[mutter/wip/carlosg/no-null-preedit-repeat: 17/17] wayland: Avoid repeated NULL preedit string updates

[Marge Bot <marge-bot src gnome org>]

commit f361e8032c12a6802358733e4acf3e183277619a
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sat Apr 30 13:51:28 2022 +0200

    wayland: Avoid repeated NULL preedit string updates
    
    Simply signal preedit string changes from/to NULL once, in order
    to avoid unwanted activity in the client side. We do still need to
    send the preedit once each .done event, if there is one, in order
    to behave according to the protocol when it matters the most.
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2395>

 src/wayland/meta-wayland-text-input.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)
---
diff --git a/src/wayland/meta-wayland-text-input.c b/src/wayland/meta-wayland-text-input.c
index 17e0b683e7..cf40f02183 100644
--- a/src/wayland/meta-wayland-text-input.c
+++ b/src/wayland/meta-wayland-text-input.c
@@ -79,6 +79,7 @@ struct _MetaWaylandTextInput
     char *string;
     uint32_t cursor;
     uint32_t anchor;
+    gboolean changed;
   } preedit;
 
   guint done_idle_id;
@@ -136,10 +137,15 @@ clutter_input_focus_send_done (ClutterInputFocus *focus)
 
   wl_resource_for_each (resource, &text_input->focus_resource_list)
     {
-      zwp_text_input_v3_send_preedit_string (resource,
-                                             text_input->preedit.string,
-                                             text_input->preedit.cursor,
-                                             text_input->preedit.anchor);
+      if (text_input->preedit.string || text_input->preedit.changed)
+        {
+          zwp_text_input_v3_send_preedit_string (resource,
+                                                 text_input->preedit.string,
+                                                 text_input->preedit.cursor,
+                                                 text_input->preedit.anchor);
+          text_input->preedit.changed = FALSE;
+        }
+
       zwp_text_input_v3_send_done (resource,
                                    lookup_serial (text_input, resource));
     }
@@ -260,6 +266,7 @@ meta_wayland_text_input_focus_set_preedit_text (ClutterInputFocus *focus,
 
   text_input->preedit.cursor = pos;
   text_input->preedit.anchor = pos;
+  text_input->preedit.changed = TRUE;
 
   meta_wayland_text_input_focus_defer_done (focus);
 }