Taken from gimp!1154

It is possible to use GCC on macOS.

Though the models may itself be registered with a similarly named
attribute to mean they encode alpha, babl_format_has_alpha() in
particular works by verifying if any of the components
represents/encodes alpha. As a consequence, the function was failing to
consider e.g. HSVA as a model encoding alpha.

See also: gegl!142

Again, even though it's basically the same as float or half for a CLI
tool (where all these floating point values are just converted from
string representation), it is still interesting since the tool is doing
actual conversion with a fish using the requested formats. Therefore
it's a nice way to quickly test conversions in terminal.

While apparently fixing the compilation for Windows (and still compiling
on Linux), my previous commit was in fact crashing the CLI tool when it
runs babl_init() in some infinite loop (it looks like it's crashing
inside babl logging code, hence the infinite looping).

Anyway this was annoying me that we had to build-in more than necessary
from babl-internal when all I wanted was to share 2 functions. So I
split babl-util with a new babl-shared-util. The latter is to be used
only for the few utility functions which we might want to share with the
CLI tool (so far, only the 2 half to/from float (en|de)coders).

This time, I've not only compiled but also run the CLI tool both on
Linux and with Wine for the Windows cross-build.

While I didn't have a problem for Linux builds, when cross-compiling for
Windows, these errors occur:

> babl-util.c:296: undefined reference to `babl_strcat'

(and a few similar other "undefined reference" as this one gets fixed)

This is because we include babl-internal.h in bin/babl.c but don't add
the right compilation unit sources. The build was still finding them (or
maybe ignoring them as the functions were unused in the babl CLI tool
code) on Linux, but not on Windows.

The code to encode half values into and from float values was moved from
type-half.c to babl-util.h as an internal function, to make it usable by
the CLI code.

It may not seem totally useful to have half support since anyway we
convert from/to string for the CLI tool (in this regard, half and float
are the same). But since the tool performs an actual babl conversion,
it's actually a good way to test quickly that half conversion works
properly too.

Similar to babl_space_is_cmyk|gray() functions, because right now to
know whether a space is RGB, we have to test whether it's **not** any of
the other. And such code would break as soon as we will add new values
to BablICCType.

This way, we'll be able to host the generated reference and have
automatic links created between GIMP, GEGL and babl API docs.

John Marshall authored Mar 19, 2021 and John Marshall committed Jul 25, 2023

 - pluginsdir: to set BABL_PATH
 - girdir: location of introspection gir file
 - typelibdir: location of introspection typelib file

Keep alpha (0xff) as computed rather than stripping and reapplying.

Fixing issue #92.

Babl uses matrices which have been bit-optimized - which is a time consuming
task done at every startup. As reported in now fixed issue #67.

We are crashing due to endian assumptions - we now only try to do the LUT
optimizations on little endian - no functionality is lost on big-endian
though conversion might be a tad slower. Hopefully fixing issue #91

As per issue #87 this is the minimum we can build with - and 0.56.x is
available in debian stable which we is used as a bar for inclusion.

Thus fixing issue #89

We protect this behind a mutex, initialization of color managed code from
multiple threads have been known to trigger babl races in GEGL/GIMP code.

Not neccesary while the static strings are 512 bytes, in regular
use we might however want to reduce this to 256bytes.

babl-format: make more more defensive

The BABL_LUT environment variable still controls whether it is enabled, to
turn off the LUT usage set BABL_LUT=0.

Use alpha=255 in seeding of premultiplied - this might not be enough
we might also have to disassociate and reassociate alpha during conversion.

The code marking LUTs as available for fishes is now protected behind an
environment variable BABL_LUT if it is set, the LUT code is re-enabled.