view: decouple always-on-top windows from the omnipresent state

Before this commit, always-on-{top,bottom} windows were always visible
on all workspaces (omnipresent) because the they were not in
per-workspace trees like normal windows.

This commit fixes this by introducing per-layer trees in
`struct workspace`.

I also added `enum view_layer` and `view->layer` for simplicity.

include/config/types.h

@@ -62,10 +62,7 @@ enum lab_view_criteria {
 	/* No filter -> all focusable views */
 	LAB_VIEW_CRITERIA_NONE = 0,
 
-	/*
-	 * Includes always-on-top views, e.g.
-	 * what is visible on the current workspace
-	 */
+	/* Includes omnipresent (visible on all desktops) views */
 	LAB_VIEW_CRITERIA_CURRENT_WORKSPACE       = 1 << 0,
 
 	/* Positive criteria */

include/labwc.h

@@ -231,10 +231,6 @@ struct server {
 	 * them to this dedicated tree
 	 */
 	struct wlr_scene_tree *xdg_popup_tree;
-
-	/* Tree for all non-layer xdg/xwayland-shell surfaces with always-on-top/below */
-	struct wlr_scene_tree *view_tree_always_on_top;
-	struct wlr_scene_tree *view_tree_always_on_bottom;
 #if HAVE_XWAYLAND
 	/* Tree for unmanaged xsurfaces without initialized view (usually popups) */
 	struct wlr_scene_tree *unmanaged_tree;

include/view.h

@@ -82,6 +82,12 @@ enum view_wants_focus {
 	VIEW_WANTS_FOCUS_UNLIKELY,
 };
 
+enum view_layer {
+	VIEW_LAYER_NORMAL = 0,
+	VIEW_LAYER_ALWAYS_ON_TOP,
+	VIEW_LAYER_ALWAYS_ON_BOTTOM,
+};
+
 struct view;
 struct wlr_surface;
 struct foreign_toplevel;
@@ -183,6 +189,7 @@ struct view {
 	bool fullscreen;
 	bool tearing_hint;
 	enum lab_tristate force_tearing;
+	enum view_layer layer;
 	bool visible_on_all_workspaces;
 	enum lab_edge tiled;
 	enum lab_edge edges_visible;
@@ -527,9 +534,6 @@ void view_toggle_maximize(struct view *view, enum view_axis axis);
 bool view_wants_decorations(struct view *view);
 void view_toggle_decorations(struct view *view);
 
-bool view_is_always_on_top(struct view *view);
-bool view_is_always_on_bottom(struct view *view);
-bool view_is_omnipresent(struct view *view);
 void view_toggle_always_on_top(struct view *view);
 void view_toggle_always_on_bottom(struct view *view);
 void view_toggle_visible_on_all_workspaces(struct view *view);

include/workspaces.h

@@ -16,6 +16,7 @@ struct workspace {
 
 	char *name;
 	struct wlr_scene_tree *tree;
+	struct wlr_scene_tree *view_trees[3];
 
 	struct lab_cosmic_workspace *cosmic_workspace;
 	struct {

src/debug.c

@@ -88,9 +88,25 @@ get_view_part(struct view *view, struct wlr_scene_node *node)
 	return ssd_debug_get_node_name(view->ssd, node);
 }
 
