A per-frame callback. Returning true says "I changed what the next render
draws" and makes this tick render; false says it changed nothing drawn.
The return is REQUIRED (not void | boolean) so every registration has to
state which it is: a callback that mutated drawn state and returned nothing
would leave a stale frame on screen until something else redraws, and the
compiler now catches the one that forgets. Camera motion needs no true
(the view signature catches it), nor does a DOM-only overlay.
A per-frame callback. Returning
truesays "I changed what the next render draws" and makes this tick render;falsesays it changed nothing drawn. The return is REQUIRED (notvoid | boolean) so every registration has to state which it is: a callback that mutated drawn state and returned nothing would leave a stale frame on screen until something else redraws, and the compiler now catches the one that forgets. Camera motion needs notrue(the view signature catches it), nor does a DOM-only overlay.