Chromium Code Reviews Chromium Code Reviews
Issue 1971423002:
Implement bounce suppression in ScrollAnchor. (Closed)
Base URL: https://chromium.googlesource.com/chromium/src.git@master| OLD | NEW |
|---|---|
| (Empty) | |
| 1 <!DOCTYPE html> | |
| 2 <script src="../../../resources/js-test.js"></script> | |
|
ymalik
2016/05/16 17:34:40
I think we want to write tests using testharness.j
skobes
2016/05/18 01:24:30
Done.
| |
| 3 <style> | |
| 4 | |
| 5 body { margin: 80px 0; height: 5000px; } | |
| 6 #a, #b { height: 200px; width: 200px; } | |
| 7 #c { height: 400px; } | |
| 8 #left, #c { display: inline-block; width: 200px; vertical-align: top; } | |
| 9 #a.f { position: fixed; top: 30px; left: 150px; } | |
| 10 #a { background-color: #fcc; } | |
| 11 #b { background-color: #cfc; } | |
| 12 #c { background-color: #ccf; } | |
| 13 | |
| 14 </style> | |
| 15 <div id="left"> | |
| 16 <div id="a"></div> | |
| 17 <div id="b"></div> | |
| 18 </div><div id="c"></div> | |
| 19 <div id="console"></div> | |
| 20 <script> | |
| 21 | |
| 22 var jsTestIsAsync = true; | |
| 23 description("Tests if scroll anchoring plays nicely with scroll event handlers." ); | |
| 24 | |
| 25 internals.runtimeFlags.scrollAnchoringEnabled = true; | |
| 26 | |
| 27 // The scroll handler marks #a as position: fixed when scroll offset > 300px. | |
| 28 // This triggers layout during which we anchor to #b, which has moved up 200px. | |
| 29 // After our anchoring adjustment, the scroll offset is < 300px again, so the | |
| 30 // scroll handler removes position: fixed from #a, triggering a second layout, | |
| 31 // during which #b "bounces" back to its original location. | |
| 32 // | |
| 33 // The desired behavior here is for ScrollAnchor to follow #b back the first | |
| 34 // time it bounces, but not follow a second bounce. | |
| 35 // | |
| 36 // There are two failure modes we are concerned about: | |
| 37 // | |
| 38 // - If ScrollAnchor doesn't follow #b back to its original position during the | |
| 39 // FIRST bounce, we've "trapped" the user above 300px. Every time they try to | |
| 40 // scroll past this point we will push them back up. | |
| 41 // | |
| 42 // - If ScrollAnchor follows #b religiously, we get stuck in an infinite cycle | |
| 43 // of continuous bouncing, which looks hilariously broken. | |
| 44 | |
| 45 var a = document.querySelector('#a'); | |
| 46 var fixed = false; | |
| 47 onscroll = function() { | |
| 48 var y = scrollY; | |
| 49 if (fixed == (y > 300)) | |
| 50 return; | |
| 51 if (y < 130) { | |
| 52 // Clear the scroll anchor. | |
| 53 scrollBy(0, 10); | |
| 54 scrollBy(0, -10); | |
| 55 } | |
| 56 a.className = (fixed = !fixed) ? "f" : ""; | |
| 57 }; | |
| 58 | |
| 59 shouldSettleAt = function(expectedScrollY, completion) { | |
| 60 expectedScrollY = String(expectedScrollY); | |
| 61 shouldBecomeEqual("scrollY", expectedScrollY, function() { | |
| 62 var waitFrames = function(frames, check, then) { | |
| 63 if (check) | |
| 64 shouldBe("scrollY", expectedScrollY); | |
|
ymalik
2016/05/16 17:34:40
Do we want to check intermediate values as well?
skobes
2016/05/18 01:24:30
I'm not sure we are guaranteed to get raf calls in
| |
| 65 if (!frames) | |
| 66 then(); | |
| 67 else | |
| 68 requestAnimationFrame(function() { | |
| 69 waitFrames(frames - 1, check, then); | |
| 70 }); | |
| 71 }; | |
| 72 waitFrames(3, false, function() { | |
| 73 waitFrames(3, true, completion); | |
| 74 }); | |
| 75 }); | |
| 76 }; | |
| 77 | |
| 78 onload = function() { | |
| 79 // The 320px offset tests for the first failure mode. | |
| 80 eventSender.mouseScrollBy(0, -8); | |
|
ymalik
2016/05/16 17:34:40
Nit: continuousMouseScrollBy to make the pixel cou
skobes
2016/05/18 01:24:30
Done.
| |
| 81 shouldSettleAt(320, function() { | |
| 82 scrollTo(0, 0); | |
| 83 requestAnimationFrame(function() { | |
| 84 // The 360px offset tests for the second failure mode. | |
| 85 eventSender.mouseScrollBy(0, -9); | |
| 86 shouldSettleAt(360, finishJSTest); | |
| 87 }); | |
| 88 }); | |
| 89 } | |
| 90 | |
| 91 </script> | |
| OLD | NEW |
