Remove set_on_ usage for ported widgets.

android/src/toga_android/app.py

@@ -209,9 +209,6 @@ def show_about_dialog(self):
     def exit(self):
         pass
 
-    def set_on_exit(self, value):
-        pass
-
     async def intent_result(self, intent):
         """Calls an Intent and waits for its result.
 

android/src/toga_android/widgets/button.py

@@ -15,7 +15,7 @@ def __init__(self, button_impl):
         self.button_impl = button_impl
 
     def onClick(self, _view):
-        self.button_impl.interface.on_press()
+        self.button_impl.interface.on_press(None)
 
 
 class Button(TextViewWidget):
@@ -33,10 +33,6 @@ def set_text(self, text):
     def set_enabled(self, value):
         self.native.setEnabled(value)
 
-    def set_on_press(self, handler):
-        # No special handling required
-        pass
-
     def set_background_color(self, value):
         # Do not use self.native.setBackgroundColor - this messes with the button style!
         self.native.getBackground().setColorFilter(

android/src/toga_android/widgets/slider.py

@@ -11,8 +11,7 @@ def __init__(self, impl):
         self.impl = impl
 
     def onProgressChanged(self, _view, _progress, _from_user):
-        if self.impl.interface.on_change:
-            self.impl.interface.on_change(widget=self.impl.interface)
+        self.impl.interface.on_change(None)
 
     # Add two unused methods so that the Java interface is completely implemented.
     def onStartTrackingTouch(self, native_seekbar):
@@ -73,13 +72,3 @@ def rehint(self):
         )
         self.interface.intrinsic.width = at_least(self.native.getMeasuredWidth())
         self.interface.intrinsic.height = self.native.getMeasuredHeight()
-
-    def set_on_change(self, handler):
-        # No special handling required
-        pass
-
-    def set_on_press(self, handler):
-        self.interface.factory.not_implemented("Slider.set_on_press()")
-
-    def set_on_release(self, handler):
-        self.interface.factory.not_implemented("Slider.set_on_release()")

android/src/toga_android/widgets/switch.py

@@ -14,7 +14,7 @@ def __init__(self, impl):
         self._impl = impl
 
     def onCheckedChanged(self, _button, _checked):
-        self._impl.interface.on_change()
+        self._impl.interface.on_change(None)
 
 
 class Switch(TextViewWidget):
@@ -38,10 +38,6 @@ def set_value(self, value):
     def get_value(self):
         return self.native.isChecked()
 
-    def set_on_change(self, handler):
-        # No special handling required
-        pass
-
     def rehint(self):
         if not self.native.getLayoutParams():
             return

cocoa/src/toga_cocoa/app.py

@@ -367,9 +367,6 @@ def show_about_dialog(self):
     def exit(self):
         self.loop.stop()
 
-    def set_on_exit(self, value):
-        pass
-
     def current_window(self):
         return self.native.keyWindow
 

cocoa/src/toga_cocoa/widgets/button.py

@@ -21,7 +21,7 @@ class TogaButton(NSButton):
 
     @objc_method
     def onPress_(self, obj) -> None:
-        self.interface.on_press()
+        self.interface.on_press(None)
 
 
 class Button(Widget):
@@ -71,10 +71,6 @@ def get_text(self):
     def set_text(self, text):
         self.native.title = text
 
-    def set_on_press(self, handler):
-        # No special handling required
-        pass
-
     def set_background_color(self, color):
         if color == TRANSPARENT or color is None:
             self.native.bezelColor = None

cocoa/src/toga_cocoa/widgets/slider.py

@@ -19,14 +19,11 @@ class TogaSlider(NSSlider):
     def onSlide_(self, sender) -> None:
         event_type = sender.window.currentEvent().type
         if event_type == NSEventType.LeftMouseDown:
-            if self.interface.on_press:
-                self.interface.on_press(self.interface)
+            self.interface.on_press(None)
         elif event_type == NSEventType.LeftMouseUp:
-            if self.interface.on_release:
-                self.interface.on_release(self.interface)
+            self.interface.on_release(None)
 
