Add idle inhibitor support

With this, some apps (e.g. mpv) can block the idle tracker from
kicking in. This way, the screen won't blank (or whatever you
configured) when the application doesn't want it to.

cage.c

@@ -21,6 +21,7 @@
 #include <wlr/types/wlr_compositor.h>
 #include <wlr/types/wlr_data_device.h>
 #include <wlr/types/wlr_idle.h>
+#include <wlr/types/wlr_idle_inhibit_v1.h>
 #include <wlr/types/wlr_output_layout.h>
 #if CAGE_HAS_XWAYLAND
 #include <wlr/types/wlr_xcursor_manager.h>
@@ -31,6 +32,7 @@
 #include <wlr/xwayland.h>
 #endif
 
+#include "idle_inhibit_v1.h"
 #include "output.h"
 #include "seat.h"
 #include "server.h"
@@ -159,6 +161,16 @@ main(int argc, char *argv[])
 		goto end;
 	}
 
+	server.idle_inhibit_v1 = wlr_idle_inhibit_v1_create(server.wl_display);
+	if (!server.idle_inhibit_v1) {
+		wlr_log(WLR_ERROR, "Cannot create the idle inhibitor");
+		ret = 1;
+		goto end;
+	}
+	server.new_idle_inhibitor_v1.notify = handle_idle_inhibitor_v1_new;
+	wl_signal_add(&server.idle_inhibit_v1->events.new_inhibitor, &server.new_idle_inhibitor_v1);
+	wl_list_init(&server.inhibitors);
+		
 	xdg_shell = wlr_xdg_shell_create(server.wl_display);
 	if (!xdg_shell) {
 		wlr_log(WLR_ERROR, "Unable to create the XDG shell interface");
@@ -236,6 +248,7 @@ end:
 	wlr_xcursor_manager_destroy(xcursor_manager);
 #endif
 	wlr_xdg_shell_destroy(xdg_shell);
+	wlr_idle_inhibit_v1_destroy(server.idle_inhibit_v1);
 	if (server.idle) {
 		wlr_idle_destroy(server.idle);
 	}

idle_inhibit_v1.c

@@ -0,0 +1,69 @@
+/*
+ * Cage: A Wayland kiosk.
+ * 
+ * Copyright (C) 2018-2019 Jente Hidskes
+ *
+ * See the LICENSE file accompanying this file.
+ */
+
+#include <stdlib.h>
+#include <wayland-server.h>
+#include <wlr/types/wlr_idle.h>
+#include <wlr/types/wlr_idle_inhibit_v1.h>
+
+#include "idle_inhibit_v1.h"
+#include "server.h"
+
+struct cg_idle_inhibitor_v1 {
+	struct cg_server *server;
+
+	struct wl_list link; // server::inhibitors
+	struct wl_listener destroy;
+};
+
+static void
+idle_inhibit_v1_check_active(struct cg_server *server)
+{
+	/* Due to Cage's unique window management, we don't need to
+	   check for visibility. In the worst cage, the inhibitor is
+	   spawned by a dialog that _may_ be obscured by another
+	   dialog, but this is really an edge case that, until
+	   reported, does not warrant the additional complexity.
+	   Hence, we simply check for any inhibitors and inhibit
+	   accordingly. */
+	bool inhibited = !wl_list_empty(&server->inhibitors);
+	wlr_idle_set_enabled(server->idle, NULL, !inhibited);
+}
+
+static void
+handle_destroy(struct wl_listener *listener, void *data)
+{
+	struct cg_idle_inhibitor_v1 *inhibitor = wl_container_of(listener, inhibitor, destroy);
+	struct cg_server *server = inhibitor->server;
+
+	wl_list_remove(&inhibitor->link);
+	wl_list_remove(&inhibitor->destroy.link);
+	free(inhibitor);
+
+	idle_inhibit_v1_check_active(server);
+}
+
+void
+handle_idle_inhibitor_v1_new(struct wl_listener *listener, void *data)
+{
+	struct cg_server *server = wl_container_of(listener, server, new_idle_inhibitor_v1);
+	struct wlr_idle_inhibitor_v1 *wlr_inhibitor = data;
+
+	struct cg_idle_inhibitor_v1 *inhibitor = calloc(1, sizeof(struct cg_idle_inhibitor_v1));
+	if (!inhibitor) {
+		return;
+	}
+
+	inhibitor->server = server;
+	wl_list_insert(&server->inhibitors, &inhibitor->link);
+
+	inhibitor->destroy.notify = handle_destroy;
+	wl_signal_add(&wlr_inhibitor->events.destroy, &inhibitor->destroy);
+
+	idle_inhibit_v1_check_active(server);
+}

idle_inhibit_v1.h

@@ -0,0 +1,8 @@
+#ifndef CG_IDLE_INHIBIT_H
+#define CG_IDLE_INHIBIT_H
+
+#include <wayland-server.h>
+
+void handle_idle_inhibitor_v1_new(struct wl_listener *listener, void *data);
+
+#endif

meson.build

@@ -56,6 +56,7 @@ conf_data.set10('CAGE_HAS_XWAYLAND', get_option('xwayland'))
 
 cage_sources = [
   'cage.c',
+  'idle_inhibit_v1.c',
   'output.c',
   'seat.c',
   'view.c',
@@ -66,6 +67,7 @@ cage_headers = [
   configure_file(input: 'config.h.in',
 		 output: 'config.h',
 		 configuration: conf_data),
+  'idle_inhibit_v1.h',
   'output.h',
   'seat.h',
   'server.h',

server.h

@@ -6,6 +6,7 @@
 #include <wayland-server.h>
 #include <wlr/backend.h>
 #include <wlr/types/wlr_idle.h>
+#include <wlr/types/wlr_idle_inhibit_v1.h>
 #include <wlr/types/wlr_output_layout.h>
 #if CAGE_HAS_XWAYLAND
 #include <wlr/xwayland.h>
@@ -23,6 +24,9 @@ struct cg_server {
 
 	struct cg_seat *seat;
 	struct wlr_idle *idle;
+	struct wlr_idle_inhibit_manager_v1 *idle_inhibit_v1;
+	struct wl_listener new_idle_inhibitor_v1;
+	struct wl_list inhibitors;
 
 	struct wlr_output_layout *output_layout;
 	struct cg_output *output;