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<!DOCTYPE HTML>
<html>
<head>
  <meta charset="utf-8">
  <title>Tests for CSSOM-View Smooth-Scroll DOM API Methods and MSD Animation</title>
  <style>
    #scroll_behavior_test_body {
      width: 100000px;
      height: 100000px;
    }
    .scroll_to_target {
      position: absolute;
      left: 20000px;
      top: 10000px;
      width: 200px;
      height: 200px;
      background-color: rgb(0, 0, 255);
    }
  </style>
  <script src="/tests/SimpleTest/SimpleTest.js"></script>
  <script src="/tests/SimpleTest/paint_listener.js"></script>
  <script src="/tests/gfx/layers/apz/test/mochitest/apz_test_utils.js"></script>
  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
  <script type="application/javascript">

  SimpleTest.waitForExplicitFinish();

  function clamp(val, minVal, maxVal) {
    return Math.max(minVal, Math.min(maxVal, val));
  }

  window.addEventListener("load", async function(event) {
    if (event.target != document) {
      return;
    }
    await testScrollBehaviorInterruption();
    await testScrollBehaviorFramerate();
    window.scrollTo(0,0);
    SimpleTest.finish();
  });

  async function testScrollBehaviorInterruption() {
    // Take control of refresh driver
    SpecialPowers.DOMWindowUtils.advanceTimeAndRefresh(0);
    await promiseApzFlushedRepaints();

    window.scrollTo(10, 9);
    ok(window.scrollX == 10 && window.scrollY == 9,
      "instant scroll-behavior must be synchronous when setting initial position");

    window.scrollTo(15, 16);
    ok(window.scrollX == 15 && window.scrollY == 16,
      "instant scroll-behavior must be synchronous when setting new position");

    window.scrollTo({left: 100, top: 200, behavior: 'smooth'});
    ok(window.scrollX == 15 && window.scrollY == 16,
      "smooth scroll-behavior must be asynchronous");

    SpecialPowers.DOMWindowUtils.advanceTimeAndRefresh(100);
    await promiseApzFlushedRepaints();

    ok(window.scrollX != 15 && window.scrollY != 16
       && window.scrollX != 100 && window.scrollY != 200,
      "smooth scroll-behavior must be triggered by window.scrollTo");

    window.scrollTo(50, 52);
    ok(window.scrollX == 50 && window.scrollY == 52,
      "instant scroll-behavior must interrupt smooth scroll-behavior animation");

    SpecialPowers.DOMWindowUtils.advanceTimeAndRefresh(100);
    await promiseApzFlushedRepaints();

    ok(window.scrollX == 50 && window.scrollY == 52,
      "smooth scroll-behavior animation must stop after being interrupted");

    // Release control of refresh driver
    SpecialPowers.DOMWindowUtils.restoreNormalRefresh();
    await promiseApzFlushedRepaints();
  }

  async function testScrollBehaviorFramerate() {
    /**
     *  CSSOM-View scroll-behavior smooth scroll animations must produce the
     *  same results indendently of frame-rate:
     *
     *   - Reference samples of scroll position for each frame are captured from
     *     a smooth scroll at 120fps for variations in X-Distance, Y-Distance.
     *   - Test samples are captured from an animation with the same parameters
     *     at varying framerates.
     *   - Variance in position at each sampled interval is compared to the
     *     120fps reference.  To pass the test, the position of each test
     *     sample must match the reference position with a tolerance of one test
     *     sample frame's range of motion.  This range of motion is calculated
     *     by the position delta of the reference samples one test frame duration
     *     before and after.
     *   - The duration of the reference sample animation and the test sample
     *     animation must match within 1 frame to pass the test.
     *   - The simulation driving the animation must converge and stop on the
     *     destination position for the test to pass.
     */

    // Use 120hz for reference samples
    var referenceFrameRate = 120;

    var frameRates = [ 13, 60 ];
    var deltas = [ {x: 0, y: 0},
                   {x: 1, y: 100},
                   {x: -100, y: 50000} ];

    for (var deltaIndex = 0; deltaIndex < deltas.length; deltaIndex++) {
      var deltaX = deltas[deltaIndex].x;
      var deltaY = deltas[deltaIndex].y;

      // startX and startY must be at least as big as the greatest negative
      // number in the deltas array in order to prevent the animation from
      // being interrupted by scroll range boundaries.
      var startX = 1000;
      var startY = 1000;
      var endX = startX + deltaX;
      var endY = startY + deltaY;
      var referenceTimeStep = Math.floor(1000 / referenceFrameRate);

      let refSamples = await sampleAnimation(startX, startY, endX, endY,
                      referenceTimeStep);

      var referenceDuration = refSamples.length * referenceTimeStep; // ms

      for (var frameRateIndex = 0; frameRateIndex < frameRates.length; frameRateIndex++) {
        var frameRate = frameRates[frameRateIndex];

        var testTimeStep = Math.floor(1000 / frameRate);

        let testSamples = await sampleAnimation(startX, startY, endX, endY,
                        testTimeStep);
        var testDuration = testSamples.length * testTimeStep; // ms