-        if self.interface.on_change:
-            self.interface.on_change(self.interface)
+        self.interface.on_change(None)
 
 
 class Slider(Widget):
@@ -63,12 +60,3 @@ def rehint(self):
         content_size = self.native.intrinsicContentSize()
         self.interface.intrinsic.height = content_size.height
         self.interface.intrinsic.width = at_least(self.interface.MIN_WIDTH)
-
-    def set_on_change(self, handler):
-        pass
-
-    def set_on_press(self, handler):
-        pass
-
-    def set_on_release(self, handler):
-        pass

cocoa/src/toga_cocoa/widgets/switch.py

@@ -20,7 +20,7 @@ class TogaSwitch(NSButton):
 
     @objc_method
     def onPress_(self, obj) -> None:
-        self.interface.on_change()
+        self.interface.on_change(None)
 
 
 class Switch(Widget):
@@ -63,6 +63,3 @@ def rehint(self):
         content_size = self.native.intrinsicContentSize()
         self.interface.intrinsic.height = content_size.height
         self.interface.intrinsic.width = at_least(content_size.width)
-
-    def set_on_change(self, handler):
-        pass

cocoa/src/toga_cocoa/window.py

@@ -310,9 +310,6 @@ def get_visible(self):
     def set_full_screen(self, is_full_screen):
         self.interface.factory.not_implemented("Window.set_full_screen()")
 
-    def set_on_close(self, handler):
-        pass
-
     def cocoa_windowShouldClose(self):
         if self.interface.on_close:
             # The on_close handler has a cleanup method that will enforce

core/src/toga/app.py

@@ -118,9 +118,10 @@ def on_close(self, handler):
         Args:
             handler (:obj:`callable`): The handler passed.
         """
-        raise AttributeError(
-            "Cannot set on_close handler for the main window. Use the app on_exit handler instead"
-        )
+        if handler:
+            raise AttributeError(
+                "Cannot set on_close handler for the main window. Use the app on_exit handler instead"
+            )
 
 
 class App:
@@ -551,7 +552,7 @@ def main_loop(self):
 
     def exit(self):
         """Quit the application gracefully."""
-        self.on_exit()
+        self.on_exit(None)
 
     @property
     def on_exit(self):
@@ -579,7 +580,6 @@ def cleanup(app, should_exit):
                 app._impl.exit()
 
         self._on_exit = wrapped_handler(self, handler, cleanup=cleanup)
-        self._impl.set_on_exit(self._on_exit)
 
     def add_background_task(self, handler):
         """Schedule a task to run in the background.
@@ -592,7 +592,7 @@ def add_background_task(self, handler):
 
         :param handler: A coroutine, generator or callable.
         """
-        self._impl.loop.call_soon_threadsafe(wrapped_handler(self, handler))
+        self._impl.loop.call_soon_threadsafe(wrapped_handler(self, handler), None)
 
 
 class DocumentApp(App):

core/src/toga/handlers.py

@@ -55,7 +55,7 @@ def wrapped_handler(interface, handler, cleanup=None):
         if isinstance(handler, NativeHandler):
             return handler.native
 
-        def _handler(*args, **kwargs):
+        def _handler(widget, *args, **kwargs):
             if asyncio.iscoroutinefunction(handler):
                 asyncio.ensure_future(
                     handler_with_cleanup(handler, cleanup, interface, *args, **kwargs)
@@ -77,7 +77,7 @@ def _handler(*args, **kwargs):
 
     else:
         # A dummy no-op handler
-        def _handler(*args, **kwargs):
+        def _handler(widget, *args, **kwargs):
             pass
 
