chrome/browser/mac/relauncher.h

// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CHROME_BROWSER_MAC_RELAUNCHER_H_
#define CHROME_BROWSER_MAC_RELAUNCHER_H_

// mac_relauncher implements main browser application relaunches on the Mac.
// When a browser wants to relaunch itself, it can't simply fork off a new
// process and exec a new browser from within. That leaves open a window
// during which two browser applications might be running concurrently. If
// that happens, each will wind up with a distinct Dock icon, which is
// especially bad if the user expected the Dock icon to be persistent by
// choosing Keep in Dock from the icon's contextual menu.
//
// mac_relauncher approaches this problem by introducing an intermediate
// process (the "relauncher") in between the original browser ("parent") and
// replacement browser ("relaunched"). The helper executable is used for the
// relauncher process; because it's an LSUIElement, it doesn't get a Dock
// icon and isn't visible as a running application at all. The parent will
// start a relauncher process, giving it the "writer" side of a pipe that it
// retains the "reader" end of. When the relauncher starts up, it will
// establish a kqueue to wait for the parent to exit, and will then write to
// the pipe. The parent, upon reading from the pipe, is free to exit. When the
// relauncher is notified via its kqueue that the parent has exited, it
// proceeds, launching the relaunched process. The handshake to synchronize
// the parent with the relauncher is necessary to avoid races: the relauncher
// needs to be sure that it's monitoring the parent and not some other process
// in light of PID reuse, so the parent must remain alive long enough for the
// relauncher to set up its kqueue.

#include <string>
#include <vector>

namespace content {
struct MainFunctionParams;
}

namespace mac_relauncher {

// Relaunches the application using the helper application associated with the
// currently running instance of Chrome in the parent browser process as the
// executable for the relauncher process. |args| is an argv-style vector of
// command line arguments of the form normally passed to execv. args[0] is
// also the path to the relaunched process. Because the relauncher process
// will ultimately launch the relaunched process via Launch Services, args[0]
// may be either a pathname to an executable file or a pathname to an .app
// bundle directory. The caller should exit soon after RelaunchApp returns
// successfully. Returns true on success, although some failures can occur
// after this function returns true if, for example, they occur within the
// relauncher process. Returns false when the relaunch definitely failed.
bool RelaunchApp(const std::vector<std::string>& args);

// Identical to RelaunchApp, but uses |helper| as the path to the relauncher
// process, and allows additional arguments to be supplied to the relauncher
// process in relauncher_args. Unlike args[0], |helper| must be a pathname to
// an executable file. The helper path given must be from the same version of
// Chrome as the running parent browser process, as there are no guarantees
// that the parent and relauncher processes from different versions will be
// able to communicate with one another. This variant can be useful to
// relaunch the same version of Chrome from another location, using that
// location's helper.
bool RelaunchAppWithHelper(const std::string& helper,
                           const std::vector<std::string>& relauncher_args,
                           const std::vector<std::string>& args);

namespace internal {

// The entry point from ChromeMain into the relauncher process. This is not a
// user API. Don't call it if your name isn't ChromeMain.
int RelauncherMain(const content::MainFunctionParams& main_parameters);

}  // namespace internal

}  // namespace mac_relauncher

#endif  // CHROME_BROWSER_MAC_RELAUNCHER_H_