eglGetDisplay(EGL_DEFAULT_DISPLAY)

[Thiago Milczarek Sayão]

Thank you very much, Pekka.


Em ter., 30 de abr. de 2024 às 11:39, Pekka Paalanen <
pekka.paalanen at haloniitty.fi> escreveu:

> On Tue, 30 Apr 2024 09:58:32 -0300
> Thiago Milczarek Sayão <thiago.sayao at gmail.com> wrote:
>
> > Hi,
> >
> > I'm looking the docs at
> > https://registry.khronos.org/EGL/sdk/docs/man/html/eglGetDisplay.xhtml
> >
> > But I'm still in doubt how it actually works, especially on Mesa.
> >
> > Will it detect which platform it's on if I pass EGL_DEFAULT_DISPLAY ? For
> > example, if I want to use the same code for Wayland and X11.
>
> I think Mesa EGL will first look at environment variable EGL_PLATFORM
> for a hard-override of the chosen platform. Otherwise, it tries to
> detect a platform from the native display passed in, which
> EGL_DEFAULT_DISPLAY does not provide. Finally there is a build-time
> chosen fallback.
>
> eglGetDisplay itself is a bit problematic since it was not intended to
> support choosing the platform at runtime (only at EGL implementation
> build time). New code would be better using eglGetPlatformDisplay(EXT)
> if at all possible, especially when you want it to work on multiple
> platforms, or just to be safe that EGL does not guess wrong what kind
> of native display you are passing in. Guessing it wrong would cause
> nonsensical errors or crashes. This is also why using EGL_PLATFORM
> environment variable is not a good idea.
>
> FWIW, on Wayland, EGL_DEFAULT_DISPLAY will not allow you to render into
> a window. It would open a new Wayland connection, but your application
> windows are created through a connection you made yourself, so EGL
> would not be able to target your windows. Each wl_surface is private to
> the connection where it was created.
>
>
> Thanks,
> pq
>
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