
   GtkListBoxRow *row;
   GtkPlacesSidebarPlaceType place_type;
   gchar *drop_target_uri = NULL;
   gint row_index;
   gint row_placeholder_index;
+  const GValue *value;
 
   sidebar->dragging_over = TRUE;
   action = 0;
@@ -1716,17 +1659,16 @@ drag_motion_callback (GtkDropTarget *dest,
 
   gtk_list_box_drag_unhighlight_row (GTK_LIST_BOX (sidebar->list_box));
 
-  /* Nothing to do if no drag data */
-  if (!sidebar->drag_data_received &&
-      !get_drag_data (sidebar, dest, drop, row))
+  /* Nothing to do if no value yet */
+  value = gtk_drop_target_get_value (target);
+  if (value == NULL)
     goto out;
 
   /* Nothing to do if the target is not valid drop destination */
-  if (!check_valid_drop_target (sidebar, GTK_SIDEBAR_ROW (row)))
+  if (!check_valid_drop_target (sidebar, GTK_SIDEBAR_ROW (row), value))
     goto out;
 
-  if (sidebar->drag_data_received &&
-      sidebar->drag_data_info == DND_GTK_SIDEBAR_ROW)
+  if (G_VALUE_HOLDS (value, GTK_TYPE_SIDEBAR_ROW))
     {
       /* Dragging bookmarks always moves them to another position in the bookmarks list */
       action = GDK_ACTION_MOVE;
@@ -1783,7 +1725,7 @@ drag_motion_callback (GtkDropTarget *dest,
       gtk_list_box_prepend (GTK_LIST_BOX (sidebar->list_box),
                             sidebar->row_placeholder);
     }
-  else
+  else if (G_VALUE_HOLDS (value, GDK_TYPE_FILE_LIST))
     {
       gtk_list_box_drag_highlight_row (GTK_LIST_BOX (sidebar->list_box), row);
 
@@ -1795,32 +1737,33 @@ drag_motion_callback (GtkDropTarget *dest,
        * file move/copy operation itself, or if we should only try to
        * create bookmarks out of the dragged URIs.
        */
-      if (sidebar->drag_list != NULL)
+      if (place_type == PLACES_DROP_FEEDBACK)
         {
-          if (place_type == PLACES_DROP_FEEDBACK)
-            {
-              action = GDK_ACTION_COPY;
-            }
-          else
+          action = GDK_ACTION_COPY;
+        }
+      else
+        {
+          /* uri may be NULL for unmounted volumes, for example, so we don't allow drops there */
+          if (drop_target_uri != NULL)
             {
-              /* uri may be NULL for unmounted volumes, for example, so we don't allow drops there */
-              if (drop_target_uri != NULL)
-                {
-                  GFile *dest_file = g_file_new_for_uri (drop_target_uri);
+              GFile *dest_file = g_file_new_for_uri (drop_target_uri);
 
-                  action = emit_drag_action_requested (sidebar, dest_file, sidebar->drag_list);
+              action = emit_drag_action_requested (sidebar, dest_file, g_value_get_boxed (value));
 
-                  g_object_unref (dest_file);
-                }
+              g_object_unref (dest_file);
             }
         }
 
       g_free (drop_target_uri);
     }
+  else
+    {
+      g_assert_not_reached ();
+    }
 
  out:
-  start_drop_feedback (sidebar);
-  gdk_drop_status (drop, action);
+  start_drop_feedback (sidebar, value);
+  return action;
 }
 
 /* Reorders the bookmark to the specified position */
@@ -1867,51 +1810,26 @@ drop_files_as_bookmarks (GtkPlacesSidebar *sidebar,
     }
 }
 
