layer: improve keyboard-interactivity

- Process layer-shell keyboard interactivity in the map and commit
  handlers only, rather than in layers_arrange(). This allows handling of
  the layer-surface that emitted the event rather than iterating over all
  surfaces in the output layer-tree, and therefore avoids having to guess
  which surface should have keyboard preference (and it might not be the
  last one added to the list which was the assumption previously).

- Prevent seat_focus_surface() from setting keyboard focus if a layer-shell
  surface with exclusive keyboard-interactivity has the focus.

- Set cursor_context type for layer-surfaces without node-descriptors
  in order to set keyboard focus correctly in cursor_button_press().

Tested satisfactorily with xfce4-panel and gtk-layer-demo.

Fixes #725 and #704

src/desktop.c

@@ -323,6 +323,7 @@ get_cursor_context(struct server *server)
 		ret.type = LAB_SSD_ROOT;
 		return ret;
 	}
+
 #if HAVE_XWAYLAND
 	if (node->type == WLR_SCENE_NODE_BUFFER) {
 		struct wlr_surface *surface = lab_wlr_surface_from_node(node);
@@ -382,6 +383,9 @@ get_cursor_context(struct server *server)
 		if (node->type == WLR_SCENE_NODE_BUFFER) {
 			struct wlr_surface *surface = lab_wlr_surface_from_node(node);
 			if (surface) {
+				if (wlr_surface_is_layer_surface(surface)) {
+					ret.type = LAB_SSD_LAYER_SURFACE;
+				}
 				if (is_layer_descendant(node)) {
 					/*
 					 * layer-shell subsurfaces need to be

src/layers.c

@@ -75,38 +75,6 @@ layers_arrange(struct output *output)
 	}
 
 	output->usable_area = usable_area;
-
-	/* Find topmost keyboard interactive layer, if such a layer exists */
-	uint32_t layers_above_views[] = {
-		ZWLR_LAYER_SHELL_V1_LAYER_OVERLAY,
-		ZWLR_LAYER_SHELL_V1_LAYER_TOP,
-	};
-	size_t nlayers = sizeof(layers_above_views) / sizeof(layers_above_views[0]);
-	struct lab_layer_surface *topmost = NULL;
-	struct wlr_scene_node *node;
-	for (size_t i = 0; i < nlayers; ++i) {
-		struct wlr_scene_tree *tree = output->layer_tree[layers_above_views[i]];
-		/* Iterate in reverse to give most recent node preference */
-		wl_list_for_each_reverse(node, &tree->children, link) {
-			struct lab_layer_surface *surface = node_layer_surface_from_node(node);
-			struct wlr_scene_layer_surface_v1 *scene = surface->scene_layer_surface;
-			if (scene->layer_surface->current.keyboard_interactive) {
-				topmost = surface;
-				break;
-			}
-		}
-		if (topmost) {
-			break;
-		}
-	}
-	struct seat *seat = &output->server->seat;
-	if (topmost) {
-		seat_set_focus_layer(seat,
-			topmost->scene_layer_surface->layer_surface);
-	} else if (seat->focused_layer &&
-			!seat->focused_layer->current.keyboard_interactive) {
-		seat_set_focus_layer(seat, NULL);
-	}
 }
 
 static void
@@ -118,6 +86,48 @@ handle_output_destroy(struct wl_listener *listener, void *data)
 	wlr_layer_surface_v1_destroy(layer->scene_layer_surface->layer_surface);
 }
 
