Re: [Buildroot] [PATCH RFC 1/2] package/python-pillow: install libImaging headers

["J. Neuschäfer via buildroot" <buildroot@buildroot.org>]

On Sun, Dec 28, 2025 at 12:14:15AM +0100, Thomas Petazzoni wrote:
> Hello J,
> 
> Thanks for your patch!
> 
> On Fri, 26 Dec 2025 17:07:10 +0100
> J. Neuschäfer via buildroot <buildroot@buildroot.org> wrote:
> 
> > python-rgbmatrix depends[1] on Imaging.h since commit bf45676 ("Refactor
> > broken unsafe SetImagePillow()").
> 
> You should clarify here: "and therefore changing python-pillow to
> install this header is needed prior to bumping python-rgbmatrix".

Will do

> 
> > Debian only installs four headers[2], but this seems insufficient,
> > because Imaging.h includes at least one header that is not on this list
> > (Arrow.h).
> > 
> > [1]: https://github.com/hzeller/rpi-rgb-led-matrix/pull/1818
> 
> Please point to the commit that has been merged, not some "random" PR.

Will do, it's

https://github.com/hzeller/rpi-rgb-led-matrix/commit/bf45676acb9aad3e453833c3a13033ab0650abb3

> 
> > [2]: https://sources.debian.org/src/pillow/12.0.0-1/debian/rules#L106
> 
> Please add your Signed-off-by line here.

Indeed, I forgot!

> Curious: python-pillow would for me be a... Python module. And so would
> be python-rgbmatrix. But with your patch, we install some C/C++
> headers. So python-pillow includes a native library, and
> python-rgbmatrix directly links against this library? How was it
> working prior to this change?

Pretty much. python-pillow is a Python module, but it's partially
implemented in C. python-rgbmatrix (the Python module for the
rpi-rgb-led-matrix C++ library) accesses internal state of objects
created by python-pillow. There is no direct linking, both native
libraries exist in the same process because they are loaded as part of
their respective Python modules. Prior to this commit, python-rgbmatrix
included its own definition of struct ImagingMemoryInstance (called
PillowImagingInstance). With this commit, pillow's Imaging.h is included
to get the struct layout and ultimately the offset of the "image32"
member.

Thanks!
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