bpo-37902: IDLE: Add scrolling for IDLE browsers. (#15368)

Modify the wheel event handler so it can also be used for module, path, and stack browsers.
Patch by George Zhang.

Lib/idlelib/editor.py

@@ -26,6 +26,7 @@ from idlelib import pyparse
 from idlelib import query
 from idlelib import replace
 from idlelib import search
+from idlelib.tree import wheel_event
 from idlelib import window
 
 # The default tab setting for a Text widget, in average-width characters.
@@ -151,9 +152,10 @@ class EditorWindow(object):
         else:
             # Elsewhere, use right-click for popup menus.
             text.bind("<3>",self.right_menu_event)
-        text.bind('<MouseWheel>', self.mousescroll)
-        text.bind('<Button-4>', self.mousescroll)
-        text.bind('<Button-5>', self.mousescroll)
+
+        text.bind('<MouseWheel>', wheel_event)
+        text.bind('<Button-4>', wheel_event)
+        text.bind('<Button-5>', wheel_event)
         text.bind('<Configure>', self.handle_winconfig)
         text.bind("<<cut>>", self.cut)
         text.bind("<<copy>>", self.copy)
@@ -502,23 +504,6 @@ class EditorWindow(object):
         self.text.yview(event, *args)
         return 'break'
 
-    def mousescroll(self, event):
-        """Handle scrollwheel event.
-
-        For wheel up, event.delta = 120*n on Windows, -1*n on darwin,
-        where n can be > 1 if one scrolls fast.  Flicking the wheel
-        generates up to maybe 20 events with n up to 10 or more 1.
-        Macs use wheel down (delta = 1*n) to scroll up, so positive
-        delta means to scroll up on both systems.
-
-        X-11 sends Control-Button-4 event instead.
-        """
-        up = {EventType.MouseWheel: event.delta > 0,
-              EventType.Button: event.num == 4}
-        lines = -5 if up[event.type] else 5
-        self.text.yview_scroll(lines, 'units')
-        return 'break'
-
     rmenu = None
 
     def right_menu_event(self, event):