font: Improve quirks mode performance, DeferredFace, Group refactor
This was motivated by #331. I realized with #331 that this added a lot of overhead on every render frame, because for each text run being rendered, we were (1) reloading the font name (unknown performance cost on macOS due to closed source, looks like [it ain't exactly free in Freetype](https://sourcegraph.com/github.com/freetype/freetype@4d8db130ea4342317581bab65fc96365ce806b77/-/blob/src/base/ftsnames.c?L44)) (2) doing multiple string compares (3) multiple function call overhead. And realistically, quirks mode will be _rare_, so paying a very active cost for a rare thing is 💩 .
In investigating that I finally shaved some yaks I've been wanting to shave on this path... the end result is that overall we should be doing [very] slightly less work no matter what and using slightly less memory. And on the renderer path, we're doing _way_ less work.
- All loaded font `Face` structures must also check and cache their quirks mode settings. This makes #331 a single boolean check per text run which is effectively free compared to the actual shaping task. The cost is one additional byte on the face structure (well, whatever the alignment is).
- `DeferredFace` now only represents an _unloaded_ face (that can be loaded multiple times). This lowers memory usage significantly (`Face` was large) per deferred face.
- `DeferredFace.name()` now takes a buffer for output instead of just failing on no static space, weird decision. No performance impact but makes this function more robust.
- `Group.addFace` now takes a tagged union representing either a deferred or loaded face, this gets rid of all the weird `DeferredFace.initLoaded` wrappers that were unnecessary and dumb. No real performance impact.
- When a font face is loaded in `Group` (lots of things trigger this), the DeferredFace it came from is now deinitialized immediately. This should save on memory significantly because we free all the font discovery information. We can do this because a deferred face is only ever loaded _once_ when its part of a `Group`, and the group owns the deferred face.
- Auto-italicize moves into `Group` and is no longer duplicated between Deferred and normal Face. No performance change, less code.
* font: disable default font features for Menlo and Monaco
Both of these fonts have a default ligature on "fi" which makes terminal
rendering super ugly. The easiest thing to do is special-case these
fonts and disable ligatures. It appears other terminals do the same
thing.
macOS translates inputs such as shift+tab into the control character tab
(ascii 0x09). Linux/GTK does not translate character inputs except to
printable characters. We don't want control character translations
because these are all handled manually by our key encoder (i.e.
translating ctrl+c to 0x03).
U+226A is 1-char wide according to the Unicode database but renders very
wide in many fonts. This causes it to leak outside of its grid cell. We
should scale down by x the same way we scale down by y.
Mitchell Hashimoto