[mutter] wayland/keyboard: Accept key down serial after key up for popups

[Jonas Ådahl <jadahl src gnome org>]

commit 2dbacfa8d6a520a8099d4c153124497397bea1ee
Author: Jonas Ådahl <jadahl gmail com>
Date:   Wed Jul 25 16:18:36 2018 +0200

    wayland/keyboard: Accept key down serial after key up for popups
    
    If a client maps a popup in response to a key-down event, but the
    mapping doesn't occur until after the user has already released the same
    button, we'd immediately dismiss the popup. This is problematic, as one
    often presses and releases a key quite quickly, meaning any popup mapped
    on key-down are likely to be dismissed.
    
    Avoid this race condition by accepting serials for key down events, if
    the most recent key-up event had the same keycode.
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/180

 src/wayland/meta-wayland-keyboard.c | 21 ++++++++++++++++-----
 src/wayland/meta-wayland-keyboard.h |  7 ++++++-
 2 files changed, 22 insertions(+), 6 deletions(-)
---
diff --git a/src/wayland/meta-wayland-keyboard.c b/src/wayland/meta-wayland-keyboard.c
index d4ae4508d..7ad14c88a 100644
--- a/src/wayland/meta-wayland-keyboard.c
+++ b/src/wayland/meta-wayland-keyboard.c
@@ -298,14 +298,23 @@ meta_wayland_keyboard_broadcast_key (MetaWaylandKeyboard *keyboard,
     {
       MetaWaylandInputDevice *input_device =
         META_WAYLAND_INPUT_DEVICE (keyboard);
+      uint32_t serial;
 
-      keyboard->key_serial =
-        meta_wayland_input_device_next_serial (input_device);
+      serial = meta_wayland_input_device_next_serial (input_device);
 
-      wl_resource_for_each (resource, &keyboard->focus_resource_list)
+      if (state)
+        {
+          keyboard->key_down_serial = serial;
+          keyboard->key_down_keycode = key;
+        }
+      else
         {
-          wl_keyboard_send_key (resource, keyboard->key_serial, time, key, state);
+          keyboard->key_up_serial = serial;
+          keyboard->key_up_keycode = key;
         }
+
+      wl_resource_for_each (resource, &keyboard->focus_resource_list)
+        wl_keyboard_send_key (resource, serial, time, key, state);
     }
 
   /* Eat the key events if we have a focused surface. */
@@ -1026,7 +1035,9 @@ gboolean
 meta_wayland_keyboard_can_popup (MetaWaylandKeyboard *keyboard,
                                  uint32_t             serial)
 {
-  return keyboard->key_serial == serial;
+  return (keyboard->key_down_serial == serial ||
+          ((keyboard->key_down_keycode == keyboard->key_up_keycode) &&
+           keyboard->key_up_serial == serial));
 }
 
 void
diff --git a/src/wayland/meta-wayland-keyboard.h b/src/wayland/meta-wayland-keyboard.h
index 39f06ef17..88899712d 100644
--- a/src/wayland/meta-wayland-keyboard.h
+++ b/src/wayland/meta-wayland-keyboard.h
@@ -89,7 +89,12 @@ struct _MetaWaylandKeyboard
   MetaWaylandSurface *focus_surface;
   struct wl_listener focus_surface_listener;
   uint32_t focus_serial;
-  uint32_t key_serial;
+
+  uint32_t key_down_keycode;
+  uint32_t key_down_serial;
+
+  uint32_t key_up_keycode;
+  uint32_t key_up_serial;
 
   MetaWaylandXkbInfo xkb_info;
   enum xkb_state_component mods_changed;