Fix #345 - add scroll wheel support

asciimatics/event.py

@@ -46,6 +46,9 @@ class MouseEvent(Event):
     LEFT_CLICK = 1
     RIGHT_CLICK = 2
     DOUBLE_CLICK = 4
+    # Note: older versions of curses (e.g. in pypy) do not support up/down
+    SCROLL_UP = 8
+    SCROLL_DOWN = 16
 
     def __init__(self, x: int, y: int, buttons: int):
         """

asciimatics/screen.py

@@ -2213,8 +2213,15 @@ def get_event(self):
                             button |= MouseEvent.LEFT_CLICK
                         if event.ButtonState & win32con.RIGHTMOST_BUTTON_PRESSED != 0:
                             button |= MouseEvent.RIGHT_CLICK
-                    elif event.EventFlags & win32con.DOUBLE_CLICK != 0:
-                        button |= MouseEvent.DOUBLE_CLICK
+                    else:
+                        if event.EventFlags & win32con.MOUSE_WHEELED:
+                            direction = (event.ButtonState & 0xFFFF0000) // 0x10000
+                            if direction & 0x8000 == 0:
+                                button |= MouseEvent.SCROLL_UP
+                            else:
+                                button |= MouseEvent.SCROLL_DOWN
+                        if event.EventFlags & win32con.DOUBLE_CLICK != 0:
+                            button |= MouseEvent.DOUBLE_CLICK
 
                     return MouseEvent(event.MousePosition.X, event.MousePosition.Y, button)
 
@@ -2599,6 +2606,11 @@ def get_event(self) -> Optional[Event]:
                         buttons |= MouseEvent.LEFT_CLICK
                     if (bstate & curses.BUTTON3_PRESSED != 0 or bstate & curses.BUTTON3_CLICKED != 0):
                         buttons |= MouseEvent.RIGHT_CLICK
+                    if hasattr(curses, "BUTTON5_PRESSED"):
+                        if (bstate & curses.BUTTON4_PRESSED != 0 or bstate & curses.BUTTON4_CLICKED != 0):
+                            buttons |= MouseEvent.SCROLL_UP
+                        if (bstate & curses.BUTTON5_PRESSED != 0 or bstate & curses.BUTTON5_CLICKED != 0):
+                            buttons |= MouseEvent.SCROLL_DOWN
                     if bstate & curses.BUTTON1_DOUBLE_CLICKED != 0:
                         buttons |= MouseEvent.DOUBLE_CLICK
                     return MouseEvent(x, y, buttons)

asciimatics/widgets/frame.py

@@ -231,8 +231,8 @@ def add_effect(self, effect: Effect):
 
         :param effect: The Effect to be added.
         """
-        assert self._scene is not None
-        effect.register_scene(self._scene)
+        if self._scene:
+            effect.register_scene(self._scene)
         self._effects.append(effect)
 
     def fix(self):

samples/interactive.py

@@ -55,6 +55,12 @@ def process_event(self, event):
             elif event.buttons & MouseEvent.RIGHT_CLICK != 0:
                 # Try to whack the other sprites when mouse is clicked
                 self._sprite.whack("CRASH!")
+            elif event.buttons & MouseEvent.SCROLL_UP != 0:
+                # Try to whack the other sprites when mouse is clicked
+                self._sprite.whack("OOOOH!")
+            elif event.buttons & MouseEvent.SCROLL_DOWN != 0:
+                # Try to whack the other sprites when mouse is clicked
+                self._sprite.whack("AAAAH!")
         else:
             return event
 

tests/test_screen.py

@@ -698,19 +698,30 @@ def _inject_mouse(screen, x, y, button):
                 event.ButtonState |= win32con.FROM_LEFT_1ST_BUTTON_PRESSED
             if button & MouseEvent.RIGHT_CLICK != 0:
                 event.ButtonState |= win32con.RIGHTMOST_BUTTON_PRESSED
+            if button & MouseEvent.SCROLL_UP != 0:
+                event.EventFlags |= win32con.MOUSE_WHEELED
+                event.ButtonState = 120
+            if button & MouseEvent.SCROLL_DOWN != 0:
+                event.EventFlags |= win32con.MOUSE_WHEELED
+                event.ButtonState = -120
             if button & MouseEvent.DOUBLE_CLICK != 0:
                 event.EventFlags |= win32con.DOUBLE_CLICK
             screen._stdin.WriteConsoleInput([event])
         else:
             # Curses doesn't like no value in some cases - use a dummy button
             # click which we don't use instead.
-            bstate = curses.BUTTON4_CLICKED
+            bstate = curses.BUTTON2_CLICKED
             if button & MouseEvent.LEFT_CLICK != 0:
                 bstate |= curses.BUTTON1_CLICKED
             if button & MouseEvent.RIGHT_CLICK != 0:
                 bstate |= curses.BUTTON3_CLICKED
             if button & MouseEvent.DOUBLE_CLICK != 0:
                 bstate |= curses.BUTTON1_DOUBLE_CLICKED
+            if sys.platform != "win32" and hasattr(curses, "BUTTON5_PRESSED"):
+                if button & MouseEvent.SCROLL_UP != 0:
+                    bstate |= curses.BUTTON4_CLICKED
+                if button & MouseEvent.SCROLL_DOWN != 0:
+                    bstate |= curses.BUTTON5_CLICKED
             curses.ungetmouse(0, x, y, 0, bstate)
 
     def test_key_input(self):
@@ -787,6 +798,24 @@ def internal_checks(screen):
             self.assertEqual(ev.buttons, MouseEvent.DOUBLE_CLICK)
             self.assertIsNone(screen.get_event())
 
+            # Not all curses versions support scrolling...
+            if sys.platform == "win32" or hasattr(curses, "BUTTON5_PRESSED"):
+                # Check scroll up
+                self._inject_mouse(screen, 1, 1, MouseEvent.SCROLL_UP)
+                ev = screen.get_event()
+                self.assertEqual(ev.x, 1)
+                self.assertEqual(ev.y, 1)
+                self.assertEqual(ev.buttons, MouseEvent.SCROLL_UP)
+                self.assertIsNone(screen.get_event())
+
+                # Check scroll up
+                self._inject_mouse(screen, 1, 1, MouseEvent.SCROLL_DOWN)
+                ev = screen.get_event()
+                self.assertEqual(ev.x, 1)
+                self.assertEqual(ev.y, 1)
+                self.assertEqual(ev.buttons, MouseEvent.SCROLL_DOWN)
+                self.assertIsNone(screen.get_event())
+
         Screen.wrapper(internal_checks, height=15)
 
     def test_windows_input(self):