[PATCH] libcamera: meson: Fix libyuv detection

[Kieran Bingham]

Quoting Barnabás Pőcze (2025-01-14 21:39:40)
> Hi
> 
> 
> 2025. január 14., kedd 22:24 keltezéssel, Kieran Bingham <kieran.bingham at ideasonboard.com> írta:
> 
> > Quoting Kieran Bingham (2025-01-14 21:19:35)
> > > From: Dylan Aïssi <daissi at debian.org>
> > >
> > > We already fall back to a subproject to support the libyuv package when
> > > it can not be discovered through the usual dependency() mechanism.
> > >
> > > Unfortunately libyuv may be packaged without any corresponding
> > > pkg-config support as can be seen at [0], so further extend the
> > > dependency search by using an explicit cc.find_library() call.
> > >
> > > [0] https://packages.debian.org/bookworm/amd64/libyuv-dev/filelist
> > >
> > > Signed-off-by: Dylan Aïssi <dylan.aissi at collabora.com>
> > 
> > I've posted this patch on Dylan's behalf from
> > https://salsa.debian.org/multimedia-team/libcamera/-/commit/685482827a0e6fe5dfe19778e633ab95b703cef4
> > though I have reworded the commit message and comment inline, but the
> > core functional change is direct from Dylan's patch...
> > 
> > 
> > On Ubuntu 22.04.5 LTS:
> > 
> > $ sudo apt install libyuv-dev
> > 
> > ...
> > libcamera$ meson setup ...
> > ...
> > Found pkg-config: YES (/usr/bin/pkg-config) 0.29.2
> > Found CMake: /usr/bin/cmake (3.22.1)
> > Run-time dependency libyuv found: NO (tried pkgconfig and cmake)
> > Library yuv found: YES
> > Library atomic found: YES
> > ...
> > 
> > (Based on the second Library yuv found: YES)
> > 
> > Tested-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> 
> This is the change I have locally to achieve the same:
> 
> diff --git a/src/meson.build b/src/meson.build
> index 76198e953..8cb4af61a 100644
> --- a/src/meson.build
> +++ b/src/meson.build
> @@ -30,7 +30,20 @@ endif
>  # libyuv, used by the Android adaptation layer and the virtual pipeline handler.
>  # Fallback to a subproject if libyuv isn't found, as it's typically not provided
>  # by distributions.
> -libyuv_dep = dependency('libyuv', required : false)
> +
> +if not get_option('force_fallback_for').contains('libyuv')
> +    libyuv_dep = dependency('libyuv', required : false)
> +
> +    if not libyuv_dep.found()
> +        libyuv_dep = cxx.find_library(

I guess using cxx is the toolchain we're compiling the rest of the
project with so that likely makes sense.

> +            'yuv',
> +            required : false,
> +            has_headers : 'libyuv.h',
> +        )
> +    endif
> +else
> +    libyuv_dep = dependency('', required : false)

is the '' intentional ? What does that do or how does it work ?

> +endif
>  
>  if (pipelines.contains('virtual') or get_option('android').allowed()) and \
>     not libyuv_dep.found()
> 
> This has two advantages in my opinion:
>   * the `force_fallback_for=libyuv` meson option works;

Do we need to repeat all of this for gtest and libyaml too as
subprojects? Or are they already handled correctly ?

>   * the presence of at least `libyuv.h` is checked

the has_headers check is a very good addition also.

>     (I imagine this may be relevant for distributions where the development files
>      are placed in different packages).
> 
> `meson` has recently added experimental cmake wraps:
> https://mesonbuild.com/Wrap-dependency-system-manual.html#cmake-wraps
> I think this could make the dependency lookup simpler, but it is probably too new.
> 
> Or potentially `libyuv` could be added to the meson wrapdb,
> which could also enable some simplification.

Perhaps adding it to the wrapdb sounds good, but I don't know how to go
about that.

Our subprojects/libyuv.wrap probably needs an update too - it's still
set at a revision by 9109bcf22c7f ("subprojects: Add libyuv and built if
-Dandroid=enabled") in 2021 ... so must be quite dated!

> 
> 
> Regards,
> Barnabás Pőcze
> 
> 
> > 
> > > Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> > > ---
> > >  src/meson.build | 11 ++++++++---
> > >  1 file changed, 8 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/src/meson.build b/src/meson.build
> > > index 76198e9535db..0a9cdff8e7dc 100644
> > > --- a/src/meson.build
> > > +++ b/src/meson.build
> > > @@ -27,10 +27,15 @@ else
> > >      ipa_sign_module = false
> > >  endif
> > >
> > > -# libyuv, used by the Android adaptation layer and the virtual pipeline handler.
> > > -# Fallback to a subproject if libyuv isn't found, as it's typically not provided
> > > -# by distributions.
> > > +# libyuv, used by the Android adaptation layer and the virtual pipeline
> > > +# handler. Fallback to a subproject if libyuv isn't found, as it's typically
> > > +# not provided by distributions. Where libyuv is provided by a distribution, it
> > > +# may not always supply a pkg-config implementation, requiring cc.find_library()
> > > +# to search for it.
> > >  libyuv_dep = dependency('libyuv', required : false)
> > > +if not libyuv_dep.found()
> > > +    libyuv_dep = cc.find_library('yuv', required: false)
> > > +endif
> > >
> > >  if (pipelines.contains('virtual') or get_option('android').allowed()) and \
> > >     not libyuv_dep.found()
> > > --
> > > 2.47.1
> > >
> >