InputSource

Position in the list, not the browser's slot — GamepadView.index answers that, and is what a consumer pins a player to. The distinction shows itself when a pad is unplugged: the list closes up, and a caller holding a slot wants index.

A disabled source is inert rather than absent, and disabling the gamepad stops the poll outright — so an application that does not want controllers pays for no snapshot a frame.

Called once an animation frame by this source's own loop unless autoPoll is false, and public so a consumer can pin the sample to its own fixed tick instead — which is what a recorded replay needs, since a sample taken on a frame callback is not reproducible.

getGamepads() allocates, an array and the objects behind it, and that cost is the browser's rather than something this engine can pool. So it is called exactly once here and never from a read: every accessor on a view is a lookup on numbers already copied out. A frame that runs three simulation ticks polls once, which is also the correct semantics — the hardware cannot have changed between two ticks of one frame.

The keyboard's half of the pair GamepadView.pressed documents: use this to draw, and consumeKeyPress to act, so a slow frame running the fixed-step loop twice cannot act twice.

A browser opens its context menu on the right button's release; a game binding that button cancels contextmenu on its canvas, which is a decision about the page and not this source's.