81 lines
2.2 KiB
TypeScript
81 lines
2.2 KiB
TypeScript
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import type { ViewportSelectionState } from '../core/waveformChartTypes'
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export interface ViewportGestureStart {
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trackIndex: number
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independent: boolean
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startX: number
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startY: number
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pointerId: number
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kind: 'box' | 'pan'
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xDomain: [number, number]
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yDomains: Record<string, [number, number]>
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}
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export interface ViewportGesturePosition {
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currentX: number
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currentY: number
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}
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function cloneState(state: ViewportSelectionState | null): ViewportSelectionState | null {
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if (!state) return null
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return {
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...state,
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xDomain: [...state.xDomain],
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yDomains: Object.fromEntries(
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Object.entries(state.yDomains).map(([key, domain]) => [key, [...domain] as [number, number]]),
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),
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}
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}
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/** Owns the legal lifecycle of one active viewport pointer gesture. */
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export class ViewportInteractionStateMachine {
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private current: ViewportSelectionState | null = null
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get state(): ViewportSelectionState | null {
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return cloneState(this.current)
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}
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begin(input: ViewportGestureStart): boolean {
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if (this.current) return false
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this.current = {
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...input,
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currentX: input.startX,
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currentY: input.startY,
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xDomain: [...input.xDomain],
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yDomains: Object.fromEntries(
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Object.entries(input.yDomains).map(([key, domain]) => [
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key,
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[...domain] as [number, number],
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]),
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),
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}
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return true
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}
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move(pointerId: number, position: ViewportGesturePosition): ViewportSelectionState | null {
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if (!this.current || this.current.pointerId !== pointerId) return null
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this.current = { ...this.current, ...position }
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return this.state
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}
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finish(pointerId: number, position: ViewportGesturePosition): ViewportSelectionState | null {
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if (!this.current || this.current.pointerId !== pointerId) return null
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this.current = { ...this.current, ...position }
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const completed = this.state
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this.current = null
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return completed
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}
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cancel(pointerId?: number): boolean {
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if (!this.current || (pointerId !== undefined && this.current.pointerId !== pointerId)) {
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return false
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}
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this.current = null
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return true
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}
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reset(): void {
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this.current = null
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}
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}
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