core: Handle redirection changes in and out of ClutterGrab grabs

Wayland event processing and WM operations are themselves outside the
ClutterGrab loop so far. Until this is sorted out, these pieces of
event handling have got to learn to stay aside while there is a
ClutterGrab going on.

So, synchronize foci and other state when grabs come in or out, and
make it sure that Wayland event processing does not happen while
grabs happen.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2099>

clutter/clutter/clutter-stage.c

@@ -3677,7 +3677,8 @@ clutter_stage_notify_grab_on_pointer_entry (ClutterStage       *stage,
                                      grab_actor : old_grab_actor,
                                      entry->coords,
                                      CLUTTER_CURRENT_TIME);
-      _clutter_actor_handle_event (deepmost, topmost, event);
+      if (!_clutter_event_process_filters (event))
+        _clutter_actor_handle_event (deepmost, topmost, event);
       clutter_event_free (event);
     }
 }

src/compositor/compositor-private.h

@@ -82,6 +82,9 @@ gboolean meta_compositor_is_switching_workspace (MetaCompositor *compositor);
 
 MetaLaters * meta_compositor_get_laters (MetaCompositor *compositor);
 
+void meta_compositor_grab_begin (MetaCompositor *compositor);
+void meta_compositor_grab_end (MetaCompositor *compositor);
+
 /*
  * This function takes a 64 bit time stamp from the monotonic clock, and clamps
  * it to the scope of the X server clock, without losing the granularity.

src/compositor/compositor.c

@@ -374,13 +374,13 @@ grab_devices (MetaModalOptions  options,
   return FALSE;
 }
 
-static void
+void
 meta_compositor_grab_begin (MetaCompositor *compositor)
 {
   META_COMPOSITOR_GET_CLASS (compositor)->grab_begin (compositor);
 }
 
-static void
+void
 meta_compositor_grab_end (MetaCompositor *compositor)
 {
   META_COMPOSITOR_GET_CLASS (compositor)->grab_end (compositor);

src/core/display-private.h

@@ -197,6 +197,7 @@ struct _MetaDisplay
 
   /* Opening the display */
   unsigned int display_opening : 1;
+  unsigned int grabbed_in_clutter : 1;
 
   /* Closing down the display */
   int closing;

src/core/events.c

@@ -28,6 +28,7 @@
 #include "backends/meta-idle-manager.h"
 #include "backends/x11/meta-backend-x11.h"
 #include "backends/x11/meta-input-device-x11.h"
+#include "compositor/compositor-private.h"
 #include "compositor/meta-window-actor-private.h"
 #include "core/display-private.h"
 #include "core/window-private.h"
@@ -67,6 +68,16 @@ stage_has_key_focus (void)
   return clutter_stage_get_key_focus (CLUTTER_STAGE (stage)) == stage;
 }
 
+static gboolean
+stage_has_grab (MetaDisplay *display)
+{
+  MetaContext *context = meta_display_get_context (display);
+  MetaBackend *backend = meta_context_get_backend (context);
+  ClutterActor *stage = meta_backend_get_stage (backend);
+
+  return clutter_stage_get_grab_actor (CLUTTER_STAGE (stage)) != NULL;
+}
+
 static MetaWindow *
 get_window_for_event (MetaDisplay        *display,
                       const ClutterEvent *event)
@@ -207,6 +218,31 @@ meta_display_handle_event (MetaDisplay        *display,
   G_GNUC_UNUSED gboolean bypass_wayland = FALSE;
   MetaGestureTracker *gesture_tracker;
   ClutterEventSequence *sequence;
+  gboolean has_grab;
+
+  has_grab = stage_has_grab (display);
+
+  if (display->grabbed_in_clutter != has_grab)
+    {
+      MetaCompositor *compositor = meta_display_get_compositor (display);
+
+#ifdef HAVE_WAYLAND
+      if (meta_is_wayland_compositor ())
+        meta_display_sync_wayland_input_focus (display);
+#endif
+
+      if (!display->grabbed_in_clutter && has_grab)
+        {
+          display->grabbed_in_clutter = TRUE;
+          meta_display_cancel_touch (display);
+          meta_compositor_grab_begin (compositor);
+        }
+      else if (display->grabbed_in_clutter && !has_grab)
+        {
+          display->grabbed_in_clutter = FALSE;
+          meta_compositor_grab_end (compositor);
+        }
+    }
 
   sequence = clutter_event_get_event_sequence (event);
 
@@ -394,6 +430,13 @@ meta_display_handle_event (MetaDisplay        *display,
       goto out;
     }
 
+  if (stage_has_grab (display))
+    {
+      bypass_wayland = TRUE;
+      bypass_clutter = FALSE;
+      goto out;
+    }
+
   if (window)
     {
       /* Events that are likely to trigger compositor gestures should

src/wayland/meta-wayland-pointer.c

@@ -268,9 +268,11 @@ sync_focus_surface (MetaWaylandPointer *pointer)
   MetaCursorTracker *cursor_tracker = meta_backend_get_cursor_tracker (backend);
   ClutterBackend *clutter_backend = clutter_get_default_backend ();
   ClutterSeat *clutter_seat = clutter_backend_get_default_seat (clutter_backend);
+  ClutterStage *stage = CLUTTER_STAGE (meta_backend_get_stage (backend));
 
-  if (!meta_cursor_tracker_get_pointer_visible (cursor_tracker) &&
-      !clutter_seat_is_unfocus_inhibited (clutter_seat))
+  if (clutter_stage_get_grab_actor (stage) != NULL ||
+      (!meta_cursor_tracker_get_pointer_visible (cursor_tracker) &&
+       !clutter_seat_is_unfocus_inhibited (clutter_seat)))
     {
       meta_wayland_pointer_set_focus (pointer, NULL);
       return;
@@ -441,10 +443,14 @@ default_grab_focus (MetaWaylandPointerGrab *grab,
   MetaCursorTracker *cursor_tracker = meta_backend_get_cursor_tracker (backend);
   ClutterBackend *clutter_backend = clutter_get_default_backend ();
   ClutterSeat *clutter_seat = clutter_backend_get_default_seat (clutter_backend);
+  ClutterStage *stage = CLUTTER_STAGE (meta_backend_get_stage (backend));
 
   if (!meta_wayland_seat_has_pointer (seat))
     return;
 
+  if (clutter_stage_get_grab_actor (stage) != NULL)
+    return;
+
   if (!meta_cursor_tracker_get_pointer_visible (cursor_tracker) &&
       !clutter_seat_is_unfocus_inhibited (clutter_seat))
     return;

src/wayland/meta-wayland-tablet-tool.c

@@ -553,6 +553,14 @@ sync_focus_surface (MetaWaylandTabletTool *tool,
                     const ClutterEvent    *event)
 {
   MetaDisplay *display = meta_get_display ();
+  MetaBackend *backend = meta_get_backend ();
+  ClutterStage *stage = CLUTTER_STAGE (meta_backend_get_stage (backend));
+
+  if (clutter_stage_get_grab_actor (stage))
+    {
+      meta_wayland_tablet_tool_set_focus (tool, NULL, event);
+      return;
+    }
 
   switch (display->event_route)
     {