util: add Util.spawn and friends

Add Util.spawn, Util.spawnCommandLine, and Util.spawnDesktop for
spawning a command/argv/.desktop file in the background, automatically
handling errors via MessageTray.SystemNotificationSource(), and
Util.trySpawn, Util.trySpawnCommandLine, and Utils.trySpawnDesktop
that don't do automatic error handling (but do at least clean up the
error message in the exception a bit).

Update various other bits of code around the shell to use the new
methods.

https://bugzilla.gnome.org/show_bug.cgi?id=635089

js/misc/util.js

@@ -1,5 +1,16 @@
 /* -*- mode: js2; js2-basic-offset: 4; indent-tabs-mode: nil -*- */
 
+const Gdk = imports.gi.Gdk;
+const Gio = imports.gi.Gio;
+const GLib = imports.gi.GLib;
+const Shell = imports.gi.Shell;
+
+const Main = imports.ui.main;
+const MessageTray = imports.ui.messageTray;
+
+const Gettext = imports.gettext.domain('gnome-shell');
+const _ = Gettext.gettext;
+
 /* http://daringfireball.net/2010/07/improved_regex_for_matching_urls */
 const _urlRegexp = new RegExp('\b(([a-z][\w-]+:(/{1,3}|[a-z0-9%])|www\d{0,3}[.]|[a-z0-9.\-]+[.][a-z]{2,4}/)([^\s()<>]+|\(([^\s()<>]+|(\([^\s()<>]+\)))*\))+(\(([^\s()<>]+|(\([^\s()<>]+\)))*\)|[^\s`!()\[\]{};:\'".,<>?«»“”‘’]))', 'gi');
 
@@ -17,3 +28,123 @@ function findUrls(str) {
         res.push({ url: match[0], pos: match.index });
     return res;
 }
+
+// spawn:
+// @argv: an argv array
+//
+// Runs @argv in the background, handling any errors that occur
+// when trying to start the program.
+function spawn(argv) {
+    try {
+        trySpawn(argv);
+    } catch (err) {
+        _handleSpawnError(argv[0], err);
+    }
+}
+
+// spawnCommandLine:
+// @command_line: a command line
+//
+// Runs @command_line in the background, handling any errors that
+// occur when trying to parse or start the program.
+function spawnCommandLine(command_line) {
+    try {
+        let [success, argc, argv] = GLib.shell_parse_argv(command_line);
+        trySpawn(argv);
+    } catch (err) {
+        _handleSpawnError(command_line, err);
+    }
+}
+
+// spawnDesktop:
+// @id: a desktop file ID
+//
+// Spawns the desktop file identified by @id using startup notification,
+// etc, handling any errors that occur when trying to find or start
+// the program.
+function spawnDesktop(id) {
+    try {
+        trySpawnDesktop(id);
+    } catch (err) {
+        _handleSpawnError(id, err);
+    }
+}
+
+// trySpawn:
+// @argv: an argv array
+//
+// Runs @argv in the background. If launching @argv fails,
+// this will throw an error.
+function trySpawn(argv)
+{
+    try {
+        GLib.spawn_async(null, argv, null,
+                         GLib.SpawnFlags.SEARCH_PATH,
+                         null, null);
+    } catch (err) {
+        // The exception from gjs contains an error string like:
+        //   Error invoking GLib.spawn_command_line_async: Failed to
+        //   execute child process "foo" (No such file or directory)
+        // We are only interested in the part in the parentheses. (And
+        // we can't pattern match the text, since it gets localized.)
+        err.message = err.message.replace(/.*\((.+)\)/, '$1');
+        throw err;
+    }
+}
+
+// trySpawnCommandLine:
+// @command_line: a command line
+//
+// Runs @command_line in the background. If launching @command_line
+// fails, this will throw an error.
+function trySpawnCommandLine(command_line) {
+    let success, argc, argv;
+
+    try {
+        [success, argc, argv] = GLib.shell_parse_argv(command_line);
+    } catch (err) {
+        // Replace "Error invoking GLib.shell_parse_argv: " with
+        // something nicer
+        err.message = err.message.replace(/[^:]*: /, _("Could not parse command:") + "\n");
+        throw err;
+    }
+
+    trySpawn(argv);
+}
+
+// trySpawnDesktop:
+// @id: a desktop file ID
+//
+// Spawns the desktop file identified by @id using startup notification.
+// On error, throws an exception.
+function trySpawnDesktop(id) {
+    let app;
+
+    // shell_app_system_load_from_desktop_file() will end up returning
+    // a stupid error message if the desktop file doesn't exist, but
+    // that's the only case it returns an error for, so we just
+    // substitute our own error in instead
+    try {
+        app = Shell.AppSystem.get_default().load_from_desktop_file(id + '.desktop');
+    } catch (err) {
+        throw new Error(_("No such application"));
+    }
+
+    try {
+        app.launch();
+    } catch(err) {
+        // see trySpawn
+        err.message = err.message.replace(/.*\((.+)\)/, '$1');
+        throw err;
+    }
+}
+
+function _handleSpawnError(command, err) {
+    let title = _("Execution of '%s' failed:").format(command);
+
+    let source = new MessageTray.SystemNotificationSource();
+    Main.messageTray.add(source);
+    let notification = new MessageTray.Notification(source, title, err.message);
+    notification.setTransient(true);
+    source.notify(notification);
+}