ef3d6af042
Many things are not enabled currently (e.g. Skottie, Paragraph), but we can render many APIs using WebGL. To turn on Paragraph, etc, we'll need to tackle fonts, which is a separate effort. This also changes where the build artifacts go. ./build/ is easier to deal with than the old way of sticking them in ./npm_build/bin Change-Id: Ia377360af580a887d03630670438fea2e3157e90 Bug: skia:12541 Reviewed-on: https://skia-review.googlesource.com/c/skia/+/470682 Reviewed-by: Leandro Lovisolo <lovisolo@google.com> Reviewed-by: Ben Wagner <bungeman@google.com>
180 lines
6.7 KiB
HTML
180 lines
6.7 KiB
HTML
<!DOCTYPE html>
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<title>WIP Shaping in JS Demo</title>
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<meta charset="utf-8" />
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<meta http-equiv="X-UA-Compatible" content="IE=edge">
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<style>
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canvas {
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border: 1px dashed #AAA;
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}
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#input {
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height: 300px;
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}
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</style>
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<h2> (Really Bad) Shaping in JS </h2>
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<textarea id=input></textarea>
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<canvas id=shaped_text width=300 height=300></canvas>
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<script type="text/javascript" src="/build/canvaskit.js"></script>
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<script type="text/javascript" charset="utf-8">
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let CanvasKit = null;
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const cdn = 'https://storage.googleapis.com/skia-cdn/misc/';
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const ckLoaded = CanvasKitInit({locateFile: (file) => '/build/'+file});
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const loadFont = fetch(cdn + 'Roboto-Regular.ttf').then((response) => response.arrayBuffer());
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// This font works with interobang.
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//const loadFont = fetch('https://storage.googleapis.com/skia-cdn/google-web-fonts/SourceSansPro-Regular.ttf').then((response) => response.arrayBuffer());
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document.getElementById('input').value = 'An aegis protected the fox!?';
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// Examples requiring external resources.
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Promise.all([ckLoaded, loadFont]).then((results) => {
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ShapingJS(...results);
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});
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function ShapingJS(CanvasKit, fontData) {
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if (!CanvasKit || !fontData) {
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return;
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}
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const surface = CanvasKit.MakeCanvasSurface('shaped_text');
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if (!surface) {
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console.error('Could not make surface');
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return;
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}
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const typeface = CanvasKit.Typeface.MakeFreeTypeFaceFromData(fontData);
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const paint = new CanvasKit.Paint();
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paint.setColor(CanvasKit.BLUE);
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paint.setStyle(CanvasKit.PaintStyle.Stroke);
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const textPaint = new CanvasKit.Paint();
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const textFont = new CanvasKit.Font(typeface, 20);
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textFont.setLinearMetrics(true);
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textFont.setSubpixel(true);
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textFont.setHinting(CanvasKit.FontHinting.Slight);
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// Only care about these characters for now. If we get any unknown characters, we'll replace
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// them with the first glyph here (the replacement glyph).
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// We put the family code point second to make sure we handle >16 bit codes correctly.
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const alphabet = "<22>👪abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789 _.,?!æ‽";
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const ids = textFont.getGlyphIDs(alphabet);
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const unknownCharacterGlyphID = ids[0];
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// char here means "string version of unicode code point". This makes the code below a bit more
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// readable than just integers. We just have to take care when reading these in that we don't
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// grab the second half of a 32 bit code unit.
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const charsToGlyphIDs = {};
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// Indexes in JS correspond to a 16 bit or 32 bit code unit. If a code point is wider than
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// 16 bits, it overflows into the next index. codePointAt will return a >16 bit value if the
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// given index overflows. We need to check for this and skip the next index lest we get a
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// garbage value (the second half of the Unicode code point.
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let glyphIdx = 0;
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for (let i = 0; i < alphabet.length; i++) {
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charsToGlyphIDs[alphabet[i]] = ids[glyphIdx];
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if (alphabet.codePointAt(i) > 65535) {
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i++; // skip the next index because that will be the second half of the code point.
