canvaskit/npm_build/paragraphs.html

<!DOCTYPE html>
<title>CanvasKit Paragraph (with & without ICU)</title>
<meta charset="utf-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">

<script type="text/javascript" src="/build/canvaskit.js"></script>

<style>
  canvas {
    border: 1px dashed #AAA;
  }
  #withICU {
    border-color: red;
  }
  #withoutICU {
    border-color: green;
  }
  #sampleText {
    width: 400px;
    height: 200px;
  }
</style>

<table>
  <thead>
    <th><h2 style="color: red;">With ICU</h2></th>
    <th></th>
    <th><h2 style="color: green;">Without ICU</h2></th>
  </thead>
  <tr>
    <td><canvas id="withICU" width=600 height=600></canvas></td>
    <td style="width: 20px;"></td>
    <td><canvas id="withoutICU" width=600 height=600 tabindex='-1'></canvas></td>
  </tr>
</table>

<textarea id="sampleText">The لاquick ��(brown) fox
واحد (اثنان) ثلاثة
ate a hamburger.
</textarea>

<script type="text/javascript" charset="utf-8">

  var CanvasKit = null;
  var fonts = null;
  var sampleText = null;

  var cdn = 'https://storage.googleapis.com/skia-cdn/misc/';

  const ckLoaded = CanvasKitInit({locateFile: (file) => '/build/'+file});

  const loadFonts = [
    fetch(cdn + 'Roboto-Regular.ttf').then((response) => response.arrayBuffer()),
    fetch('https://fonts.gstatic.com/s/notoemoji/v26/bMrnmSyK7YY-MEu6aWjPDs-ar6uWaGWuob-r0jwvS-FGJCMY.ttf').then((response) => response.arrayBuffer()),
    fetch('https://fonts.gstatic.com/s/notosansarabic/v18/nwpxtLGrOAZMl5nJ_wfgRg3DrWFZWsnVBJ_sS6tlqHHFlhQ5l3sQWIHPqzCfyGyvu3CBFQLaig.ttf').then((response) => response.arrayBuffer()),
  ];

  let paragraphWithICU;
  let paragraphWithoutICU;

  Promise.all([ckLoaded, ...loadFonts]).then(([_CanvasKit, ..._fonts]) => {
    CanvasKit = _CanvasKit;
    fonts = _fonts;

    const textarea = document.getElementById('sampleText');
    sampleText = textarea.value;
    textarea.addEventListener('input', (e) => {
      sampleText = e.target.value;
      paragraphWithICU = ParagraphWithICU();
      paragraphWithoutICU = ParagraphWithoutICU();
    });

    paragraphWithICU = ParagraphWithICU();
    paragraphWithoutICU = ParagraphWithoutICU();

    continuousRendering('withICU', () => paragraphWithICU);
    continuousRendering('withoutICU', () => paragraphWithoutICU);
  });

  const fontFamilies = [
    'Roboto',
    'Noto Emoji',
    'Noto Sans Arabic',
  ];

  function continuousRendering(elementId, getParagraph) {
    const surface = CanvasKit.MakeCanvasSurface(elementId);
    if (!surface) {
      throw new Error('Could not make surface');
    }

    function drawFrame(canvas) {
      drawParagraph(canvas, getParagraph());
      surface.requestAnimationFrame(drawFrame);
    }
    surface.requestAnimationFrame(drawFrame);
  }

  function ParagraphWithICU() {
    if (!CanvasKit || !fonts) {
      throw new Error('CanvasKit or fonts not loaded');
    }

    const fontMgr = CanvasKit.FontMgr.FromData(fonts);

    const paraStyle = new CanvasKit.ParagraphStyle({
        textStyle: {
            color: CanvasKit.BLACK,
            fontFamilies: fontFamilies,
            fontSize: 50,
        },
        textAlign: CanvasKit.TextAlign.Left,
        maxLines: 4,
    });

    const builder = CanvasKit.ParagraphBuilder.Make(paraStyle, fontMgr);
    builder.addText(sampleText);
    const paragraph = builder.build();

