Re: [Qemu-devel] [RfC PATCH 0/3] sdl2: add opengl rendering support

[Daniel P. Berrange]

On Thu, Dec 11, 2014 at 12:05:53PM +0100, Gerd Hoffmann wrote:
>   Hi,
> 
> This series add support for screen rendering using opengl.  This only
> blits classic DisplaySurfaces to the screen using opengl, it does not
> (yet) enable gfx emulation use opengl for rendering.
> 
> It depends on the "sdl2: fixes, cleanups and opengl preparation"
> series just posted.
> 
> The big question mark (and the reason this is RfC) is how we are going
> to enable/disable opengl at runtime.  The options I see are:
> 
>  (1) make that a ui option, i.e. '-display sdl,opengl={on,off}'.
>  (2) make that a global option, i.e. -opengl={on,off}
> 
> I'd tend to go for (2).
> 
> First, because we have a initialization order issue once gfx emulation
> starts using opengl:  ui code is initialized after device code (and this
> can't be changed easily because devices need register displays before we
> init the ui).  Therefore with (1) the device emulation doesn't know at
> init time time whenever opengl is available or not.
> 
> Second for the long term there will be 3d support in a number of UIs:
> I expect sdl2, gtk, egl (using render nodes, for headless) and spice.
> Having a global switch for them all looks easier.

In libvirt we model the ability to turn on 3d support for guests against
the video device, rather than the backend device, since it is a guest
visible feature. So should we do this against the virtual virtio-vga
device and have the backends just tie their behaviour to that ?

Regards,
Daniel
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