Proprosed break in libGL / DRI driver ABI

[Brian Paul]

Julien Lafon wrote:
> On Apr 6, 2005 3:37 PM, Brian Paul <brian.paul at tungstengraphics.com> wrote:
> 
>>Julien Lafon wrote:
>>
>>>On Apr 5, 2005 10:11 PM, Brian Paul <brian.paul at tungstengraphics.com> wrote:
>>>Will increasing MAX_WIDTH/HEIGHT affect applications which run in
>>>small windows or only those which use resolutions exceeding the 4Kx4K
>>>limit?
>>
>>Increasing MAX_WIDTH/HEIGHT will result in more memory usage
>>regardless of window size.
> 
> Do you know how much memory is additionally allocated? If it is less
> than 1MB then it may not be worth to worry about...

If you do a grep in the sources for MAX_WIDTH you'll see that it's 
used in lots of places.  Some are for stack allocations, others are 
for heap allocations.  It would take some effort to determine exactly 
how much more memory would be used.  I know of at least one structure 
that contains arrays dimensioned according to MAX_WIDTH that's 
currently just under 1MB.  That's probably the largest.


>>As is, you can't exceed 4K x 4K resolution without increasing
>>MAX_WIDTH/HEIGHT.  Your glViewport call will be clamped to those
>>limits if you specify larger.
> 
> Let me reformulate my question: Will increasing MAX_WIDTH/HEIGHT break
> any existing application at normal video screen sizes?

Probably not, but I'm not 100% sure.


>>>>But there probably aren't too many people generating 4Kx4K images.
>>>
>>>We've been running tests with the glutdemo applications and Xprint at
>>>higher resolutions (6Kx8K window size) and did not notice any bad
>>>rendering using the software rasterizer.
>>
>>How large are your triangles?
> 
> I thought we have tested all combinations ranging from very small
> triangles up to full window size.

Try a sliver triangle that goes from the lower-left corner of the 
viewport to the upper-right.  Verify that the two long edges exactly 
meet at the upper-right.


>>The interpolation error will accumulate and be most noticable with
>>very large triangles.
> 
> Can you point me to one of the glutdemo applications which may likely fail?

I can't.  It would be easier to write a new program that stressed the 
scenario that's likely to fail.

-Brian