On Fri, 2009-08-21 at 11:45 +0200, Tom Cooksey wrote: > > When using glX, we have no guarantee over what state the back buffer will be > in > after swap buffers. So, whenever an application needs to update, it must re- > render the entire window. This makes things slow (we have to invoke every > child widget's paint event). To overcome this, we try to use a 3rd buffer as > a > back buffer, usually a multi-sampled FBO or PBuffer. We direct rendering to > the > FBO/PBuffer, bind it as a texture (after blitting it to a non multi-sampled > FBO > if needed), draw the whole buffer to the window's back buffer then call swap > buffers. Eughhh! But at least the PBuffer/FBO contents aren't destroyed. What > would be really nice is to be able to have an EGL_SWAP_BEHAVIOR == > EGL_BUFFER_PRESERVED equivalent on glX.
There's the GLX_OML_swap_method extension, but I'm not sure how well it's supported by our drivers at this point. Any issues there might not be hard to fix up though. > I think I can work around this by making a glx context current on a GLXPixamp > (from a XPixmap). Pixmaps are single buffered and so don't get destroyed on > swap buffers (in fact I don't even call swap buffers). I can then post > updates > using XCopyArea which will also cause the Xserver to generate an appropriate > XDamage region for the compositor. The only down side is that I have to > glFinish before calling XCopyArea. Actually you should only need glXWaitGL(), assuming the implementation of that meets the requirements of the GLX spec. > While I have this working, it seems a little hacky and isn't widely > supported (I have it working on 1 driver build for 1 bit of hardware). If you mean rendering to pixmaps isn't widely supported, that should be getting better with DRI2. -- Earthling Michel Dänzer | http://www.vmware.com Libre software enthusiast | Debian, X and DRI developer ------------------------------------------------------------------------------ Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day trial. Simplify your report design, integration and deployment - and focus on what you do best, core application coding. Discover what's new with Crystal Reports now. http://p.sf.net/sfu/bobj-july -- _______________________________________________ Dri-devel mailing list Dri-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/dri-devel
