tests: move set_opaque_rect() to client helpers

I will be needing it in a new test, so let's share it.

For convenience, this also adds client back-pointer in struct surface so
that I don't need to pass client explicitly.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>

tests/alpha-blending-test.c

@@ -80,19 +80,6 @@ fixture_setup(struct weston_test_harness *harness, const struct setup_args *arg)
 }
 DECLARE_FIXTURE_SETUP_WITH_ARG(fixture_setup, my_setup_args, meta);
 
-static void
-set_opaque_rect(struct client *client,
-		struct surface *surface,
-		const struct rectangle *rect)
-{
-	struct wl_region *region;
-
-	region = wl_compositor_create_region(client->wl_compositor);
-	wl_region_add(region, rect->x, rect->y, rect->width, rect->height);
-	wl_surface_set_opaque_region(surface->wl_surface, region);
-	wl_region_destroy(region);
-}
-
 static uint32_t
 premult_color(uint32_t a, uint32_t r, uint32_t g, uint32_t b)
 {
@@ -400,7 +387,7 @@ TEST(alpha_blend)
 	client->surface->width = width;
 	client->surface->height = height;
 	client->surface->buffer = bg; /* pass ownership */
-	set_opaque_rect(client, client->surface,
+	surface_set_opaque_rect(client->surface,
 				&(struct rectangle){ 0, 0, width, height });
 
 	/* foreground blended content */

tests/weston-test-client-helper.c

@@ -976,6 +976,7 @@ create_test_surface(struct client *client)
 
 	surface = xzalloc(sizeof *surface);
 
+	surface->client = client;
 	surface->wl_surface =
 		wl_compositor_create_surface(client->wl_compositor);
 	assert(surface->wl_surface);
@@ -998,6 +999,17 @@ surface_destroy(struct surface *surface)
 	free(surface);
 }
 
+void
+surface_set_opaque_rect(struct surface *surface, const struct rectangle *rect)
+{
+	struct wl_region *region;
+
+	region = wl_compositor_create_region(surface->client->wl_compositor);
+	wl_region_add(region, rect->x, rect->y, rect->width, rect->height);
+	wl_surface_set_opaque_region(surface->wl_surface, region);
+	wl_region_destroy(region);
+}
+
 struct client *
 create_client_and_test_surface(int x, int y, int width, int height)
 {

tests/weston-test-client-helper.h

@@ -172,6 +172,8 @@ struct buffer {
 };
 
 struct surface {
+	struct client *client; /* not owned */
+
 	struct wl_surface *wl_surface;
 	struct output *output; /* not owned */
 	int x;
@@ -205,6 +207,9 @@ create_test_surface(struct client *client);
 void
 surface_destroy(struct surface *surface);
 
+void
+surface_set_opaque_rect(struct surface *surface, const struct rectangle *rect);
+
 struct client *
 create_client_and_test_surface(int x, int y, int width, int height);