        // Variance in duration of animation must be accurate to within one
        // frame interval
        var durationVariance = Math.max(0, Math.abs(testDuration - referenceDuration) - testTimeStep);
        is(durationVariance, 0, 'Smooth scroll animation duration must not '
           + 'be framerate dependent at deltaX: ' + deltaX + ', deltaY: '
           + deltaY + ', frameRate: ' + frameRate + 'fps');

        var maxVariance = 0;
        testSamples.forEach(function(sample, sampleIndex) {

          var testToRef = refSamples.length / testSamples.length;
          var refIndexThisFrame = clamp(Math.floor(sampleIndex * testToRef),
                                        0, refSamples.length - 1);
          var refIndexPrevFrame = clamp(Math.floor((sampleIndex - 1) * testToRef),
                                        0, refSamples.length - 1);
          var refIndexNextFrame = clamp(Math.floor((sampleIndex + 1) * testToRef),
                                        0, refSamples.length - 1);

          var refSampleThisFrame = refSamples[refIndexThisFrame];
          var refSamplePrevFrame = refSamples[refIndexPrevFrame];
          var refSampleNextFrame = refSamples[refIndexNextFrame];

          var refXMin = Math.min(refSamplePrevFrame[0],
                                refSampleThisFrame[0],
                                refSampleNextFrame[0]);

          var refYMin = Math.min(refSamplePrevFrame[1],
                                refSampleThisFrame[1],
                                refSampleNextFrame[1]);

          var refXMax = Math.max(refSamplePrevFrame[0],
                                refSampleThisFrame[0],
                                refSampleNextFrame[0]);

          var refYMax = Math.max(refSamplePrevFrame[1],
                                refSampleThisFrame[1],
                                refSampleNextFrame[1]);

          // Varience is expected to be at most 1 pixel beyond the range,
          // due to integer rounding of pixel position.
          var positionTolerance = 1; // 1 pixel

          maxVariance = Math.max(maxVariance,
                                 refXMin - sample[0] - positionTolerance,
                                 sample[0] - refXMax - positionTolerance,
                                 refYMin - sample[1] - positionTolerance,
                                 sample[1] - refYMax - positionTolerance);
        });

        is(maxVariance, 0, 'Smooth scroll animated position must not be '
           + 'framerate dependent at deltaX: ' + deltaX + ', deltaY: '
           + deltaY + ', frameRate: ' + frameRate + 'fps');
      }

      await promiseApzFlushedRepaints();
    }
  }

  async function sampleAnimation(startX, startY, endX, endY, timeStep) {
    // The animation must be stopped at the destination position for
    // minStoppedFrames consecutive frames to detect that the animation has
    // completed.
    var minStoppedFrames = 15; // 15 frames

    // In case the simulation fails to converge, the test will time out after
    // processing maxTime milliseconds of animation.
    var maxTime = 10000; // 10 seconds

    var positionSamples = [];

    var frameCountAtDestination = 0;

    // Take control of refresh driver so we can synthesize
    // various frame rates
    SpecialPowers.DOMWindowUtils.advanceTimeAndRefresh(0);
    await promiseApzFlushedRepaints();

    window.scrollTo(startX, startY);
    window.scrollTo({left: endX, top: endY, behavior: 'smooth'});

    var currentTime = 0; // ms

    while (currentTime < maxTime && frameCountAtDestination < 15) {
      positionSamples.push([window.scrollX, window.scrollY]);

      currentTime += timeStep;
      SpecialPowers.DOMWindowUtils.advanceTimeAndRefresh(timeStep);
      await promiseApzFlushedRepaints();
      if (window.scrollX == endX && window.scrollY == endY) {
        frameCountAtDestination++;
      } else {
        frameCountAtDestination = 0;
      }
    }

    isnot(frameCountAtDestination, 0,
          'Smooth scrolls must always end at their destination '
          + 'unless they are interrupted, at deltaX: '
          + (endX - startX) + ', deltaY: ' + (endY - startY));

    window.scrollTo(0, 0);

    // Release control of refresh driver
    SpecialPowers.DOMWindowUtils.restoreNormalRefresh();

    await promiseApzFlushedRepaints();

    // We must not include the duplicated frames at the animation
    // destination as the tests are dependant on the total duration of
    // the animation to be accurate.
    positionSamples.splice(1 - minStoppedFrames,
                           minStoppedFrames - 1);

    return positionSamples;
  }

  </script>
</head>
<body>
<pre id="test">
</pre>

<div id="scroll_behavior_test_body">
      <div id="scroll_to_target" class="scroll_to_target"></div>
</body>
</html>