2021-12-01 02:14:25 +00:00
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// Copyright 2021 Signal Messenger, LLC
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// SPDX-License-Identifier: AGPL-3.0-only
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import { useEffect, useState } from 'react';
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import { fabric } from 'fabric';
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import EventEmitter from 'events';
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import type { ImageStateType } from './ImageStateType';
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import { MediaEditorFabricIText } from './MediaEditorFabricIText';
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import { MediaEditorFabricPath } from './MediaEditorFabricPath';
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import { MediaEditorFabricSticker } from './MediaEditorFabricSticker';
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export function useFabricHistory(
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canvas: fabric.Canvas | undefined
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): FabricHistory | undefined {
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const [history, setHistory] = useState<FabricHistory | undefined>();
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// We need this type of precision so that when serializing/deserializing
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// the floats don't get rounded off and we maintain proper image state.
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// http://fabricjs.com/fabric-gotchas
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fabric.Object.NUM_FRACTION_DIGITS = 16;
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// Attach our custom classes to the global Fabric instance. Unfortunately, Fabric
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// doesn't make it easy to deserialize into a custom class without polluting the
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// global namespace. See <http://fabricjs.com/fabric-intro-part-3#subclassing>.
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Object.assign(fabric, {
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MediaEditorFabricIText,
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MediaEditorFabricPath,
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MediaEditorFabricSticker,
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});
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useEffect(() => {
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if (canvas) {
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const fabricHistory = new FabricHistory(canvas);
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setHistory(fabricHistory);
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}
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}, [canvas]);
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return history;
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}
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const LIMIT = 1000;
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type SnapshotStateType = {
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canvasState: string;
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imageState: ImageStateType;
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2021-12-01 02:14:25 +00:00
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};
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export class FabricHistory extends EventEmitter {
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private readonly canvas: fabric.Canvas;
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private highWatermark: number;
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private isTimeTraveling: boolean;
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private snapshots: Array<SnapshotStateType>;
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constructor(canvas: fabric.Canvas) {
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super();
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this.canvas = canvas;
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this.highWatermark = 0;
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this.isTimeTraveling = false;
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this.snapshots = [];
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this.canvas.on('object:added', this.onObjectModified.bind(this));
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this.canvas.on('object:modified', this.onObjectModified.bind(this));
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this.canvas.on('object:removed', this.onObjectModified.bind(this));
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}
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private applyState({ canvasState, imageState }: SnapshotStateType): void {
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this.canvas.loadFromJSON(canvasState, () => {
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this.emit('appliedState', imageState);
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this.emit('historyChanged');
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this.isTimeTraveling = false;
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});
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}
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private getState(): string {
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return JSON.stringify(this.canvas.toDatalessJSON());
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}
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private onObjectModified({ target }: fabric.IEvent): void {
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if (target?.excludeFromExport) {
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return;
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}
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this.emit('pleaseTakeSnapshot');
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}
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private getUndoState(): SnapshotStateType | undefined {
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if (!this.canUndo()) {
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return;
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}
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this.highWatermark -= 1;
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return this.snapshots[this.highWatermark];
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}
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private getRedoState(): SnapshotStateType | undefined {
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if (this.canRedo()) {
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this.highWatermark += 1;
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}
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return this.snapshots[this.highWatermark];
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}
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public takeSnapshot(imageState: ImageStateType): void {
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if (this.isTimeTraveling) {
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return;
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}
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if (this.canRedo()) {
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this.snapshots.splice(this.highWatermark, this.snapshots.length);
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}
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this.snapshots.push({ canvasState: this.getState(), imageState });
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if (this.snapshots.length > LIMIT) {
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this.snapshots.shift();
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}
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this.highWatermark = this.snapshots.length - 1;
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this.emit('historyChanged');
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}
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public undo(): void {
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const undoState = this.getUndoState();
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if (!undoState) {
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return;
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}
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this.isTimeTraveling = true;
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this.applyState(undoState);
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}
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public redo(): void {
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const redoState = this.getRedoState();
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if (!redoState) {
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return;
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}
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this.isTimeTraveling = true;
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this.applyState(redoState);
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}
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public canUndo(): boolean {
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return this.highWatermark > 0;
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}
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public canRedo(): boolean {
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return this.highWatermark < this.snapshots.length - 1;
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}
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}
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