The virtual method is moved to doRenderGlyph(), for plugin implementers
it means that the function only needs to be renamed (and moved to private
section) and plugin version interface needs to be updated.
The common layouting code allows to remove many redundant code from
Renderer and also ability to test cursor position/bounding rectangle
updated properly. Rectangle updating now treats rectangle with zero size
as invalid and replaces it with glyph quad instead of merging the two. It
means that the returned rectangle now wraps the text more tightly and
does not always contain origin.
Vladimír Vondruš