BF: Allow mouse wheel scrolling in Routine canvas

Author: Todd

psychopy/app/builder/builder.py

@@ -1514,6 +1514,7 @@ def __init__(self, notebook, id=wx.ID_ANY, routine=None):
         self.Bind(wx.EVT_PAINT, self.OnPaint)
         self.Bind(wx.EVT_ERASE_BACKGROUND, lambda x: None)
         self.Bind(wx.EVT_MOUSE_EVENTS, self.OnMouse)
+        self.Bind(wx.EVT_MOUSEWHEEL, self.OnScroll)
         self.Bind(wx.EVT_SIZE, self.onResize)
         # crashes if drop on OSX:
         # self.SetDropTarget(FileDropTarget(builder = self.frame))
@@ -1574,6 +1575,11 @@ def OnMouse(self, event):
             except IndexError:
                 self.frame.SetStatusText("")
 
+    def OnScroll(self, event):
+        xy = self.GetViewStart()
+        multiplier = self.dpi / 1600
+        self.Scroll(xy[0], xy[1] - event.WheelRotation*multiplier)
+
     def showContextMenu(self, component, xy):
         menu = wx.Menu()
         for item in self.contextMenuItems: