startup-notification: Delay cursor feedback updates

A Wayland client repeatedly requesting activation of its surface using
the xdg-activation protocol would make mutter constantly update the
cursor.

To avoid needlessly updating the cursor back and forth between busy and
default, add a timeout to delay the update.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2849>

1 files changed, 38 insertions, 3 deletions

diff --git a/src/core/startup-notification.c b/src/core/startup-notification.c
index 371ec35ff..21b88dea8 100644
--- a/src/core/startup-notification.c
+++ b/src/core/startup-notification.c
@@ -38,6 +38,7 @@
  * might decide they need to launch it again.
  */
 #define STARTUP_TIMEOUT_MS 15000
+#define UPDATE_CURSOR_TIMEOUT_MS 20
 
 enum
 {
@@ -92,6 +93,8 @@ struct _MetaStartupNotification
 
   GSList *startup_sequences;
   guint startup_sequence_timeout_id;
+  guint update_cursor_timeout_id;
+  MetaCursor cursor;
 };
 
 typedef struct
@@ -133,22 +136,53 @@ meta_startup_notification_has_pending_sequences (MetaStartupNotification *sn)
 }
 
 static void
-meta_startup_notification_update_feedback (MetaStartupNotification *sn)
+meta_startup_notification_update_cursor (MetaStartupNotification *sn)
 {
   MetaDisplay *display = sn->display;
+  MetaCursor cursor;
 
   if (meta_startup_notification_has_pending_sequences (sn))
     {
       meta_topic (META_DEBUG_STARTUP,
                   "Setting busy cursor");
-      meta_display_set_cursor (display, META_CURSOR_BUSY);
+      cursor = META_CURSOR_BUSY;
     }
   else
     {
       meta_topic (META_DEBUG_STARTUP,
                   "Setting default cursor");
-      meta_display_set_cursor (display, META_CURSOR_DEFAULT);
+      cursor = META_CURSOR_DEFAULT;
     }
+
+  if (sn->cursor != cursor)
+    {
+      meta_display_set_cursor (display, cursor);
+      sn->cursor = cursor;
+    }
+}
+
+static gboolean
+meta_startup_notification_cursor_timeout (gpointer user_data)
+{
+  MetaStartupNotification *sn = user_data;
+
+  meta_startup_notification_update_cursor (sn);
+  sn->update_cursor_timeout_id = 0;
+
+  return G_SOURCE_REMOVE;
+}
+
+static void
+meta_startup_notification_update_feedback (MetaStartupNotification *sn)
+{
+  if (sn->update_cursor_timeout_id)
+    return;
+
+  meta_startup_notification_update_cursor (sn);
+  sn->update_cursor_timeout_id =
+    g_timeout_add (UPDATE_CURSOR_TIMEOUT_MS,
+                   meta_startup_notification_cursor_timeout,
+                   sn);
 }
 
 static void
@@ -631,6 +665,7 @@ meta_startup_notification_finalize (GObject *object)
   MetaStartupNotification *sn = META_STARTUP_NOTIFICATION (object);
 
   g_clear_handle_id (&sn->startup_sequence_timeout_id, g_source_remove);
+  g_clear_handle_id (&sn->update_cursor_timeout_id, g_source_remove);
 
   g_slist_free_full (sn->startup_sequences, g_object_unref);
   sn->startup_sequences = NULL;