index.ts

/*
Copyright 2024 New Vector Ltd.
Copyright 2021-2023 The Matrix.org Foundation C.I.C.
Copyright 2022 Arseny Uskov

SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Commercial
Please see LICENSE files in the repository root for full details.
*/

import type ICanvasEffect from "../ICanvasEffect";
import { arrayFastClone } from "../../utils/arrays";

type HeartOptions = {
    /**
     * The maximum number of hearts to render at a given time
     */
    maxCount: number;
    /**
     * The amount of gravity to apply to the hearts
     */
    gravity: number;
    /**
     * The maximum amount of drift (horizontal sway) to apply to the hearts. Each heart varies.
     */
    maxDrift: number;
    /**
     * The maximum amount of tilt to apply to the heart. Each heart varies.
     */
    maxRot: number;
};

type Heart = {
    x: number;
    y: number;
    xCol: number;
    scale: number;
    maximumDrift: number;
    maximumRot: number;
    gravity: number;
    color: string;
};

export const DefaultOptions: HeartOptions = {
    maxCount: 120,
    gravity: 3.2,
    maxDrift: 5,
    maxRot: 5,
};

const KEY_FRAME_INTERVAL = 15; // 15ms, roughly

export default class Hearts implements ICanvasEffect {
    private readonly options: HeartOptions;

    public constructor(options: Partial<HeartOptions>) {
        this.options = { ...DefaultOptions, ...options };
    }

    private context: CanvasRenderingContext2D | null = null;
    private particles: Array<Heart> = [];
    private lastAnimationTime = 0;

    private colours = [
        "rgba(194,210,224,1)",
        "rgba(235,214,219,1)",
        "rgba(255,211,45,1)",
        "rgba(255,190,174,1)",
        "rgba(255,173,226,1)",
        "rgba(242,114,171,1)",
        "rgba(228,55,116,1)",
        "rgba(255,86,130,1)",
        "rgba(244,36,57,1)",
        "rgba(247,126,157,1)",
        "rgba(243,142,140,1)",
        "rgba(252,116,183,1)",
    ];

    public isRunning = false;

    public start = async (canvas: HTMLCanvasElement, timeout = 3000): Promise<void> => {
        if (!canvas) {
            return;
        }
        this.context = canvas.getContext("2d");
        this.particles = [];
        const count = this.options.maxCount;
        while (this.particles.length < count) {
            this.particles.push(this.resetParticle({} as Heart, canvas.width, canvas.height));
        }
        this.isRunning = true;
        requestAnimationFrame(this.renderLoop);
        if (timeout) {
            window.setTimeout(this.stop, timeout);
        }
    };

    public stop = async (): Promise<void> => {
        this.isRunning = false;
    };

    private resetParticle = (particle: Heart, width: number, height: number): Heart => {
        particle.color = this.colours[(Math.random() * this.colours.length) | 0];
        particle.x = Math.random() * width;
        particle.y = Math.random() * height + height;
        particle.xCol = particle.x;
        particle.scale = Math.random() * 0.07 + 0.04;
        particle.maximumDrift = Math.random() * this.options.maxDrift + 3.5;
        particle.maximumRot = Math.random() * this.options.maxRot + 3.5;
        particle.gravity = this.options.gravity + Math.random() * 4.8;
        return particle;
    };

    private renderLoop = (): void => {
        if (!this.context || !this.context.canvas) {
            return;
        }
        if (this.particles.length === 0) {
            this.context.clearRect(0, 0, this.context.canvas.width, this.context.canvas.height);
        } else {
            const timeDelta = Date.now() - this.lastAnimationTime;
            if (timeDelta >= KEY_FRAME_INTERVAL || !this.lastAnimationTime) {
                // Clear the screen first
                this.context.clearRect(0, 0, this.context.canvas.width, this.context.canvas.height);

                this.lastAnimationTime = Date.now();
                this.animateAndRenderHearts();
            }
            requestAnimationFrame(this.renderLoop);
        }
    };

    private animateAndRenderHearts(): void {
        if (!this.context || !this.context.canvas) {
            return;
        }
        for (const particle of arrayFastClone(this.particles)) {
            particle.y -= particle.gravity;

            // We treat the drift as a sine function to have a more fluid-like movement instead
            // of a pong-like movement off walls of the X column. This means that for
            // $x=A\sin(\frac{2\pi}{P}y)$ we use the `maximumDrift` as the amplitude (A) and a
            // large multiplier to create a very long waveform through P.
            const peakDistance = 75 * particle.maximumDrift;
            const PI2 = Math.PI * 2;
            particle.x = 6 * particle.maximumDrift * Math.sin(0.7 * (PI2 / peakDistance) * particle.y);
            particle.x += particle.xCol; // bring the particle to the right place

            const posScale = 1 / particle.scale;
            const x = particle.x * posScale;
            const y = particle.y * posScale;

            this.context.save();
            this.context.scale(particle.scale, particle.scale);
            this.context.beginPath();

            // Rotate the heart about its centre.
            // The tilt of the heart is modelled similarly to its horizontal drift,
            // using a sine function.
            this.context.translate(248 + x, 215 + y);
            this.context.rotate((1 / 10) * particle.maximumRot * Math.sin((PI2 / peakDistance) * particle.y * 0.8));
            this.context.translate(-248 - x, -215 - y);

            // Use bezier curves to draw a heart using pre-calculated coordinates.
            this.context.moveTo(140 + x, 20 + y);
            this.context.bezierCurveTo(73 + x, 20 + y, 20 + x, 74 + y, 20 + x, 140 + y);
            this.context.bezierCurveTo(20 + x, 275 + y, 156 + x, 310 + y, 248 + x, 443 + y);
            this.context.bezierCurveTo(336 + x, 311 + y, 477 + x, 270 + y, 477 + x, 140 + y);
            this.context.bezierCurveTo(477 + x, 74 + y, 423 + x, 20 + y, 357 + x, 20 + y);
            this.context.bezierCurveTo(309 + x, 20 + y, 267 + x, 48 + y, 248 + x, 89 + y);
            this.context.bezierCurveTo(229 + x, 48 + y, 188 + x, 20 + y, 140 + x, 20 + y);
            this.context.closePath();

            this.context.fillStyle = particle.color;
            this.context.fill();

            this.context.restore();

            // Remove any dead hearts after a 100px wide margin.
            if (particle.y < -100) {
                const idx = this.particles.indexOf(particle);
                this.particles.splice(idx, 1);
            }
        }
    }
}