alt-tab preview: restore functionality after move to scene-graph

include/common/scene-helpers.h

@@ -1,7 +1,17 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
-#include <wlr/types/wlr_scene.h>
+struct wlr_scene_node;
+struct wlr_scene_rect;
+struct wlr_scene_tree;
+struct wlr_surface;
 
 struct wlr_scene_rect *lab_wlr_scene_get_rect(struct wlr_scene_node *node);
 struct wlr_scene_tree *lab_scene_tree_from_node(struct wlr_scene_node *node);
 struct wlr_surface *lab_wlr_surface_from_node(struct wlr_scene_node *node);
+
+/**
+ * lab_get_prev_node - return previous (sibling) node
+ * @node: node to find the previous node from
+ * Return NULL if previous link is list-head which means node is bottom-most
+ */
+struct wlr_scene_node *lab_wlr_scene_get_prev_node(struct wlr_scene_node *node);

include/labwc.h

@@ -233,6 +233,7 @@ struct server {
 	/* Set when in cycle (alt-tab) mode */
 	struct osd_state {
 		struct view *cycle_view;
+		bool preview_was_enabled;
 		struct wlr_scene_node *preview_node;
 		struct wlr_scene_node *preview_anchor;
 	} osd_state;
@@ -577,9 +578,12 @@ void server_init(struct server *server);
 void server_start(struct server *server);
 void server_finish(struct server *server);
 
-/* update onscreen display 'alt-tab' buffer */
+/* Updates onscreen display 'alt-tab' buffer */
-void osd_finish(struct server *server);
 void osd_update(struct server *server);
+/* Closes the OSD */
+void osd_finish(struct server *server);
+/* Moves preview views back into their original stacking order and state */
+void osd_preview_restore(struct server *server);
 
 /*
  * wlroots "input inhibitor" extension (required for swaylock) blocks

src/common/scene-helpers.c

@@ -32,3 +32,15 @@ lab_wlr_surface_from_node(struct wlr_scene_node *node)
 	}
 	return NULL;
 }
+
+struct wlr_scene_node *
+lab_wlr_scene_get_prev_node(struct wlr_scene_node *node)
+{
+	assert(node);
+	struct wlr_scene_node *prev;
+	prev = wl_container_of(node->link.prev, node, link);
+	if (&prev->link == &node->parent->children) {
+		return NULL;
+	}
+	return prev;
+}

src/desktop.c

@@ -203,6 +203,9 @@ desktop_cycle_view(struct server *server, struct view *start_view,
 	/* Scene nodes are ordered like last node == displayed topmost */
 	iter = dir == LAB_CYCLE_DIR_FORWARD ? get_prev_item : get_next_item;
 
+	/* Make sure to have all nodes in their actual ordering */
+	osd_preview_restore(server);
+
 	do {
 		list_item = iter(list_item);
 		if (list_item == list_head) {

src/keyboard.c

@@ -150,6 +150,7 @@ handle_compositor_keybindings(struct wl_listener *listener,
 			for (int i = 0; i < nsyms; i++) {
 				if (syms[i] == XKB_KEY_Escape) {
 					/* cancel */
+					osd_preview_restore(server);
 					/* osd_finish() additionally resets cycle_view to NULL */
 					osd_finish(server);
 					return true;

src/osd.c

@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0-only
 #include "config.h"
+#include <assert.h>
 #include <cairo.h>
 #include <drm_fourcc.h>
 #include <pango/pangocairo.h>
@@ -8,6 +9,7 @@
 #include "common/buf.h"
 #include "common/font.h"
 #include "common/graphic-helpers.h"
+#include "common/scene-helpers.h"
 #include "config/rcxml.h"
 #include "labwc.h"
 #include "theme.h"
@@ -110,6 +112,8 @@ void
 osd_finish(struct server *server)
 {
 	server->osd_state.cycle_view = NULL;
+	server->osd_state.preview_node = NULL;
+	server->osd_state.preview_anchor = NULL;
 
 	struct output *output;
 	wl_list_for_each(output, &server->outputs, link) {
@@ -123,6 +127,53 @@ osd_finish(struct server *server)
 	}
 }
 
+void
+osd_preview_restore(struct server *server)
+{
+	struct osd_state *osd_state = &server->osd_state;
+	if (osd_state->preview_node) {
+		if (osd_state->preview_anchor) {
+			wlr_scene_node_place_above(osd_state->preview_node,
+				osd_state->preview_anchor);
+		} else {
+			/* Selected view was the first node */
+			wlr_scene_node_lower_to_bottom(osd_state->preview_node);
+		}
+
+		/* Node was disabled / minimized before, disable again */
+		if (!osd_state->preview_was_enabled) {
+			wlr_scene_node_set_enabled(osd_state->preview_node, false);
+		}
+		osd_state->preview_node = NULL;
+		osd_state->preview_anchor = NULL;
+	}
+}
+
+static void
+preview_cycled_view(struct view *view)
+{
+	assert(view);
+	assert(view->scene_tree);
+	struct osd_state *osd_state = &view->server->osd_state;
+
+	/* Move previous selected node back to its original place */
+	osd_preview_restore(view->server);
+
+	/* Remember the sibling right before the selected node */
+	osd_state->preview_node = &view->scene_tree->node;
+	osd_state->preview_anchor = lab_wlr_scene_get_prev_node(
+		osd_state->preview_node);
+
+	/* Store node enabled / minimized state and force-enable if disabled */
+	osd_state->preview_was_enabled = osd_state->preview_node->enabled;
+	if (!osd_state->preview_was_enabled) {
+		wlr_scene_node_set_enabled(osd_state->preview_node, true);
+	}
+
+	/* Finally raise selected node to the top */
+	wlr_scene_node_raise_to_top(osd_state->preview_node);
+}
+
 void
 osd_update(struct server *server)
 {
@@ -294,4 +345,8 @@ osd_update(struct server *server)
 		wlr_scene_node_set_enabled(&output->osd_tree->node, true);
 	}
 	free(buf.buf);
+
+	if (rc.cycle_preview_contents) {
+		preview_cycled_view(server->osd_state.cycle_view);
+	}
 }

src/view.c

@@ -3,6 +3,7 @@
 #include <stdio.h>
 #include <strings.h>
 #include <xcb/xcb_icccm.h>
+#include "common/scene-helpers.h"
 #include "labwc.h"
 #include "ssd.h"
 #include "menu/menu.h"
@@ -833,8 +834,16 @@ view_destroy(struct view *view)
 	}
 
 	if (view->scene_tree) {
+		struct wlr_scene_node *node = &view->scene_tree->node;
+		if (osd_state->preview_anchor == node) {
+			/*
+			 * If we are the anchor for the current OSD selected view,
+			 * replace the anchor with the node before us.
+			 */
+			osd_state->preview_anchor = lab_wlr_scene_get_prev_node(node);
+		}
 		ssd_destroy(view);
-		wlr_scene_node_destroy(&view->scene_tree->node);
+		wlr_scene_node_destroy(node);
 		view->scene_tree = NULL;
 	}