UpdateLayeredWindow in pywin32

[livibetter]

Hi!

I am trying to making an On-Screen Display, which is implemented by
wx.Frame.
Basically I created a wx.Frame with style like

	super(OSDBase, self).__init__(parent, id, title,
								  style = wx.STAY_ON_TOP |
								  wx.FRAME_NO_TASKBAR |
								  wx.TRANSPARENT_WINDOW |
								  wx.NO_BORDER)
	self.SetTransparent(128)

But if I try to draw an image with alpha channel(like PNG format), I
always get
a background behind this image. But I don't want the background.

Then I read this article, http://www.codeproject.com/csharp/OSDwindow.asp
The demo program is written in C#. I understand that I need to use
UpdateLayeredWindow to update visual content of a layered window.

But I always got an error:

	Traceback (most recent call last):
	  File "osd_post.py", line 60, in <module>
		osd.Update()
	  File "osd_post.py", line 56, in Update
		2)
	pywintypes.error: (87, 'UpdateLayeredWindow', 'The parameter is
incorrect.')

I am not sure did I use UpdateLayeredWindow correctly.

Any help would be appreciated.


My Python is 2.5, pywin32 is 210, wxPython is 2.8.1

UpdateLayeredWindow Function Help from MSDN:
	http://msdn2.microsoft.com/en-us/library/ms633556.aspx

UpdateLayeredWindow Function Help from pywin32:
	http://aspn.activestate.com/ASPN/docs/ActivePython/2.4/pywin32/win32gui__UpdateLayeredWindow_meth.html

My source code:

"""pyitctrl - OSD"""
# Created Date : 2007/03/14
# Author: livibetter

import wx, winxpgui, win32con

class OSDBase(wx.Frame):
    def __init__(self, parent, id, title):
        super(OSDBase, self).__init__(parent, id, title,
                                      style = wx.STAY_ON_TOP |
                                      wx.FRAME_NO_TASKBAR |
                                      wx.TRANSPARENT_WINDOW |
                                      wx.NO_BORDER)
        self.SetTransparent(128)

        print hex(winxpgui.GetWindowLong(self.GetHandle(),
win32con.GWL_EXSTYLE))
        print winxpgui.GetLayeredWindowAttributes(self.GetHandle())

        self.img = wx.Image("icon.png")
        self.bmp = self.img.ConvertToBitmap()
        w, h = self.bmp.GetWidth(), self.bmp.GetHeight()
        self.SetClientSize( (w, h) )

    def Update(self):
        print "Update"

        screenDC = winxpgui.GetDC(winxpgui.GetDesktopWindow())
        print screenDC
        cScreenDC = winxpgui.CreateCompatibleDC(0)
        print cScreenDC

        (w, h) = self.GetSizeTuple()
        bmp = wx.EmptyBitmap(w, h)
        tmpDC = wx.MemoryDC()
        tmpDC.SelectObject(bmp)
        tmpDC.SetBackground(wx.Brush("BLACK"))
        tmpDC.Clear()
        tmpDC.DrawBitmap(self.bmp,0,0, True)
        tmpDC.Destroy()
        del tmpDC

        winxpgui.SelectObject(cScreenDC, bmp.GetHandle())

        winxpgui.UpdateLayeredWindow(self.GetHandle(),
                                     screenDC,
                                     self.GetPositionTuple(),
                                     self.GetSizeTuple(),
                                     cScreenDC,
                                     (0,0),
                                     0,
                                     (0,0,128,1),
                                     win32con.ULW_ALPHA)

app = wx.App(False)
osd = OSDBase(None, wx.ID_ANY, 'OSD Frame')
osd.Update()
osd.Show()

app.MainLoop()