    fontMgr.delete();

    return paragraph;
  }

  function ParagraphWithoutICU() {
    if (!CanvasKit || !fonts) {
      throw new Error('CanvasKit or fonts not loaded');
    }

    const fontMgr = CanvasKit.FontMgr.FromData(fonts);

    const paraStyle = new CanvasKit.ParagraphStyle({
        textStyle: {
          color: CanvasKit.BLACK,
          fontFamilies: fontFamilies,
          fontSize: 50,
        },
        maxLines: 4,
        textAlign: CanvasKit.TextAlign.Left,
    });

    const builder = CanvasKit.ParagraphBuilder.Make(paraStyle, fontMgr);
    builder.addText(sampleText);

    const text = sampleText;

    // Pass the entire text as one word. It's only used for the method
    // getWords.
    const mallocedWords = CanvasKit.Malloc(Uint32Array, 2);
    mallocedWords.toTypedArray().set([0, text.length]);

    const graphemeBoundaries = getGraphemeBoundaries(text);
    const mallocedGraphemes = CanvasKit.Malloc(Uint32Array, graphemeBoundaries.length);
    mallocedGraphemes.toTypedArray().set(graphemeBoundaries);

    const lineBreaks = getLineBreaks(text);
    const mallocedLineBreaks = CanvasKit.Malloc(Uint32Array, lineBreaks.length);
    mallocedLineBreaks.toTypedArray().set(lineBreaks);

    console.log('RequiresClientICU:', CanvasKit.ParagraphBuilder.RequiresClientICU());

    builder.setWordsUtf16(mallocedWords);
    builder.setGraphemeBreaksUtf16(mallocedGraphemes);
    builder.setLineBreaksUtf16(mallocedLineBreaks);
    const paragraph = builder.build();

    fontMgr.delete();

    return paragraph;
  }

  function drawParagraph(canvas, paragraph) {
    const fontPaint = new CanvasKit.Paint();
    fontPaint.setStyle(CanvasKit.PaintStyle.Fill);
    fontPaint.setAntiAlias(true);

    canvas.clear(CanvasKit.WHITE);
    const wrapTo = 350 + 150 * Math.sin(Date.now() / 4000);
    paragraph.layout(wrapTo);

    const rects = [
      ...paragraph.getRectsForRange(2, 8, CanvasKit.RectHeightStyle.Tight, CanvasKit.RectWidthStyle.Tight),
      ...paragraph.getRectsForRange(12, 16, CanvasKit.RectHeightStyle.Tight, CanvasKit.RectWidthStyle.Tight),
    ];
    const rectPaint = new CanvasKit.Paint();
    const colors = [CanvasKit.CYAN, CanvasKit.MAGENTA, CanvasKit.BLUE, CanvasKit.YELLOW];
    for (const rect of rects) {
      rectPaint.setColor(colors.shift() || CanvasKit.RED);
      canvas.drawRect(rect, rectPaint);
    }

    canvas.drawParagraph(paragraph, 0, 0);

    canvas.drawLine(wrapTo, 0, wrapTo, 400, fontPaint);
  }

  const SOFT = 0;
  const HARD = 1;

  function getLineBreaks(text) {
    const breaks = [0, SOFT];

    const iterator = new Intl.v8BreakIterator(['en'], {type: 'line'});
    iterator.adoptText(text);
    iterator.first();

    while (iterator.next() != -1) {
      breaks.push(iterator.current(), getBreakType(iterator.breakType()));
    }

    return breaks;
  }

  function getBreakType(v8BreakType) {
    return v8BreakType == 'none' ? SOFT : HARD;
  }

  function getGraphemeBoundaries(text) {
    const segmenter = new Intl.Segmenter(['en'], {type: 'grapheme'});
    const segments = segmenter.segment(text);

    const graphemeBoundaries = [];
    for (const segment of segments) {
      graphemeBoundaries.push(segment.index);
    }
    graphemeBoundaries.push(text.length);
    return graphemeBoundaries;
  }
</script>