Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!cs.utexas.edu!sun-barr!apple!metaphor!solrac!rimola
From: rimola@solrac.metaphor.com (Carlos Rimola)
Newsgroups: comp.os.os2.programmer
Subject: Drawing & Clipping
Keywords: PM, Clipping
Message-ID: <1385@metaphor.Metaphor.COM>
Date: 25 Aug 90 00:53:58 GMT
Sender: news@metaphor.Metaphor.COM
Reply-To: rimola@solrac.metaphor.com (Carlos Rimola)
Organization: Metaphor Computer Systems, Mountain View, CA
Lines: 35


A basic (I hope) PM question:

I have an analog clock application that experiences a clipping peculiarity
when it is partly overlayed by a dialog or a pull down menu.  eg:

	+-------+
	|\   	| (1)
  (2) +======+	|
      +======+	|
	|   \	|
	+-------+

(1) is the main window, (2) is a dialog that is partly overlaying the
window, the "\" symbols represent a line that is partly overlayed by
the dialog.  The problem is that often the drawing that takes place outside
of the overlayed area (outside not under it) is incorrect.  eg:      

	1) draw a line
	2) overlay window with a dialog, partly covering the line
	3) erase the line by redrawing it using the background color
	4) remove the dialog 

At the end of this operation I end up with the line partly erased, the
portion under the dialog is correct but that portion not covered by the
dialog is not.  eg:

	+-------+
	|\   	| 
  	|	|
      	|	|
	|   \	|
	+-------+

Can someone explain why this is happening and what can be done to fix it?