背景
我有一个可平移的应用程序窗口,它通过监听 mousemove
事件然后使用 transform: translate3d(...)
相应地移动屏幕来工作。这是一个大型应用程序,并且有大量相关的 UI 工作来促进此功能。 MCVE 来了,其中真实的工作负载由一个虚拟的 for
循环模拟:
var container = document.getElementById("container");
var contents = document.getElementById("contents");
var input = document.getElementById("iterations");
var posX = 50;
var posY = 50;
var previousX = null;
var previousY = null;
var mousedownHandler = function (e) {
window.onmousemove = globalMousemoveHandler;
window.onmouseup = globalMouseupHandler;
previousX = e.clientX;
previousY = e.clientY;
}
var globalMousemoveHandler = function (e) {
var now = Date.now();
for (var i = 0, n = parseInt(input.value); i < n; i++);
var elapsed = Date.now() - now;
posX += e.clientX - previousX;
posY += e.clientY - previousY;
previousX = e.clientX;
previousY = e.clientY;
contents.style.transform = "translate3d(" + posX + "px, " + posY + "px, 0)";
contents.innerText = elapsed + "ms";
}
var globalMouseupHandler = function (e) {
window.onmousemove = null;
window.onmouseup = null;
previousX = null;
previousY = null;
}
container.onmousedown = mousedownHandler;
contents.style.transform = "translate3d(" + posX + "px, " + posY + "px, 0)";
#container {
height: 180px;
width: 600px;
background-color: #ccc;
overflow: hidden;
cursor: -webkit-grab;
cursor: -moz-grab;
cursor: grab;
-moz-user-select: none;
-ms-user-select: none;
-webkit-user-select: none;
user-select: none;
}
#container:active {
cursor: move;
cursor: -webkit-grabbing;
cursor: -moz-grabbing;
cursor: grabbing;
}
<label>Iterations: <input id="iterations" type="number" value="20000000" step="5000000" /></label>
<div id="container">
<div id="contents">
Pannable container contents...
</div>
</div>
JSFiddle example with larger drag-area
请按住并拖动示例。
每次 mousemove
触发时,这个基本片段都会运行一个虚拟的 for
循环,并且循环完成所需的持续时间会显示在可拖动容器中。这需要证明下面的问题。您可能需要调整迭代次数,使循环运行时间超过 10 毫秒,但不会太长。
问题
此代码段在 Google Chrome 中运行得尽可能快,没有问题。未经 Firefox 测试。
但是,在 Microsoft Edge (可能还有 IE11) 如果 globalMousemoveHandler
运行时间超过 10 毫秒,浏览器就会开始无情地限制事件,使其触发频率要低得多,并且将平移进度变成爬行。
同样很奇怪的是,for
循环实际上在 Microsoft Edge 中比在 Chrome 中运行更快(快了将近 50%),但事件仍然触发很多 不太频繁。
从上述浏览器查看时,可以在上面的代码片段中观察到这一点。现在我明白了这个功能背后的理论需求,但它使我的应用程序在这些浏览器上不可用——我也不太明白在 16 毫秒以下开始节流有什么意义 (我远远低于 60 FPS 的帧预算),但这不是现在的问题(尽管我很高兴听到有关此的一些细节)。
我怎样才能防止这种情况发生?
最佳答案
这是一个使用 requestAnimationFrame 的例子.
var container = document.getElementById("container");
var contents = document.getElementById("contents");
var input = document.getElementById("iterations");
var posX = 50;
var posY = 50;
var previousX = null;
var previousY = null;
var mousedownHandler = function (e) {
window.onmousemove = globalMousemoveHandler;
window.onmouseup = globalMouseupHandler;
previousX = e.clientX;
previousY = e.clientY;
}
var globalMousemoveHandler = function (e) {
posX += e.clientX - previousX;
posY += e.clientY - previousY;
previousX = e.clientX;
previousY = e.clientY;
window.requestAnimationFrame(function () {
var now = Date.now();
for (var i = 0, n = parseInt(input.value); i < n; i++);
var elapsed = Date.now() - now;
contents.style.transform = "translate3d(" + posX + "px, " + posY + "px, 0)";
contents.innerText = elapsed + "ms";
});
}
var globalMouseupHandler = function (e) {
window.onmousemove = null;
window.onmouseup = null;
previousX = null;
previousY = null;
}
container.onmousedown = mousedownHandler;
contents.style.transform = "translate3d(" + posX + "px, " + posY + "px, 0)";
#container {
height: 180px;
width: 600px;
background-color: #ccc;
overflow: hidden;
cursor: -webkit-grab;
cursor: -moz-grab;
cursor: grab;
-moz-user-select: none;
-ms-user-select: none;
-webkit-user-select: none;
user-select: none;
}
#container:active {
cursor: move;
cursor: -webkit-grabbing;
cursor: -moz-grabbing;
cursor: grabbing;
}
<label>Iterations: <input id="iterations" type="number" value="20000000" step="5000000" /></label>
<div id="container">
<div id="contents">
Pannable container contents...
</div>
</div>
这会阻止处理程序函数的繁重工作,有效地防止问题发生,但代价是延迟增加 16 毫秒。
关于javascript - 如何防止 IE11 和 Microsoft Edge 积极限制事件?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/40265157/