Support lcms2 in MS-Windows builds

* lisp/term/w32-win.el (dynamic-library-alist): Include
association for the lcms2 library.

* src/lcms.c [WINDOWSNT]: Include windows.h and w32.h.  Use
DEF_DLL_FN to define pointers to dynamically loaded lcms2
functions.
(cmsCIE2000DeltaE, cmsCIECAM02Init, cmsCIECAM02Forward)
(cmsCIECAM02Done): New macros.
(init_lcms_functions, Flcms2_available_p): New functions.
(Flcms_cie_de2000, Flcms_cam02_ucs) [WINDOWSNT]: Call
init_lcms_functions.
(syms_of_lcms2): Defsubr lcms2-available-p.
* src/w32fns.c (syms_of_w32fns): DEFSYM Qlcms2.

* configure.ac: Include lcms2 in the final report and in
emacs_config_features.

* nt/INSTALL:
* nt/INSTALL.W64: Update with the information about lcms2 library.

6 files changed, 99 insertions, 2 deletions

diff --git a/configure.ac b/configure.ac
index 1cce2107dc2..39f7cfb8978 100644
--- a/configure.ac
+++ b/configure.ac
@@ -5367,7 +5367,7 @@ emacs_config_features=
 for opt in XAW3D XPM JPEG TIFF GIF PNG RSVG CAIRO IMAGEMAGICK SOUND GPM DBUS \
   GCONF GSETTINGS NOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT \
   LIBOTF XFT ZLIB TOOLKIT_SCROLL_BARS X_TOOLKIT OLDXMENU X11 NS MODULES \
-  XWIDGETS LIBSYSTEMD CANNOT_DUMP; do
+  XWIDGETS LIBSYSTEMD CANNOT_DUMP LCMS2; do
 
     case $opt in
       CANNOT_DUMP) eval val=\${$opt} ;;
@@ -5400,6 +5400,7 @@ AS_ECHO(["  Does Emacs use -lXaw3d?                                 ${HAVE_XAW3D
   Does Emacs use a png library?                           ${HAVE_PNG} $LIBPNG
   Does Emacs use -lrsvg-2?                                ${HAVE_RSVG}
   Does Emacs use cairo?                                   ${HAVE_CAIRO}
+  Does Emacs use -llcms2?                                 ${HAVE_LCMS2}
   Does Emacs use imagemagick (version 6)?                 ${HAVE_IMAGEMAGICK}
   Does Emacs support sound?                               ${HAVE_SOUND}
   Does Emacs use -lgpm?                                   ${HAVE_GPM}
diff --git a/lisp/term/w32-win.el b/lisp/term/w32-win.el
index bd16145756e..4e0e54ae179 100644
--- a/lisp/term/w32-win.el
+++ b/lisp/term/w32-win.el
@@ -275,7 +275,8 @@ See the documentation of `create-fontset-from-fontset-spec' for the format.")
 	   '(gnutls "libgnutls-30.dll")
 	 '(gnutls "libgnutls-28.dll" "libgnutls-26.dll"))
        '(libxml2 "libxml2-2.dll" "libxml2.dll")
-       '(zlib "zlib1.dll" "libz-1.dll")))
+       '(zlib "zlib1.dll" "libz-1.dll")
+       '(lcms2 "liblcms2-2.dll")))
 
 ;;; multi-tty support
 (defvar w32-initialized nil
diff --git a/nt/INSTALL b/nt/INSTALL
index b7f47a5d7c2..c6182c22cef 100644
--- a/nt/INSTALL
+++ b/nt/INSTALL
@@ -486,6 +486,8 @@ build will run on Windows 9X and newer systems).
        Does Emacs use a gif library?                           yes
        Does Emacs use a png library?                           yes
        Does Emacs use -lrsvg-2?                                yes
+       Does Emacs use cairo?                                   no
+       Does Emacs use -llcms2?                                 yes
        Does Emacs use imagemagick?                             no
        Does Emacs support sound?                               no
        Does Emacs use -lgpm?                                   no
@@ -797,6 +799,13 @@ build will run on Windows 9X and newer systems).
   (This library is also a prerequisite for several image libraries, so
   you may already have it; look for zlib1.dll or libz-1.dll.)
 
+* Optional support for lcms2 library
+
+  Emacs can expose some capabilities of the Little CMS color
+  management engine to Lisp programs using the lcms2 library.
+  Prebuilt binaries of lcms2 DLL (for 32-bit builds of Emacs) are
+  available from the ezwinports site and from the MSYS2 project.
+
 
 This file is part of GNU Emacs.
 
diff --git a/nt/INSTALL.W64 b/nt/INSTALL.W64
index b40f2238b5e..cb134735738 100644
--- a/nt/INSTALL.W64
+++ b/nt/INSTALL.W64
@@ -63,6 +63,7 @@ packages (you can copy and paste it into the shell with Shift + Insert):
   mingw-w64-x86_64-libpng \
   mingw-w64-x86_64-libjpeg-turbo \
   mingw-w64-x86_64-librsvg \
+  mingw-w64-x86_64-liblcms2 \
   mingw-w64-x86_64-libxml2 \
   mingw-w64-x86_64-gnutls \
   mingw-w64-x86_64-zlib
diff --git a/src/lcms.c b/src/lcms.c
index 10c79ae24a0..49af402327a 100644
--- a/src/lcms.c
+++ b/src/lcms.c
@@ -25,6 +25,48 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 
 #include "lisp.h"
 
