Thanks Robert. That answered most of my questions. Below, when you say "lack of any equivalent to GLX TFP extension", I am assuming that the GLX TFP extn. is not available as an EGLX extn. Am I right? OR is this a limitation in the OpenGL ES?
On Tue, Dec 23, 2008 at 7:07 PM, Robert Bragg <[email protected]> wrote: > On Tue, 2008-12-23 at 17:11 -0800, Bipin George Mathew wrote: > > Hi, > > > > I am evaluating whether I can use Clutter to write an X Window Manager > > on a device which supports/accelerates OpenGL ES. Is my answer > > metacity-clutter - since Clutter abstracts OpenGL/OpenGL ES OR will > > metacity-clutter need to be changed to accomodate OpenGL ES? > > Also, what backend option do I build Clutter with - eglx or eglnative? > > Is there any advantage choosing one over the other? > > > > One problem you will likely come across is the lack of any equivalent to > the GLX texture from pixmap extension. Without this you will need to > e.g. use XSHM to fetch the contents of your windows so that they can be > uploaded as textures and this may cause some performance issues. > Depending on the details of your system though, you may get away with > this. > > Another problem you might have is the lack of driver support for > redirecting other GLES apps offscreen. Depending on the style you try to > achieve with your composite manager you may see artifacts due to the > fact that other GLES apps are being directly rendering to your > framebuffer. For example if your composite manager warps application > windows when they minimize, then it's quite likely that won't work for > GLES applications. If you only plan to use GLES for the composite > manager and not for other applications, or you are very careful about > how you handle other GLES based applications, then this might not be a > problem for you. > > Regarding eglx vs eglnative, you may be able to get away with either. > If you need to support GLES applications as well as the composite > manager then you will need eglx. If you don't then either may be used to > create a fullscreen window, and if for example you can get your > eglnative driver drawing to your framebuffer over the top of Xfbdev, it > might just be a a question of comparing other factors, such as > stability/performance. > > If you are to go ahead with creating a GLES based composite manager, > metacity-clutter may be a reasonable starting place. One thing you may > find though is that metacity hasn't been heavily optimised for low > memory devices, so depending on your constraints you might need to do > some profiling, but I can't see why that couldn't be done. > > I hope that helps you a bit, > kind regards, > - Robert > > -- > Robert Bragg, Intel Open Source Technology Center > >
