Refactor window closing and app exit handling

examples/dialogs/dialogs/app.py

@@ -104,12 +104,73 @@ def action_save_file_dialog(self, widget):
         except ValueError:
             self.label.text = "Save file dialog was canceled"
 
+    def window_close_handler(self, window):
+        # This handler is called before the window is closed, so there
+        # still are 1 more windows than the number of secondary windows
+        # after it is closed
+        # Return False if the window should stay open
+
+        # Check to see if there has been a previous close attempt.
+        if window in self.close_attempts:
+            # If there has, allow the close to proceed
+            self.set_window_label_text(len(self.windows)-2)
+            return True
+        else:
+            window.info_dialog(f'Abort {window.title}!', 'Maybe try that again...')
+            self.close_attempts.add(window)
+            return False
+
+    def action_open_secondary_window(self, widget):
+        self.window_counter += 1
+        window = toga.Window(title=f"New Window {self.window_counter}")
+        # Both self.windows.add() and self.windows += work:
+        self.windows += window
+
+        self.set_window_label_text()
+        secondary_label = toga.Label(text="You are in a secondary window!")
+        window.content = toga.Box(
+            children=[
+                secondary_label
+            ],
+            style=Pack(
+                flex=1,
+                direction=COLUMN,
+                padding=10
+            )
+        )
+        window.on_close = self.window_close_handler
+        window.show()
+
+    def action_close_secondary_windows(self, widget):
+        for window in list(self.windows):
+            if window._WINDOW_CLASS != 'MainWindow':
+                window.close()
+
+    def exit_handler(self, app):
+        # Return True if app should close, and False if it should remain open
+        if self.main_window.confirm_dialog('Toga', 'Are you sure you want to quit?'):
+            print(f"Label text was '{self.label.text}' when you quit the app")
+            return True
+        else:
+            self.label.text = 'Exit canceled'
+            return False
+
+    def set_window_label_text(self, num_windows=None):
+        if num_windows is None:
+            num_windows = len(self.windows) - 1
+        self.window_label.text = f"{num_windows} secondary window(s) open"
+
     def startup(self):
         # Set up main window
         self.main_window = toga.MainWindow(title=self.name)
+        self.on_exit = self.exit_handler
 
         # Label to show responses.
         self.label = toga.Label('Ready.', style=Pack(padding_top=20))
+        self.window_label = toga.Label('', style=Pack(padding_top=20))
+        self.window_counter = 0
+        self.close_attempts = set()
+        self.set_window_label_text()
 
         # Buttons
         btn_style = Pack(flex=1)
@@ -135,6 +196,16 @@ def startup(self):
             on_press=self.action_select_folder_dialog_multi,
             style=btn_style
         )
+        btn_open_secondary_window = toga.Button(
+            'Open Secondary Window',
+            on_press=self.action_open_secondary_window,
+            style=btn_style
+        )
+        btn_close_secondary_window = toga.Button(
+            'Close All Secondary Windows',
+            on_press=self.action_close_secondary_windows,
+            style=btn_style
+        )
 
         btn_clear = toga.Button('Clear', on_press=self.do_clear, style=btn_style)
 
@@ -151,8 +222,11 @@ def startup(self):
                 btn_select,
                 btn_select_multi,
                 btn_open_multi,
+                btn_open_secondary_window,
+                btn_close_secondary_window,
                 btn_clear,
-                self.label
+                self.label,
+                self.window_label
             ],
             style=Pack(
                 flex=1,

src/cocoa/toga_cocoa/app.py

@@ -36,16 +36,11 @@
 
 
 class MainWindow(Window):
-    def on_close(self):
+    def toga_on_close(self):
         self.interface.app.exit()
 
 
 class AppDelegate(NSObject):
-    @objc_method
-    def applicationWillTerminate_(self, sender):
-        if self.interface.app.on_exit:
-            self.interface.app.on_exit(self.interface.app)
-
     @objc_method
     def applicationDidFinishLaunching_(self, notification):
         self.native.activateIgnoringOtherApps(True)
@@ -261,7 +256,9 @@ def show_about_dialog(self):
         self.native.orderFrontStandardAboutPanelWithOptions(options)
 
     def exit(self):
-        self.native.terminate(None)
+        should_exit = self.interface.on_exit(self)
+        if should_exit:
+            self.native.terminate(self.native)
 
     def set_on_exit(self, value):
         pass

src/cocoa/toga_cocoa/window.py

@@ -49,8 +49,8 @@ def height(self):
 
 class WindowDelegate(NSObject):
     @objc_method
-    def windowWillClose_(self, notification) -> None:
-        self.interface.on_close()
+    def windowShouldClose_(self, notification) -> bool:
+        return self.impl.toga_on_close()
 
