Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!gatech!ncsuvx!cccvs1.ncsu.edu!rcb
From: rcb@cccvs1.ncsu.edu (Randy Buckland)
Newsgroups: comp.windows.x
Subject: Save under problem
Message-ID: <3018@ncsuvx.ncsu.edu>
Date: 18 May 89 13:43:04 GMT
Sender: news@ncsuvx.ncsu.edu
Reply-To: rcb@cccvs1.ncsu.edu (Randy Buckland)
Organization: North Carolina State University
Lines: 32

I am having a problem using save-under attribute that and wondered if anyone
had seen this.

I have a main window with a drawing in it. I have a child of this window
that is unmapped that will overlay part of the drawing and has the
attributes save-under set to true and backing-store set to always (the
contents of the child never change, it's a menu) When I run the program,
everything works ok except that save-under is not being used. I get an expose
event for the main window every time I unmap the child. Now you might
be thinking that save under is not implemented on my workstation, but it is.
I have a vaxstation II monochrome running MIT X11R3 under ultrix 3.0.

I know the save-under works since I can make it start working in my window
in only one way as follows. After the window is created and I verify that
save under is not working, I make sure the child window is mapped and then
push the main window under another window (xterm window). When I recall the
window, the main window is redrawn and the child is not because of the
backing store. At this point, I can unmap the child and the region of the
main under the child is redrawn. Then when I map and unmap the child, the 
save-under works and I don't get an expose event for the main window.

This only works if the child is mapped when the main window is obscured by
another window. If the child is unmapped when the main is pushed down and
brought back, the behavior does not change and I still continue to get
expose events for the main when the child is unmapped.

I also just ran some more tests and find the same behavior on a 
vaxstation 2000 (B&W) running MIT X11R3 and on an IBM PC/RT running IBM's
Xwindows for AIX

Randy Buckland
rcb@ncsuvx.ncsu.edu