This adds a new configuration "font-synthetic-style" to enable or
disable synthetic styles. This is different from "font-style-*" which
specifies a named style or disables a style completely.
Instead, "font-synthetic-style" will disable only the creation of
synthetic styles in the case a font does not support a given style.
This is useful for users who want to obviously know when a font doesn't
support a given style or a user who wants to explicitly only use the
styles that were designed by the font designer.
The default value is to enable all synthetic styles.
At certain font sizes, this avoids clipping the text. This is due to a
limitation of the CoreText API, which does not provide a way to measure
the exact size of the text that will be rendered when antialiasing is
enabled.
Fixes#2081
Many fonts have a bad ligature for "fl", "fi", or "st". We previously
maintained a list of such fonts in quirks.zig. However, these are so
common that it was suggested we do something more systematic and this
commit is that.
This commit changes our text run splitting algorithm to always split on
`fl`, `fi`, and `st`. This will cause some more runs for well behaved
fonts but the combination of those characters is rare enough and our
caching algorithm is good enough that it should be minimal overhead.
This commit renders our existing quirks fonts obsolete but I kept that
logic around so we can add to it if/when we find other quirky font
behaviors.
Some CoreFoundation objects, such as those produced by CoreText, have
expensive callbacks that run when they are released. By offloading the
CFRelease calls to another thread, we can avoid important threads being
blocked by unexpectedly expensive callbacks.
This commit also changes the way that the coretext shaper's run iterator
builds its string. Rather than using a CFMutableString, an ArrayList of
unichars is built which is passed to CFStringCreateWithCharactersNoCopy,
which is a lot more efficient since it avoids all the CoreFoundation
overhead.