+static struct workspace *
+get_workspace_from_node(struct server *server, struct wlr_scene_node *node)
+{
+	struct workspace *workspace;
+	wl_list_for_each(workspace, &server->workspaces.all, link) {
+		if (&workspace->tree->node == node) {
+			return workspace;
+		}
+	}
+	return NULL;
+}
+
 static const char *
 get_special(struct server *server, struct wlr_scene_node *node)
 {
+	struct wlr_scene_tree *grand_parent =
+		node->parent ? node->parent->node.parent : NULL;
+	struct wlr_scene_tree *grand_grand_parent =
+		grand_parent ? grand_parent->node.parent : NULL;
 	if (node == &server->scene->tree.node) {
 		return "server->scene";
 	}
@@ -100,21 +116,28 @@ get_special(struct server *server, struct wlr_scene_node *node)
 	if (node == &server->view_tree->node) {
 		return "server->view_tree";
 	}
-	if (node == &server->view_tree_always_on_bottom->node) {
-		return "server->always_on_bottom";
-	}
-	if (node == &server->view_tree_always_on_top->node) {
-		return "server->always_on_top";
-	}
 	if (node->parent == server->view_tree) {
-		struct workspace *workspace;
-		wl_list_for_each(workspace, &server->workspaces.all, link) {
-			if (&workspace->tree->node == node) {
-				return workspace->name;
-			}
+		struct workspace *workspace = get_workspace_from_node(server, node);
+		if (workspace) {
+			return workspace->name;
 		}
 		return "unknown workspace";
 	}
+	if (grand_parent == server->view_tree) {
+		struct workspace *workspace =
+			get_workspace_from_node(server, &node->parent->node);
+		if (workspace) {
+			struct wlr_scene_tree **trees = workspace->view_trees;
+			if (node == &trees[VIEW_LAYER_NORMAL]->node) {
+				return "normal";
+			} else if (node == &trees[VIEW_LAYER_ALWAYS_ON_TOP]->node) {
+				return "always_on_top";
+			} else if (node == &trees[VIEW_LAYER_ALWAYS_ON_BOTTOM]->node) {
+				return "always_on_bottom";
+			}
+		}
+		return "unknown tree";
+	}
 	if (node->parent == &server->scene->tree) {
 		struct output *output;
 		wl_list_for_each(output, &server->outputs, link) {
@@ -160,12 +183,7 @@ get_special(struct server *server, struct wlr_scene_node *node)
 		return "server->unmanaged_tree";
 	}
 #endif
-	struct wlr_scene_tree *grand_parent =
-		node->parent ? node->parent->node.parent : NULL;
-	if (grand_parent == server->view_tree && node->data) {
-		last_view = node_view_from_node(node);
-	}
-	if (node->parent == server->view_tree_always_on_top && node->data) {
+	if (grand_grand_parent == server->view_tree && node->data) {
 		last_view = node_view_from_node(node);
 	}
 	const char *view_part = get_view_part(last_view, node);

src/desktop.c

@@ -96,9 +96,9 @@ desktop_focus_view(struct view *view, bool raise)
 
 	/*
 	 * Switch workspace if necessary to make the view visible
-	 * (unnecessary for "always on {top,bottom}" views).
+	 * (unnecessary for omnipresent views).
 	 */
-	if (!view_is_always_on_top(view) && !view_is_always_on_bottom(view)) {
+	if (!view->visible_on_all_workspaces) {
 		workspaces_switch_to(view->workspace, /*update_focus*/ false);
 	}
 

src/server.c

@@ -576,16 +576,12 @@ server_init(struct server *server)
 	 * | output->layer_tree[2]              | top layer surfaces (e.g. waybar)
 	 * | server->unmanaged_tree             | unmanaged X11 surfaces (e.g. dmenu)
 	 * | server->xdg_popup_tree             | xdg popups on xdg windows
-	 * | server->view_tree_always_on_top    | always-on-top xdg/X11 windows
-	 * | server->view_tree                  | normal xdg/X11 windows (e.g. firefox)
-	 * | server->view_tree_always_on_bottom | always-on-bottom xdg/X11 windows
+	 * | server->view_tree                  | xdg/X11 windows (e.g. firefox)
 	 * | output->layer_tree[1]              | bottom layer surfaces
 	 * | output->layer_tree[0]              | background layer surfaces (e.g. swaybg)
 	 */
 
