dnd: Notify about events during compositor grab from event filter

Since the introduction of ClutterGrabs, MetaDnd now no longer gets
notified about input events on the stage during grabs (for example while
the alt-tab popup is shown) and thus can't move the grab feedback actor
anymore.

To fix this, forward events to MetaDnD directly from
meta_display_handle_event() when a ClutterGrab is in effect.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2308>

src/backends/meta-dnd-private.h

@@ -36,6 +36,9 @@ void meta_dnd_init_xdnd (MetaX11Display *x11_display);
 #ifdef HAVE_WAYLAND
 void meta_dnd_wayland_handle_begin_modal (MetaCompositor *compositor);
 void meta_dnd_wayland_handle_end_modal   (MetaCompositor *compositor);
+
+void meta_dnd_wayland_maybe_handle_event (MetaDnd            *dnd,
+                                          const ClutterEvent *event);
 #endif
 
 #endif /* META_DND_PRIVATE_H */

src/compositor/meta-dnd.c

@@ -46,10 +46,7 @@ typedef struct _MetaDndPrivate MetaDndPrivate;
 struct _MetaDndPrivate
 {
 #ifdef HAVE_WAYLAND
-  gulong handler_id[3];
-
-  MetaCompositor *compositor;
-  MetaWaylandCompositor *wl_compositor;
+  gboolean dnd_during_modal;
 #else
   /* to avoid warnings (g_type_class_add_private: assertion `private_size > 0' failed) */
   gchar dummy;
@@ -230,54 +227,73 @@ meta_dnd_handle_xdnd_event (MetaBackend       *backend,
 
 #ifdef HAVE_WAYLAND
 static void
-meta_dnd_wayland_on_motion_event (ClutterActor *actor,
-                                  ClutterEvent *event,
-                                  MetaDnd      *dnd)
+meta_dnd_wayland_on_motion_event (MetaDnd            *dnd,
+                                  const ClutterEvent *event)
 {
-  MetaDndPrivate *priv = meta_dnd_get_instance_private (dnd);
   MetaWaylandDragGrab *current_grab;
   gfloat event_x, event_y;
+  MetaWaylandCompositor *wl_compositor = meta_wayland_compositor_get_default ();
 
   g_return_if_fail (event != NULL);
 
   clutter_event_get_coords (event, &event_x, &event_y);
   meta_dnd_notify_dnd_position_change (dnd, (int)event_x, (int)event_y);
 
-  current_grab = meta_wayland_data_device_get_current_grab (&priv->wl_compositor->seat->data_device);
+  current_grab = meta_wayland_data_device_get_current_grab (&wl_compositor->seat->data_device);
   if (current_grab)
     meta_wayland_drag_grab_update_feedback_actor (current_grab, event);
 }
 
 static void
-meta_dnd_wayland_end_notify (ClutterActor *actor,
-                             ClutterEvent *event,
-                             MetaDnd      *dnd)
+meta_dnd_wayland_end_notify (MetaDnd *dnd)
 {
   MetaDndPrivate *priv = meta_dnd_get_instance_private (dnd);
+  MetaWaylandCompositor *wl_compositor = meta_wayland_compositor_get_default ();
 
-  meta_wayland_data_device_end_drag (&priv->wl_compositor->seat->data_device);
-  meta_dnd_wayland_handle_end_modal (priv->compositor);
+  meta_wayland_data_device_end_drag (&wl_compositor->seat->data_device);
+
+  priv->dnd_during_modal = FALSE;
+
+  meta_dnd_notify_dnd_leave (dnd);
 }
 
 static void
-meta_dnd_wayland_on_button_released (ClutterActor *actor,
-                                     ClutterEvent *event,
-                                     MetaDnd      *dnd)
+meta_dnd_wayland_on_button_released (MetaDnd            *dnd,
+                                     const ClutterEvent *event)
 {
-  meta_dnd_wayland_end_notify (actor, event, dnd);
+  meta_dnd_wayland_end_notify (dnd);
 }
 
 static void
-meta_dnd_wayland_on_key_pressed (ClutterActor *actor,
-                                 ClutterEvent *event,
-                                 MetaDnd      *dnd)
+meta_dnd_wayland_on_key_pressed (MetaDnd            *dnd,
+                                 const ClutterEvent *event)
 {
   guint key = clutter_event_get_key_symbol (event);
 
   if (key != CLUTTER_KEY_Escape)
     return;
 
