Glynn Clements glynn at
Wed Sep 7 12:11:26 PDT 2005

Peter J. Bismuti wrote:

> Day 2, running into problems creating a window using XCreateWindow.  It is 
> failing and I haven't been able to pinpoint the cause.  I'm setting _Xdebug = 
> 1 in the debugger and printing the stack tracke within _XError, but it does 
> give consistent results.  Sometimes it crashes within XCreateWindow, other 
> times it crashes within XAllocColorCells.   It is said that debuggers are 
> unreliable, how can I be certain where the problem is?  Is the X protocol 
> error message always correct?

The error message is just a textual representation of the response
which the X server sends back. It doesn't depend upon the client's
execution context.

> It says that it is a "BadMatch", an error the 
> docs say cannot occur in XAllocColorCells.

The error message which you posted refers to XCreateWindow, not

> Once I'm certain that it the 
> problem is in XCreateWindow, what next? Trial-and-error doesn't seem to be 
> working.  Any help would be appreciated.

What arguments are you passing to XCreateWindow? Do the visual and
depth match one of the supported combinations as reported by xdpyinfo?

Glynn Clements <glynn at>

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