@ue-too/board / index / ObservableInputTracker

Class: ObservableInputTracker

Defined in: packages/board/src/input-interpretation/input-state-machine/kmt-input-context.ts:717

Production implementation of KmtInputContext that tracks input state for the state machine.

Remarks

This class provides the concrete implementation of the KMT input context, maintaining all state required by the state machine to recognize and track gestures:

State Tracking:

• Initial cursor position for calculating pan deltas
• Input modality score to distinguish mouse vs trackpad
• Determined input mode (kmt/trackpad/TBD)
• Coordinate system alignment preference

Input Modality Detection: The kmtTrackpadTrackScore accumulates evidence about the input device:

• Positive values indicate mouse behavior (middle-click, no horizontal scroll)
• Negative values indicate trackpad behavior (horizontal scroll, two-finger gestures)
• Score is used to determine zoom behavior (Ctrl+Scroll for mouse vs Scroll for trackpad)

Design Pattern: This class follows the Context pattern from the @ue-too/being state machine library, providing stateful data and operations that states can access and modify during transitions.

Example

const canvasProxy = new CanvasProxy(canvasElement);
const context = new ObservableInputTracker(canvasProxy);
const stateMachine = createKmtInputStateMachine(context);

// Context tracks state as the state machine processes events
stateMachine.happens("leftPointerDown", {x: 100, y: 200});
console.log(context.initialCursorPosition); // {x: 100, y: 200}

Implements

• KmtInputContext

Constructors

Constructor

new ObservableInputTracker(canvasOperator): ObservableInputTracker

Defined in: packages/board/src/input-interpretation/input-state-machine/kmt-input-context.ts:725

Parameters

canvasOperator

Canvas

Returns

ObservableInputTracker

Accessors

alignCoordinateSystem

Get Signature

get alignCoordinateSystem(): boolean

Defined in: packages/board/src/input-interpretation/input-state-machine/kmt-input-context.ts:774

Whether to use standard screen coordinate system (vs inverted Y-axis)

Returns

boolean

Set Signature

set alignCoordinateSystem(value): void

Defined in: packages/board/src/input-interpretation/input-state-machine/kmt-input-context.ts:786

Whether to use standard screen coordinate system (vs inverted Y-axis)

Parameters

value

boolean

Returns

void

Whether to use standard screen coordinate system (vs inverted Y-axis)

Implementation of

KmtInputContext.alignCoordinateSystem

---

canvas

Get Signature

get canvas(): Canvas

Defined in: packages/board/src/input-interpretation/input-state-machine/kmt-input-context.ts:778

Canvas accessor for dimensions and cursor control

Returns

Canvas

Canvas accessor for dimensions and cursor control

Implementation of

KmtInputContext.canvas

---

initialCursorPosition

Get Signature

get initialCursorPosition(): Point

Defined in: packages/board/src/input-interpretation/input-state-machine/kmt-input-context.ts:782

The cursor position when a pan gesture started

Returns

Point

The cursor position when a pan gesture started

Implementation of

KmtInputContext.initialCursorPosition

---

kmtTrackpadTrackScore

Get Signature

get kmtTrackpadTrackScore(): number

Defined in: packages/board/src/input-interpretation/input-state-machine/kmt-input-context.ts:748

Score tracking input modality: >0 for mouse, <0 for trackpad, 0 for undetermined

Returns

number

Score tracking input modality: >0 for mouse, <0 for trackpad, 0 for undetermined

Implementation of

KmtInputContext.kmtTrackpadTrackScore

---

mode

Get Signature

get mode(): "kmt" | "trackpad" | "TBD"

Defined in: packages/board/src/input-interpretation/input-state-machine/kmt-input-context.ts:733

The current input modality: 'kmt' (mouse), 'trackpad', or 'TBD' (to be determined)

Returns

"kmt" | "trackpad" | "TBD"

The current input modality: 'kmt' (mouse), 'trackpad', or 'TBD' (to be determined)

Implementation of

KmtInputContext.mode

Methods

addKmtTrackpadTrackScore()

addKmtTrackpadTrackScore(): void

Defined in: packages/board/src/input-interpretation/input-state-machine/kmt-input-context.ts:763

Increases the score toward mouse

Returns

void

Implementation of

KmtInputContext.addKmtTrackpadTrackScore

---

cancelCurrentAction()

cancelCurrentAction(): void

Defined in: packages/board/src/input-interpretation/input-state-machine/kmt-input-context.ts:790

Cancels the current action and resets cursor position

Returns

void

Implementation of

KmtInputContext.cancelCurrentAction

---

cleanup()

cleanup(): void

Defined in: packages/board/src/input-interpretation/input-state-machine/kmt-input-context.ts:798

Returns

void

Implementation of

KmtInputContext.cleanup

---

enableInputModeDetection()

enableInputModeDetection(): void

Defined in: packages/board/src/input-interpretation/input-state-machine/kmt-input-context.ts:742

Returns

void

---

setInitialCursorPosition()

setInitialCursorPosition(position): void

Defined in: packages/board/src/input-interpretation/input-state-machine/kmt-input-context.ts:794

Sets the initial cursor position when starting a pan gesture

Parameters

position

Point

Returns

void

Implementation of

KmtInputContext.setInitialCursorPosition

---

setMode()

setMode(mode): void

Defined in: packages/board/src/input-interpretation/input-state-machine/kmt-input-context.ts:737

Sets the determined input modality

Parameters

mode

"kmt" | "trackpad" | "TBD"

Returns

void

Implementation of

KmtInputContext.setMode

---

setup()

setup(): void

Defined in: packages/board/src/input-interpretation/input-state-machine/kmt-input-context.ts:800

Returns

void

Implementation of

KmtInputContext.setup

---

subtractKmtTrackpadTrackScore()

subtractKmtTrackpadTrackScore(): void

Defined in: packages/board/src/input-interpretation/input-state-machine/kmt-input-context.ts:752

Decreases the score toward trackpad

Returns

void

Implementation of

KmtInputContext.subtractKmtTrackpadTrackScore