RE: Question about multi-displays control on wayland protocol‏

[Yang Andy]

Hi Pekka


Thank you very much for your reply.

>It would definitely be easier if you only need one EGLDisplay, and
>can use the EGLNativeWindowType argument of eglCreateWindowSurface() to
>choose the target output for the EGLSurface. In this case the required
>modifications would be limited to your version of compositor-fbdev.c.Now,i have adopted above solution.

Best regards.

Andy
> Date: Fri, 10 Oct 2014 09:29:24 +0300
> From: ppaalanen at gmail.com
> To: williamyang13 at hotmail.com
> CC: wayland-devel at lists.freedesktop.org
> Subject: Re: Question about multi-displays control on wayland protocol‏
> 
> On Fri, 10 Oct 2014 03:35:28 +0000
> Yang Andy <williamyang13 at hotmail.com> wrote:
> 
> > Hi Pekka
> > 
> > Thank you very much for your reply.
> > 
> > I got your meaning,but i have another question.
> > 
> > Is there any necessary for modify weston/compositor?
> > 
> > Because i investigate source code[compositor-fbdev.c],and find that compositor open device [/dev/fb0].
> > 
> > It seems that the compositor is constant with /dev/fb0,how does compositor direct surfaces to specific outputs(fb0/fb1...)
> > 
> 
> Right, if you have multiple monitors attached, the legacy fbdev
> interface is not going to be enough at all. Therefore you cannot use
> compositor-fbdev.c. Even the EGL support in compositor-fbdev.c is a far
> stretch we do not really like, because fbdev should just die.
> 
> The recommended solution is to move to a kernel DRM driver, and use the
> compositor-drm.c backend. I understand it might not be feasible for
> you, if you don't have a DRM driver and an EGL stack to go with it, but
> that is the direction you should be pushing for in the long run.
> 
> If you really are stuck with using fbdev, you will need to write (fork)
> and maintain your own fbdev backend.
> 
> I'm not sure how your EGL integration would work, because obviously
> EGL_DEFAULT_DISPLAY cannot specify which output to target. Probably
> your proprietary EGL stack has proprietary ways to choose the right
> /dev/fb* to target, but for that too you will need to modify the
> existing code in Weston.
> 
> If you need several EGLdisplays, e.g. one per /dev/fb*, then you may
> need to modify Weston even more, because I don't think it supports
> multiple renderer instances at the same time, and currently gl-renderer
> assumes a single EGLDisplay. Furthermore, if you create multiple
> EGLDisplays, then initializing EGL_WL_bind_wayland_display extension
> properly may be an issue: will you initialize it for each EGLDisplay
> separately, or for just one? Both ways cause side-effects that your EGL
> stack needs to correctly handle, and they are probably unexpected (not
> implemented or never tested), so proceed with caution.
> 
> It would definitely be easier if you only need one EGLDisplay, and
> can use the EGLNativeWindowType argument of eglCreateWindowSurface() to
> choose the target output for the EGLSurface. In this case the required
> modifications would be limited to your version of compositor-fbdev.c.
> 
> It all depends on the EGL implementation you have.
> 
> If you could use compositor-drm.c, it would all just work without
> modifications.
> 
> 
> Thanks,
> pq
 		 	   		  
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