desktop-shell: Clean up fullscreen black view code

Rationalise it a little bit so we don't need pre-declarations of static
functions, and the order of creation more closely matches the others,
including making the same calls to explicitly set the output.

Doing this makes the behaviour match the other users of the same code
pattern. In making them the same, we make desktop-shell code a little
less magically divergent where people might wonder what the correct
pattern is to use. After we have moved all users to a uniform pattern,
later commits are then able to migrate these users to common helper
code, which reduces code duplication, improves code clarity as it is no
longer necessary to wonder about the exact semantics of every
special-case user of this common pattern, and makes it easier to make
interface changes which improve and clarify the patterns which are
prevalent throughout the desktop-shell code.

Signed-off-by: Daniel Stone <daniels@collabora.com>

desktop-shell/shell.c

@@ -2061,24 +2061,21 @@ black_surface_get_label(struct weston_surface *surface, char *buf, size_t len)
 }
 
 static void
-black_surface_committed(struct weston_surface *es, int32_t sx, int32_t sy);
+black_surface_committed(struct weston_surface *es, int32_t sx, int32_t sy)
+{
+}
 
-static struct weston_view *
-create_black_surface(struct weston_compositor *ec,
-		     struct weston_view *fs_view,
-		     float x, float y, int w, int h)
+static bool
+is_black_surface_view(struct weston_view *view, struct weston_view **fs_view)
 {
-	struct weston_curtain_params curtain_params = {
-		.r = 0.0, .g = 0.0, .b = 0.0, .a = 1.0,
-		.x = x, .y = y,
-		.width = w, .height = h,
-		.surface_committed = black_surface_committed,
-		.get_label = black_surface_get_label,
-		.surface_private = fs_view,
-	};
-	struct weston_view *view = weston_curtain_create(ec, &curtain_params);
+	struct weston_surface *surface = view->surface;
 
-	return view;
+	if (surface->committed == black_surface_committed) {
+		if (fs_view)
+			*fs_view = surface->committed_private;
+		return true;
+	}
+	return false;
 }
 
 static void
@@ -2086,17 +2083,26 @@ shell_ensure_fullscreen_black_view(struct shell_surface *shsurf)
 {
 	struct weston_surface *surface =
 		weston_desktop_surface_get_surface(shsurf->desktop_surface);
+	struct weston_compositor *ec = surface->compositor;
 	struct weston_output *output = shsurf->fullscreen_output;
+	struct weston_curtain_params curtain_params = {
+		.r = 0.0, .g = 0.0, .b = 0.0, .a = 1.0,
+		.x = output->x, .y = output->y,
+		.width = output->width, .height = output->height,
+		.surface_committed = black_surface_committed,
+		.get_label = black_surface_get_label,
+		.surface_private = shsurf->view,
+	};
 
 	assert(weston_desktop_surface_get_fullscreen(shsurf->desktop_surface));
 
-	if (!shsurf->fullscreen.black_view)
+	if (!shsurf->fullscreen.black_view) {
 		shsurf->fullscreen.black_view =
-			create_black_surface(surface->compositor,
-			                     shsurf->view,
-			                     output->x, output->y,
-			                     output->width,
-			                     output->height);
+			weston_curtain_create(ec, &curtain_params);
+	}
+
+	weston_view_set_output(shsurf->fullscreen.black_view, output);
+	shsurf->fullscreen.black_view->is_mapped = true;
 
 	weston_layer_entry_remove(&shsurf->fullscreen.black_view->layer_link);
 	weston_layer_entry_insert(&shsurf->view->layer_link,
@@ -2104,7 +2110,6 @@ shell_ensure_fullscreen_black_view(struct shell_surface *shsurf)
 	weston_view_geometry_dirty(shsurf->fullscreen.black_view);
 	weston_surface_damage(surface);
 
-	shsurf->fullscreen.black_view->is_mapped = true;
 	shsurf->state.lowered = false;
 }
 
@@ -3726,25 +3731,6 @@ activate(struct desktop_shell *shell, struct weston_view *view,
 	}
 }
 
-/* no-op func for checking black surface */
-static void
-black_surface_committed(struct weston_surface *es, int32_t sx, int32_t sy)
-{
-}
-
-static bool
-is_black_surface_view(struct weston_view *view, struct weston_view **fs_view)
-{
-	struct weston_surface *surface = view->surface;
-
-	if (surface->committed == black_surface_committed) {
-		if (fs_view)
-			*fs_view = surface->committed_private;
-		return true;
-	}
-	return false;
-}
-
 static void
 activate_binding(struct weston_seat *seat,
 		 struct desktop_shell *shell,