core: Change behavior of "application is alive" checks

Change some things in these "app is alive" checks:
- The dialog timeout is separated from the ping timeout, in order
  to show it again at a constant rate after dismissing, despite in
  flight pings. It still shows immediately after the first failed
  ping.
- As we want to tap further into is-alive logic, MetaWindow now
  made it a property, that other places in code can fetch and
  subscribe.
- Motion events trigger ping (as long as there was none other in
  flight for the same window), and are counted between ping and
  pong, in order to preemptively declare the window as not alive
  before there is trouble with event queues being overflown.

This results in a separate logic between "the application does
not respond" and "we are showing the close dialog" so that the
former may get triggered independently.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2122>

src/core/delete.c

@@ -22,6 +22,8 @@
 
 #define _XOPEN_SOURCE /* for kill() */
 
+#define MAX_QUEUED_EVENTS 400
+
 #include "config.h"
 
 #include <errno.h>
@@ -39,6 +41,8 @@ close_dialog_response_cb (MetaCloseDialog         *dialog,
 {
   if (response == META_CLOSE_DIALOG_RESPONSE_FORCE_CLOSE)
     meta_window_kill (window);
+  else
+    meta_window_ensure_close_dialog_timeout (window);
 }
 
 static void
@@ -57,15 +61,8 @@ meta_window_ensure_close_dialog (MetaWindow *window)
 }
 
 void
-meta_window_set_alive (MetaWindow *window,
+meta_window_show_close_dialog (MetaWindow *window)
-                       gboolean    is_alive)
 {
-  if (is_alive && window->close_dialog)
-    {
-      meta_close_dialog_hide (window->close_dialog);
-    }
-  else if (!is_alive)
-    {
   meta_window_ensure_close_dialog (window);
   meta_close_dialog_show (window->close_dialog);
 
@@ -73,7 +70,13 @@ meta_window_set_alive (MetaWindow *window,
       window->display->event_route == META_EVENT_ROUTE_NORMAL &&
       window == window->display->focus_window)
     meta_close_dialog_focus (window->close_dialog);
-    }
+}
+
+void
+meta_window_hide_close_dialog (MetaWindow *window)
+{
+  if (window->close_dialog)
+    meta_close_dialog_hide (window->close_dialog);
 }
 
 void
@@ -83,6 +86,21 @@ meta_window_check_alive (MetaWindow *window,
   meta_display_ping_window (window, timestamp);
 }
 
+void
+meta_window_check_alive_on_event (MetaWindow *window,
+                                  uint32_t    timestamp)
+{
+  if (!meta_window_can_ping (window))
+    return;
+
+  meta_display_ping_window (window, timestamp);
+
+  window->events_during_ping++;
+
+  if (window->events_during_ping > MAX_QUEUED_EVENTS)
+    meta_window_set_alive (window, FALSE);
+}
+
 void
 meta_window_delete (MetaWindow  *window,
                     guint32      timestamp)

src/core/display.c

@@ -2146,6 +2146,7 @@ meta_display_ping_timeout (gpointer data)
   MetaDisplay *display = window->display;
 
   meta_window_set_alive (window, FALSE);
+  meta_window_show_close_dialog (window);
 
   ping_data->ping_timeout_id = 0;
 
@@ -2235,6 +2236,8 @@ meta_display_ping_window (MetaWindow *window,
               serial, window->desc);
 
   META_WINDOW_GET_CLASS (window)->ping (window, serial);
+
+  window->events_during_ping = 0;
 }
 
 /**

src/core/events.c

@@ -202,7 +202,7 @@ meta_display_handle_event (MetaDisplay        *display,
                            const ClutterEvent *event)
 {
   MetaBackend *backend = meta_get_backend ();
-  MetaWindow *window;
+  MetaWindow *window = NULL;
   gboolean bypass_clutter = FALSE;
   G_GNUC_UNUSED gboolean bypass_wayland = FALSE;
   MetaGestureTracker *gesture_tracker;
@@ -475,6 +475,10 @@ meta_display_handle_event (MetaDisplay        *display,
 #ifdef HAVE_WAYLAND
   if (compositor && !bypass_wayland)
     {
+      if (window && event->type == CLUTTER_MOTION &&
+          event->any.time != CLUTTER_CURRENT_TIME)
+        meta_window_check_alive_on_event (window, event->any.time);
+
       if (meta_wayland_compositor_handle_event (compositor, event))
         bypass_clutter = TRUE;
     }

src/core/window-private.h

@@ -437,6 +437,9 @@ struct _MetaWindow
   /* whether focus should be restored on map */
   guint restore_focus_on_map : 1;
 
+  /* Whether the window is alive */
+  guint is_alive : 1;
+
   /* if non-NULL, the bounds of the window frame */
   cairo_region_t *frame_bounds;
 
