Fix errors with the pynput mouse implementation used on macOS

Re: #368.

The Mouse action class can now be used to double/triple click, and
scroll the mouse wheel, on macOS.

dragonfly/actions/mouse/_pynput.py

@@ -96,15 +96,15 @@ def get_button(name):
 }
 
 PLATFORM_WHEEL_FLAGS = {
-    # ((button, event_type), scroll_count)
-    "wheelup": ((get_button("scroll_up"), 1), 3),
-    "stepup": ((get_button("scroll_up"), 1), 1),
-    "wheeldown": ((get_button("scroll_down"), 1), 3),
-    "stepdown": ((get_button("scroll_down"), 1), 1),
-    "wheelright": ((get_button("scroll_right"), 1), 3),
-    "stepright": ((get_button("scroll_right"), 1), 1),
-    "wheelleft": ((get_button("scroll_left"), 1), 3),
-    "stepleft": ((get_button("scroll_left"), 1), 1),
+    # button  ->  ((button, event_type), step_count)
+    "wheelup":    (("stepup",    1),  3),
+    "stepup":     (("stepup",    1),  1),
+    "wheeldown":  (("stepdown",  1), -3),
+    "stepdown":   (("stepdown",  1), -1),
+    "wheelright": (("stepright", 1),  3),
+    "stepright":  (("stepright", 1),  1),
+    "wheelleft":  (("stepleft",  1), -3),
+    "stepleft":   (("stepleft",  1), -1),
 }
 
 
@@ -118,17 +118,50 @@ def execute(self, window):
         # Initialize the pynput mouse controller, if necessary.
         _init_controller()
 
-        # Process button events.
-        for ((button, event_type), flag) in self._flags:
-            # Check if the button is unknown.
+        # Pre-process event flags.
+        # - Raise an error if an unsupported event is found.
+        # - Combine down/up events so that the `click' function may be used
+        #    where appropriate.
+        events = []
+        last_event = None
+        for event in self._flags:
+            ((button, event_type), flag) = event
             if button is None:
-                event_type_s = "button" if event_type == 0 else "scroll"
-                raise ValueError("Unsupported %s event" % event_type_s)
+                message = "Unsupported mouse %s event"
+                if event_type == 0: message = message % "scroll"
+                else:               message = message % "button"
+                raise ValueError(message)
+
+            if last_event is None:
+                last_event = event
+                continue
+
+            # Is this event compatible with the last one?
+            # Note: Button events are joined like this because the *pynput*
+            #  `click' controller method must be used for double/triple
+            #  clicking on macOS.
+            ((last_button, last_event_type), last_flag) = last_event
+            if (last_event_type == event_type == 0 and last_flag and
+                    not flag and last_button == button):
+                last_event = None
+                event = ((button, 0), last_flag + 1)
+                events.append(event)
+            else:
+                events.append(last_event)
+                events.append(event)
 
+        # Process button events.
+        for event in self._flags:
+            ((button, event_type), flag) = event
             if event_type == 0:  # Button press event
-                if flag:
+                if flag == 1:
                     _controller.press(button)
+                elif flag > 1:
+                    _controller.click(button, flag)
                 else:
                     _controller.release(button)
             elif event_type == 1:  # Scroll event
-                _controller.click(button, flag)
+                if button == "stepup" or button == "stepdown":
+                    _controller.scroll(0, flag)
+                else:
+                    _controller.scroll(flag, 0)