Add a function to get a font from a css style

Similar in spirit to
gtk_style_context_get (ctx, state, "font", ...)
but avoids the need for a style context.
This will be used to for css-styled text rendering
from css subnodes.

gtk/gtkcssstyle.c

@@ -264,3 +264,22 @@ gtk_css_style_get_pango_attributes (GtkCssStyle *style)
 
   return attrs;
 }
+
+static GtkCssValue *
+query_func (guint    id,
+            gpointer values)
+{
+  return gtk_css_style_get_value (values, id);
+}
+
+PangoFontDescription *
+gtk_css_style_get_pango_font (GtkCssStyle *style)
+{
+  GtkStyleProperty *prop;
+  GValue value = { 0, };
+
+  prop = _gtk_style_property_lookup ("font");
+  _gtk_style_property_query (prop, &value, query_func, style);
+
+  return (PangoFontDescription *)g_value_get_boxed (&value);
+}

gtk/gtkcssstyleprivate.h

@@ -76,6 +76,7 @@ gboolean                gtk_css_style_print                     (GtkCssStyle
                                                                  gboolean                skip_initial);
 PangoAttrList *         gtk_css_style_get_pango_attributes      (GtkCssStyle            *style);
 
+PangoFontDescription *  gtk_css_style_get_pango_font            (GtkCssStyle            *style);
 
 G_END_DECLS