         _handler._raw = None

core/src/toga/widgets/button.py

@@ -71,4 +71,3 @@ def on_press(self):
     @on_press.setter
     def on_press(self, handler):
         self._on_press = wrapped_handler(self, handler)
-        self._impl.set_on_press(self._on_press)

core/src/toga/widgets/slider.py

@@ -77,8 +77,9 @@ def __init__(
         self.range = range
         self.tick_count = tick_count
 
-        # IMPORTANT NOTE: Setting value before on_change in order to not
-        # call it in constructor. Please do not move it from here.
+        # Set a dummy handler before installing the actual on_change, because we do not want
+        # on_change triggered by the initial value being set
+        self.on_change = None
         self.value = value
 
         if on_slide:
@@ -116,8 +117,7 @@ def value(self, value):
                 )
             )
         self._impl.set_value(final)
-        if self.on_change:
-            self.on_change(self)
+        self.on_change(self)
 
     @property
     def range(self):
@@ -192,7 +192,6 @@ def on_change(self):
     @on_change.setter
     def on_change(self, handler):
         self._on_change = wrapped_handler(self, handler)
-        self._impl.set_on_change(self._on_change)
 
     @property
     def on_press(self):
@@ -206,7 +205,6 @@ def on_press(self):
     @on_press.setter
     def on_press(self, handler):
         self._on_press = wrapped_handler(self, handler)
-        self._impl.set_on_press(self._on_press)
 
     @property
     def on_release(self):
@@ -220,7 +218,6 @@ def on_release(self):
     @on_release.setter
     def on_release(self, handler):
         self._on_release = wrapped_handler(self, handler)
-        self._impl.set_on_release(self._on_release)
 
     @property
     def on_slide(self):

core/src/toga/widgets/switch.py

@@ -155,7 +155,6 @@ def on_change(self):
     @on_change.setter
     def on_change(self, handler):
         self._on_change = wrapped_handler(self, handler)
-        self._impl.set_on_change(self._on_change)
 
     @property
     def value(self):

core/src/toga/window.py

@@ -70,9 +70,7 @@ def __init__(
 
         self._toolbar = CommandSet(widget=self, on_change=self._impl.create_toolbar)
 
-        self._on_close = None
-        if on_close is not None:
-            self.on_close = on_close
+        self.on_close = on_close
 
     @property
     def id(self):
@@ -255,7 +253,6 @@ def cleanup(window, should_close):
                 window.close()
 
         self._on_close = wrapped_handler(self, handler, cleanup=cleanup)
-        self._impl.set_on_close(self._on_close)
 
     def close(self):
         self.app.windows -= self

core/tests/test_window.py

@@ -204,7 +204,7 @@ def test_full_screen_set(self):
     def test_on_close(self):
         with patch.object(self.window, "_impl"):
             self.app.windows += self.window
-            self.assertIsNone(self.window._on_close)
+            self.assertIsNone(self.window.on_close._raw)
 
             # set a new callback
             def callback(window, **extra):
@@ -213,7 +213,7 @@ def callback(window, **extra):
             self.window.on_close = callback
             self.assertEqual(self.window.on_close._raw, callback)
             self.assertEqual(
-                self.window.on_close(a=1),
+                self.window.on_close(None, a=1),
                 "called <class 'toga.window.Window'> with {'a': 1}",
             )
 
@@ -226,7 +226,7 @@ def callback(window, **extra):
 
         self.assertEqual(window.on_close._raw, callback)
         self.assertEqual(
-            window.on_close(a=1),
+            window.on_close(None, a=1),
             "called <class 'toga.window.Window'> with {'a': 1}",
         )
 

core/tests/widgets/test_button.py

@@ -58,11 +58,8 @@ def test_button_on_press(button):
 
     assert button.on_press._raw == handler
 
-    # Backend has the wrapped version
-    assert attribute_value(button, "on_press") == button._on_press
-
     # Invoke the callback
-    button.on_press(a=1)
+    button._impl.simulate_press()
 
     # Callback was invoked
-    handler.assert_called_once_with(button, a=1)
+    handler.assert_called_once_with(button)