compositor: Dont set the opaque region if we have an overall surface alpha
diff --git a/src/compositor.c b/src/compositor.c
index 6a1bebd..a95837e 100644
--- a/src/compositor.c
+++ b/src/compositor.c
@@ -335,9 +335,13 @@
 				  surface->geometry.width,
 				  surface->geometry.height);
 
-	pixman_region32_copy(&surface->transform.opaque, &surface->opaque);
-	pixman_region32_translate(&surface->transform.opaque,
-				  surface->geometry.x, surface->geometry.y);
+	if (surface->alpha == 255) {
+		pixman_region32_copy(&surface->transform.opaque,
+				     &surface->opaque);
+		pixman_region32_translate(&surface->transform.opaque,
+					  surface->geometry.x,
+					  surface->geometry.y);
+	}
 }
 
 static int