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

[Jordan C. <jc...@co...>]

Michel Dänzer wrote:
> 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. :)

Agreed.  It should behave the same as if you had any busy X client that 
didn't repaint its window after a resize.  A stretch blit would be just 
as jarring to the eye as an unpainted window (though in a different way).

Jordan

-- 
Jordan Crouse
Qualcomm Innovation Center
Qualcomm Innovation Center is a member of Code Aurora Forum