-static void
-drag_data_received_callback (GObject      *source,
-                             GAsyncResult *result,
-                             gpointer      user_data)
+static gboolean
+drag_drop_callback (GtkDropTarget    *target,
+                    const GValue     *value,
+                    double            x,
+                    double            y,
+                    GtkPlacesSidebar *sidebar)
 {
-  GdkDrop *drop = GDK_DROP (source);
-  GtkWidget *list_box = user_data;
-  GtkPlacesSidebar *sidebar = GTK_PLACES_SIDEBAR (gtk_widget_get_ancestor (list_box, GTK_TYPE_PLACES_SIDEBAR));
   gint target_order_index;
   GtkPlacesSidebarPlaceType target_place_type;
   GtkPlacesSidebarSectionType target_section_type;
   gchar *target_uri;
   GtkListBoxRow *target_row;
-  GdkDragAction real_action;
-  const GValue *value;
-
-  value = gdk_drop_read_value_finish (drop, result, NULL);
-
-  if (!sidebar->drag_data_received)
-    {
-      if (G_VALUE_HOLDS (value, GDK_TYPE_FILE_LIST))
-        {
-          /* Free spurious drag data from previous drags if present */
-          if (sidebar->drag_list != NULL)
-            g_slist_free_full (sidebar->drag_list, g_object_unref);
-          sidebar->drag_list = g_slist_copy_deep (g_value_get_boxed (value), (GCopyFunc) g_object_ref, NULL);
-          sidebar->drag_data_info = DND_TEXT_URI_LIST;
-        }
-      else if (G_VALUE_HOLDS (value, GTK_TYPE_SIDEBAR_ROW))
-        {
-          sidebar->drag_list = NULL;
-          sidebar->drag_data_info = DND_GTK_SIDEBAR_ROW;
-        }
-      sidebar->drag_data_received = TRUE;
-    }
+  gboolean result;
 
-  if (!sidebar->drop_occurred)
-    return;
-
-  target_row = g_object_get_data (G_OBJECT (drop), "places-sidebar-row");
+  target_row = gtk_list_box_get_row_at_y (GTK_LIST_BOX (sidebar->list_box), y);
   if (target_row == NULL)
-    return;
+    return FALSE;
 
-  if (!check_valid_drop_target (sidebar, GTK_SIDEBAR_ROW (target_row)))
-    return;
+  if (!check_valid_drop_target (sidebar, GTK_SIDEBAR_ROW (target_row), value))
+    return FALSE;
 
   g_object_get (target_row,
                 "place-type", &target_place_type,
@@ -1919,9 +1837,9 @@ drag_data_received_callback (GObject      *source,
                 "order-index", &target_order_index,
                 "uri", &target_uri,
                 NULL);
-  real_action = 0;
+  result = FALSE;
 
-  if (sidebar->drag_data_info == DND_GTK_SIDEBAR_ROW)
+  if (G_VALUE_HOLDS (value, GTK_TYPE_SIDEBAR_ROW))
     {
       GtkWidget **source_row;
       /* A bookmark got reordered */
@@ -1934,41 +1852,37 @@ drag_data_received_callback (GObject      *source,
         g_object_get (sidebar->row_placeholder, "order-index", &target_order_index, NULL);
 
       reorder_bookmarks (sidebar, GTK_SIDEBAR_ROW (*source_row), target_order_index);
-      real_action = GDK_ACTION_MOVE;
+      result = TRUE;
     }
-  else
+  else if (G_VALUE_HOLDS (value, GDK_TYPE_FILE_LIST))
     {
       /* Dropping URIs! */
-
-      /* file transfer requested */
-      real_action = gdk_drop_get_actions (drop);
-
-      if (!gdk_drag_action_is_unique (real_action))
-        real_action = emit_drag_action_ask (sidebar, real_action);
-
-      if (real_action > 0)
+      if (target_place_type == PLACES_DROP_FEEDBACK)
         {
-          if (target_place_type == PLACES_DROP_FEEDBACK)
-            {
-              drop_files_as_bookmarks (sidebar, sidebar->drag_list, target_order_index);
-            }
-          else
-            {
-              GFile *dest_file = g_file_new_for_uri (target_uri);
-
-              emit_drag_perform_drop (sidebar, dest_file, sidebar->drag_list, real_action);
+          drop_files_as_bookmarks (sidebar, g_value_get_boxed (value), target_order_index);
+        }
+      else
+        {
+          GFile *dest_file = g_file_new_for_uri (target_uri);
+          
+          emit_drag_perform_drop (sidebar,
+                                  dest_file,
+                                  g_value_get_boxed (value),
+                                  gdk_drop_get_actions (gtk_drop_target_get_drop (target)));
 
-              g_object_unref (dest_file);
-            }
+          g_object_unref (dest_file);
         }
+      result = TRUE;
+    }
+  else
+    {
+      g_assert_not_reached ();
     }
 
 out:
-  sidebar->drop_occurred = FALSE;
-  g_object_set_data (G_OBJECT (drop), "places-sidebar-row", NULL);
-  gdk_drop_finish (drop, real_action);
   stop_drop_feedback (sidebar);
   g_free (target_uri);
+  return result;
 }
 
 static void
@@ -2010,28 +1924,7 @@ drag_leave_callback (GtkDropTarget *dest,
       sidebar->drop_state = DROP_STATE_NORMAL;
     }
 