-	server->view_tree_always_on_bottom = wlr_scene_tree_create(&server->scene->tree);
 	server->view_tree = wlr_scene_tree_create(&server->scene->tree);
-	server->view_tree_always_on_top = wlr_scene_tree_create(&server->scene->tree);
 	server->xdg_popup_tree = wlr_scene_tree_create(&server->scene->tree);
 #if HAVE_XWAYLAND
 	server->unmanaged_tree = wlr_scene_tree_create(&server->scene->tree);

src/view.c

@@ -267,13 +267,7 @@ matches_criteria(struct view *view, enum lab_view_criteria criteria)
 		return false;
 	}
 	if (criteria & LAB_VIEW_CRITERIA_CURRENT_WORKSPACE) {
-		/*
-		 * Always-on-top views are always on the current desktop and are
-		 * special in that they live in a different tree.
-		 */
-		struct server *server = view->server;
-		if (view->scene_tree->node.parent != server->workspaces.current->tree
-				&& !view_is_always_on_top(view)) {
+		if (view->workspace != view->server->workspaces.current) {
 			return false;
 		}
 	}
@@ -283,7 +277,7 @@ matches_criteria(struct view *view, enum lab_view_criteria criteria)
 		}
 	}
 	if (criteria & LAB_VIEW_CRITERIA_ALWAYS_ON_TOP) {
-		if (!view_is_always_on_top(view)) {
+		if (view->layer != VIEW_LAYER_ALWAYS_ON_TOP) {
 			return false;
 		}
 	}
@@ -293,7 +287,7 @@ matches_criteria(struct view *view, enum lab_view_criteria criteria)
 		}
 	}
 	if (criteria & LAB_VIEW_CRITERIA_NO_ALWAYS_ON_TOP) {
-		if (view_is_always_on_top(view)) {
+		if (view->layer == VIEW_LAYER_ALWAYS_ON_TOP) {
 			return false;
 		}
 	}
@@ -303,11 +297,7 @@ matches_criteria(struct view *view, enum lab_view_criteria criteria)
 		}
 	}
 	if (criteria & LAB_VIEW_CRITERIA_NO_OMNIPRESENT) {
-		/*
-		 * TODO: Once always-on-top views use a per-workspace
-		 *       sub-tree we can remove the check from this condition.
-		 */
-		if (view->visible_on_all_workspaces || view_is_always_on_top(view)) {
+		if (view->visible_on_all_workspaces) {
 			return false;
 		}
 	}
@@ -1549,48 +1539,30 @@ view_toggle_decorations(struct view *view)
 	}
 }
 
-bool
-view_is_always_on_top(struct view *view)
-{
-	assert(view);
-	return view->scene_tree->node.parent ==
-		view->server->view_tree_always_on_top;
-}
-
 void
 view_toggle_always_on_top(struct view *view)
 {
 	assert(view);
-	if (view_is_always_on_top(view)) {
-		view->workspace = view->server->workspaces.current;
-		wlr_scene_node_reparent(&view->scene_tree->node,
-			view->workspace->tree);
+	if (view->layer == VIEW_LAYER_ALWAYS_ON_TOP) {
+		view->layer = VIEW_LAYER_NORMAL;
 	} else {
-		wlr_scene_node_reparent(&view->scene_tree->node,
-			view->server->view_tree_always_on_top);
+		view->layer = VIEW_LAYER_ALWAYS_ON_TOP;
 	}
-}
-
-bool
-view_is_always_on_bottom(struct view *view)
-{
-	assert(view);
-	return view->scene_tree->node.parent ==
-		view->server->view_tree_always_on_bottom;
+	wlr_scene_node_reparent(&view->scene_tree->node,
+		view->workspace->view_trees[view->layer]);
 }
 
 void
 view_toggle_always_on_bottom(struct view *view)
 {
 	assert(view);
-	if (view_is_always_on_bottom(view)) {
-		view->workspace = view->server->workspaces.current;
-		wlr_scene_node_reparent(&view->scene_tree->node,
-			view->workspace->tree);
+	if (view->layer == VIEW_LAYER_ALWAYS_ON_BOTTOM) {
+		view->layer = VIEW_LAYER_NORMAL;
 	} else {
-		wlr_scene_node_reparent(&view->scene_tree->node,
-			view->server->view_tree_always_on_bottom);
+		view->layer = VIEW_LAYER_ALWAYS_ON_BOTTOM;
 	}
+	wlr_scene_node_reparent(&view->scene_tree->node,
+		view->workspace->view_trees[view->layer]);
 }
 
