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From: hill@luke.lanl.GOV (Jeff Hill)
Newsgroups: comp.windows.x
Subject: Re:  Is there some way to find out what a BadMatch is about?
Message-ID: <9106241731.AA20764@luke.lanl.gov>
Date: 24 Jun 91 17:31:06 GMT
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 53

>> I've got this program which works fine on monochrome screens, but
>> when I try running it on a PseudoColor screen I get BadMatch errors
>> from innocuous calls like XDrawPoint and XFillRectangle.  So I was
>> just wondering if anyone has any tricks for finding out what the
>> server thinks doesn't match.  I suppose I could run the server in a
>> debugger, but that's a hassle.
>
>Run it under xscope, that's what I find is generally best.  That way
>you can see precisely what requests are being sent....

Another (perhaps easier) way to track down what call caused the bad 
match is to use XSynchronize(). Many X applications and most Xt 
applications have this as a command line option. This works even better 
if you have installed your own X exception handler which dumps core.
You can then investigate the cause from a debugger (the default X exception
handler calls exit() leaving no trace of what happened). 
					Jeff
PS: An example code follows:

#include <Xlib.h>
main()
{	
	

	/*
	 * install an error handler that makes a core file when
	 * an X Error occurs. This can be usefull if XSync is on.
	 *
	 */
	XSetErrorHandler(opi_x_error_handler);
}

/*
 *
 *	X Error Handler
 *	(with core dump)
 *
 */
int x_error_handler(d, pev)
Display		*d;
XErrorEvent	*pev;
{
	char	message[256];

	XGetErrorText(d, pev->error_code, message, sizeof(message));


	printf("Sorry a fatal X Window System error has occured\n");
	printf("\tThe cause: %s\n", message);
	printf("\tResource Id. %x\n", pev->resourceid);
	printf("Core Dumped\n");
	abort();
}