gnu: gd: Fix test failure with FreeType 2.7.

* gnu/packages/patches/gd-freetype-test-failure.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/gd.scm (gd)[source]: Use it.

gnu/local.mk

@@ -581,6 +581,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/gd-fix-gd2-read-test.patch		\
   %D%/packages/patches/gd-fix-tests-on-i686.patch		\
   %D%/packages/patches/gd-fix-truecolor-format-correction.patch	\
+  %D%/packages/patches/gd-freetype-test-failure.patch		\
   %D%/packages/patches/gegl-CVE-2012-4433.patch			\
   %D%/packages/patches/geoclue-config.patch			\
   %D%/packages/patches/ghc-dont-pass-linker-flags-via-response-files.patch	\

gnu/packages/gd.scm

@@ -51,7 +51,8 @@
               (base32
                "1rp4v7n1dq38b92kl7gkvpvqqkw7nvdfnz6d5kip5klkxfki6zqk"))
              (patches (search-patches "gd-fix-gd2-read-test.patch"
-                                      "gd-fix-tests-on-i686.patch"))))
+                                      "gd-fix-tests-on-i686.patch"
+                                      "gd-freetype-test-failure.patch"))))
     (build-system gnu-build-system)
     (arguments
      `(#:phases

gnu/packages/patches/gd-freetype-test-failure.patch

@@ -0,0 +1,59 @@
+Fix a test failure with freetype 2.7:
+
+https://github.com/libgd/libgd/commit/a5570d3ed30ff76c2a8bdd54f4ab1825acca0143
+
+Patch copied from upstream source repository:
+
+https://github.com/libgd/libgd/commit/a5570d3ed30ff76c2a8bdd54f4ab1825acca0143
+
+From a5570d3ed30ff76c2a8bdd54f4ab1825acca0143 Mon Sep 17 00:00:00 2001
+From: "Christoph M. Becker" <cmbecker69@gmx.de>
+Date: Sun, 29 Jan 2017 17:07:50 +0100
+Subject: [PATCH] Fix #302: Test suite fails with freetype 2.7
+
+Actually, the test failures are not necessarily related to freetype
+2.7, but rather are caused by subpixel hinting which is enabled by
+default in freetype 2.7. Subpixel hinting is, however, already
+available in freetype 2.5 and in versions having the "Infinality"
+patch.
+
+To get the expected results in all environments, we have to disable
+subpixel hinting, what is easily done by setting a respective
+environment variable.
+
+See also:
+* https://www.freetype.org/freetype2/docs/subpixel-hinting.html
+* https://www.freetype.org/freetype2/docs/reference/ft2-tt_driver.html
+---
+ tests/freetype/bug00132.c                    | 3 +++
+ tests/gdimagestringft/gdimagestringft_bbox.c | 3 +++
+ 2 files changed, 6 insertions(+)
+
+diff --git a/tests/freetype/bug00132.c b/tests/freetype/bug00132.c
+index 713dd2d..42ed5b1 100644
+--- a/tests/freetype/bug00132.c
++++ b/tests/freetype/bug00132.c
+@@ -11,6 +11,9 @@ int main()
+ 	char *path;
+ 	char *ret = NULL;
+ 
++	/* disable subpixel hinting */
++	putenv("FREETYPE_PROPERTIES=truetype:interpreter-version=35");
++
+ 	im = gdImageCreateTrueColor(50, 30);
+ 
+ 	if (!im) {
+diff --git a/tests/gdimagestringft/gdimagestringft_bbox.c b/tests/gdimagestringft/gdimagestringft_bbox.c
+index 0161ec8..1596a9e 100644
+--- a/tests/gdimagestringft/gdimagestringft_bbox.c
++++ b/tests/gdimagestringft/gdimagestringft_bbox.c
+@@ -38,6 +38,9 @@ int main()
+ 	int error = 0;
+ 	FILE *fp;
+ 
++	/* disable subpixel hinting */
++	putenv("FREETYPE_PROPERTIES=truetype:interpreter-version=35");
++
+ 	path = gdTestFilePath("freetype/DejaVuSans.ttf");
+ 	im = gdImageCreate(800, 800);
+ 	gdImageColorAllocate(im, 0xFF, 0xFF, 0xFF); /* allocate white for background color */