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);
'>path: <a href='/guix/log/?id=3dbd04d7cac67948c0b02615be3637499e4f3f03'>root</a>/<a href='/guix/log/gnu?id=3dbd04d7cac67948c0b02615be3637499e4f3f03'>gnu</a>/<a href='/guix/log/gnu/bootloader.scm?id=3dbd04d7cac67948c0b02615be3637499e4f3f03'>bootloader.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/gnu/bootloader.scm?id=3dbd04d7cac67948c0b02615be3637499e4f3f03&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-11-17 16:03:03 +0100'>2020-11-17</span></td><td><a href='/guix/commit/gnu/bootloader.scm?id=ede4117f7f18e118003f2599f5c8e985dfbdf9a5'>gnu: bootloader: efi-bootloader-chain: Allow multiple HOOKS.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/bootloader.scm (efi-bootloader-profile): Allow multiple HOOKS.
(efi-bootloader-chain): Allow multiple HOOKS.

Signed-off-by: Danny Milosavljevic &lt;dannym@scratchpost.org&gt;
</span></span></td><td>Stefan</td></tr>
<tr><td><span title='2020-11-16 10:33:18 +0100'>2020-11-16</span></td><td><a href='/guix/commit/gnu/bootloader.scm?id=74eeb11daee906cb012f10b6bb3afd254f9ea5c2'>gnu: bootloader: Support chain loading to an EFI bootloader.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/bootloader.scm (efi-bootloader-profile): New function.
(efi-bootloader-chain): New function.

Signed-off-by: Danny Milosavljevic &lt;dannym@scratchpost.org&gt;
</span></span></td><td>Stefan</td></tr>
<tr><td><span title='2020-06-08 13:51:18 +0200'>2020-06-08</span></td><td><a href='/guix/commit/gnu/bootloader.scm?id=21acd8d6c11b85d06c82b168807b35cb7d2d0adf'>bootloader: Extend `&lt;menu-entry&gt;' for multiboot.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/bootloader.scm (&lt;menu-entry&gt;)[multiboot-kernel,multiboot-arguments,
multiboot-modules]: New fields.
[linux,initrd]: Add default value '#f'.
(menu-entry-&gt;sexp, sexp-&gt;menu-entry): Support multiboot entry.
* doc/guix.texi (Bootloader Configuration): Document them.
</span></span></td><td>Jan (janneke) Nieuwenhuizen</td></tr>
<tr><td><span title='2020-05-29 08:37:13 +0200'>2020-05-29</span></td><td><a href='/guix/commit/gnu/bootloader.scm?id=7feefb3b82186be382725ac2d6b7e9f8953e4a83'>bootloader: Add 'disk-image-installer'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/bootloader.scm (&lt;bootloader&gt;)[disk-image-installer]: New field,
(bootloader-disk-image-installer): export it.
* gnu/bootloader/grub.scm (install-grub-disk-image): New procedure ...
(grub-bootloader): ... used as "disk-image-installer" here.
(grub-efi-bootloader): set "disk-image-installer" to #f.
* gnu/system/image.scm (root-partition?, find-root-partition): Move to
"Helpers" section.
(root-partition-index): New procedure.
(system-disk-image): Honor disk-image-installer, and
use it to install the bootloader directly on the disk-image, if supported.
</span></span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2019-08-30 01:33:45 +0200'>2019-08-30</span></td><td><a href='/guix/commit/gnu/bootloader.scm?id=a28cfee841e9c5ab179291d3065f1486fd065e7e'>system: Add 'bootloader-menu-entries' field to &lt;boot-parameters&gt;.</a><span class='msg-avail'>...<span class='msg-tooltip'>This allows us to keep track of the extra menu entries specified in the
OS configuration.

* gnu/system.scm (&lt;boot-parameters&gt;)[bootloader-menu-entries]: New field.
(read-boot-parameters): Initialize it.
(operating-system-boot-parameters): Likewise.
(operating-system-boot-parameters-file): Serialize it.
* gnu/bootloader.scm (menu-entry-&gt;sexp, sexp-&gt;menu-entry): New
procedures.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-08-30 01:33:45 +0200'>2019-08-30</span></td><td><a href='/guix/commit/gnu/bootloader.scm?id=ac9cd78ea9e6a3cf850b33fb2111b85e2bbf533d'>bootloader: Fix comment about 'menu-entries'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/bootloader.scm (&lt;bootloader-configuration&gt;)[menu-entries]: Fix
margin comment.
</span></span></td><td>Ludovic Courtès</td></tr>