After more than two years of puzzlement Jurjen Bos found the reason for

the double-scroll problem: when you pass a tracker function to TrackControl
you shouldn't call your hit function again afterwards. Fixes #711989.

diff --git a/Mac/Tools/IDE/Wcontrols.py b/Mac/Tools/IDE/Wcontrols.py
index 3d523836370793f81c25660496d7f5c6723581fc..58fc31bfb962f2313006e66f784b345344dd718b 100644 (file)
--- a/Mac/Tools/IDE/Wcontrols.py
+++ b/Mac/Tools/IDE/Wcontrols.py
@@ -380,8 +380,6 @@ class Scrollbar(ControlWidget):
                        if part:
                                self._hit(part)
                part = self._control.TrackControl(point, hitter)
-               if part:
-                       self._hit(part)
        
        def _hit(self, part):
                value = None