+#ifdef WINDOWSNT
+# include <windows.h>
+# include "w32.h"
+
+DEF_DLL_FN (cmsFloat64Number, cmsCIE2000DeltaE,
+	    (const cmsCIELab* Lab1, const cmsCIELab* Lab2, cmsFloat64Number Kl,
+	     cmsFloat64Number Kc, cmsFloat64Number Kh));
+DEF_DLL_FN (cmsHANDLE, cmsCIECAM02Init,
+	    (cmsContext ContextID, const cmsViewingConditions* pVC));
+DEF_DLL_FN (void, cmsCIECAM02Forward,
+	    (cmsHANDLE hModel, const cmsCIEXYZ* pIn, cmsJCh* pOut));
+DEF_DLL_FN (void, cmsCIECAM02Done, (cmsHANDLE hModel));
+
+static bool lcms_initialized;
+
+static bool
+init_lcms_functions (void)
+{
+  HMODULE library = w32_delayed_load (Qlcms2);
+
+  if (!library)
+    return false;
+
+  LOAD_DLL_FN (library, cmsCIE2000DeltaE);
+  LOAD_DLL_FN (library, cmsCIECAM02Init);
+  LOAD_DLL_FN (library, cmsCIECAM02Forward);
+  LOAD_DLL_FN (library, cmsCIECAM02Done);
+  return true;
+}
+
+# undef cmsCIE2000DeltaE
+# undef cmsCIECAM02Init
+# undef cmsCIECAM02Forward
+# undef cmsCIECAM02Done
+
+# define cmsCIE2000DeltaE   fn_cmsCIE2000DeltaE
+# define cmsCIECAM02Init    fn_cmsCIECAM02Init
+# define cmsCIECAM02Forward fn_cmsCIECAM02Forward
+# define cmsCIECAM02Done    fn_cmsCIECAM02Done
+
+#endif	/* WINDOWSNT */
+
 static bool
 parse_lab_list (Lisp_Object lab_list, cmsCIELab *color)
 {
@@ -58,6 +100,16 @@ chroma, and hue, respectively. The parameters each default to 1. */)
   cmsCIELab Lab1, Lab2;
   cmsFloat64Number Kl, Kc, Kh;
 
+#ifdef WINDOWSNT
+  if (!lcms_initialized)
+    lcms_initialized = init_lcms_functions ();
+  if (!lcms_initialized)
+    {
+      message1 ("lcms2 library not found");
+      return Qnil;
+    }
+#endif
+
   if (!(CONSP (color1) && parse_lab_list (color1, &Lab1)))
     signal_error ("Invalid color", color1);
   if (!(CONSP (color2) && parse_lab_list (color2, &Lab2)))
@@ -112,6 +164,16 @@ Optional argument is the XYZ white point, which defaults to illuminant D65. */)
   double Jp1, ap1, bp1, Jp2, ap2, bp2;
   double Mp1, Mp2, FL, k, k4;
 
+#ifdef WINDOWSNT
+  if (!lcms_initialized)
+    lcms_initialized = init_lcms_functions ();
+  if (!lcms_initialized)
+    {
+      message1 ("lcms2 library not found");
+      return Qnil;
+    }
+#endif
+
   if (!(CONSP (color1) && parse_xyz_list (color1, &xyz1)))
     signal_error ("Invalid color", color1);
   if (!(CONSP (color2) && parse_xyz_list (color2, &xyz2)))
@@ -170,6 +232,27 @@ Optional argument is the XYZ white point, which defaults to illuminant D65. */)
                            (bp2 - bp1) * (bp2 - bp1)));
 }
 
+DEFUN ("lcms2-available-p", Flcms2_available_p, Slcms2_available_p, 0, 0, 0,
+       doc: /* Return t if lcms2 color calculations are available in this instance of Emacs.  */)
+     (void)
+{
+#ifdef WINDOWSNT
+  Lisp_Object found = Fassq (Qlcms2, Vlibrary_cache);
+  if (CONSP (found))
+    return XCDR (found);
+  else
+    {
+      Lisp_Object status;
+      lcms_initialized = init_lcms_functions ();
+      status = lcms_initialized ? Qt : Qnil;
+      Vlibrary_cache = Fcons (Fcons (Qlcms2, status), Vlibrary_cache);
+      return status;
+    }
+#else  /* !WINDOWSNT */
+  return Qt;
+#endif
+}
+
 
 /* Initialization */
 void
@@ -177,6 +260,7 @@ syms_of_lcms2 (void)
 {
   defsubr (&Slcms_cie_de2000);
   defsubr (&Slcms_cam02_ucs);
+  defsubr (&Slcms2_available_p);
 
   Fprovide (intern_c_string ("lcms2"), Qnil);
 }
diff --git a/src/w32fns.c b/src/w32fns.c
index 6b93afa8b8d..a77464465ec 100644
--- a/src/w32fns.c
+++ b/src/w32fns.c
@@ -10405,6 +10405,7 @@ syms_of_w32fns (void)
   DEFSYM (Qlibxml2, "libxml2");
   DEFSYM (Qserif, "serif");
   DEFSYM (Qzlib, "zlib");
+  DEFSYM (Qlcms2, "lcms2");
 
   Fput (Qundefined_color, Qerror_conditions,
 	listn (CONSTYPE_PURE, 2, Qundefined_color, Qerror));