2d.text.measure.actualBoundingBox.small-font.worker.js

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This test has a WPT meta file that expects 1 subtest issues.
This WPT test may be referenced by the following Test IDs:
- /html/canvas/offscreen/text/2d.text.measure.actualBoundingBox.small-font.worker.html - WPT Dashboard Interop Dashboard

// DO NOT EDIT! This test has been generated by /html/canvas/tools/gentest.py.

// OffscreenCanvas test in a worker:2d.text.measure.actualBoundingBox.small-font

// Description:Testing that actualBoundingBox metrics are precise at small font sizes

// Note:

importScripts("/resources/testharness.js");

importScripts("/html/canvas/resources/canvas-tests.js");

promise_test(async t => {

  var canvas = new OffscreenCanvas(100, 50);

  var ctx = canvas.getContext('2d');

  var f = new FontFace("CanvasTest", "url('/fonts/CanvasTest.ttf')");

  f.load();

  self.fonts.add(f);

  await self.fonts.ready;

  ctx.font = '1.5px CanvasTest';

  ctx.direction = 'ltr';

  ctx.textAlign = 'left';

  ctx.textBaseline = 'alphabetic';

  // At small font sizes, Skia may store glyph bounds as integers, causing

  // loss of precision (crbug.com/479240778). The CanvasTest 'E' glyph fills

  // the em square (0, -0.25em) to (1em, 0.75em), so at 1.5px:

  //   actualBoundingBoxRight  ≈ 1.5   (1em)

  //   actualBoundingBoxAscent ≈ 1.125 (0.75em)

  //   actualBoundingBoxDescent≈ 0.375 (0.25em)

  // With integer quantization these would snap to 2, 2, 1 respectively.

  // Use ±0.25 tolerances so quantized values are reliably caught.

  var m = ctx.measureText('E');

  _assert(m.actualBoundingBoxRight > 1.25, "m.actualBoundingBoxRight > 1.25");

  _assert(m.actualBoundingBoxRight < 1.75, "m.actualBoundingBoxRight < 1.75");

  _assert(m.actualBoundingBoxAscent > 0.875, "m.actualBoundingBoxAscent > 0.875");

  _assert(m.actualBoundingBoxAscent < 1.375, "m.actualBoundingBoxAscent < 1.375");

  _assert(m.actualBoundingBoxDescent > 0.125, "m.actualBoundingBoxDescent > 0.125");

  _assert(m.actualBoundingBoxDescent < 0.625, "m.actualBoundingBoxDescent < 0.625");

}, "Testing that actualBoundingBox metrics are precise at small font sizes");

done();