osd: show alt-tab switcher center-aligned on all outputs

Fixes issue #283

include/labwc.h

@@ -183,8 +183,6 @@ struct server {
 #endif
 	/* Tree for built in menu */
 	struct wlr_scene_tree *menu_tree;
-	/* Tree for built in OSD / app switcher */
-	struct wlr_scene_tree *osd_tree;
 
 	struct wl_list outputs;
 	struct wl_listener new_output;
@@ -225,6 +223,7 @@ struct output {
 	struct wl_list layers[LAB_NR_LAYERS];
 	struct wlr_scene_tree *layer_tree[LAB_NR_LAYERS];
 	struct wlr_scene_tree *layer_popup_tree;
+	struct wlr_scene_tree *osd_tree;
 	struct wlr_box usable_area;
 
 	struct lab_data_buffer *osd_buffer;

src/debug.c

@@ -87,15 +87,15 @@ get_special(struct server *server, struct wlr_scene_node *node,
 	if (node == &server->scene->node) {
 		return "server->scene";
 	}
-	if (node == &server->osd_tree->node) {
-		return "server->osd_tree";
-	}
 	if (node == &server->menu_tree->node) {
 		return "server->menu_tree";
 	}
 	if (node->parent == &server->scene->node) {
 		struct output *output;
 		wl_list_for_each(output, &server->outputs, link) {
+			if (node == &output->osd_tree->node) {
+				return "output->osd_tree";
+			}
 			for (int i = 0; i < 4; i++) {
 				if (node == &output->layer_tree[i]->node) {
 					return get_layer_name(i);

src/desktop.c

@@ -284,7 +284,6 @@ desktop_node_and_view_at(struct server *server, double lx, double ly,
 		}
 #endif
 	}
-	struct wlr_scene_node *osd = &server->osd_tree->node;
 	while (node) {
 		struct node_descriptor *desc = node->data;
 		/* TODO: convert to switch() */
@@ -307,10 +306,6 @@ desktop_node_and_view_at(struct server *server, double lx, double ly,
 				return NULL;
 			}
 		}
-		if (node == osd) {
-			*view_area = LAB_SSD_OSD;
-			return NULL;
-		}
 		node = node->parent;
 	}
 	if (!node) {

src/osd.c

@@ -75,10 +75,10 @@ get_osd_height(struct wl_list *views)
 }
 
 static void
-destroy_osd_nodes(struct server *server)
+destroy_osd_nodes(struct output *output)
 {
 	struct wlr_scene_node *child, *next;
-	struct wl_list *children = &server->osd_tree->node.state.children;
+	struct wl_list *children = &output->osd_tree->node.state.children;
 	wl_list_for_each_safe(child, next, children, state.link) {
 		wlr_scene_node_destroy(child);
 	}
@@ -87,18 +87,25 @@ destroy_osd_nodes(struct server *server)
 void
 osd_finish(struct server *server)
 {
-	destroy_osd_nodes(server);
-	wlr_scene_node_set_enabled(&server->osd_tree->node, false);
+	struct output *output;
+	wl_list_for_each(output, &server->outputs, link) {
+		destroy_osd_nodes(output);
+		wlr_scene_node_set_enabled(&output->osd_tree->node, false);
+	}
 }
 
 void
 osd_update(struct server *server)
 {
+	if (wl_list_empty(&server->views)) {
+		return;
+	}
+
 	struct theme *theme = server->theme;
 
-	destroy_osd_nodes(server);
 	struct output *output;
 	wl_list_for_each(output, &server->outputs, link) {
+		destroy_osd_nodes(output);
 		float scale = output->wlr_output->scale;
 		int w = (OSD_ITEM_WIDTH + (2 * OSD_BORDER_WIDTH)) * scale;
 		int h = get_osd_height(&server->views) * scale;
@@ -201,10 +208,17 @@ osd_update(struct server *server)
 		cairo_surface_flush(surf);
 
 		struct wlr_scene_buffer *scene_buffer = wlr_scene_buffer_create(
-			&server->osd_tree->node, &output->osd_buffer->base);
+			&output->osd_tree->node, &output->osd_buffer->base);
 
-		/* TODO: set position properly */
-		wlr_scene_node_set_position(&scene_buffer->node, 10, 10);
-		wlr_scene_node_set_enabled(&server->osd_tree->node, true);
+		/* Center OSD */
+		struct wlr_box output_box;
+		wlr_output_layout_get_box(output->server->output_layout,
+			output->wlr_output, &output_box);
+		int lx = output->usable_area.x + output->usable_area.width / 2
+			- w / 2 + output_box.x;
+		int ly = output->usable_area.y + output->usable_area.height / 2
+			- h / 2 + output_box.y;
+		wlr_scene_node_set_position(&output->osd_tree->node, lx, ly);
+		wlr_scene_node_set_enabled(&output->osd_tree->node, true);
 	}
 }

src/output.c

@@ -142,6 +142,9 @@ new_output_notify(struct wl_listener *listener, void *data)
 	output->layer_popup_tree = wlr_scene_tree_create(&server->scene->node);
 	node_descriptor_create(&output->layer_popup_tree->node,
 		LAB_NODE_DESC_TREE, NULL);
+	output->osd_tree = wlr_scene_tree_create(&server->scene->node);
+	node_descriptor_create(&output->osd_tree->node,
+		LAB_NODE_DESC_TREE, NULL);
 
 	/*
 	 * Set the z-positions to achieve the following order (from top to

src/server.c

@@ -240,7 +240,6 @@ server_init(struct server *server)
 	server->unmanaged_tree = wlr_scene_tree_create(&server->scene->node);
 #endif
 	server->menu_tree = wlr_scene_tree_create(&server->scene->node);
-	server->osd_tree = wlr_scene_tree_create(&server->scene->node);
 
 	output_init(server);