+static void
+process_keyboard_interactivity(struct lab_layer_surface *layer)
+{
+	struct wlr_layer_surface_v1 *layer_surface = layer->scene_layer_surface->layer_surface;
+	struct seat *seat = &layer->server->seat;
+
+	if (layer_surface->current.keyboard_interactive
+			&& layer_surface->current.layer >= ZWLR_LAYER_SHELL_V1_LAYER_TOP) {
+		/*
+		 * Give keyboard focus to surface if
+		 * - keyboard-interactivity is 'exclusive' or 'on-demand'; and
+		 * - surface is in top/overlay layers; and
+		 * - currently focused layer has a lower precedence
+		 *
+		 * In other words, when dealing with two surfaces with
+		 * exclusive/on-demand keyboard-interactivity (firstly the
+		 * currently focused 'focused_layer' and secondly the
+		 * 'layer_surface' for which we're just responding to a
+		 * map/commit event), the following logic applies:
+		 *
+		 * | focused_layer | layer_surface | who gets keyboard focus |
+		 * |---------------|---------------|-------------------------|
+		 * | overlay       | top           | focused_layer           |
+		 * | overlay       | overlay       | layer_surface           |
+		 * | top           | top           | layer_surface           |
+		 * | top           | overlay       | layer_surface           |
+		 */
+
+		if (!seat->focused_layer || seat->focused_layer->current.layer
+				<= layer_surface->current.layer) {
+			seat_set_focus_layer(seat, layer_surface);
+		}
+	} else if (seat->focused_layer
+			&& !seat->focused_layer->current.keyboard_interactive) {
+		/*
+		 * Clear focus if keyboard-interactivity has been set to
+		 * ZWLR_LAYER_SURFACE_V1_KEYBOARD_INTERACTIVITY_NONE
+		 */
+		seat_set_focus_layer(seat, NULL);
+	}
+}
+
 static void
 handle_surface_commit(struct wl_listener *listener, void *data)
 {
@@ -140,6 +150,10 @@ handle_surface_commit(struct wl_listener *listener, void *data)
 		wlr_scene_node_reparent(&layer->scene_layer_surface->tree->node,
 			output->layer_tree[layer_surface->current.layer]);
 	}
+	/* Process keyboard-interactivity change */
+	if (committed & WLR_LAYER_SURFACE_V1_STATE_KEYBOARD_INTERACTIVITY) {
+		process_keyboard_interactivity(layer);
+	}
 
 	if (committed || layer->mapped != layer_surface->mapped) {
 		layer->mapped = layer_surface->mapped;
@@ -158,6 +172,12 @@ handle_node_destroy(struct wl_listener *listener, void *data)
 	struct lab_layer_surface *layer =
 		wl_container_of(listener, layer, node_destroy);
 
+	/*
+	 * TODO: Determine if this layer is being used by an exclusive client.
+	 * If it is, try and find another layer owned by this client to pass
+	 * focus to.
+	 */
+
 	wl_list_remove(&layer->map.link);
 	wl_list_remove(&layer->unmap.link);
 	wl_list_remove(&layer->surface_commit.link);
@@ -197,6 +217,8 @@ handle_map(struct wl_listener *listener, void *data)
 	 * automatically based on the position of the surface and outputs in
 	 * the scene. See wlr_scene_surface_create() documentation.
 	 */
+
+	process_keyboard_interactivity(layer);
 }
 
 static void

src/seat.c

@@ -440,8 +440,8 @@ seat_reconfigure(struct server *server)
 	}
 }
 
-void
+static void
-seat_focus_surface(struct seat *seat, struct wlr_surface *surface)
+seat_focus(struct seat *seat, struct wlr_surface *surface)
 {
 	if (!surface) {
 		wlr_seat_keyboard_notify_clear_focus(seat->seat);
@@ -469,6 +469,17 @@ seat_focus_surface(struct seat *seat, struct wlr_surface *surface)
 	constrain_cursor(server, constraint);
 }
 
+void
+seat_focus_surface(struct seat *seat, struct wlr_surface *surface)
+{
+	/* Respect layer-shell exlusive keyboard-interactivity. */
+	if (seat->focused_layer && seat->focused_layer->current.keyboard_interactive
+			== ZWLR_LAYER_SURFACE_V1_KEYBOARD_INTERACTIVITY_EXCLUSIVE) {
+		return;
+	}
+	seat_focus(seat, surface);
+}
+
 void
 seat_set_focus_layer(struct seat *seat, struct wlr_layer_surface_v1 *layer)
 {
@@ -477,7 +488,7 @@ seat_set_focus_layer(struct seat *seat, struct wlr_layer_surface_v1 *layer)
 		desktop_focus_topmost_mapped_view(seat->server);
 		return;
 	}
-	seat_focus_surface(seat, layer->surface);
+	seat_focus(seat, layer->surface);
 	if (layer->current.layer >= ZWLR_LAYER_SHELL_V1_LAYER_TOP) {
 		seat->focused_layer = layer;
 	}