tor-browser

The Tor Browser
git clone https://git.dasho.dev/tor-browser.git
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test_flex_interrupt.html (3402B)

      1 <!doctype html>
      2 <title>Test for bug 1579929</title>
      3 <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css">
      4 <script src="/tests/SimpleTest/SimpleTest.js"></script>
      5 <script src="/tests/SimpleTest/EventUtils.js"></script>
      6 <style>
      7  .container {
      8    display: flex;
      9    flex-direction: column;
     10    overflow-y: scroll;
     11  }
     12  #outer {
     13    width: 500px;
     14    height: 300px;
     15  }
     16 </style>
     17 <div class="container" id="outer">
     18  <div class="item" id="firstItem" style="width: 50px">
     19    <!--popuplated by script-->
     20  </div>
     21  <div class="container">
     22    <div class="container">
     23      <div class="container">
     24        <div class="container">
     25          <div class="container">
     26            <div class="item">Item</div>
     27          </div>
     28        </div>
     29      </div>
     30    </div>
     31  </div>
     32 </div>
     33 <script>
     34 SimpleTest.waitForExplicitFinish();
     35 
     36 // Globals/constants:
     37 
     38 const gUtils = SpecialPowers.DOMWindowUtils;
     39 
     40 // This needs to match/exceed nsPresContext::sInterruptChecksToSkip in order
     41 // for us to actually be able to trigger the mHasPendingInterrupt=true codepath
     42 // in this test.  Each of these "dummy" blocks will trigger a call to
     43 // nsPresContext::CheckForInterrupt, and after 200, we'll actually trigger an
     44 // interrupt.
     45 const gInterruptCheckThreshold = 200;
     46 
     47 // Expected to match the inline style="width:..." for #firstItem (we slowly
     48 // increment it to trigger reflows):
     49 let gFirstItemWidthPX = 50;
     50 
     51 function main() {
     52  const outer = document.getElementById("outer");
     53  const firstItem = document.getElementById("firstItem");
     54 
     55  // Insert a bunch of elements to be sure we actually get interrupted.
     56  // (See description of gInterruptCheckThreshold above)
     57  for (let i = 0; i < gInterruptCheckThreshold; i++) {
     58    let dummyBlock = document.createElement("div");
     59    dummyBlock.innerText = "dummy";
     60    firstItem.appendChild(dummyBlock);
     61  }
     62 
     63  // Flush any pending relayout:
     64  outer.offsetHeight;
     65 
     66  // Take control of the refresh driver
     67  gUtils.advanceTimeAndRefresh(0);
     68 
     69  // Force reflow and store the "cost" (in num-frames-reflowed)
     70  const costOfNormalReflow = forceReflow();
     71 
     72  // Sanity-check: do that again and remeasure cost, to be sure it's stable:
     73  const costOfNormalReflow2 = forceReflow();
     74  is(costOfNormalReflow, costOfNormalReflow2,
     75     "Our forceReflow function is expected to reliably trigger " +
     76     "the same set of frames to be reflowed. If this fails, there's a " +
     77     "bug in the test, or non-determinism in layout code.");
     78 
     79  // Now, we force the next reflow to get interrupted, and then measure the
     80  // cost under those conditions:
     81  gUtils.forceReflowInterrupt();
     82  const costOfInterruptedReflow = forceReflow();
     83 
     84  // Hopefully the interrupted one was less expensive...
     85  ok(costOfInterruptedReflow <= costOfNormalReflow,
     86     "num frames reflowed in interrupted reflow (" +
     87     costOfInterruptedReflow +
     88     ") shouldn't exceed the num frames reflowed in normal reflow (" +
     89     costOfNormalReflow + ")");
     90 
     91  gUtils.restoreNormalRefresh();
     92  SimpleTest.finish();
     93 }
     94 
     95 // This function dirties firstItem's width, forces a reflow, and
     96 // returns the number of frames that were reflowed as a result.
     97 function forceReflow() {
     98  gFirstItemWidthPX++;
     99  firstItem.style.width = gFirstItemWidthPX + "px";
    100 
    101  const origFramesReflowed = gUtils.framesReflowed;
    102  gUtils.advanceTimeAndRefresh(0);
    103  return gUtils.framesReflowed - origFramesReflowed;
    104 }
    105 
    106 main();
    107 </script>