swaybar: add overlay mode (fix #1620)

Overlay mode puts the bar above normal windows and passes through/ignores any
touch/mouse/keyboard events that would be sent to it.

include/swaybar/bar.h

@@ -58,6 +58,7 @@ struct swaybar_output {
 	struct zxdg_output_v1 *xdg_output;
 	struct wl_surface *surface;
 	struct zwlr_layer_surface_v1 *layer_surface;
+	struct wl_region *input_region;
 	uint32_t wl_name;
 
 	struct wl_list workspaces; // swaybar_workspace::link

sway/commands/bar/mode.c

@@ -20,6 +20,8 @@ static struct cmd_results *bar_set_mode(struct bar_config *bar, const char *mode
 		bar->mode = strdup("hide");
 	} else if (strcasecmp("invisible", mode) == 0) {
 		bar->mode = strdup("invisible");
+	} else if (strcasecmp("overlay", mode) == 0) {
+		bar->mode = strdup("overlay");
 	} else {
 		return cmd_results_new(CMD_INVALID, "Invalid value %s", mode);
 	}

sway/sway-bar.5.scd

@@ -84,11 +84,13 @@ Sway allows configuring swaybar in the sway configuration file.
 	debug-events`. To disable the default behavior for a button, use the
 	command _nop_.
 
-*mode* dock|hide|invisible
+*mode* dock|hide|invisible|overlay
 	Specifies the visibility of the bar. In _dock_ mode, it is permanently
 	visible at one edge of the screen. In _hide_ mode, it is hidden unless the
 	modifier key is pressed, though this behaviour depends on the hidden state.
-	In _invisible_ mode, it is permanently hidden. Default is _dock_.
+	In _invisible_ mode, it is permanently hidden. In _overlay_ mode, it is
+	permanently visible on top of other windows. (In _overlay_ mode the bar is
+	transparent to input events.) Default is _dock_.
 
 *hidden_state* hide|show
 	Specifies the behaviour of the bar when it is in _hide_ mode. When the

swaybar/bar.c

@@ -51,6 +51,9 @@ static void swaybar_output_free(struct swaybar_output *output) {
 	if (output->surface != NULL) {
 		wl_surface_destroy(output->surface);
 	}
+	if (output->input_region != NULL) {
+		wl_region_destroy(output->input_region);
+	}
 	zxdg_output_v1_destroy(output->xdg_output);
 	wl_output_destroy(output->output);
 	destroy_buffer(&output->buffers[0]);
@@ -100,16 +103,25 @@ static void add_layer_surface(struct swaybar_output *output) {
 
 	struct swaybar_config *config = bar->config;
 	bool hidden = strcmp(config->mode, "hide") == 0;
+	bool overlay = !hidden && strcmp(config->mode, "overlay") == 0;
 	output->layer_surface = zwlr_layer_shell_v1_get_layer_surface(
 			bar->layer_shell, output->surface, output->output,
-			hidden ? ZWLR_LAYER_SHELL_V1_LAYER_OVERLAY :
+			hidden || overlay ? ZWLR_LAYER_SHELL_V1_LAYER_OVERLAY :
 			ZWLR_LAYER_SHELL_V1_LAYER_BOTTOM, "panel");
 	assert(output->layer_surface);
 	zwlr_layer_surface_v1_add_listener(output->layer_surface,
 			&layer_surface_listener, output);
 
+	if (overlay) {
+		// Empty input region
+		output->input_region = wl_compositor_create_region(bar->compositor);
+		assert(output->input_region);
+
+		wl_surface_set_input_region(output->surface, output->input_region);
+	}
+
 	zwlr_layer_surface_v1_set_anchor(output->layer_surface, config->position);
-	if (hidden) {
+	if (hidden || overlay) {
 		zwlr_layer_surface_v1_set_exclusive_zone(output->layer_surface, -1);
 	}
 }