- applications don't need to bother about hinting algorithms and
their arcane parameters, they simply specify what kind of surface
they want the outlines optimized for. This let us improve the
hinters in subsequent releases of the library without changing
application sources or binaries.
- it's relatively simple to produce a new "target mode" if a new
incredibly smart new hinting technique comes in, or when we'd like
to support optimisations specific to other kinds of displays (TVs for
example, can benefit from a hinting scheme where you _avoid_ aligning
stems to the pixel grid, in order to reduce flickering effects).