forked from mirrors/gecko-dev
56e5e14ea5
Differential Revision: https://phabricator.services.mozilla.com/D53313 --HG-- extra : moz-landing-system : lando
107 lines
3.3 KiB
HTML
107 lines
3.3 KiB
HTML
<!doctype html>
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<title>Test for bug 1579929</title>
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<link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css">
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<script src="/tests/SimpleTest/SimpleTest.js"></script>
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<script src="/tests/SimpleTest/EventUtils.js"></script>
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<style>
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.container {
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display: flex;
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flex-direction: column;
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overflow-y: scroll;
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}
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#outer {
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width: 500px;
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height: 300px;
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}
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</style>
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<div class="container" id="outer">
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<div class="item" id="firstItem" style="width: 50px">
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<!--popuplated by script-->
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</div>
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<div class="container">
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<div class="container">
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<div class="container">
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<div class="container">
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<div class="container">
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<div class="item">Item</div>
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</div>
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</div>
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</div>
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</div>
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</div>
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</div>
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<script>
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SimpleTest.waitForExplicitFinish();
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// Globals/constants:
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const gUtils = SpecialPowers.DOMWindowUtils;
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// This needs to match/exceed nsPresContext::sInterruptChecksToSkip in order
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// for us to actually be able to trigger the mHasPendingInterrupt=true codepath
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// in this test. Each of these "dummy" blocks will trigger a call to
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// nsPresContext::CheckForInterrupt, and after 200, we'll actually trigger an
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// interrupt.
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const gInterruptCheckThreshold = 200;
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// Expected to match the inline style="width:..." for #firstItem (we slowly
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// increment it to trigger reflows):
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let gFirstItemWidthPX = 50;
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function main() {
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const outer = document.getElementById("outer");
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const firstItem = document.getElementById("firstItem");
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// Insert a bunch of elements to be sure we actually get interrupted.
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// (See description of gInterruptCheckThreshold above)
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for (let i = 0; i < gInterruptCheckThreshold; i++) {
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let dummyBlock = document.createElement("div");
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dummyBlock.innerText = "dummy";
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firstItem.appendChild(dummyBlock);
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}
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// Flush any pending relayout:
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outer.offsetHeight;
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// Take control of the refresh driver
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gUtils.advanceTimeAndRefresh(0);
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// Force reflow and store the "cost" (in num-frames-reflowed)
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const costOfNormalReflow = forceReflow();
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// Sanity-check: do that again and remeasure cost, to be sure it's stable:
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const costOfNormalReflow2 = forceReflow();
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is(costOfNormalReflow, costOfNormalReflow2,
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"Our forceReflow function is expected to reliably trigger " +
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"the same set of frames to be reflowed. If this fails, there's a " +
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"bug in the test, or non-determinism in layout code.");
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// Now, we force the next reflow to get interrupted, and then measure the
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// cost under those conditions:
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gUtils.forceReflowInterrupt();
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const costOfInterruptedReflow = forceReflow();
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// Hopefully the interrupted one was less expensive...
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ok(costOfInterruptedReflow <= costOfNormalReflow,
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"num frames reflowed in interrupted reflow (" +
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costOfInterruptedReflow +
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") shouldn't exceed the num frames reflowed in normal reflow (" +
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costOfNormalReflow + ")");
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gUtils.restoreNormalRefresh();
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SimpleTest.finish();
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}
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// This function dirties firstItem's width, forces a reflow, and
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// returns the number of frames that were reflowed as a result.
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function forceReflow() {
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gFirstItemWidthPX++;
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firstItem.style.width = gFirstItemWidthPX + "px";
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const origFramesReflowed = gUtils.framesReflowed;
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gUtils.advanceTimeAndRefresh(0);
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return gUtils.framesReflowed - origFramesReflowed;
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}
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main();
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</script>
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