@@ -564,11 +567,14 @@ struct _MetaWindow
   } placement;
 
   guint unmanage_idle_id;
+  guint close_dialog_timeout_id;
 
   pid_t client_pid;
 
   gboolean has_valid_cgroup;
   GFile *cgroup_path;
+
+  unsigned int events_during_ping;
 };
 
 struct _MetaWindowClass
@@ -877,6 +883,11 @@ void meta_window_grab_op_began (MetaWindow *window, MetaGrabOp op);
 void meta_window_grab_op_ended (MetaWindow *window, MetaGrabOp op);
 
 void meta_window_set_alive (MetaWindow *window, gboolean is_alive);
+gboolean meta_window_get_alive (MetaWindow *window);
+
+void meta_window_show_close_dialog (MetaWindow *window);
+void meta_window_hide_close_dialog (MetaWindow *window);
+void meta_window_ensure_close_dialog_timeout (MetaWindow *window);
 
 gboolean meta_window_has_pointer (MetaWindow *window);
 
@@ -898,4 +909,8 @@ gboolean meta_window_is_focus_async (MetaWindow *window);
 GFile *meta_window_get_unit_cgroup (MetaWindow *window);
 gboolean meta_window_unit_cgroup_equal (MetaWindow *window1,
                                         MetaWindow *window2);
+
+void meta_window_check_alive_on_event (MetaWindow *window,
+                                       uint32_t    timestamp);
+
 #endif

src/core/window.c

@@ -214,6 +214,7 @@ enum
   PROP_GTK_APP_MENU_OBJECT_PATH,
   PROP_GTK_MENUBAR_OBJECT_PATH,
   PROP_ON_ALL_WORKSPACES,
+  PROP_IS_ALIVE,
 
   PROP_LAST,
 };
@@ -633,6 +634,13 @@ meta_window_class_init (MetaWindowClass *klass)
                           FALSE,
                           G_PARAM_READABLE | G_PARAM_STATIC_STRINGS);
 
+  obj_props[PROP_IS_ALIVE] =
+    g_param_spec_boolean ("is-alive",
+                          "Is alive",
+                          "Whether the window responds to pings",
+                          TRUE,
+                          G_PARAM_READABLE | G_PARAM_STATIC_STRINGS);
+
   g_object_class_install_properties (object_class, PROP_LAST, obj_props);
 
   window_signals[WORKSPACE_CHANGED] =
@@ -729,6 +737,7 @@ meta_window_init (MetaWindow *self)
 {
   self->stamp = next_window_stamp++;
   meta_prefs_add_listener (prefs_changed_callback, self);
+  self->is_alive = TRUE;
 }
 
 static gboolean
@@ -1457,6 +1466,7 @@ meta_window_unmanage (MetaWindow  *window,
   window->unmanaging = TRUE;
 
   g_clear_handle_id (&window->unmanage_idle_id, g_source_remove);
+  g_clear_handle_id (&window->close_dialog_timeout_id, g_source_remove);
 
   g_signal_emit (window, window_signals[UNMANAGING], 0);
 
@@ -8816,3 +8826,55 @@ meta_window_get_client_type (MetaWindow *window)
 {
   return window->client_type;
 }
+
+static gboolean
+meta_window_close_dialog_timeout (MetaWindow *window)
+{
+  meta_window_show_close_dialog (window);
+  window->close_dialog_timeout_id = 0;
+
+  return G_SOURCE_REMOVE;
+}
+
+void
+meta_window_ensure_close_dialog_timeout (MetaWindow *window)
+{
+  guint check_alive_timeout = meta_prefs_get_check_alive_timeout ();
+
+  if (window->is_alive)
+    return;
+  if (window->close_dialog_timeout_id != 0)
+    return;
+  if (check_alive_timeout == 0)
+    return;
+
+  window->close_dialog_timeout_id =
+    g_timeout_add (check_alive_timeout,
+                   (GSourceFunc) meta_window_close_dialog_timeout,
+                   window);
+  g_source_set_name_by_id (window->close_dialog_timeout_id,
+                           "[mutter] meta_window_close_dialog_timeout");
+}
+
+void
+meta_window_set_alive (MetaWindow *window,
+                       gboolean    is_alive)
+{
+  if (window->is_alive == is_alive)
+    return;
+
+  window->is_alive = is_alive;
+  g_object_notify_by_pspec (G_OBJECT (window), obj_props[PROP_IS_ALIVE]);
+
+  if (is_alive)
+    {
+      g_clear_handle_id (&window->close_dialog_timeout_id, g_source_remove);
+      meta_window_hide_close_dialog (window);
+    }
+}
+
+gboolean
+meta_window_get_alive (MetaWindow *window)
+{
+  return window->is_alive;
+}