As extensively discussed and documented in #1484, Core Text does
not operate in 96 DPI. Core Text doesn't actually have a concept of
DPI internally, as it doesn't rasterize anything by itself, it just
generates vector paths that get passed along to Core Graphics.
In practice this means Core Text operates in the classical macOS
logical DPI of 72, with one typographic point corresponding to one
point in the Core Graphics coordinate system, which for a normal
bitmap context then corresponds to one pixel -- or two pixels for
a "retina" context with a 2x scale transform.
As of f401f85a5a, we no longer apply
any assumptions in HB about the target DPI being different than the
72 DPI used by CT, for example to account for the Web's standard of
96 DPI, so let's remove the documentation that still indicated this
was necessary.
Tor Arne Vestbø
