case VTE_ANTI_ALIAS_FORCE_ENABLE:
        case VTE_ANTI_ALIAS_FORCE_DISABLE:
                font_options = cairo_font_options_copy (pango_cairo_context_get_font_options (context));
                cairo_font_options_set_antialias (font_options, antialias == VTE_ANTI_ALIAS_FORCE_ENABLE);
                pango_cairo_context_set_font_options (context, font_options);

So, if FORCE_ENABLE it sets antialias to 1, which is CAIRO_ANTIALIAS_NONE, otherwise to 0 which is CAIRO_ANTIALIAS_DEFAULT. This is obviously wrong :)

For FORCE_DISABLE, CAIRO_ANTIALIAS_NONE is the right value. I'm not sure what to use for FORCE_ENABLE in case the gdkscreen's font options don't have antialias set: use DEFAULT, GRAY or SUBPIXEL?

FORCE_ENABLE is only used by g-t to force the xft backend to antialias even when no xrender is present; is this necessary at all with the pangocairo backend?