[gnome-shell/gnome-3-28] ui: Theme lookup should respect XDG_DATA_DIRS

[Marco Trevisan <marcotrevi src gnome org>]

commit da96408098cdf1735b2c7a1b1c722ecb2a263ce9
Author: Didier Roche <didrocks ubuntu com>
Date:   Fri Mar 30 09:44:14 2018 +0200

    ui: Theme lookup should respect XDG_DATA_DIRS
    
    Modes, extensions and other GNOME Shell assets are searched in appropriate
    subdirectories of each directory in XDG_DATA_DIRS, falling back
    to global.datadir.
    However, this isn't the case for themes, which are currently always expected
    in global.datadir, even when referenced by a mode in a different XDG_DATA_DIR.
    
    The fix is to have the theme finding pattern follow the same logic as other
    elements.
    Fixes #167.
    
    
    (cherry picked from commit d6d09fd3c82dd39dac1a764073040b57baeb8659)

 js/ui/main.js | 8 ++++++++
 1 file changed, 8 insertions(+)
---
diff --git a/js/ui/main.js b/js/ui/main.js
index 2cfe941be..d86cf9e81 100644
--- a/js/ui/main.js
+++ b/js/ui/main.js
@@ -256,6 +256,14 @@ function _getStylesheet(name) {
     if (stylesheet.query_exists(null))
         return stylesheet;
 
+    let dataDirs = GLib.get_system_data_dirs();
+    for (let i = 0; i < dataDirs.length; i++) {
+        let path = GLib.build_filenamev([dataDirs[i], 'gnome-shell', 'theme', name]);
+        let stylesheet = Gio.file_new_for_path(path);
+        if (stylesheet.query_exists(null))
+            return stylesheet;
+    }
+
     stylesheet = Gio.File.new_for_path(global.datadir + '/theme/' + name);
     if (stylesheet.query_exists(null))
         return stylesheet;