Input conditions

Every object built by InputCombination implements InputCondition:

interface InputCondition {
  evaluate(input: InputDevices): boolean;
  reset(): void;
}

interface InputDevices {
  readonly keyboard: Keyboard;
  readonly mouse: Mouse;
  readonly gamepad: Gamepad;
}

evaluate() reads the current frame state from the devices. An Input satisfies InputDevices. reset() clears condition-owned progress. Atomic conditions have no progress to clear; composite conditions forward the reset to their children.

InputCondition and every concrete condition class on this page are exported from the package root.

AtomicInput

The InputCombination.key(), mouse(), and gamepad() factories return an AtomicInput. It can also be constructed directly:

new AtomicInput(
  type: "key",
  action: InputKeyboardAction,
  state?: CombinedInputState
)

new AtomicInput(
  type: "mouse",
  action: InputMouseAction,
  state?: CombinedInputState
)

new AtomicInput(
  type: "gamepad",
  action: [GamepadIndex, number | keyof typeof GamepadButton],
  state?: CombinedInputState
)

The state defaults to "pressed". evaluate() delegates to the matching keyboard, mouse, or gamepad query on Input.

The package also exports the low-level CombinedInputType and AtomicInputAction unions used by this class.

For the factory overloads and combined action strings, see InputCombination.

Composite conditions

The three stateless composites accept an array of child conditions:

new AllInputs(conditions: InputCondition[])
new AtLeastOneInput(conditions: InputCondition[])
new NoneInputs(conditions: InputCondition[])

AllInputs returns true when every child evaluates to true. With no children, it returns true.

AtLeastOneInput returns true when any child evaluates to true. With no children, it returns false.

NoneInputs returns true when every child evaluates to false. With no children, it returns true.

The corresponding InputCombination.all(), atLeastOne(), and none() factories also accept combined keyboard action strings and convert them into atomic conditions.

Calling reset() on a composite resets each child. Its evaluation stops as soon as the result is known, so later children may not be evaluated during that call.

Stateful composition is provided by SequenceInputs and HoldInput.

Binding to an Input

interface BoundInputCondition {
  (): boolean;
  reset(): void;
}

bindInputCondition(
  condition: InputCondition,
  input: InputDevices
): BoundInputCondition

The returned function calls condition.evaluate(input). Its reset() method calls condition.reset(). Any InputCondition can be bound, including a custom implementation.

const dash = bindInputCondition(
  InputCombination.all(
    InputCombination.key("ShiftLeft", "down"),
    InputCombination.key("ArrowRight", "pressed")
  ),
  input
);

function gameLoop() {
  input.update();

  if (dash()) {
    console.log("Dash");
  }

  requestAnimationFrame(gameLoop);
}

A bound function does not copy the condition. Functions bound from the same condition share its state. A SequenceInputs instance bound to two inputs, for example, advances when either function evaluates it. Call a bound sequence once per frame, as with evaluate().

BoundInputCondition and bindInputCondition() are exported from the package root.