Re: [Mesa3d-dev] Mesa and complex clipping?

[Brian P. <br...@tu...>]

Kendall Bennett wrote:
> Brian Paul <br...@tu...> wrote:
> 
> 
>>>I am not familiar with how Mesa handles complex clipping on X11, when
>>>drawing to the front buffer. Does Mesa use a shadow buffer in system
>>>memory and draw into that, and then blit? Or does Mesa have hooks such
>>>that it can get a complex clip list from X11 and then do the clipping
>>>that way?
>>
>>It's up to the Mesa device driver, since this is a window 
>>system-specific issue.
> 
> 
> Cool. I expected that, so it is nice to know the functionality is there.
> 
> 
>>For the DRI drivers, the XF86DRIGetDrawableInfo() function (part
>>of the XF86DRI X extension) returns the cliprects for the named
>>window. The drivers call this function whenever they obtain the
>>drawing lock. 
> 
> 
> Ok. I can get that info easily enough also as our SNAP drivers have the 
> ability to grab all the necessary clip lists from DirectX (or actually 
> whatever underlying platform is used).
> 
> 
>>>We have the ability to handle complex clip lists in the SciTech MGL so
>>>we can render directly to the front buffer (via DirectX ;-), and now
>>>that I have the latest Mesa integrated I wanted make sure Mesa would
>>>correctly honor the clip lists as well. Then general technique in the
>>>MGL is to take the complex clip list and traverse it, re-drawing the
>>>primitive object over and over for each of the clip rects in the entire
>>>list. The same idea could be used for Mesa, but I am not sure if there
>>>are hooked in there already for this (ie: exceute a cassette multiple
>>>times to iterate over the clip list)?
>>
>>The DRI drivers loop over the rects in the clipping list when they
>>render anything. 
> 
> 
> Is that done with a hook in the generic code, or do the DRI drivers 
> implement their own versions of the rendering pipeline to handle this? 
> Can you point me at a module to look at for an example?

The code is in each of the drivers, but I don't remember off-hand 
exactly where.  I'm sure you can find it with a little grepping.

-Brian