Re: Can GTK+ make use of XSHM extension from MIT

[Tapani Pälli <tapani palli nokia com>]

Hello;

ext Bin Chen wrote:
> On Jan 10, 2008 4:26 PM, Tapani Pälli <tapani palli nokia com> wrote:
>   
> > Hello;
> >
> > ext Bin Chen wrote:
> >     
> > > Hello,
> > >
> > > I am running GTK+ in a singal machine, the machine is slow so I want
> > > make GTK+ use XSHM extension to accelerate the drawing speed.
> > >
> > > By taking a look at both GTK+ source code and the MIT-SHM paper, my
> > > conclusion is :
> > >
> > > 1) The XSHM can only support XImage and Pixmap.
> > >
> > >       
> > It is supporting the creation of XImage structure in shared memory and
> > 'transferring' it to X-server to be used as a pixmap.
> >
> >     
> > > 2) The GTK+ engine update the image using XCopyArea, so its impossible
> > > to accelerate the entire process.
> > >
> > > I am thinking a case, we do all the rendering process in GTK+
> > > side(such as use pango to render text, use other library to render
> > > image), the transfer the rendered image to XServer using XSHM, then
> > > draw this Image to the window.
> > >
> > >
> > >       
> > SHM extension is made to 'accelerate' data transfer between X client and
> > server when they reside on same machine. When data is on server end, it
> > can be used and manipulated via Xlib commands such as XCopyArea and the
> > operation is done on server side. Operation performance depends on the
> > X-server driver implementation.
> >
> >     
> > > Will this work?
> > >
> > >       
> > Your usecase is valid, but are you facing some performance issues with
> > current implementation? Have you profiled where the time is actually
> > spent? You might want to create these buffers (images) beforehand and
> > then transfer them to server. See also XRender API for rendering and
> > manipulating buffers on server-side.
> >
> >     
> I am not doing very detailed profiling against this, but by comparing
> the frame rate in my player against using pure framebuffer
> implementation. The performance difference is large. If not using
> shared memory to transfer the decoded image data, obviously the
> performance can't be good in slow machine.
>   

You did not mention a 'player' before. Video playback is very much of a
special case. Are you drawing/compositing other elements on top of
video? If so, you are entering very experimental areas here. You might
want to check out Xv extension which is available for video. I don't
know much about video so I'll stop here, good luck :-)

> The GTK+ can draw pixbuf and image to the drawable, is there any
> existing method for me to choose to force the low level gdk to use SHM
> extension?
>
> Thanks.
> Bin
>
>   


// Tapani Pälli

-- 
Software Engineer
Open Source Software Operations