TypecastFont using `metrics.getAscentFU() - metrics.getDescentFU()` for ascent used for all undefined and whitespace Glyphs w/o a spatial outline, leads to a potential exceeding height compared to the actual used bounding box of the rendered text. This in turn leads to layout issues, e.g. button labels are placed too low. Solution: - Whitespace/Undefined: Drop full height 'metrics.getAscentFU() - metrics.getDescentFU()', b/c of non-existing shape height. - Otherwise, layout on AABBox or created empty shape would pick up such default hhea-table ascent which might exceed actual string height. Sideeffect would be if user relies on height of a whitespace. However, knowing this fact - a user may always pick the hhea-table's ascent metric values as exposed in Font and Font.Metric. This resolves remaining layout issues, including button labels.