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  • §

    Demo Canvas 033

    User preferences: prefers-color-scheme; prefers-reduced-motion

  • §

    Run code

    import * as scrawl from '../source/scrawl.js';
    
    import { reportSpeed } from './utilities.js';
  • §

    Scene setup

    const canvas = scrawl.library.canvas.mycanvas;
    
    const background_dark = '#404040',
        text_dark = '#c0ffc0',
        background_light = '#f0f0f0',
        text_light = '#408f40';
  • §

    Create the demo Oval entity

    const track = scrawl.makeOval({
    
        name: 'loader-track',
    
        radiusX: '22%',
        radiusY: '12%',
    
        start: ['center', 'center'],
        handle: ['center', 'center'],
    
        strokeStyle: '#808080',
        lineWidth: 10,
        method: 'draw',
    
        delta: {
            roll: 0.2
        },
    
        useAsPath: true,
        precision: 0.1
    });
  • §

    Create the three Phrase entitys that will animate around the oval

    • We give them their own group to make updating their attributes easier
    const textGroup = scrawl.makeGroup({
    
        name: 'text-group',
        host: canvas.base.name,
    });
    
    scrawl.makePhrase({
    
        name: 'loader-text-1',
        group: textGroup,
    
        weight: 'bold',
    
        text: 'Loading',
        size: '50px',
        justify: 'center',
    
        textPath: 'loader-track',
        handleY: '120%',
    
        delta: {
          textPathPosition: -0.002
        },
    
    }).clone({
    
        name: 'loader-text-2',
        textPathPosition: 0.333,
    
    }).clone({
    
        name: 'loader-text-3',
        textPathPosition: 0.667,
    });
  • §

    prefers-color-scheme actions

    Setup the actions to take, to match the animation scene to the user’s preference for dark or light (default) color scheme

    canvas.setColorSchemeDarkAction(() => {
    
        canvas.set({ backgroundColor: background_dark});
        textGroup.setArtefacts({ fillStyle: text_dark});
    });
    
    canvas.setColorSchemeLightAction(() => {
        
        canvas.set({ backgroundColor: background_light});
        textGroup.setArtefacts({ fillStyle: text_light});
    });
  • §

    Scene animation

    Function to display frames-per-second data, and other information relevant to the demo

    const report = reportSpeed('#reportmessage');
  • §

    Create the Display cycle animation

    const demoAnimation = scrawl.makeRender({
    
        name: "demo-animation",
        target: canvas,
        afterShow: report,
    });
  • §

    prefers-reduced-motion actions

    const checkE = (e) => {
        if (e) {
            if ("keydown" === e.type) {
                if (32 === e.keycode) return true; // spacebar
                if (13 === e.keycode) return true; // enter key
            }
            if ("click" === e.type) return true; // mouse click
            if ("touchend" === e.type) return true; // tap
        }
        return false;
    };
    
    const startAnimation = (e) => {
        if (e === "reduced-motion" || checkE(e)) {
            track.set({ noDeltaUpdates: false });
            textGroup.setArtefacts({ noDeltaUpdates: false });
        }
    };
    
    const stopAnimation = (e) => {
        if (e === "reduced-motion" || checkE(e)) {
            track.set({ noDeltaUpdates: true });
            textGroup.setArtefacts({ noDeltaUpdates: true });
        }
    };
    
    canvas.setReduceMotionAction(() => setTimeout(() => stopAnimation("reduced-motion"), 5000));
    
    canvas.setNoPreferenceMotionAction(() => startAnimation("reduced-motion"));
    
    const startButton = scrawl.addNativeListener(['click', 'keydown', 'touchend'], startAnimation, '#play');
    
    const stopButton = scrawl.addNativeListener(['click', 'keydown', 'touchend'], stopAnimation, '#pause');
  • §

    Development and testing

    In chrome browsers, open the inspector and enable the Rendering view - this includes selectors to emulate both prefers-reduced-motion and prefers-color-scheme user choices.

    console.log(scrawl.library);