Testing slowdown on OS X 10.11

custom_list_draw_test.py

import wxversion
wxversion.select('3.0')

import wx

SB_ITEM_NORMAL = 0
SB_ITEM_HIGHLIGHTED = 2

class LineItem(wx.Window):
    def __init__(self, parent, text="", id=wx.ID_ANY, pos=wx.DefaultPosition, size=(50,16)):
        wx.Window.__init__(self, parent, id, pos, size)

        self.highlighted = False
        self.bkBitmap = None
        self.padding = 4
        self.text = text

        self.Bind(wx.EVT_PAINT, self.OnPaint)
        self.Bind(wx.EVT_ERASE_BACKGROUND, self.OnEraseBackground)

        self.Bind(wx.EVT_ENTER_WINDOW, self.OnEnterWindow)
        self.Bind(wx.EVT_LEAVE_WINDOW, self.OnLeaveWindow)

    def OnEraseBackground(self, event):
        pass

    def OnEnterWindow(self, event):
        self.SetHighlighted(True)
        self.Refresh()
        event.Skip()

    def OnLeaveWindow(self, event):
        self.SetHighlighted(False)
        self.Refresh()
        event.Skip()

    def SetHighlighted(self, highlight = True):
        self.highlighted = highlight

    def GetState(self):
        if self.highlighted:
            state = SB_ITEM_HIGHLIGHTED
        else:
            state = SB_ITEM_NORMAL

        return state

    def RenderBackground(self):
        rect = self.GetRect()
        state = self.GetState()

        bkBitmap = wx.EmptyBitmap(rect.width, rect.height)

        mdc = wx.MemoryDC()
        mdc.SelectObject(bkBitmap)

        if state == SB_ITEM_HIGHLIGHTED:
            mdc.SetBackground(wx.Brush(wx.YELLOW))
        else:
            mdc.SetBackground(wx.Brush(wx.WHITE))

        mdc.Clear()

        mdc.SelectObject(wx.NullBitmap)
        return bkBitmap

    def OnPaint(self, event):
        mdc = wx.PaintDC(self)
        mdc.DrawBitmap(self.RenderBackground(), 0, 0)

        rect = self.GetRect()

        font = wx.SystemSettings_GetFont(wx.SYS_DEFAULT_GUI_FONT)

        if self.GetState() == SB_ITEM_HIGHLIGHTED:
            font.SetWeight(wx.FONTWEIGHT_BOLD)

        mdc.SetFont(font)
        wtext, htext = mdc.GetTextExtent(self.text)

        x = self.padding
        y = (rect.height - htext) / 2

        mdc.DrawText(self.text, x, y)


if __name__ == "__main__":

    class TestPanel(wx.Panel):
        def __init__(self, parent, size=(500, 500)):
            wx.Panel.__init__(self, parent, size=size)
            max_elements = 40
            self.box = wx.BoxSizer(wx.VERTICAL)

            grid = wx.FlexGridSizer(max_elements, 5)

            for t in xrange(max_elements*5):
                item = LineItem(self, "test %d" % t, size=(100, 16))
                grid.Add(item, 0, wx.ALL, 0)

            self.box.Add(grid, 0, wx.ALL, 0)

            self.SetSizer(self.box)
            self.Layout()

    class Frame(wx.Frame):
        def __init__(self, title, size=(500, 650)):
            wx.Frame.__init__(self, None, title=title, size=size)
            self.statusbar = self.CreateStatusBar()
            main_sizer = wx.BoxSizer(wx.VERTICAL)
            panel = TestPanel(self, size=size)
            main_sizer.Add(panel)
            self.SetSizer(main_sizer)

    app = wx.App(redirect=False)   # Error messages go to popup window
    top = Frame("Test Window")
    top.Show()
    app.MainLoop()

Video of test script on OS X 10.11 (notice lag with highlighting compared to pointer): https://vid.me/hbDl
Video of test script on OS X 10.10 (no / unnoticable lag): https://vid.me/qvjp