Re: No support for ImageMagick 7 in emacs-26

[Ulrich Mueller]

>>>>> On Mon, 26 Nov 2018, Eli Zaretskii wrote:

>> Sorry, but where do you see a change that could affect behaviour of
>> v6.x? Effectively, the only code change in the consolidated patch is the
>> following in image.c:
>> 
>> -      MagickRealType color_scale = 65535.0 / QuantumRange;
>> +      double quantum_range = QuantumRange;
>> +      MagickRealType color_scale = 65535.0 / quantum_range;

> This is one part that I'd rather not do on the release branch

We could put a conditional around it (but it looks silly):

#ifdef HAVE_IMAGEMAGICK7
      double quantum_range = QuantumRange;
      MagickRealType color_scale = 65535.0 / quantum_range;
#else
      MagickRealType color_scale = 65535.0 / QuantumRange;
#fi

> (why is it needed, anyway?).

According to the commit message (commit 42ed35c68b):
    
    * src/image.c (imagemagick_load_image): Use double division, and
    eliminate a cast.  This avoids a -Wdouble-promotion warning with
    GCC 7.3 on Ubuntu 18.04.

> The other one is that inclusion of a header file was moved to a
> different place for some reason.  (Yes, I'm being paranoid ;-)

For v6 it still includes <wand/MagickWand.h> and <magick/version.h> at
the same place and in the same order. So unless I am missing something,
nothing was moved at all.

IMHO it would be shortsighted to support only a version that ImageMagick
upstream considers legacy. (And yes, it can be fixed at the distro
level, but that just means duplicate work.)