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);
s='path'>path: <a href='/guix/log/?id=f2acd45eae3697c798716e6b99c32565babbf70f'>root</a>/<a href='/guix/log/etc?id=f2acd45eae3697c798716e6b99c32565babbf70f'>etc</a>/<a href='/guix/log/etc/completion?id=f2acd45eae3697c798716e6b99c32565babbf70f'>completion</a>/<a href='/guix/log/etc/completion/fish?id=f2acd45eae3697c798716e6b99c32565babbf70f'>fish</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/etc/completion/fish?id=f2acd45eae3697c798716e6b99c32565babbf70f&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-04-20 12:13:16 +0200'>2021-04-20</span></td><td><a href='/guix/commit/etc/completion/fish?id=d95168321f4a9bf6857b598da0a183b45a868d54'>import: Remove Nix importer.</a><span class='msg-avail'>...<span class='msg-tooltip'>This importer has suffered from bitrot and no longer works with current
Nix and Nixpkgs.  See &lt;https://bugs.gnu.org/32339&gt; and
&lt;https://bugs.gnu.org/36255&gt;.

* guix/import/snix.scm, guix/scripts/import/nix.scm,
tests/snix.scm: Remove.
* Makefile.am (MODULES, SCM_TESTS): Remove them.
* guix/scripts/import.scm (importers): Remove "nix".
* build-aux/test-env.in: Remove NIXPKGS variable.
* configure.ac: Remove '--with-nixpkgs' option.
* doc/guix.texi (Invoking guix import): Remove bit about "guix import
nix".
* etc/completion/fish/guix.fish: Likewise.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-02-17 10:52:28 +0100'>2021-02-17</span></td><td><a href='/guix/commit/etc/completion/fish?id=ee2a5da80a9bda25542c00a7a35a9ddddcbd58af'>scripts: system: Remove 'vm-image' command.</a><span class='msg-avail'>...<span class='msg-tooltip'>Remove the 'vm-image' command that has been superseded by the 'image'
command.

* gnu/system/vm.scm (system-qemu-image): Remove it.
* guix/scripts/system.scm (system-derivation-for-action): Mark 'vm-image'
command as deprecated and use the image API to produce the VM image.
(perform-action, show-help): Adapt accordingly.
* tests/guix-system.sh: Ditto.
* doc/guix.texi (Invoking guix system,
Running Guix in a VM): Ditto.
* etc/completion/fish/guix.fish: Ditto.
* etc/completion/zsh/_guix: Ditto.
</span></span></td><td>Mathieu Othacehe</td></tr>