Why X protocol/server forbid zero width/height?

[Dmitry Yu. Bolkhovityanov]

On Wed, 23 Nov 2005, Russell Shaw wrote:

> Jim Gettys wrote:
>> I have no clue; I certainly don't remember any reason for this in the
>> dusty attic of my brain. 				- Jim
>> b
>> 
>> On Wed, 2005-11-23 at 11:35 +0600, Dmitry Yu. Bolkhovityanov wrote:
>>
>>>  	Hi!
>>>
>>>  	As specs say, and as practice confirms, attempt to set XWindow's 
>>> width and/or height to 0 results in BadValue error.
>>>
>>>  	BUT: why such a design decision was made (19 years ago?)?
>>>
>>>  	Zero width and/or height seem to be a natural concept (so that
>>> windows can exist and be "invisible" when they have no content -- this is 
>>> particularly useful for container windows).  And forbidding zero size 
>>> creates a "hole" in "size space", so that all widgets have to avoid zero 
>>> size, including unnatural code like "if (width==0) width=1".
>>>
>>>  	Googling through Usenet gave no answer to this question.
>>> 
>>> P.S. Of course, now this can't be changed -- but the reasons of that
>>>       decision are of interest for better understanding of X ideology.
>
> It should be able to be changed if you do your own extension. I'm going
> to fix lots of things for my own uses.

 	Well, in this case -- no.  The check is hardcoded in 
xc/programs/Xserver/dix/window.c::ConfigureWindow(), lines 2236-2240:

 	if (!w || !h)
 	{
 	    client->errorValue = 0;
 	    return BadValue;
 	}

 	What I'm curious about is -- why?  Why is that check at all there?

 	_________________________________________
 	  Dmitry Yu. Bolkhovityanov
 	  The Budker Institute of Nuclear Physics
 	  Novosibirsk, Russia