scene_graph: Implement toplevel clipping

include/sway/tree/view.h

@@ -274,7 +274,7 @@ void view_map(struct sway_view *view, struct wlr_surface *wlr_surface,
 void view_unmap(struct sway_view *view);
 
 void view_update_size(struct sway_view *view);
-void view_center_surface(struct sway_view *view);
+void view_center_and_clip_surface(struct sway_view *view);
 
 struct sway_view *view_from_wlr_xdg_surface(
 	struct wlr_xdg_surface *xdg_surface);

sway/desktop/transaction.c

@@ -248,7 +248,7 @@ static void apply_container_state(struct sway_container *container,
 		// the container. This is important for fullscreen views which
 		// refuse to resize to the size of the output.
 		if (view->surface) {
-			view_center_surface(view);
+			view_center_and_clip_surface(view);
 		}
 	}
 }

sway/desktop/xdg_shell.c

@@ -306,9 +306,9 @@ static void handle_commit(struct wl_listener *listener, void *data) {
 					view->geometry.height);
 			}
 			transaction_commit_dirty_client();
-		} else {
-			view_center_surface(view);
 		}
+
+		view_center_and_clip_surface(view);
 	}
 
 	if (view->container->node.instruction) {

sway/desktop/xwayland.c

@@ -436,9 +436,9 @@ static void handle_commit(struct wl_listener *listener, void *data) {
 		if (container_is_floating(view->container)) {
 			view_update_size(view);
 			transaction_commit_dirty_client();
-		} else {
-			view_center_surface(view);
 		}
+
+		view_center_and_clip_surface(view);
 	}
 
 	if (view->container->node.instruction) {

sway/tree/view.c

@@ -893,14 +893,29 @@ void view_update_size(struct sway_view *view) {
 	container_set_geometry_from_content(con);
 }
 
-void view_center_surface(struct sway_view *view) {
+void view_center_and_clip_surface(struct sway_view *view) {
 	struct sway_container *con = view->container;
+
+	if (container_is_floating(con)) {
 		// We always center the current coordinates rather than the next, as the
 		// geometry immediately affects the currently active rendering.
 		int x = (int) fmax(0, (con->current.content_width - view->geometry.width) / 2);
 		int y = (int) fmax(0, (con->current.content_height - view->geometry.height) / 2);
 
 		wlr_scene_node_set_position(&view->content_tree->node, x, y);
+	} else {
+		wlr_scene_node_set_position(&view->content_tree->node, 0, 0);
+	}
+
+	// only make sure to clip the content if there is content to clip
+	if (!wl_list_empty(&con->view->content_tree->children)) {
+		wlr_scene_subsurface_tree_set_clip(&con->view->content_tree->node, &(struct wlr_box){
+			.x = con->view->geometry.x,
+			.y = con->view->geometry.y,
+			.width = con->current.content_width,
+			.height = con->current.content_height,
+		});
+	}
 }
 
 struct sway_view *view_from_wlr_surface(struct wlr_surface *wlr_surface) {