Structs
If you don’t ever need to refer to objects in a World, you can auto-assign dummy IDs.
This provides a builder API for adding objects to a World.
A World manages objects that exist in “map-space”, the zoomable and pannable canvas. These
objects can be drawn, hovered on, clicked, dragged, etc.
Enums
The result of a World handling an event
Traits
Objects in a World are uniquely identified by this caller-specified type