     @objc_method
     def windowDidResize_(self, notification) -> None:
@@ -246,11 +246,24 @@ def show(self):
     def set_full_screen(self, is_full_screen):
         self.interface.factory.not_implemented('Window.set_full_screen()')
 
-    def on_close(self):
+    def set_on_close(self, handler):
         pass
 
+    def toga_on_close(self):
+        if self.interface.on_close:
+            should_close = self.interface.on_close(self)
+        else:
+            should_close = True
+
+        if should_close:
+            self.interface.app.windows -= self.interface
+
+        return should_close
+
     def close(self):
-        self.native.close()
+        # Calling performClose instead of close ensures that the on_close
+        # handlers in the delegates will be called
+        self.native.performClose(self.native)
 
     def info_dialog(self, title, message):
         return dialogs.info(self.interface, title, message)

src/core/tests/test_app.py

@@ -88,6 +88,10 @@ def test_is_full_screen(self):
         self.assertFalse(self.app.is_full_screen)
 
     def test_app_exit(self):
+        def exit_handler():
+            return
+        self.app.on_exit = exit_handler
+        self.assertIs(self.app.on_exit._raw, exit_handler)
         self.app.exit()
 
         self.assertActionPerformed(self.app, 'exit')
@@ -104,6 +108,54 @@ def test_full_screen(self):
         self.app.set_full_screen()
         self.assertFalse(self.app.is_full_screen)
 
+    def test_add_window(self):
+        test_window = toga.Window(factory=toga_dummy.factory)
+
+        self.assertEqual(len(self.app.windows), 0)
+        self.app.windows += test_window
+        self.assertEqual(len(self.app.windows), 1)
+        self.app.windows += test_window
+        self.assertEqual(len(self.app.windows), 1)
+        self.assertIs(test_window.app, self.app)
+
+        not_a_window = 'not_a_window'
+        with self.assertRaises(TypeError):
+            self.app.windows += not_a_window
+
+    def test_remove_window(self):
+        test_window = toga.Window(factory=toga_dummy.factory)
+        self.app.windows += test_window
+        self.assertEqual(len(self.app.windows), 1)
+        self.app.windows -= test_window
+        self.assertEqual(len(self.app.windows), 0)
+
+        not_a_window = 'not_a_window'
+        with self.assertRaises(TypeError):
+            self.app.windows -= not_a_window
+
+        test_window_not_in_app = toga.Window(factory=toga_dummy.factory)
+        with self.assertRaises(AttributeError):
+            self.app.windows -= test_window_not_in_app
+
+    def test_app_contains_window(self):
+        test_window = toga.Window(factory=toga_dummy.factory)
+        self.assertFalse(test_window in self.app.windows)
+        self.app.windows += test_window
+        self.assertTrue(test_window in self.app.windows)
+
+    def test_window_iteration(self):
+        test_windows = [
+            toga.Window(id=1, factory=toga_dummy.factory),
+            toga.Window(id=2, factory=toga_dummy.factory),
+            toga.Window(id=3, factory=toga_dummy.factory),
+        ]
+        for window in test_windows:
+            self.app.windows += window
+        self.assertEqual(len(self.app.windows), 3)
+
+        for window in self.app.windows:
+            self.assertIn(window, test_windows)
+
 
 class DocumentAppTests(TestCase):
     def setUp(self):

src/core/tests/test_window.py

@@ -10,12 +10,17 @@ class TestWindow(TestCase):
     def setUp(self):
         super().setUp()
         self.window = toga.Window(factory=toga_dummy.factory)
+        self.app = toga.App('test_name', 'id.app', factory=toga_dummy.factory)
+
+    def test_raises_error_when_app_not_set(self):
+        self.app = None
+        with self.assertRaises(AttributeError):
+            self.window.show()
 
     def test_widget_created(self):
         self.assertIsNotNone(self.window.id)
-        app = toga.App('test_name', 'id.app', factory=toga_dummy.factory)
         new_app = toga.App('error_name', 'id.error', factory=toga_dummy.factory)
-        self.window.app = app
+        self.window.app = self.app
         with self.assertRaises(Exception):
             self.window.app = new_app
 
@@ -62,8 +67,19 @@ def test_full_screen_set(self):
 
     def test_on_close(self):
         with patch.object(self.window, '_impl'):
-            self.window.on_close()
-            self.window._impl.on_close.assert_called_once_with()
+            self.app.windows += self.window
+            self.assertIsNone(self.window._on_close)
+
+            # set a new callback
+            def callback(window, **extra):
+                return 'called {} with {}'.format(type(window), extra)
+
+            self.window.on_close = callback
+            self.assertEqual(self.window.on_close._raw, callback)
+            self.assertEqual(
+                self.window.on_close('widget', a=1),
+                "called <class 'toga.window.Window'> with {'a': 1}"
+            )
 
     def test_close(self):
         with patch.object(self.window, "_impl"):