xwayland: Add xwl_present_unrealize_window

When a window is unrealized, a pending frame callback may never be
called, which could result in repeatedly freezing until the frame timer
fires after a second.

Fixes these symptoms when switching from fullscreen to windowed mode in
sauerbraten.

(cherry picked from commit 8c9538573c)

hw/xwayland/xwayland-present.c

@@ -524,6 +524,22 @@ xwl_present_flips_stop(WindowPtr window)
     xwl_present_reset_timer(xwl_present_window);
 }
 
+void
+xwl_present_unrealize_window(WindowPtr window)
+{
+    struct xwl_present_window *xwl_present_window = xwl_present_window_priv(window);
+
+    if (!xwl_present_window || !xwl_present_window->frame_callback)
+        return;
+
+    /* The pending frame callback may never be called, so drop it and shorten
+     * the frame timer interval.
+     */
+    wl_callback_destroy(xwl_present_window->frame_callback);
+    xwl_present_window->frame_callback = NULL;
+    xwl_present_reset_timer(xwl_present_window);
+}
+
 static present_wnmd_info_rec xwl_present_info = {
     .version = PRESENT_SCREEN_INFO_VERSION,
     .get_crtc = xwl_present_get_crtc,

hw/xwayland/xwayland.c

@@ -609,6 +609,11 @@ xwl_unrealize_window(WindowPtr window)
     xwl_screen->UnrealizeWindow = screen->UnrealizeWindow;
     screen->UnrealizeWindow = xwl_unrealize_window;
 
+#ifdef GLAMOR_HAS_GBM
+    if (xwl_screen->present)
+        xwl_present_unrealize_window(window);
+#endif
+
     xwl_window = xwl_window_get(window);
     if (!xwl_window)
         return ret;

hw/xwayland/xwayland.h

@@ -454,6 +454,7 @@ void xwl_glamor_egl_make_current(struct xwl_screen *xwl_screen);
 #ifdef GLAMOR_HAS_GBM
 Bool xwl_present_init(ScreenPtr screen);
 void xwl_present_cleanup(WindowPtr window);
+void xwl_present_unrealize_window(WindowPtr window);
 #endif /* GLAMOR_HAS_GBM */
 
 #ifdef XV