Path: utzoo!censor!geac!torsqnt!hybrid!scifi!bywater!uunet!vicorp!daniel
From: daniel@vicorp.com (Daniel Dee)
Newsgroups: mail.xpert,comp.windows.x
Subject: Question (Bug?) in XCopyArea
Message-ID: <1991Feb27.025708.14467@vicorp.com>
Date: 27 Feb 91 02:57:08 GMT
Reply-To: daniel@vicorp.UUCP (Daniel Dee)
Distribution: na
Organization: V. I. Corporation, Amherst, Massachusetts
Lines: 49

I wonder if anybody can give me some insight into this. Or maybe 
tell me if it is a bug.

I am using XCopyArea to copy a region in a window into a pixmap
and then to copy it back from the pixmap to the window. The problem
I am encountering is this: the region is being copied onto the
window with a black band on top and on the right side of the
pixmap exactly equal in size to the position of the origin of
the window from the upper-left hand corner of the screen. 
That is,

       Pixmap                   Screen

       +------+        +-----------------------------+
       |      |        |    Window                   |
       |      |        |  +-----------------+        |
       |   |  |        |  |                 |        |
       +---|--+        |  |  +------+       |        |
           |           |  |  |XXXXXX|       |        | 
           +-XCopyArea------>|X +---|       |        | 
                       |  |  |X |   |       |        | 
                       |  |  +------+       |        |
                       |  +-----------------+        | 
                       |                             | 
                       |                             | 
                       |                             | 
                       +-----------------------------+



If the origin of the Window is (X,Y) from the upper-left hand corner
of the Screen, then the copied Pixmap will leave a band (shown as
XXXXX region in the diagram above) on the left with width X,
and top with height Y.

The rest of the Pixmap seems to copy correctly. As far as I can tell,
I am not doing anything wrong. All I can figure out is that 
XCopyArea thought that Pixmap is the Window and like the 
Window, it is offset (X,Y) from the origin of the Screen. It then 
thinks that the region from (0,0) to (X,Y) on the Pixmap is outside 
the valid display region, which is true for the Window and not 
for the Pixmap. Hence only the region starting from (X,Y) of the 
Pixmap is copied onto the window by XCopyArea.

Am I wrong? If I am right, then this seems like a bug.
Anybody has any idea. Any insight will be appreciated. 
Thank you.

-- Daniel (ddee@vicorp.com)