[PATCH xserver 2/4 v3] xwayland: add a server sync before repeating keys

[Olivier Fourdan]

Key repeat is handled by the X server, but input events need to be
processed and forwarded by the Wayland compositor first.

Make sure the Wayland compositor is actually processing events, to
avoid repeating keys in Xwayland while the Wayland compositor cannot
deal with input events for whatever reason, thus not dispatching key
release events, leading to repeated keys while the user has already
released the key.

Bugzilla: https://bugzilla.gnome.org/show_bug.cgi?id=762618
Signed-off-by: Olivier Fourdan <ofourdan at redhat.com>
---
 v2: A slightly less hack-y-ish version of the patch
     Use xwl_seat to store the pending sync, set up callback fpr keyboard
     in seat_handle_capabilities() and add a call to _dispatch_pending()
     in the callback function to make sure we didn't miss a reply
 v3: Small clean-up,
     Remove the call to wl_display_dispatch_pending() that we added
     in v2 as we shall do it in two other separate patches to follow.

 hw/xwayland/xwayland-input.c | 38 ++++++++++++++++++++++++++++++++++++++
 hw/xwayland/xwayland.h       |  2 ++
 2 files changed, 40 insertions(+)

diff --git a/hw/xwayland/xwayland-input.c b/hw/xwayland/xwayland-input.c
index f9e3255..28d8b54 100644
--- a/hw/xwayland/xwayland-input.c
+++ b/hw/xwayland/xwayland-input.c
@@ -527,6 +527,40 @@ keyboard_handle_modifiers(void *data, struct wl_keyboard *keyboard,
 }
 
 static void
+sync_callback(void *data, struct wl_callback *callback, uint32_t serial)
+{
+    struct xwl_seat *xwl_seat = data;
+
+    xwl_seat->sync_pending = FALSE;
+    wl_callback_destroy(callback);
+}
+
+static const struct wl_callback_listener sync_listener = {
+   sync_callback
+};
+
+static Bool
+keyboard_check_repeat (DeviceIntPtr dev, XkbSrvInfoPtr xkbi, unsigned key)
+{
+    struct xwl_seat *xwl_seat = dev->public.devicePrivate;
+    struct xwl_screen *xwl_screen = xwl_seat->xwl_screen;
+    struct wl_callback *callback;
+
+    if (!xwl_seat->sync_pending) {
+        callback = wl_display_sync (xwl_screen->display);
+        wl_callback_add_listener(callback, &sync_listener, xwl_seat);
+        xwl_seat->sync_pending = TRUE;
+
+        return TRUE;
+    }
+
+    ErrorF("Key repeat discarded, Wayland compositor doesn't seem to "
+           "be processing events fast enough!\n");
+
+    return FALSE;
+}
+
+static void
 keyboard_handle_repeat_info (void *data, struct wl_keyboard *keyboard,
                              int32_t rate, int32_t delay)
 {
@@ -716,6 +750,7 @@ seat_handle_capabilities(void *data, struct wl_seat *seat,
                          enum wl_seat_capability caps)
 {
     struct xwl_seat *xwl_seat = data;
+    DeviceIntPtr master;
 
     if (caps & WL_SEAT_CAPABILITY_POINTER && xwl_seat->wl_pointer == NULL) {
         xwl_seat->wl_pointer = wl_seat_get_pointer(seat);
@@ -748,6 +783,9 @@ seat_handle_capabilities(void *data, struct wl_seat *seat,
             ActivateDevice(xwl_seat->keyboard, TRUE);
         }
         EnableDevice(xwl_seat->keyboard, TRUE);
+        master = GetMaster(xwl_seat->keyboard, MASTER_KEYBOARD);
+        if (master)
+            master->key->xkbInfo->checkRepeat = keyboard_check_repeat;
     } else if (!(caps & WL_SEAT_CAPABILITY_KEYBOARD) && xwl_seat->wl_keyboard) {
         wl_keyboard_release(xwl_seat->wl_keyboard);
         xwl_seat->wl_keyboard = NULL;
diff --git a/hw/xwayland/xwayland.h b/hw/xwayland/xwayland.h
index 2a54183..aaf3b40 100644
--- a/hw/xwayland/xwayland.h
+++ b/hw/xwayland/xwayland.h
@@ -138,6 +138,8 @@ struct xwl_seat {
     size_t keymap_size;
     char *keymap;
     struct wl_surface *keyboard_focus;
+
+    Bool sync_pending;
 };
 
 struct xwl_output {
-- 
2.5.0