[Mesa-dev] Why are pbuffers backed by a pixmaps (Was Re: [PATCH] egl: Fix leak of X11 pixmaps backing pbuffers in DRI3.)

[Emil Velikov]

Hi Adam,

On 9 August 2018 at 17:41, Adam Jackson <ajax at redhat.com> wrote:
> On Thu, 2018-08-09 at 17:20 +0100, Emil Velikov wrote:
>
>> If you have a moment, I'd be interested to know why we're creating a X
>> primitive for pbuffer surface.
>> IIRC pbuffers are used of off-screen rendering, thus having zero
>> knowledge/dependency on the underlying platform.
>
> pbuffers might be offscreen, but they're still window-system objects.
>
Double-checking we're using the same terminology.

Window-system: EGL/GLX/WGL
Underlying platform: X/Wayland/Android/etc, when EGL is used

Agreed, they are window-system objects. Although I cannot see any
reason why we'd need a pixmap here (EGL).
In the GLX case, it's required due to server-side rendering. One needs
a separate primitive for each pbuffer, thus the information can be
passed long the wire.

Feel free to share links which might shed some light.

Thanks
Emil