Path: utzoo!mnetor!uunet!husc6!mit-eddie!uw-beaver!cornell!rochester!bbn!uwmcsd1!ig!agate!ucbvax!latlog.UUCP!PAYNE
From: PAYNE@latlog.UUCP
Newsgroups: comp.windows.x
Subject: XCopyArea
Message-ID: <620.8802111345@latlog.co.uk>
Date: 11 Feb 88 13:45:37 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 34

I have a query about the use of XCopyArea:

When trying to use XCopyArea to scroll the contents of a window I do the 
following:

Scroll-left: I use XCopyArea to move an area the full size of the window
	     from x=0 to x=-100 (say). This moves the image to the left
	     and generates a graphics expose event for the portion on the
	     right because it has no information to write to that portion
	     of the screen - this is good.

Scroll-right: This time I use XCopyArea to move an area the full size of
	       the screen from x=-100 to x=0. What seems to happen is that
	      the source origin gets changed to be 0(?) so that the image
	       is not moved. If I copy an area smaller than the full window
	      size then I do not get a graphics expose event so I can not
	      find out what part of the screen I need to refresh.


	1) Firstly, is this behaviour right, and if so is there a good
	   reason why the source origin is truncated (or whatever) ?

	2) I realize that this is not perhaps how you envisaged XCopyArea
	   to be used(?) but given that the scroll-left works just fine
	   in this case is there a way of getting identical behaviour
	   when I do a scroll-right?

	3) Alternatively am I doing something wrong?

Thanks in advance.

Julian Payne, European Silicon Structures (ES2
).
(payne@latlog.uucp)