[mutter/wip/carlosg/input-refactors-pt1: 3/30] wayland: Simplify wl_touch.frame handling

[Carlos Garnacho <carlosg src gnome org>]

commit 6b0e5c65df064215c1137f75a955c6557b1a0454
Author: Carlos Garnacho <carlosg gnome org>
Date:   Wed May 6 13:26:15 2020 +0200

    wayland: Simplify wl_touch.frame handling
    
    We want to coalesce multiple touch events into the same wl_touch.frame
    event. Instead of poking internals to peek the touch events (and their
    slots) coming at us before we handle them, simplify things by queueing
    the event at a slightly lower priority than events, so we are ensured
    to handle all pending input events before sending the event.
    
    If there's no pending events, we can just send the frame event. As it
    doesn't make sense to hold any longer.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1486

 src/wayland/meta-wayland-touch.c | 60 +++++++++++++++-------------------------
 src/wayland/meta-wayland-touch.h |  3 +-
 2 files changed, 23 insertions(+), 40 deletions(-)
---
diff --git a/src/wayland/meta-wayland-touch.c b/src/wayland/meta-wayland-touch.c
index 9c2cfc9df6..928c0031b2 100644
--- a/src/wayland/meta-wayland-touch.c
+++ b/src/wayland/meta-wayland-touch.c
@@ -401,35 +401,34 @@ touch_send_frame_event (MetaWaylandTouch *touch)
   g_list_free (surfaces);
 }
 
-static void
-check_send_frame_event (MetaWaylandTouch   *touch,
-                        const ClutterEvent *event)
+static gboolean
+queue_frame_event_cb (MetaWaylandTouch *touch)
 {
-  gboolean send_frame_event;
-#ifdef HAVE_NATIVE_BACKEND
-  MetaBackend *backend = meta_get_backend ();
-  ClutterEventSequence *sequence;
-  gint32 slot;
+  touch_send_frame_event (touch);
+  touch->queued_frame_id = 0;
 
-  if (META_IS_BACKEND_NATIVE (backend))
+  return G_SOURCE_REMOVE;
+}
+
+static void
+send_or_queue_frame_event (MetaWaylandTouch *touch)
+{
+  if (clutter_events_pending ())
     {
-      sequence = clutter_event_get_event_sequence (event);
-      slot = meta_event_native_sequence_get_slot (sequence);
-      touch->frame_slots &= ~(1 << slot);
-
-      if (touch->frame_slots == 0)
-        send_frame_event = TRUE;
-      else
-        send_frame_event = FALSE;
+      if (touch->queued_frame_id == 0)
+        {
+          touch->queued_frame_id =
+            g_idle_add_full (CLUTTER_PRIORITY_EVENTS + 1,
+                             (GSourceFunc) queue_frame_event_cb,
+                             touch, NULL);
+        }
     }
   else
-#endif /* HAVE_NATIVE_BACKEND */
     {
-      send_frame_event = TRUE;
+      /* There's no more events */
+      g_clear_handle_id (&touch->queued_frame_id, g_source_remove);
+      touch_send_frame_event (touch);
     }
-
-  if (send_frame_event)
-    touch_send_frame_event (touch);
 }
 
 gboolean
@@ -454,7 +453,7 @@ meta_wayland_touch_handle_event (MetaWaylandTouch   *touch,
       return FALSE;
     }
 
-  check_send_frame_event (touch, event);
+  send_or_queue_frame_event (touch);
   return FALSE;
 }
 
@@ -520,21 +519,6 @@ evdev_filter_func (struct libinput_event *event,
 
   switch (libinput_event_get_type (event))
     {
-    case LIBINPUT_EVENT_TOUCH_DOWN:
-    case LIBINPUT_EVENT_TOUCH_UP:
-    case LIBINPUT_EVENT_TOUCH_MOTION: {
-      struct libinput_event_touch *touch_event;
-      int32_t slot;
-
-      touch_event = libinput_event_get_touch_event (event);
-      slot = libinput_event_touch_get_slot (touch_event);
-
-      /* XXX: Could theoretically overflow, 64 slots should be
-       * enough for most hw/usecases though.
-       */
-      touch->frame_slots |= (1 << slot);
-      break;
-    }
     case LIBINPUT_EVENT_TOUCH_CANCEL:
       /* Clutter translates this into individual CLUTTER_TOUCH_CANCEL events,
        * which are not so useful when sending a global signal as the protocol
diff --git a/src/wayland/meta-wayland-touch.h b/src/wayland/meta-wayland-touch.h
index f2efcb1ba9..304d8227e9 100644
--- a/src/wayland/meta-wayland-touch.h
+++ b/src/wayland/meta-wayland-touch.h
@@ -41,10 +41,9 @@ struct _MetaWaylandTouch
 
   struct wl_list resource_list;
 
+  guint queued_frame_id;
   GHashTable *touch_surfaces; /* HT of MetaWaylandSurface->MetaWaylandTouchSurface */
   GHashTable *touches; /* HT of sequence->MetaWaylandTouchInfo */
-
-  guint64 frame_slots;
 };
 
 void meta_wayland_touch_enable (MetaWaylandTouch *touch);