TODO - Refactoring

easier way to define magic tuneable constants
- and maybe to recalculate fixedish things if they change?

Map layer

fixed precision math
- more careful geom types, with negative/positive cases
- also bounds?
- cant get rid of the ccw intersection check... different answer in some cases that looks bad
maybe also the time to split into different lane types? what's similar/not between them?
- graph querying?
- rendering (and other UI/editor interactions)?
- sim state?
- Sidewalk, Parking, Street

rename Car->Vehicle?
spawning is convoluted
- popdat trip -> Scenario SpawnTrip -> pick ped speed and make spawner's TripSpec -> create trip and schedule a Command -> last minute rewriting when executing the command

probably use f32, not f64 everywhere... but after Pt2D becomes fixed size
undo the y inversion hacks at last!
ezgui passes EventCtx and DrawCtx with appropriate things exposed.
- maybe move glyph ownership out of canvas entirely. dont need RefCell.
  - need to pass around a NonDrawCtx very uniformly first for this to work
- canvas owning text-drawing is maybe a bit weird, at least API-wise
- hide stuff inside the ctx's? canvas and prerender shouldnt even be known outside of crate
generic World with quadtree should have actions on objects
loading screen
- cleanup hack: dont put glyphbrush in canvas at all
- FileWithProgress should go directly into Timer
  - need to understand lifetimes
- cleanup abstutil Timer stuff generally