-  meta_dnd_wayland_end_notify (actor, event, dnd);
+  meta_dnd_wayland_end_notify (dnd);
+}
+
+void
+meta_dnd_wayland_maybe_handle_event (MetaDnd            *dnd,
+                                     const ClutterEvent *event)
+{
+  MetaWaylandCompositor *wl_compositor = meta_wayland_compositor_get_default ();
+  MetaDndPrivate *priv = meta_dnd_get_instance_private (dnd);
+
+  if (!meta_wayland_data_device_get_current_grab (&wl_compositor->seat->data_device))
+    return;
+
+  g_warn_if_fail (priv->dnd_during_modal);
+
+  if (event->type == CLUTTER_MOTION)
+    meta_dnd_wayland_on_motion_event (dnd, event);
+  else if (event->type == CLUTTER_BUTTON_RELEASE)
+    meta_dnd_wayland_on_button_released (dnd, event);
+  else if (event->type == CLUTTER_KEY_PRESS)
+    meta_dnd_wayland_on_key_pressed (dnd, event);
 }
 
 void
@@ -287,28 +303,10 @@ meta_dnd_wayland_handle_begin_modal (MetaCompositor *compositor)
   MetaDnd *dnd = meta_backend_get_dnd (meta_get_backend ());
   MetaDndPrivate *priv = meta_dnd_get_instance_private (dnd);
 
-  if (priv->handler_id[0] == 0 &&
+  if (!priv->dnd_during_modal &&
       meta_wayland_data_device_get_current_grab (&wl_compositor->seat->data_device) != NULL)
     {
-      ClutterStage *stage = meta_compositor_get_stage (compositor);
-
-      priv->compositor = compositor;
-      priv->wl_compositor = wl_compositor;
-
-      priv->handler_id[0] = g_signal_connect (stage,
-                                              "motion-event",
-                                              G_CALLBACK (meta_dnd_wayland_on_motion_event),
-                                              dnd);
-
-      priv->handler_id[1] = g_signal_connect (stage,
-                                              "button-release-event",
-                                              G_CALLBACK (meta_dnd_wayland_on_button_released),
-                                              dnd);
-
-      priv->handler_id[2] = g_signal_connect (stage,
-                                              "key-press-event",
-                                              G_CALLBACK (meta_dnd_wayland_on_key_pressed),
-                                              dnd);
+      priv->dnd_during_modal = TRUE;
 
       meta_dnd_notify_dnd_enter (dnd);
     }
@@ -319,17 +317,11 @@ meta_dnd_wayland_handle_end_modal (MetaCompositor *compositor)
 {
   MetaDnd *dnd = meta_backend_get_dnd (meta_get_backend ());
   MetaDndPrivate *priv = meta_dnd_get_instance_private (dnd);
-  ClutterStage *stage = meta_compositor_get_stage (compositor);
-  unsigned int i;
 
-  if (!priv->compositor)
+  if (!priv->dnd_during_modal)
     return;
 
-  for (i = 0; i < G_N_ELEMENTS (priv->handler_id); i++)
-    g_clear_signal_handler (&priv->handler_id[i], stage);
-
-  priv->compositor = NULL;
-  priv->wl_compositor = NULL;
+  priv->dnd_during_modal = FALSE;
 
   meta_dnd_notify_dnd_leave (dnd);
 }

src/core/events.c

@@ -25,6 +25,7 @@
 #include "core/events.h"
 
 #include "backends/meta-cursor-tracker-private.h"
+#include "backends/meta-dnd-private.h"
 #include "backends/meta-idle-manager.h"
 #include "backends/x11/meta-backend-x11.h"
 #include "backends/x11/meta-input-device-x11.h"
@@ -426,6 +427,11 @@ meta_display_handle_event (MetaDisplay        *display,
 
   if (stage_has_grab (display))
     {
+#ifdef HAVE_WAYLAND
+      if (wayland_compositor)
+        meta_dnd_wayland_maybe_handle_event (meta_backend_get_dnd (backend), event);
+#endif
+
       bypass_wayland = TRUE;
       bypass_clutter = FALSE;
       goto out;

src/wayland/meta-wayland-data-device.c

@@ -304,7 +304,7 @@ meta_wayland_drag_grab_get_focus (MetaWaylandDragGrab *drag_grab)
 
 void
 meta_wayland_drag_grab_update_feedback_actor (MetaWaylandDragGrab *drag_grab,
-                                              ClutterEvent        *event)
+                                              const ClutterEvent  *event)
 {
   meta_feedback_actor_update (META_FEEDBACK_ACTOR (drag_grab->feedback_actor),
                               event);

src/wayland/meta-wayland-data-device.h

@@ -86,6 +86,6 @@ void     meta_wayland_drag_grab_set_focus        (MetaWaylandDragGrab
 MetaWaylandSurface *
          meta_wayland_drag_grab_get_focus        (MetaWaylandDragGrab             *drag_grab);
 void     meta_wayland_drag_grab_update_feedback_actor (MetaWaylandDragGrab *drag_grab,
-                                                       ClutterEvent        *event);
+                                                       const ClutterEvent  *event);
 
 #endif /* META_WAYLAND_DATA_DEVICE_H */