The patch (based on an idea of Marko) checks if a multipolygon and its potential outer members has tags that are defined in the style. If not the multipolygon processing is not performed. This reduces processing time for small styles with a limited set of tags. The effect is not as big as one might expect. Although the style contains one tag only (example maxheight=*) the 53 tags defined in resources/styles/builtin-tag-list are additionally loaded. This reduces the number of skipped multipolygons quite much. Anyhow a little improvement is an improvement :-) WanMil