This patch makes GTK+ look for additional modules in a list of directories
specified by the environment variable "GUIX_GTK3_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	2015-09-20 20:09:05.060590217 +0200
+++ b/gtk/gtkmodules.c	2015-09-20 20:10:33.423124833 +0200
@@ -52,6 +52,7 @@
 get_module_path (void)
 {
   const gchar *module_path_env;
+  const gchar *module_guix_gtk3_path_env;
   const gchar *exe_prefix;
   gchar *module_path;
   gchar *default_dir;
@@ -61,6 +62,7 @@
     return result;
 
   module_path_env = g_getenv ("GTK_PATH");
+  module_guix_gtk3_path_env = g_getenv ("GUIX_GTK3_PATH");
   exe_prefix = g_getenv ("GTK_EXE_PREFIX");
 
   if (exe_prefix)
@@ -68,7 +70,13 @@
   else
     default_dir = g_build_filename (_gtk_get_libdir (), "gtk-3.0", NULL);
 
-  if (module_path_env)
+  if (module_guix_gtk3_path_env && module_path_env)
+    module_path = g_build_path (G_SEARCHPATH_SEPARATOR_S,
+				module_guix_gtk3_path_env, module_path_env, default_dir, NULL);
+  else if (module_guix_gtk3_path_env)
+    module_path = g_build_path (G_SEARCHPATH_SEPARATOR_S,
+				module_guix_gtk3_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);
   else
51fec63bd4b48f90727a00890'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/README'>
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<div class='path'>path: <a href='/guix/log/?id=62479e9420da90851fec63bd4b48f90727a00890'>root</a>/<a href='/guix/log/README?id=62479e9420da90851fec63bd4b48f90727a00890'>README</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/README?id=62479e9420da90851fec63bd4b48f90727a00890&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-05-20 01:58:04 +0200'>2021-05-20</span></td><td><a href='/guix/commit/README?id=c0087d33705f53cc3619a1a43a33602aaecc3a8b'>The #guix channel is hosted by Libera Chat.</a><span class='msg-avail'>...<span class='msg-tooltip'>* README (Contact): Update network name.
* ROADMAP: Likewise.
* doc/contributing.texi (Contributing): Likewise.
* doc/guix.texi (After System Installation): Likewise.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2020-10-23 12:57:20 -0400'>2020-10-23</span></td><td><a href='/guix/commit/README?id=b5aaa3a4fb985d21e21e2a67f48b52f13ebd4728'>doc: Update README.</a><span class='msg-avail'>...<span class='msg-tooltip'>* README (Installation): Do not mention installing Guix from Git anymore.
(Building from Git): Add section.
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2020-10-22 22:47:54 -0400'>2020-10-22</span></td><td><a href='/guix/commit/README?id=503d2bfde08f9bf97bbf430516d2f19faedd4319'>README: Refer to the manual for building from Git.</a><span class='msg-avail'>...<span class='msg-tooltip'>* README (Installing Guix from Guix): Remove section.
(Installation): For installing from Git, refer to the "Building from Git"
section of the manual and suggest using './pre-inst-env guix pull' rather than
'make install' for installing Guix.
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2020-06-02 18:55:53 +0200'>2020-06-02</span></td><td><a href='/guix/commit/README?id=c75a80189fc19f6ff8b4c82d1d1801be6763b6d2'>doc: Update README to refer to the manual.</a><span class='msg-avail'>...<span class='msg-tooltip'>* README (Requirements): Refer to the manual.
(Installation): Update URL of the manual.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-11-09 23:04:14 +0100'>2019-11-09</span></td><td><a href='/guix/commit/README?id=0758a70cc008171f31c848128deca9803536fe60'>doc: Mention value /var to localstatedir option.</a><span class='msg-avail'>...<span class='msg-tooltip'>* README (Installing Guix from Guix): Mention value /var to localstatedir option.
* doc/contributing.texi (Building from Git): Likewise.
* doc/guix.texi (Requirements): Likewise.

Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>zimoun</td></tr>
<tr><td><span title='2019-09-04 23:41:07 +0200'>2019-09-04</span></td><td><a href='/guix/commit/README?id=f475c6e53e5b6912cc45663d50f1d03dadfb60b8'>doc: Update 'README'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* README: Update intro a bit.
(Installing Guix as non-root): Remove as it's largely outdated.
(Contact): Update.
</span></span></td><td>Ludovic Courtès</td></tr>