Split OutlineBuilder from GlyphBuilder

[madig]

This complicates the process slightly because now there's a hand-off between both builders, but is conceptually nicer. I think.

[cmyr]

This seems okay on a fairly quick pass. One concern I've just noticed now is that we're passing around the hashes of the identifiers, instead of passing the identifiers themselves; is there a specific rationale for this? It seems like it could possibly cause problems.

[madig]

Inserting them into a set consumes them :D I figured we don't want that? And also avoid cloning.

[cmyr]

Okay, I think if we're worried about cloning the answer is to make sure we're using something like Arc<str> that is cheaper to clone. Hash equality is not item equality, and hash collisions are definitely not impossible.

[madig]

It does strike me as somewhat intrusive to make all identifiers Arc just so we can hand off easier from OutlineBuilder to GlyphBuilder. However, with the recent UFO spec addition of public.objectLibs, identifiers will get a more prominent role in enabling setting libs on various objects identifiable with an Identifier :o

[cmyr]

Yea sorry! I didn't mean that we should use Arc<Identifier>, but rather Identifier should be declared as Identifier<Arc>, instead of as Identifier`.

[github-actions]

🗜 Bloat check ⚖️

Comparing 2b11b7a against 1c77b74

target	old size	new size	difference
target/release/examples/open_ufo	1.49 MB	1.51 MB	20.48 KB (1.34%)
target/debug/examples/open_ufo	6.74 MB	6.8 MB	61.77 KB (0.89%)

[cmyr]

Cool, only real thing of note is that I think we can save ourselves needing to do all of these from_strs, as mentioned in the more detailed comments.

Thanks again for pushing on with this!

[github-actions]

🗜 Bloat check ⚖️

Comparing 801cc06 against 1c77b74

target	old size	new size	difference
target/release/examples/open_ufo	1.49 MB	1.51 MB	19.11 KB (1.25%)
target/debug/examples/open_ufo	6.74 MB	6.8 MB	54.48 KB (0.79%)

[github-actions]

🗜 Bloat check ⚖️

Comparing fd82edc against 1c77b74

target	old size	new size	difference
target/release/examples/open_ufo	1.49 MB	1.51 MB	19.11 KB (1.25%)
target/debug/examples/open_ufo	6.74 MB	6.8 MB	54.48 KB (0.79%)