better win32 compatibility

try to fold the patches @tumagonx maintains into libvips master, see:

https://github.com/tumagonx/pygi-mingw-patches/blob/master/vips-8.4.x.patch

still missing the bindtextdomain() patch though

configure.ac

@@ -237,7 +237,8 @@ if test x"$vips_os_darwin" = x"yes"; then
   profile_dir="/Library/ColorSync/Profiles"
 elif test x"$vips_os_win32" = x"yes"; then
   # need double escapes since this will get pasted into a #define in a C
-  # header
+  # header ... the C:\Windows is usually overrwritten with the result of
+  # GetWindowsDirectoryW()
   profile_dir="C:\\\\Windows\\\\System32\\\\spool\\\\drivers\\\\color"
 else
   profile_dir="/usr/share/color/icc"

libvips/Makefile.am

@@ -109,7 +109,7 @@ INTROSPECTION_GIRS += Vips-8.0.gir
 #   --warn-all --verbose 
 # too annoying
 Vips_8_0_gir_SCANNERFLAGS = \
-	--program=./introspect \
+	--program=./introspect$(EXEEXT) \
 	--identifier-prefix=Vips \
 	--identifier-prefix=vips \
 	--symbol-prefix=vips 

libvips/colour/colour.c

@@ -261,7 +261,7 @@ vips_colour_attach_profile( VipsImage *im, const char *filename )
 	char *data;
 	size_t data_length;
 
-	if( !(data = vips__file_read_name( filename, VIPS_ICC_DIR, 
+	if( !(data = vips__file_read_name( filename, vips__icc_dir(), 
 		&data_length )) ) 
 		return( -1 );
 	vips_image_set_blob( im, VIPS_META_ICC_NAME, 

libvips/foreign/vips2jpeg.c

@@ -357,7 +357,7 @@ static int
 write_profile_file( Write *write, const char *profile )
 {
 	if( !(write->profile_bytes = 
-		vips__file_read_name( profile, VIPS_ICC_DIR, 
+		vips__file_read_name( profile, vips__icc_dir(), 
 		&write->profile_length )) ) 
 		return( -1 );
 	write_profile_data( &write->cinfo, 

libvips/foreign/vips2tiff.c

@@ -325,7 +325,8 @@ embed_profile_file( TIFF *tif, const char *profile )
 	char *buffer;
 	size_t length;
 
-	if( !(buffer = vips__file_read_name( profile, VIPS_ICC_DIR, &length )) )
+	if( !(buffer = vips__file_read_name( profile, 
+		vips__icc_dir(), &length )) )
 		return( -1 );
 	TIFFSetField( tif, TIFFTAG_ICCPROFILE, length, buffer );
 	vips_free( buffer );

libvips/foreign/vipspng.c

@@ -954,7 +954,7 @@ write_vips( Write *write,
 			size_t length;
 
 			if( !(data = vips__file_read_name( profile, 
-				VIPS_ICC_DIR, &length )) ) 
+				vips__icc_dir(), &length )) ) 
 				return( -1 );
 
 #ifdef DEBUG

libvips/include/vips/util.h

@@ -331,6 +331,8 @@ char *vips_realpath( const char *path );
 guint32 vips__random( guint32 seed );
 guint32 vips__random_add( guint32 seed, int value );
 
+const char *vips__icc_dir( void );
+
 #ifdef __cplusplus
 }
 #endif /*__cplusplus*/

libvips/iofuncs/util.c

@@ -1929,3 +1929,43 @@ vips__random_add( guint32 seed, int value )
 
 	return( vips__random( seed ) ); 
 }
+
+static void *
+vips_icc_dir_once( void *null )
+{
+#ifdef OS_WIN32
+	/* From glib get_windows_directory_root()
+	 */
+	wchar_t wwindowsdir[MAX_PATH];
+
+	if( GetWindowsDirectoryW( wwindowsdir, G_N_ELEMENTS( wwindowsdir ) ) ) {
+		/* Usually X:\Windows, but in terminal server environments
+		 * might be an UNC path, AFAIK.
+		 */
+		char *windowsdir;
+
+		if( (windowsdir = g_utf16_to_utf8( wwindowsdir, 
+			-1, NULL, NULL, NULL)) ) {
+			gchar *full_path;
+
+			full_path = g_build_filename( windowsdir, 
+				"system32", "spool", "drivers", "color", NULL );
+			g_free( windowsdir );
+
+			return( (void *) full_path );
+		}
+	}
+#endif
+
+	return( (void *) VIPS_ICC_DIR );
+}
+
+const char *
+vips__icc_dir( void )
+{
+	static GOnce once = G_ONCE_INIT;
+
+	return( (const char *) g_once( &once, 
+		(GThreadFunc) vips_icc_dir_once, NULL ) );
+}
+