wxPython GetClientSize() returning (0, 0)

I am creating a small drawing application from a python book, "wxPython in Action", and it uses self.GetClientSize() to get the size of a window. For some reason this is return (0, 0) for me instead of the expected value (800, 600).

The program crashes when wx.EmptyBitmap is called with 0, 0 as its parameters. If I put wx.EmptyBitmap(800, 600) the entire program runs fine, minus resizing.

Here is the relevant method

    def InitBuffer(self):
        size = self.GetClientSizeTuple()
        print size
        sys.exit(1)
        self.buffer = wx.EmptyBitmap(size.width, size.height)
        dc = wx.BufferedDC(None, self.buffer)
        dc.SetBackground(wx.Brush(self.GetBackgroundColour()))
        dc.Clear()
        self.DrawLines(dc)
        self.reInitBuffer = False

And this is the complete code

#!/usr/bin/arch -i386 /usr/bin/python2.6 -tt

import sys
import wx

class SketchWindow(wx.Window):
    def __init__(self, parent, ID):
        wx.Window.__init__(self, parent, ID)
        self.SetBackgroundColour("White")
        self.color = "Black"
        self.thickness = 1
        self.pen = wx.Pen(self.color, self.thickness, wx.SOLID)
        self.lines = []
        self.curLine = []
        self.pos = (0, 0)
        self.InitBuffer()
        self.Bind(wx.EVT_LEFT_DOWN, self.OnLeftDown)
        self.Bind(wx.EVT_LEFT_UP, self.OnLeftUp)
        self.Bind(wx.EVT_SIZE, self.OnSize)
        self.Bind(wx.EVT_MOTION, self.OnMotion)
        self.Bind(wx.EVT_IDLE, self.OnIdle)
        self.Bind(wx.EVT_PAINT, self.OnPaint)

    def InitBuffer(self):
        size = self.GetClientSizeTuple()
        print size
        sys.exit(1)
        self.buffer = wx.EmptyBitmap(size.width, size.height)
        dc = wx.BufferedDC(None, self.buffer)
        dc.SetBackground(wx.Brush(self.GetBackgroundColour()))
        dc.Clear()
        self.DrawLines(dc)
        self.reInitBuffer = False

    def GetLinesData(self):
        return self.lines[:]

    def SetLinesData(self, lines):
        self.lines = lines[:]
        self.InitBuffer()
        self.Refresh()

    def OnLeftDown(self, event):
        self.curLine = []
        self.pos = event.GetPositionTuple()
        self.CaptureMouse()

    def OnLeftUp(self, event):
        if self.HasCapture():
            self.lines.append((self.color, self.thickness, self.curLine))
            self.curLine = []
            self.ReleaseMouse()

    def OnMotion(self, event):
        if event.Dragging() and event.LeftIsDown():
            dc = wx.BufferedDC(wx.ClientDC(self), self.buffer)
            self.drawMotion(dc, event)
        event.Skip()

    def drawMotion(self, dc, event):
        dc.SetPen(self.pen)
        newPos = event.GetPositionTuple()
        coords = self.pos + newPos
        self.curLine.append(coords)
        dc.DrawLine(*coords)
        self.pos = newPos

    def OnSize(self, event):
        self.reInitBuffer = True

    def OnIdle(self, event):
        if self.reInitBuffer:
            self.InitBuffer()
            self.Refresh(Fa开发者_如何转开发lse)

    def OnPaint(self, event):
        dc = wx.BufferedPaintDC(self, self.buffer)

    def DrawLines(self, dc):
        for (colour, thickness, line) in self.lines:
            pen = wx.Pen(colour, thickness, wx.SOLID)
            dc.SetPen(pen)
            for coord in line:
                dc.DrawLine(*coord)

    def SetColor(self, color):
        self.color = color
        self.pen = wx.Pen(self.color, self.thickness, wx.SOLID)

    def GetColor(self):
        return self.color

    def SetThickness(self, thickness):
        self.thickness = thickness
        self.pen = wx.Pen(self.color, self.thickness, wx.SOLID)


class SketchFrame(wx.Frame):
    def __init__(self, parent):
        wx.Frame.__init__(self, parent, -1, 'Sketch Frame', size=(800, 600))
        self.sketch = SketchWindow(self, -1)


def main():
    app = wx.PySimpleApp()
    frame = SketchFrame(None)
    frame.Show(True)
    app.MainLoop()

if __name__ == '__main__':
    main()

It's because you're calling GetSize in the __init__() method - the window isn't fully created until this method has completed. Thus, it hasn't has its width and height set properly.

You could use wx.CallAfter/CallLater to postpone the calling of this function until window creation has fully completed.

I don't know if there is a better solution, but the problem is that when the object was being initialized it didn't have a parent yet, so it didn't know what size it should be. Thus it was width 0 and height 0. However, it needed to initialize the buffer. What I did to fix this was

if size == (0, 0):
    size.width = 1
    size.height = 1

Once it is added to the frame it gets a new size and the buffer is resized. So I guess that works!

I suppose another solution would be to pass a size parameter to the init method, but i'd prefer not to have to do that if it is not required.

Please post other solutions if you have them =)