Re: [Mesa3d-dev] [mesa patch 1/3] dri2: Event driven buffer validation.

[Michel D. <mi...@da...>]

On Fri, 2010-01-22 at 08:40 -0800, Keith Whitwell wrote:
> It's a very rare application that can render half a frame to one sized
> framebuffer and the other half to another and expect to have a
> meaningful result.
> 
> It's also incredibly difficult to write a driver that produces any
> sensible result when the render-target size changes halfway through a
> frame. There are a bunch of reasons for this, including the fact that
> the driver will have unflushed command buffers referring to the old
> size that are suddenly invalid when a new size materializes. 

Right, that's why I was worrying about processing the DRI2 buffer
invalidate event in the middle of rendering a frame. But Francisco
clarified that it's only processed when the application is actively
processing X11 events, which should usually only be the case between
rendering frames.


> My pet take on this is that we should go one step further and modify
> GLX semantics to allow a stretch blit on swapbuffers to scale the
> rendered image up/down to the new window size.

I think it's better to follow the X11 window gravity than to scale. DRI2
may accidentally already be doing this for the majority of apps which
use the default gravity. :)


-- 
Earthling Michel Dänzer           |                http://www.vmware.com
Libre software enthusiast         |          Debian, X and DRI developer