Re: [PULL v2 06/10] configure / meson: Move the GBM handling to meson.build

[Peter Maydell]

On Mon, 6 Sept 2021 at 12:30, Thomas Huth <thuth@redhat.com> wrote:
>
> The GBM library detection does not need to be in the configure script,
> since it does not have any user-facing options (there are no
> --enable-gbm or --disable-gbm switches). Let's move it to meson.build
> instead, so we don't have to clutter config-host.mak with the related
> switches.
>
> Additionally, only check for GBM if it is really required, i.e. if we
> either compile with OpenGL or with virglrenderer support.
>
> Message-Id: <20210714085045.797168-1-thuth@redhat.com>
> Signed-off-by: Thomas Huth <thuth@redhat.com>

I assume this doesn't change behaviour here, so this is more of
a maybe-followup-improvement note, but the gbm checking (in the
old configure version) recently confused somebody on qemu-discuss:
https://lists.nongnu.org/archive/html/qemu-discuss/2021-09/msg00010.html
They didn't have libgbm installed, and because there's no
--enable-gbm there's no way to force configure to enable the egl-headless
UI frontend -- it is always silently falls back to "don't build that".
Ideally we ought to provide a means for distros and users to say
"make sure you build this feature or barf" the way we do with other
things, I guess.

-- PMM