Re: configure / meson: Move the GBM handling to meson.build

[Thomas Huth]

On 06/09/2021 13.37, Peter Maydell wrote:
> 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,

Right.

> 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.

Marc-André, you've introduced the GBM library in commit d52c454aa as far as 
I can see ... could you please comment on this? Was there a reason not to 
add --enable-gbm and --disable-gbm switches?

 Thomas