group tabs background/base color taken from the theme base. in the dark theme, its not quite so black and matches other base color areas

git-svn-id: svn://localhost/ardour2/branches/3.0@11723 d708f5d6-7413-0410-9779-e7cbd77b26cf

gtk2_ardour/group_tabs.cc

@@ -243,10 +243,12 @@ GroupTabs::render (cairo_t* cr)
 
 	/* background */
 
-	cairo_set_source_rgb (cr, 0, 0, 0);
+	Gdk::Color c = get_style()->get_base (Gtk::STATE_NORMAL);
+
+	cairo_set_source_rgb (cr, c.get_red_p(), c.get_green_p(), c.get_blue_p());
 	cairo_rectangle (cr, 0, 0, get_width(), get_height());
 	cairo_fill (cr);
-
+	
 	/* tabs */
 
 	for (list<Tab>::const_iterator i = _tabs.begin(); i != _tabs.end(); ++i) {