The wxPython tutorial

The Graphics Device Interfacehttp://www.zetcode.com/wxpython/gdi/import wxclass CrossHair(wx.Frame):def __init__(self, parent, id, title):wx.Frame.__init__(self, parent, id, title, size=(250, 150))self.Bind(wx.EVT_MOTION, self.OnMotion)self.Bind(wx.EVT_LEAVE_WINDOW, self.OnLeaveWindow)self.SetBackgroundColour('WHITE')self.SetCursor(wx.StockCursor(wx.CURSOR_CROSS))self.Centre()self.Show(True)def DrawCrossHair(self, a, b):dc = wx.ClientDC(self)dc.Clear()dc.SetPen(wx.Pen(wx.Colour(100, 100, 100), 1, wx.DOT))dc.CrossHair(a, b)def OnMotion(self, event):x, y = event.GetPosition()self.DrawCrossHair(x, y)def OnLeaveWindow(self, event):dc = wx.ClientDC(self)dc.SetBackground(wx.Brush('WHITE'))dc.Clear()app = wx.App()CrossHair(None, -1, 'CrossHair2')app.MainLoop()self.Bind(wx.EVT_MOTION, self.OnMotion)self.Bind(wx.EVT_LEAVE_WINDOW, self.OnLeaveWindow)We bind two events to event handlers. The wx.EVT_MOTIONevent is generated, when we move a cursor over the window.The second event wx.EVT_LEAVE_WINDOW is generated,when we leave the window with our mouse cursor.def OnMotion(self, event):x, y = event.GetPosition()self.DrawCrossHair(x, y)Every time we move a cursor over a window, the methodOnMotion() is called. In this method we figure out the currentposition of the mouse cursor and call the DrawCrossHairmethod, which is responsible for drawing the cross hair.21 de 44 27/04/2008 1:08