[meld] bin/meld: Add support for a dark theme, following the GtkSetting

[Kai Willadsen <kaiw src gnome org>]

commit f84e165dcebd2239d4c5ed0ca1847ac02b884e2d
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Sun Aug 10 09:06:19 2014 +1000

    bin/meld: Add support for a dark theme, following the GtkSetting
    
    This commit just loads the dark CSS if it's present; there still isn't
    any there. Since we're doing this, we also handle CSS files not being
    found and complain appropriately.

 bin/meld |   12 ++++++++++--
 1 files changed, 10 insertions(+), 2 deletions(-)
---
diff --git a/bin/meld b/bin/meld
index 257e38c..4fe5c56 100755
--- a/bin/meld
+++ b/bin/meld
@@ -174,15 +174,23 @@ def check_requirements():
 
 def setup_resources():
     from gi.repository import GObject
+    from gi.repository import GLib
     from gi.repository import Gtk
     from gi.repository import Gdk
 
     GObject.threads_init()
     icon_dir = os.path.join(meld.conf.DATADIR, "icons")
     Gtk.IconTheme.get_default().append_search_path(icon_dir)
-    css_file = os.path.join(meld.conf.DATADIR, "meld.css")
+
+    gtk_settings = Gtk.Settings.get_default()
+    dark_theme = gtk_settings.get_property('gtk-application-prefer-dark-theme')
+    css_name = "meld-dark" if dark_theme else "meld"
+    css_file = os.path.join(meld.conf.DATADIR, css_name + ".css")
     provider = Gtk.CssProvider()
-    provider.load_from_path(css_file)
+    try:
+        provider.load_from_path(css_file)
+    except GLib.GError as err:
+        print(_("Couldn't load Meld-specific CSS (%s)\n%s") % (css_file, err))
     Gtk.StyleContext.add_provider_for_screen(
         Gdk.Screen.get_default(), provider,
         Gtk.STYLE_PROVIDER_PRIORITY_APPLICATION)