[zenity/gtk4-port: 13/25] Add meson post-install script.

[Logan Rathbone <larathbone src gnome org>]

commit 592e2555c352fdd85643b94030473f7dcd6095c4
Author: Logan Rathbone <poprocks gmail com>
Date:   Sun Feb 14 23:00:49 2021 -0500

    Add meson post-install script.

 meson.build           |  2 ++
 meson_post_install.py | 15 +++++++++++++++
 2 files changed, 17 insertions(+)
---
diff --git a/meson.build b/meson.build
index a1a4031d..26dad82e 100644
--- a/meson.build
+++ b/meson.build
@@ -105,3 +105,5 @@ subdir('data')
 subdir('icons')
 subdir('po')
 subdir('help')
+
+meson.add_install_script('meson_post_install.py')
diff --git a/meson_post_install.py b/meson_post_install.py
new file mode 100644
index 00000000..2654e49d
--- /dev/null
+++ b/meson_post_install.py
@@ -0,0 +1,15 @@
+#!/usr/bin/env python3
+
+import os
+import subprocess
+
+prefix = os.environ.get('MESON_INSTALL_PREFIX', '/usr/local')
+datadir = os.path.join(prefix, 'share')
+
+# Packaging tools define DESTDIR and this isn't needed for them
+if 'DESTDIR' not in os.environ:
+    print('Updating icon cache...')
+    icon_cache_dir = os.path.join(datadir, 'icons', 'hicolor')
+    if not os.path.exists(icon_cache_dir):
+        os.makedirs(icon_cache_dir)
+    subprocess.call(['gtk-update-icon-cache', '-qtf', icon_cache_dir])