Merge pull request #1176 from CharlieHess/before-quit-event

App Before-Quit Event

atom/browser/api/atom_api_app.cc

@@ -131,6 +131,10 @@ App::~App() {
   Browser::Get()->RemoveObserver(this);
 }
 
+void App::OnBeforeQuit(bool* prevent_default) {
+  *prevent_default = Emit("before-quit");
+}
+
 void App::OnWillQuit(bool* prevent_default) {
   *prevent_default = Emit("will-quit");
 }

atom/browser/api/atom_api_app.h

@@ -38,6 +38,7 @@ class App : public mate::EventEmitter,
   virtual ~App();
 
   // BrowserObserver:
+  void OnBeforeQuit(bool* prevent_default) override;
   void OnWillQuit(bool* prevent_default) override;
   void OnWindowAllClosed() override;
   void OnQuit() override;

atom/browser/browser.cc

@@ -28,7 +28,9 @@ Browser* Browser::Get() {
 }
 
 void Browser::Quit() {
-  is_quiting_ = true;
+  is_quiting_ = HandleBeforeQuit();
+  if (!is_quiting_)
+    return;
 
   atom::WindowList* window_list = atom::WindowList::GetInstance();
   if (window_list->size() == 0)
@@ -114,6 +116,15 @@ void Browser::NotifyAndShutdown() {
   Shutdown();
 }
 
+bool Browser::HandleBeforeQuit() {
+  bool prevent_default = false;
+  FOR_EACH_OBSERVER(BrowserObserver,
+                    observers_,
+                    OnBeforeQuit(&prevent_default));
+
+  return !prevent_default;
+}
+
 void Browser::OnWindowCloseCancelled(NativeWindow* window) {
   if (is_quiting_)
     // Once a beforeunload handler has prevented the closing, we think the quit

atom/browser/browser.h

@@ -136,6 +136,9 @@ class Browser : public WindowListObserver {
   // Send the will-quit message and then shutdown the application.
   void NotifyAndShutdown();
 
+  // Send the before-quit message and start closing windows.
+  bool HandleBeforeQuit();
+
   bool is_quiting_;
 
  private:

atom/browser/browser_observer.h

@@ -11,6 +11,9 @@ namespace atom {
 
 class BrowserObserver {
  public:
+  // The browser is about to close all windows.
+  virtual void OnBeforeQuit(bool* prevent_default) {}
+
   // The browser has closed all windows and will quit.
   virtual void OnWillQuit(bool* prevent_default) {}
 

docs/api/app.md

@@ -34,6 +34,14 @@ user pressed `Cmd + Q`, or the developer called `app.quit()`, atom-shell would
 first try to close all windows and then emit the `will-quit` event, and in
 this case the `window-all-closed` would not be emitted.
 
+## Event: before-quit
+
+* `event` Event
+
+Emitted before the application starts closing its windows.
+Calling `event.preventDefault()` will prevent the default behaviour, which is
+terminating the application.
+
 ## Event: will-quit
 
 * `event` Event
@@ -78,9 +86,9 @@ click on the application's dock icon.
 
 ## app.quit()
 
-Try to close all windows. If all windows are successfully closed, the
-`will-quit` event will be emitted and by default the application would be
-terminated.
+Try to close all windows. The `before-quit` event will first be emitted. If all
+windows are successfully closed, the `will-quit` event will be emitted and by
+default the application would be terminated.
 
 This method guarantees all `beforeunload` and `unload` handlers are correctly
 executed. It is possible that a window cancels the quitting by returning