Optimize|Refactor|libgui|Font: Faster rich format subranges
Profiling showed that majority of the time used by FontLineWrapping was spent splitting RichFormat instances into subranges. This commit revises the implementation of RichFormat so that it is efficient to refer to a subrange of a RichFormat -- no copying or modification occurs.
Optimize|Refactor|libgui|Font: Faster rich format subranges
Profiling showed that majority of the time used by FontLineWrapping
was spent splitting RichFormat instances into subranges. This commit
revises the implementation of RichFormat so that it is efficient
to refer to a subrange of a RichFormat -- no copying or modification
occurs.