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}
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glyphIdx++;
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}
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// TODO(kjlubick): linear metrics so we get "correct" data (e.g. floats).
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const bounds = textFont.getGlyphBounds(ids, textPaint);
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const widths = textFont.getGlyphWidths(ids, textPaint);
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// See https://www.freetype.org/freetype2/docs/glyphs/glyphs-3.html
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// Note that in Skia, y-down is positive, so it is common to see yMax below be negative.
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const glyphMetricsByGlyphID = {};
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for (let i = 0; i < ids.length; i++) {
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glyphMetricsByGlyphID[ids[i]] = {
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xMin: bounds[i*4],
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yMax: bounds[i*4 + 1],
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xMax: bounds[i*4 + 2],
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yMin: bounds[i*4 + 3],
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xAdvance: widths[i],
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};
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}
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const shapeAndDrawText = (str, canvas, x, y, maxWidth, font, paint) => {
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const LINE_SPACING = 20;
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// This is a conservative estimate - it can be shorter if we have ligatures code points
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// that span multiple 16bit words.
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const glyphs = CanvasKit.MallocGlyphIDs(str.length);
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let glyphArr = glyphs.toTypedArray();
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// Turn the code points into glyphs, accounting for up to 2 ligatures.
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let shapedGlyphIdx = -1;
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for (let i = 0; i < str.length; i++) {
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const char = str[i];
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shapedGlyphIdx++;
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// POC Ligature support.
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if (charsToGlyphIDs['æ'] && char === 'a' && str[i+1] === 'e') {
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glyphArr[shapedGlyphIdx] = charsToGlyphIDs['æ'];
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i++; // skip next code point
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continue;
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}
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if (charsToGlyphIDs['‽'] && (
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(char === '?' && str[i+1] === '!') || (char === '!' && str[i+1] === '?' ))) {
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glyphArr[shapedGlyphIdx] = charsToGlyphIDs['‽'];
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i++; // skip next code point
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continue;
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}
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glyphArr[shapedGlyphIdx] = charsToGlyphIDs[char] || unknownCharacterGlyphID;
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if (str.codePointAt(i) > 65535) {
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i++; // skip the next index because that will be the second half of the code point.
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}
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}
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// Trim down our array of glyphs to only the amount we have after ligatures and code points
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// that are > 16 bits.
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glyphArr = glyphs.subarray(0, shapedGlyphIdx+1);
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// Break our glyphs into runs based on the maxWidth and the xAdvance.
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const glyphRuns = [];
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let currentRunStartIdx = 0;
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let currentWidth = 0;
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for (let i = 0; i < glyphArr.length; i++) {
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const nextGlyphWidth = glyphMetricsByGlyphID[glyphArr[i]].xAdvance;
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if (currentWidth + nextGlyphWidth > maxWidth) {
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glyphRuns.push(glyphs.subarray(currentRunStartIdx, i));
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currentRunStartIdx = i;
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currentWidth = 0;
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}
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currentWidth += nextGlyphWidth;
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}
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glyphRuns.push(glyphs.subarray(currentRunStartIdx, glyphArr.length));
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// Draw all those runs.
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for (let i = 0; i < glyphRuns.length; i++) {
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const blob = CanvasKit.TextBlob.MakeFromGlyphs(glyphRuns[i], font);
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if (blob) {
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canvas.drawTextBlob(blob, x, y + LINE_SPACING*i, paint);
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}
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blob.delete();
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}
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CanvasKit.Free(glyphs);
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}
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const drawFrame = (canvas) => {
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canvas.clear(CanvasKit.WHITE);
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canvas.drawText('a + e = ae (no ligature)',
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5, 30, textPaint, textFont);
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canvas.drawText('a + e = æ (hard-coded ligature)',
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5, 50, textPaint, textFont);
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canvas.drawRect(CanvasKit.LTRBRect(10, 80, 280, 290), paint);
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shapeAndDrawText(document.getElementById('input').value, canvas, 15, 100, 265, textFont, textPaint);
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surface.requestAnimationFrame(drawFrame)
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};
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surface.requestAnimationFrame(drawFrame);
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}
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</script>
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