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

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;