register method
Registers a component to be considered for focus and hover handling.
Must be called once for each interactive component in the UI before
handling input. Components should be re-registered every frame after
layout, since componentInstances is cleared on reset.
Implementation
void register(InteractableComponentInstance c) {
context.componentInstances.add(c);
if (context.componentInstances.length - 1 ==
context.currentComponentIndex) {
context.currentComponent = c;
context.currentComponent!.focus();
}
}