core: bind shadow immediate in initialize_backend

This simplifies the logic a bit since we know a shadow is always bound
(if needed) when the screen is redirected.

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/compton.c

@@ -758,7 +758,18 @@ static bool initialize_backend(session_t *ps) {
 				log_debug("Marking window %#010x (%s) for update after "
 				          "redirection",
 				          w->base.id, w->name);
-				w->flags |= WIN_FLAGS_IMAGES_STALE;
+				if (w->shadow) {
+					struct color c = {
+					    .red = ps->o.shadow_red,
+					    .green = ps->o.shadow_green,
+					    .blue = ps->o.shadow_blue,
+					    .alpha = ps->o.shadow_opacity,
+					};
+					win_bind_shadow(ps->backend_data, w, c,
+					                ps->gaussian_map);
+				}
+
+				w->flags |= WIN_FLAGS_PIXMAP_STALE;
 				ps->pending_updates = true;
 			}
 		}

src/win.c

@@ -292,8 +292,8 @@ static inline bool win_bind_pixmap(struct backend_base *b, struct managed_win *w
 	return true;
 }
 
-static inline bool win_bind_shadow(struct backend_base *b, struct managed_win *w,
-                                   struct color c, struct conv *kernel) {
+bool win_bind_shadow(struct backend_base *b, struct managed_win *w, struct color c,
+                     struct conv *kernel) {
 	assert(!w->shadow_image);
 	assert(w->shadow);
 	w->shadow_image = b->ops->render_shadow(b, w->widthb, w->heightb, kernel, c.red,

src/win.h

@@ -256,6 +256,9 @@ void win_process_updates(struct session *ps, struct managed_win *_w);
 void win_process_flags(session_t *ps, struct managed_win *w);
 /// Queue an update on a window. A series of sanity checks are performed
 void win_queue_update(struct managed_win *_w, enum win_update update);
+/// Bind a shadow to the window, with color `c` and shadow kernel `kernel`
+bool win_bind_shadow(struct backend_base *b, struct managed_win *w, struct color c,
+                     struct conv *kernel);
 
 /// Start the unmap of a window. We cannot unmap immediately since we might need to fade
 /// the window out.