On Mon, Mar 5, 2012 at 2:42 AM, Pekka Paalanen <[email protected]> wrote: > On Sun, 4 Mar 2012 20:37:48 -0800 > Mandeep Singh Baines <[email protected]> wrote: > >> Hi, >> >> I have recently started playing around with EGL_PLATFORM=drm. Using >> eglkms.c and compositor-drm.c as examples, I've been able to port some >> simple EGL/GLESv2 applications without much effort. But the one weird >> thing is that everything gets rendered upside down and backwards. I >> guess I could solve this with the projection matrix but just wondering >> why I'm getting this effect. How does compositor-drm deal with this. > > Look for WL_OUTPUT_FLIPPED in weston. > > I guess and if I remember right, flipped y-axis is because OpenGL > back/front buffer of a window has origin at top-left with y growing > down, but FBOs have origin at bottom-left with y growing up. Or maybe > it was vice versa, I didn't check.
I'm actually not sure about this. For a while I thought that GL framebuffer objects had a different coordinate system (origin in upper left), but Robert Bragg recently pointed out to me that that was just a mesa optimization. Which could be true and I wasn't able to find anything in the FBO spec about the coordinate system. Either way, there isn't currently anything you can do, except render upside down. We do have a new interface planned, that will let you create a struct gbm_surface, which you can then create an EGLSurface from. That way it's going to be a "system fbo" internally in mesa and the coordinate system is going to what you expect. It will also remove the need for the surfaceless extension (since now we have a real EGLSurface). The API will let you "lock" the surface frontbuffer after a swap, which gives you a gbm_bo which you can then pageflip to. It's going to require mesa master, but I hope we can land it within the next couple of weeks. http://cgit.freedesktop.org/~krh/mesa/log/?h=gbm_surface Kristian _______________________________________________ wayland-devel mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/wayland-devel
