Function publish_pointer_state 

pub fn publish_pointer_state(
    state: Option<Res<'_, PointerState>>,
    modifiers: Option<Res<'_, ModifiersState>>,
)

Publish what the input layer knows about the pointer each tick, so a read from a handler sees this tick’s position.

It reads only the pointer and modifier resources every input backend keeps, a window’s or a page’s, so every platform publishes through it.