SDL: wayland: Guard surface_frame_listener for OpenGL, document why it exists

From 20928550350d4d4c5d78f98b61e7e08d219a5475 Mon Sep 17 00:00:00 2001
From: Ethan Lee <[EMAIL REDACTED]>
Date: Sat, 1 May 2021 09:00:24 -0400
Subject: [PATCH] wayland: Guard surface_frame_listener for OpenGL, document
 why it exists

---
 src/video/wayland/SDL_waylandwindow.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/video/wayland/SDL_waylandwindow.c b/src/video/wayland/SDL_waylandwindow.c
index 50b16d12f..2e4edcda7 100644
--- a/src/video/wayland/SDL_waylandwindow.c
+++ b/src/video/wayland/SDL_waylandwindow.c
@@ -1012,8 +1012,14 @@ int Wayland_CreateWindow(_THIS, SDL_Window *window)
         wl_compositor_create_surface(c->compositor);
     wl_surface_add_listener(data->surface, &surface_listener, data);
 
-    /* fire a callback when the compositor wants a new frame rendered. */
-    wl_callback_add_listener(wl_surface_frame(data->surface), &surface_frame_listener, data);
+    /* Fire a callback when the compositor wants a new frame rendered.
+     * Right now this only matters for OpenGL; we use this callback to add a
+     * wait timeout that avoids getting deadlocked by the compositor when the
+     * window isn't visible.
+     */
+    if (window->flags & SDL_WINDOW_OPENGL) {
+        wl_callback_add_listener(wl_surface_frame(data->surface), &surface_frame_listener, data);
+    }
 
 #ifdef SDL_VIDEO_DRIVER_WAYLAND_QT_TOUCH
     if (c->surface_extension) {