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From: dtomm@sparcplug.us.oracle.com (Doug Tomm)
Newsgroups: comp.windows.x
Subject: Re:  Debugging Graphics Programs
Message-ID: <1990Sep18.165816.21969@oracle.com>
Date: 18 Sep 90 16:58:16 GMT
Distribution: na
Organization: Oracle Corporation
Lines: 48

Somebody wrote:

> I'd like to debug a program I've written in X that simply opens a window
> and draws in it.  However, when I use dbx or gdb, the window does not
> open nor can I see any graphics being drawn as the program executes.  If
> I simply execute the program, it opens its window and draws in it just
> fine.  How can I get the debugger to open the window and draw into it as
> the program executes?

Try using XSynchronize.  You should do something like the following:

			:
			:
			:
		dpy = XOpenDisplay(displayname);
		if (!dpy)
			bail(out);
#ifdef DEBUG
		XSynchronize(dpy, 1);
#endif /* DEBUG */
			:
			:
			:

XSynchronize will enable synchronous event reporting (disabled with
XSynchronize(dpy, 0)).  This will cause the effects of events to
appear immediately, so that you can see what happens as you step
through a debugger.

Bracketing the XSynchronize as above is important because XSynchronize
will make your application run much slower.

Another way to turn on synchronous mode is to call XSynchronize from
within dbx (I don't know how to do this from within GDB).  Set a
breakpoint before your event handler, and type

	(dbx) call XSynchronize( mydpy, 1 )

where mydpy is the display pointer returned by XOpenDisplay (make sure
it isn't null).  The second approach is useful when debugging toolkit
applications.

Doug Tomm
Oracle Corporation
dtomm@oracle.com

My wife love me.  We don't agree all the time.  Oracle loves me a lot
less.  You figure it out.