[mutter/wip/carlosg/group-text-input-events] wayland: Defer text_input.done on an idle

[Jonas Ådahl <jadahl src gnome org>]

commit 63124e3e8a675725c729d4a99b994a83517a5c1a
Author: Carlos Garnacho <carlosg gnome org>
Date:   Thu Oct 18 02:08:24 2018 +0200

    wayland: Defer text_input.done on an idle
    
    IBus naturally doesn't know how to implement the text-input protocol,
    and some input methods emit event streams that are incompatible with the
    protocol, if not assumed to be part of an grouped series of events. As
    IBus doesn't have any API to let us know about such groupings, let's
    fake it by adding a specially crafted idle callback.
    
    The idle callback has a known limitation; if there is an idle callback
    with a higher priority, that either doesn't remove itself, or
    reschedules itself before the next idle, we'll never get triggered.
    This, however, is unlikely to actually be the bigger problem in such
    situations, as it'd likely mean we'd have a 100% CPU bug.
    
    https://gitlab.gnome.org/GNOME/gtk/issues/1365

 src/wayland/meta-wayland-text-input.c | 60 +++++++++++++++++++++++++++++++----
 1 file changed, 54 insertions(+), 6 deletions(-)
---
diff --git a/src/wayland/meta-wayland-text-input.c b/src/wayland/meta-wayland-text-input.c
index 868143021..0493760bd 100644
--- a/src/wayland/meta-wayland-text-input.c
+++ b/src/wayland/meta-wayland-text-input.c
@@ -70,6 +70,8 @@ struct _MetaWaylandTextInput
   uint32_t content_type_purpose;
   uint32_t text_change_cause;
   gboolean enabled;
+
+  guint done_idle_id;
 };
 
 struct _MetaWaylandTextInputFocus
@@ -114,6 +116,52 @@ increment_serial (MetaWaylandTextInput *text_input,
                        GUINT_TO_POINTER (serial + 1));
 }
 
+static gboolean
+done_idle_cb (gpointer user_data)
+{
+  ClutterInputFocus *focus = user_data;
+  MetaWaylandTextInput *text_input;
+  struct wl_resource *resource;
+
+  text_input = META_WAYLAND_TEXT_INPUT_FOCUS (focus)->text_input;
+
+  wl_resource_for_each (resource, &text_input->focus_resource_list)
+    {
+      zwp_text_input_v3_send_done (resource,
+                                   lookup_serial (text_input, resource));
+    }
+
+  text_input->done_idle_id = 0;
+  return G_SOURCE_REMOVE;
+}
+
+static void
+meta_wayland_text_input_focus_defer_done (ClutterInputFocus *focus)
+{
+  MetaWaylandTextInput *text_input;
+
+  text_input = META_WAYLAND_TEXT_INPUT_FOCUS (focus)->text_input;
+
+  if (text_input->done_idle_id != 0)
+    return;
+
+  /* This operates on 3 principles:
+   * - GDBus uses G_PRIORITY_DEFAULT to put messages in the thread default main
+   *   context.
+   * - All relevant ClutterInputFocus methods are ultimately backed by
+   *   DBus methods inside IBus.
+   * - We want to run .done after them all. The slightly lower
+   *   G_PRIORITY_DEFAULT + 1 priority should ensure we at least group
+   *   all messages seen so far.
+   *
+   * FIXME: .done may be delayed indefinitely if there's a high enough
+   *        priority idle source in the main loop. It's unlikely that
+   *        recurring idles run at this high priority though.
+   */
+  text_input->done_idle_id = g_idle_add_full (G_PRIORITY_DEFAULT + 1,
+                                              done_idle_cb, focus, NULL);
+}
+
 static void
 meta_wayland_text_input_focus_delete_surrounding (ClutterInputFocus *focus,
                                                   guint              cursor,
@@ -127,9 +175,9 @@ meta_wayland_text_input_focus_delete_surrounding (ClutterInputFocus *focus,
   wl_resource_for_each (resource, &text_input->focus_resource_list)
     {
       zwp_text_input_v3_send_delete_surrounding_text (resource, cursor, len);
-      zwp_text_input_v3_send_done (resource,
-                                   lookup_serial (text_input, resource));
     }
+
+  meta_wayland_text_input_focus_defer_done (focus);
 }
 
 static void
@@ -145,9 +193,9 @@ meta_wayland_text_input_focus_commit_text (ClutterInputFocus *focus,
     {
       zwp_text_input_v3_send_preedit_string (resource, NULL, 0, 0);
       zwp_text_input_v3_send_commit_string (resource, text);
-      zwp_text_input_v3_send_done (resource,
-                                   lookup_serial (text_input, resource));
     }
+
+  meta_wayland_text_input_focus_defer_done (focus);
 }
 
 static void
@@ -163,9 +211,9 @@ meta_wayland_text_input_focus_set_preedit_text (ClutterInputFocus *focus,
   wl_resource_for_each (resource, &text_input->focus_resource_list)
     {
       zwp_text_input_v3_send_preedit_string (resource, text, cursor, cursor);
-      zwp_text_input_v3_send_done (resource,
-                                   lookup_serial (text_input, resource));
     }
+
+  meta_wayland_text_input_focus_defer_done (focus);
 }
 
 static void