[gtk/wip/carlosg/touchpad-gesture-fixes: 1/3] gdk: Always request "flush events" frame clock phase on events

[Carlos Garnacho <carlosg src gnome org>]

commit 2b41e72196ee648ae71f8c8af393d8d8942ea0d4
Author: Carlos Garnacho <carlosg gnome org>
Date:   Wed Jan 26 15:49:29 2022 +0100

    gdk: Always request "flush events" frame clock phase on events
    
    This change is done for 2 reasons:
    
    - The logic to request this phase when compressing scroll events is
      slightly broken. If there are multiple scroll events that are
      coalesced into one, the surface frame clock will not get this request.
      The worst case is having >= 2 scroll events on every frame, as the
      compressed event will be left in the queue, and be further compressed
      on future events.
    
    - Even scroll events aside, this phase is requested in oddly specific
      places that are not enough to cover all events, others do rely on
      unrelated GdkFrameClock activity that happens to flush the events
      as well.
    
    Unify this phase request so it explicitly happens on the arrival of any
    event. This ensures that events (compressed or not) will be handled
    promptly after arrival.

 gdk/gdkevents.c  | 16 ----------------
 gdk/gdksurface.c | 10 +++++++++-
 2 files changed, 9 insertions(+), 17 deletions(-)
---
diff --git a/gdk/gdkevents.c b/gdk/gdkevents.c
index 1f4a920720..454e69ed64 100644
--- a/gdk/gdkevents.c
+++ b/gdk/gdkevents.c
@@ -719,14 +719,6 @@ gdk_event_queue_handle_scroll_compression (GdkDisplay *display)
 
       gdk_event_unref (old_event);
     }
-
-  if (g_queue_get_length (&display->queued_events) == 1 &&
-      g_queue_peek_head_link (&display->queued_events) == scrolls)
-    {
-      GdkFrameClock *clock = gdk_surface_get_frame_clock (surface);
-      if (clock) /* might be NULL if surface was destroyed */
-        gdk_frame_clock_request_phase (clock, GDK_FRAME_CLOCK_PHASE_FLUSH_EVENTS);
-    }
 }
 
 static void
@@ -832,14 +824,6 @@ _gdk_event_queue_handle_motion_compression (GdkDisplay *display)
       g_queue_delete_link (&display->queued_events, pending_motions);
       pending_motions = next;
     }
-
-  if (g_queue_get_length (&display->queued_events) == 1 &&
-      g_queue_peek_head_link (&display->queued_events) == pending_motions)
-    {
-      GdkFrameClock *clock = gdk_surface_get_frame_clock (pending_motion_surface);
-      if (clock) /* might be NULL if surface was destroyed */
-        gdk_frame_clock_request_phase (clock, GDK_FRAME_CLOCK_PHASE_FLUSH_EVENTS);
-    }
 }
 
 void
diff --git a/gdk/gdksurface.c b/gdk/gdksurface.c
index 1f176b9b87..ddfa767a99 100644
--- a/gdk/gdksurface.c
+++ b/gdk/gdksurface.c
@@ -2244,7 +2244,7 @@ _gdk_windowing_got_event (GdkDisplay *display,
                           GdkEvent   *event,
                           gulong      serial)
 {
-  GdkSurface *event_surface;
+  GdkSurface *event_surface = NULL;
   gboolean unlink_event = FALSE;
   GdkDeviceGrabInfo *button_release_grab;
   GdkPointerSurfaceInfo *pointer_info = NULL;
@@ -2336,6 +2336,14 @@ _gdk_windowing_got_event (GdkDisplay *display,
    */
   _gdk_event_queue_handle_motion_compression (display);
   gdk_event_queue_handle_scroll_compression (display);
+
+  if (event_surface)
+    {
+      GdkFrameClock *clock = gdk_surface_get_frame_clock (event_surface);
+
+      if (clock) /* might be NULL if surface was destroyed */
+        gdk_frame_clock_request_phase (clock, GDK_FRAME_CLOCK_PHASE_FLUSH_EVENTS);
+    }
 }
 
 /**