-  sidebar->drag_data_received = FALSE;
   sidebar->dragging_over = FALSE;
-  sidebar->drag_data_info = DND_UNKNOWN;
-}
-
-static gboolean
-drag_drop_callback (GtkDropTarget *dest,
-                    GdkDrop       *drop,
-                    int            x,
-                    int            y,
-                    gpointer       user_data)
-{
-  GtkPlacesSidebar *sidebar = GTK_PLACES_SIDEBAR (user_data);
-  gboolean retval = FALSE;
-  GtkListBoxRow *row;
-
-  row = gtk_list_box_get_row_at_y (GTK_LIST_BOX (sidebar->list_box), y);
-  sidebar->drop_occurred = TRUE;
- 
-  retval = get_drag_data (sidebar, dest, drop, row);
-
-  return retval;
 }
 
 static void
@@ -3842,11 +3735,10 @@ shell_shows_desktop_changed (GtkSettings *settings,
 static void
 gtk_places_sidebar_init (GtkPlacesSidebar *sidebar)
 {
-  GtkDropTarget *dest;
+  GtkDropTarget *target;
   gboolean show_desktop;
   GtkEventController *controller;
   GtkGesture *gesture;
-  GdkContentFormatsBuilder *builder;
 
   sidebar->cancellable = g_cancellable_new ();
 
@@ -3901,20 +3793,18 @@ gtk_places_sidebar_init (GtkPlacesSidebar *sidebar)
   gtk_widget_add_controller (GTK_WIDGET (sidebar), GTK_EVENT_CONTROLLER (gesture));
 
   /* DND support */
-  builder = gdk_content_formats_builder_new ();
-  gdk_content_formats_builder_add_gtype (builder, GTK_TYPE_SIDEBAR_ROW);
-  gdk_content_formats_builder_add_gtype (builder, GDK_TYPE_FILE_LIST);
-  dest = gtk_drop_target_new (gdk_content_formats_builder_free_to_formats (builder),
-                              GDK_ACTION_MOVE | GDK_ACTION_COPY | GDK_ACTION_LINK);
-  g_signal_connect (dest, "drag-motion", G_CALLBACK (drag_motion_callback), sidebar);
-  g_signal_connect (dest, "drag-drop", G_CALLBACK (drag_drop_callback), sidebar);
-  g_signal_connect (dest, "drag-leave", G_CALLBACK (drag_leave_callback), sidebar);
-  gtk_widget_add_controller (sidebar->list_box, GTK_EVENT_CONTROLLER (dest));
+  target = gtk_drop_target_new (G_TYPE_INVALID, GDK_ACTION_MOVE | GDK_ACTION_COPY | GDK_ACTION_LINK);
+  gtk_drop_target_set_preload (target, TRUE);
+  gtk_drop_target_set_gtypes (target, (GType[2]) { GTK_TYPE_SIDEBAR_ROW, GDK_TYPE_FILE_LIST }, 2);
+  g_signal_connect (target, "enter", G_CALLBACK (drag_motion_callback), sidebar);
+  g_signal_connect (target, "motion", G_CALLBACK (drag_motion_callback), sidebar);
+  g_signal_connect (target, "drop", G_CALLBACK (drag_drop_callback), sidebar);
+  g_signal_connect (target, "leave", G_CALLBACK (drag_leave_callback), sidebar);
+  gtk_widget_add_controller (sidebar->list_box, GTK_EVENT_CONTROLLER (target));
 
   sidebar->drag_row = NULL;
   sidebar->row_placeholder = NULL;
   sidebar->dragging_over = FALSE;
-  sidebar->drag_data_info = DND_UNKNOWN;
 
   gtk_container_add (GTK_CONTAINER (sidebar->swin), sidebar->list_box);
 
@@ -4071,8 +3961,6 @@ gtk_places_sidebar_dispose (GObject *object)
       sidebar->cancellable = NULL;
     }
 
-  free_drag_data (sidebar);
-
   if (sidebar->bookmarks_manager != NULL)
     {
       _gtk_bookmarks_manager_free (sidebar->bookmarks_manager);
@@ -5068,7 +4956,7 @@ gtk_places_sidebar_set_drop_targets_visible (GtkPlacesSidebar *sidebar,
   if (visible)
     {
       sidebar->drop_state = DROP_STATE_NEW_BOOKMARK_ARMED_PERMANENT;
-      start_drop_feedback (sidebar);
+      start_drop_feedback (sidebar, NULL);
     }
   else
     {