chore!: Deprecate any_color_converted_view

[marco-langer]

Description

I suggest to deprecate the function any_color_converted_view from gil/extension/dynamic_image/image_view_factory.hpp, because it has the exact same implementation as the function color_converted_view:

template <typename DstP, typename ...Views>
inline
auto color_converted_view(any_image_view<Views...> const& src)
    -> typename color_converted_view_type<any_image_view<Views...>, DstP>::type
{
    using cc_view_t = typename color_converted_view_type<any_image_view<Views...>, DstP>::type;
    return apply_operation(src, detail::color_converted_view_fn<DstP, cc_view_t>());
}

template <typename DstP, typename ...Views>
inline
auto any_color_converted_view(const any_image_view<Views...>& src)
    -> typename color_converted_view_type<any_image_view<Views...>, DstP>::type
{
    using cc_view_t = typename color_converted_view_type<any_image_view<Views...>, DstP>::type;
    return apply_operation(src, detail::color_converted_view_fn<DstP, cc_view_t>());
}

According to the documentation of any_color_converted_view, the prefix any_ was added to avoid an ambiguous overload resolution for GCC 3.4, which however, we do not have to support anymore with C++11.

Tasklist

• Ensure all CI builds pass
• Review and approve

[sdebionne]

Makes sense, thanks! Actually I wonder if we could remove it alltogether...

[striezel]

Actually I wonder if we could remove it alltogether...

As far as I understand Boost's policy with regards to deprecation there needs to be at least one version / release where stuff that will get removed has to be announced as deprecated. Then the next release can actually remove that stuff.

So it could be something like:

• Boost 1.79.0: feature X is still present.
• Boost 1.80.0: announce deprecation
• Boost 1.81.0: remove feature X

[mloskot]

Boost 1.80.0: announce deprecation

Yes, we need to deprecate it first with a release note similar to this
8b1c2d3

[striezel]

Yes, we need to deprecate it first with a release note

I've just created a pull request with the corresponding release notes to get things moving: #678.

[mloskot]

@striezel AFAIU, this PR is to be closed in favour of #678 Correct?

[striezel]

Yes, it can be closed.

However, after the release of Boost 1.80 a new PR can (and should) be created that actually removes the then deprecated any_color_converted_view.

[marco-langer]

In my PR here I also changed the implementation of the functions in order to remove the invocation of apply_operation(). This will be necessary anyway in order to complete #656 (actually I postponed further work on #656 and waited until this PR gets merged, because both have merge conflicts).

#678 hasn't changed the implementation of the deprecated functions. But I can rebase #656 later on and change the implementation again if #678 gets merged.

[mloskot]

@marco-langer Good point. Thank you very much for your help!

---

I'm closing this PR and I'm going to merge @striezel 's #678.

[marco-langer]

Since #678 got merged, I noticed that the deprecation warning is triggered with some compilers even if the function is not invoked at all:

#include <boost/gil.hpp>
#include <boost/gil/extension/io/png.hpp>

int main() {}

Compiled with gcc 10.2.1:

In file included from ../../boost/boost/gil/extension/dynamic_image/dynamic_image_all.hpp:14,
                 from ../../boost/boost/gil/extension/toolbox/dynamic_images.hpp:11,
                 from ../../boost/boost/gil/extension/toolbox/toolbox.hpp:13,
                 from ../../boost/boost/gil/io/base.hpp:11,
                 from ../../boost/boost/gil/extension/io/png/tags.hpp:11,
                 from ../../boost/boost/gil/extension/io/png/read.hpp:13,
                 from ../../boost/boost/gil/extension/io/png.hpp:11,
                 from main.cpp:2:
../../boost/boost/gil/extension/dynamic_image/image_view_factory.hpp: In function ‘typename boost::gil::color_converted_view_type<boost::gil::any_image_view<Types ...>, DstP, CC>::type boost::gil::any_color_converted_view(const boost::gil::any_image_view<Types ...>&, CC)’:
../../boost/boost/gil/extension/dynamic_image/image_view_factory.hpp:388:71: warning: ‘typename boost::gil::color_converted_view_type<boost::gil::any_image_view<Types ...>, DstP, CC>::type boost::gil::any_color_converted_view(const boost::gil::any_image_view<Types ...>&, CC)’ is deprecated: Use color_converted_view(const any_image_view<Views...>& src, CC) instead. [-Wdeprecated-declarations]
  388 |     return apply_operation(src, detail::color_converted_view_fn<DstP, cc_view_t>());
      |                                                                       ^~~~~~~~~
../../boost/boost/gil/extension/dynamic_image/image_view_factory.hpp:384:6: note: declared here
  384 | auto any_color_converted_view(const any_image_view<Views...>& src, CC)
      |      ^~~~~~~~~~~~~~~~~~~~~~~~
../../boost/boost/gil/extension/dynamic_image/image_view_factory.hpp: In function ‘typename boost::gil::color_converted_view_type<boost::gil::any_image_view<Types ...>, DstP>::type boost::gil::any_color_converted_view(const boost::gil::any_image_view<Types ...>&)’:
../../boost/boost/gil/extension/dynamic_image/image_view_factory.hpp:402:71: warning: ‘typename boost::gil::color_converted_view_type<boost::gil::any_image_view<Types ...>, DstP>::type boost::gil::any_color_converted_view(const boost::gil::any_image_view<Types ...>&)’ is deprecated: Use color_converted_view(any_image_view<Views...> const& src) instead. [-Wdeprecated-declarations]
  402 |     return apply_operation(src, detail::color_converted_view_fn<DstP, cc_view_t>());
      |                                                                       ^~~~~~~~~
../../boost/boost/gil/extension/dynamic_image/image_view_factory.hpp:398:6: note: declared here
  398 | auto any_color_converted_view(const any_image_view<Views...>& src)
      |      ^~~~~~~~~~~~~~~~~~~~~~~~

This warning is not emitted with clang 11. Currently I think it is a compiler bug in gcc 10.2.1, because we never invoke the deprecated function in the given example. Actually I already noticed this behavior while working on this PR and simply forgot to mention it as we had the discussion whether to merge this PR or #678. This PR does not emit the warning.

I will try to complete #656 ASAP in order to solve this new problem, but also in order to get the apply_operation deprecation shipped with Boost 1.80.

[mloskot]

@marco-langer

Currently I think it is a compiler bug in gcc 10.2.1

I think you may be correct: GCC Bug 95302 - function attributed to be deprecated cannot include a typedef/using
It is marked as "Known to fail: 10.2.0"
It looks like the using cc_view_t = needs to be unrolled in places of its use instead.

Thank you!