 void
@@ -1609,7 +1581,7 @@ view_move_to_workspace(struct view *view, struct workspace *workspace)
 	if (view->workspace != workspace) {
 		view->workspace = workspace;
 		wlr_scene_node_reparent(&view->scene_tree->node,
-			workspace->tree);
+			workspace->view_trees[view->layer]);
 	}
 }
 

src/workspaces.c

@@ -235,6 +235,12 @@ add_workspace(struct server *server, const char *name)
 	workspace->server = server;
 	workspace->name = xstrdup(name);
 	workspace->tree = wlr_scene_tree_create(server->view_tree);
+	workspace->view_trees[VIEW_LAYER_ALWAYS_ON_BOTTOM] =
+		wlr_scene_tree_create(workspace->tree);
+	workspace->view_trees[VIEW_LAYER_NORMAL] =
+		wlr_scene_tree_create(workspace->tree);
+	workspace->view_trees[VIEW_LAYER_ALWAYS_ON_TOP] =
+		wlr_scene_tree_create(workspace->tree);
 	wl_list_append(&server->workspaces.all, &workspace->link);
 	wlr_scene_node_set_enabled(&workspace->tree->node, false);
 
@@ -483,24 +489,17 @@ workspaces_switch_to(struct workspace *target, bool update_focus)
 	server->workspaces.current = target;
 
 	struct view *grabbed_view = server->grabbed_view;
-	if (grabbed_view && !view_is_always_on_top(grabbed_view)) {
+	if (grabbed_view) {
 		view_move_to_workspace(grabbed_view, target);
 	}
 
 	/*
 	 * Make sure we are focusing what the user sees. Only refocus if
-	 * the focus is not already on an omnipresent or always-on-top view.
-	 *
-	 * TODO: Decouple always-on-top views from the omnipresent state.
-	 *       One option for that would be to create a new scene tree
-	 *       as child of every workspace tree and then reparent a-o-t
-	 *       windows to that one. Combined with adjusting the condition
-	 *       below that should take care of the issue.
+	 * the focus is not already on an omnipresent view.
 	 */
 	if (update_focus) {
 		struct view *active_view = server->active_view;
-		if (!active_view || (!active_view->visible_on_all_workspaces
-				&& !view_is_always_on_top(active_view))) {
+		if (!(active_view && active_view->visible_on_all_workspaces)) {
 			desktop_focus_topmost_view(server);
 		}
 	}

src/xdg.c

@@ -1019,7 +1019,8 @@ handle_new_xdg_toplevel(struct wl_listener *listener, void *data)
 	}
 
 	view->workspace = server->workspaces.current;
-	view->scene_tree = wlr_scene_tree_create(view->workspace->tree);
+	view->scene_tree = wlr_scene_tree_create(
+		view->workspace->view_trees[VIEW_LAYER_NORMAL]);
 	wlr_scene_node_set_enabled(&view->scene_tree->node, false);
 
 	struct wlr_scene_tree *tree = wlr_scene_xdg_surface_create(

src/xwayland.c

@@ -1010,7 +1010,8 @@ xwayland_view_create(struct server *server,
 	xsurface->data = view;
 
 	view->workspace = server->workspaces.current;
-	view->scene_tree = wlr_scene_tree_create(view->workspace->tree);
+	view->scene_tree = wlr_scene_tree_create(
+		view->workspace->view_trees[VIEW_LAYER_NORMAL]);
 	node_descriptor_create(&view->scene_tree->node,
 		LAB_NODE_VIEW, view, /*data*/ NULL);