зеркало из https://github.com/mozilla/gecko-dev.git
126 строки
4.2 KiB
HTML
126 строки
4.2 KiB
HTML
<!DOCTYPE HTML>
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<html>
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<!--
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https://bugzilla.mozilla.org/show_bug.cgi?id=1367568
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-->
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<head>
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<meta charset="utf-8">
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<title>Test for Bug 1367568</title>
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<script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
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<link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
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</head>
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<body>
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<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=">Mozilla Bug 1367568</a>
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<div id="content">
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<!-- Some fixed-width divs that we shouldn't have to reflow when the viewport
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changes: -->
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<div style="width: 100px">
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fixed-width
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<div>(child)</div>
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</div>
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<div style="position: absolute; width: 150px">
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abs-fixed-width
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<div>(child)</div>
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</div>
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</div>
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<pre id="test">
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<script type="application/javascript">
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"use strict";
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/** Test for Bug 1367568 **/
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/**
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* This test verifies that "overflow" changes on the <body> don't cause
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* an unnecessarily large amount of reflow.
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*/
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// Vars used in setStyleAndMeasure that we really only have to look up once:
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const gUtils = SpecialPowers.getDOMWindowUtils(window);
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function setStyleAndMeasure(initialStyle, finalStyle) {
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is(document.body.style.length, 0,
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"Bug in test - body should start with empty style");
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let unusedVal = document.body.offsetHeight; // flush layout
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let constructCount = gUtils.framesConstructed;
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document.body.style = initialStyle;
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unusedVal = document.body.offsetHeight; // flush layout
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let reflowCountBeforeTweak = gUtils.framesReflowed;
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document.body.style = finalStyle;
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unusedVal = document.body.offsetHeight; // flush layout
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let reflowCountAfterTweak = gUtils.framesReflowed;
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// Clean up:
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document.body.style = "";
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is(gUtils.framesConstructed, constructCount,
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"Style tweak shouldn't have triggered frame construction");
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// ...and return the delta:
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return reflowCountAfterTweak - reflowCountBeforeTweak;
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}
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function main() {
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// First, we sanity-check that our measurement make sense -- if we leave
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// styles unchanged, we should measure no frames being reflowed:
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let count = setStyleAndMeasure("width: 50px; height: 80px",
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"width: 50px; height: 80px");
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is(count, 0,
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"Shouldn't reflow anything when we leave 'width' & 'height' unchanged");
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// Now: see how many frames are reflowed when the "width" & "height" change.
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// We'll use this as the reference when measuring reflow counts for various
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// changes to "overflow" below.
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count = setStyleAndMeasure("width: 50px; height: 80px",
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"width: 90px; height: 60px");
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ok(count > 0,
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"Should reflow some frames when 'width' & 'height' change");
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// Expected maximum number of frames reflowed for "overflow" changes
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// (+2 is to allow for reflowing scrollbars themselves):
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const expectedMax = count + 2;
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// Shared ending for messages in all ok() checks below:
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const messageSuffix =
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" shouldn't be greater than count for tweaking width/height on body (" +
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expectedMax + ")";
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// OK, here is where the relevant tests actually begin!!
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// See how many frames we reflow for various tweaks to "overflow" on
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// the body -- we expect the count to be no larger than |expectedMax|.
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count = setStyleAndMeasure("", "overflow: scroll");
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ok(count <= expectedMax,
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"Reflow count when setting 'overflow: scroll' on body (" + count + ")" +
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messageSuffix);
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count = setStyleAndMeasure("", "overflow: hidden");
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ok(count <= expectedMax,
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"Reflow count when setting 'overflow: hidden' on body (" + count + ")" +
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messageSuffix);
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// Test removal of "overflow: scroll":
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count = setStyleAndMeasure("overflow: scroll", "");
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ok(count <= expectedMax,
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"Reflow count when removing 'overflow: scroll' from body (" + count + ")" +
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messageSuffix);
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count = setStyleAndMeasure("overflow: hidden", "");
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ok(count <= expectedMax,
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"Reflow count when removing 'overflow: hidden' from body (" + count + ")" +
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messageSuffix);
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// Test change between two non-'visible' overflow values:
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count = setStyleAndMeasure("overflow: scroll", "overflow: hidden");
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ok(count <= expectedMax,
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"Reflow count when changing 'overflow' on body (" + count + ")" +
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messageSuffix);
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}
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main();
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</script>
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</pre>
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</body>
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</html>
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