This patch makes GTK+ look for additional modules in a list of directories
specified by the environment variable "GUIX_GTK2_PATH".  This can be used
instead of "GTK_PATH" to make GTK+ find modules that are incompatible with
other major versions of GTK+.

--- a/gtk/gtkmodules.c	2014-09-29 22:02:17.000000000 +0200
+++ b/gtk/gtkmodules.c	2015-12-02 18:41:53.306396938 +0100
@@ -55,6 +55,7 @@
 get_module_path (void)
 {
   const gchar *module_path_env;
+  const gchar *module_guix_gtk2_path_env;
   const gchar *exe_prefix;
   const gchar *home_dir;
   gchar *home_gtk_dir = NULL;
@@ -70,6 +71,7 @@
     home_gtk_dir = g_build_filename (home_dir, ".gtk-2.0", NULL);
 
   module_path_env = g_getenv ("GTK_PATH");
+  module_guix_gtk2_path_env = g_getenv ("GUIX_GTK2_PATH");
   exe_prefix = g_getenv ("GTK_EXE_PREFIX");
 
   if (exe_prefix)
@@ -77,9 +79,21 @@
   else
     default_dir = g_build_filename (GTK_LIBDIR, "gtk-2.0", NULL);
 
-  if (module_path_env && home_gtk_dir)
+  if (module_guix_gtk2_path_env && module_path_env && home_gtk_dir)
+    module_path = g_build_path (G_SEARCHPATH_SEPARATOR_S,
+				module_guix_gtk2_path_env, module_path_env, home_gtk_dir, default_dir, NULL);
+  else if (module_guix_gtk2_path_env && home_gtk_dir)
+    module_path = g_build_path (G_SEARCHPATH_SEPARATOR_S,
+				module_guix_gtk2_path_env, home_gtk_dir, default_dir, NULL);
+  else if (module_guix_gtk2_path_env && module_path_env)
+    module_path = g_build_path (G_SEARCHPATH_SEPARATOR_S,
+				module_guix_gtk2_path_env, module_path_env, default_dir, NULL);
+  else if (module_path_env && home_gtk_dir)
     module_path = g_build_path (G_SEARCHPATH_SEPARATOR_S,
 				module_path_env, home_gtk_dir, default_dir, NULL);
+  else if (module_guix_gtk2_path_env)
+    module_path = g_build_path (G_SEARCHPATH_SEPARATOR_S,
+				module_guix_gtk2_path_env, default_dir, NULL);
   else if (module_path_env)
     module_path = g_build_path (G_SEARCHPATH_SEPARATOR_S,
 				module_path_env, default_dir, NULL);
/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=f0a0b58bfa9b62de1839b980a2560618e56f9249'>root</a>/<a href='/guix/log/build-aux?id=f0a0b58bfa9b62de1839b980a2560618e56f9249'>build-aux</a>/<a href='/guix/log/build-aux/generate-authors.scm?id=f0a0b58bfa9b62de1839b980a2560618e56f9249'>generate-authors.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/build-aux/generate-authors.scm?id=f0a0b58bfa9b62de1839b980a2560618e56f9249&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2015-07-06 19:00:19 +0300'>2015-07-06</span></td><td><a href='/guix/commit/build-aux/generate-authors.scm?id=a8ac45b19ebb3006ced49b46342e01632829cef2'>build: Generate 'AUTHORS'.</a><span class='msg-avail'>...</span></td><td>Alex Kost</td></tr>
ibc-utf8-locales-for-target’.</a><span class='msg-avail'>...</span></td><td>Janneke Nieuwenhuizen</td></tr>
<tr><td><span title='2023-10-20 00:33:26 +0200'>2023-10-20</span></td><td><a href='/guix/commit/tests/pack.scm?id=2aa45d03475f7bd27d4ba5bc71b0cb812aa74768'>tests: Avoid three-argument ‘test-assertm’.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2023-07-18 16:56:06 -0400'>2023-07-18</span></td><td><a href='/guix/commit/tests/pack.scm?id=c75022d65f1fa18b8c4839e50f915e8f4d4fe305'>tests: pack: Fix indentation.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2023-07-18 16:56:06 -0400'>2023-07-18</span></td><td><a href='/guix/commit/tests/pack.scm?id=d5f8b50365533f2713596f59519c48019f6b1f19'>pack: Move common build code to (guix build pack).</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2023-03-17 12:14:14 -0400'>2023-03-17</span></td><td><a href='/guix/commit/tests/pack.scm?id=933051281fbed0ae71bd40c24a701faf2a02791c'>Revert "tests: pack: Fix indentation."</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2023-02-27 15:54:09 +0100'>2023-02-27</span></td><td><a href='/guix/commit/tests/pack.scm?id=fee1d08f0dd183ef78bcb9f1534d7b9e7f1df7ac'>pack: Make sure tests can run without a world rebuild.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2023-02-19 21:13:23 -0500'>2023-02-19</span></td><td><a href='/guix/commit/tests/pack.scm?id=598f4c509bbfec2b983a8ee246cce0a0fe45ec7f'>pack: Add RPM format.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2023-02-19 21:13:23 -0500'>2023-02-19</span></td><td><a href='/guix/commit/tests/pack.scm?id=ac1d530d56c1a259630c8873b2281033878a4acb'>tests: pack: Fix indentation.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2022-10-22 01:46:55 +0200'>2022-10-22</span></td><td><a href='/guix/commit/tests/pack.scm?id=a3619079f95213c4f983e69210ed12b38fd31022'>Remove now unnecessary uses of (guix grafts).</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-07-18 19:50:01 +0200'>2021-07-18</span></td><td><a href='/guix/commit/tests/pack.scm?id=0e47fcced442d8e7c1b05184fdc1c14f10ed04ec'>Merge branch 'master' into core-updates</a></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-07-18 02:02:34 -0400'>2021-07-18</span></td><td><a href='/guix/commit/tests/pack.scm?id=aeded14b8342c1e72afd014a1bc121770f8c3a1c'>pack: Allow embedding custom control files in deb packs.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>