x11/events: Filter out all pointer/touch GDK events

Mutter does its own input event processing, including for the places
where interaction is wanted with the remaining GTK UI elements
(frames), so GDK is largely disposable.

Even though the GDK display connection remains, and events will
be delivered over there due to event selections on that display,
all pointer and touch events will be handled and filtered out by
the GDK filter function.

The dedicated event processing meant for frames in src/ui/ui.c
now hooks to the display connection through
meta_display_events_x11_add_func(), added to let all event filters
run and stop processing at a single point.

src/ui/ui.c

@@ -26,6 +26,7 @@
 #include <meta/util.h>
 #include "core.h"
 #include "theme-private.h"
+#include "x11/events.h"
 
 #include <string.h>
 #include <stdlib.h>
@@ -232,15 +233,11 @@ maybe_redirect_mouse_event (XEvent *xevent)
   return TRUE;
 }
 
-static GdkFilterReturn
-ui_filter_func (GdkXEvent *xevent,
-                GdkEvent *event,
+static void
+ui_filter_func (gpointer xevent,
                 gpointer data)
 {
-  if (maybe_redirect_mouse_event (xevent))
-    return GDK_FILTER_REMOVE;
-  else
-    return GDK_FILTER_CONTINUE;
+  maybe_redirect_mouse_event (xevent);
 }
 
 MetaUI*
@@ -266,7 +263,7 @@ meta_ui_new (Display *xdisplay,
    */
   gtk_widget_show (GTK_WIDGET (ui->frames));
 
-  gdk_window_add_filter (NULL, ui_filter_func, NULL);
+  meta_display_events_x11_add_func (ui_filter_func, NULL);
 
   g_object_set_data (G_OBJECT (gdisplay), "meta-ui", ui);
 
@@ -283,7 +280,7 @@ meta_ui_free (MetaUI *ui)
   gdisplay = gdk_x11_lookup_xdisplay (ui->xdisplay);
   g_object_set_data (G_OBJECT (gdisplay), "meta-ui", NULL);
 
-  gdk_window_remove_filter (NULL, ui_filter_func, NULL);
+  meta_display_events_x11_add_func (ui_filter_func, NULL);
 
   g_free (ui);
 }

src/x11/events.c

@@ -38,6 +38,16 @@
 #include "wayland/meta-xwayland.h"
 #include "wayland/meta-wayland-private.h"
 
+typedef struct _EventFuncData EventFuncData;
+
+struct _EventFuncData
+{
+  GFunc func;
+  gpointer data;
+};
+
+static GList *event_funcs = NULL;
+
 static XIEvent *
 get_input_event (MetaDisplay *display,
                  XEvent      *event)
@@ -1801,11 +1811,37 @@ xevent_filter (GdkXEvent *xevent,
                gpointer   data)
 {
   MetaDisplay *display = data;
+  EventFuncData *event_data;
+  XIEvent *input_event;
+  GList *l;
 
-  if (meta_display_handle_xevent (display, xevent))
-    return GDK_FILTER_REMOVE;
-  else
+  meta_display_handle_xevent (display, xevent);
+
+  for (l = event_funcs; l; l = l->next)
+    {
+      event_data = l->data;
+      event_data->func (xevent, event_data->data);
+    }
+
+  input_event = get_input_event (display, xevent);
+
+  if (!input_event)
     return GDK_FILTER_CONTINUE;
+
+  /* Filter all pointer and touch events, those are emulated
+   * above by the filters, and Gdk is bypassed there on purpose.
+   */
+  if (input_event->evtype == XI_ButtonPress ||
+      input_event->evtype == XI_ButtonRelease ||
+      input_event->evtype == XI_Motion ||
+      input_event->evtype == XI_Enter ||
+      input_event->evtype == XI_Leave ||
+      input_event->evtype == XI_TouchBegin ||
+      input_event->evtype == XI_TouchUpdate ||
+      input_event->evtype == XI_TouchEnd)
+    return GDK_FILTER_REMOVE;
+
+  return GDK_FILTER_CONTINUE;
 }
 
 void
@@ -1819,3 +1855,37 @@ meta_display_free_events_x11 (MetaDisplay *display)
 {
   gdk_window_remove_filter (NULL, xevent_filter, display);
 }
+
+void
+meta_display_events_x11_add_func (GFunc    func,
+                                  gpointer user_data)
+{
+  EventFuncData *data;
+
+  data = g_slice_new0 (EventFuncData);
+  data->func = func;
+  data->data = user_data;
+  event_funcs = g_list_prepend (event_funcs, data);
+}
+
+void
+meta_display_events_x11_remove_func (GFunc    func,
+                                     gpointer user_data)
+{
+  EventFuncData *data;
+  GList *l;
+
+  data = g_slice_new0 (EventFuncData);
+
+  for (l = event_funcs; l; l = l->next)
+    {
+      data = l->data;
+
+      if (data->func != func || data->data != user_data)
+        continue;
+
+      event_funcs = g_list_delete_link (event_funcs, l);
+      g_slice_free (EventFuncData, data);
+      break;
+    }
+}

src/x11/events.h

@@ -28,4 +28,9 @@
 void meta_display_init_events_x11 (MetaDisplay *display);
 void meta_display_free_events_x11 (MetaDisplay *display);
 
+void meta_display_events_x11_add_func    (GFunc    func,
+                                          gpointer user_data);
+void meta_display_events_x11_remove_func (GFunc    func,
+                                          gpointer user_data);
+
 #endif