Javascript Chrome requestAnimationFrame问题

相关主题：

我一直在为触摸设备构建一个小部件，以实现平滑的动画效果，我找到的帮助我实现这一点的工具之一就是Chrome Memory Timeline屏幕

这对我评估rAF循环中的内存消耗有点帮助，但我现在在Chrome30中观察到的一些行为让我感到困扰

当最初进入我的页面（其中运行着rAF循环）时，我看到了这一点

看起来不错。如果我已经完成了我的工作，并且在我的内部循环中消除了对象分配，那么就不应该有锯齿。这与链接主题一致，也就是说，无论何时使用rAF，Chrome都有内置漏洞。（哎呀！）

当我开始在页面中做各种各样的事情时，它会变得更有趣

我并没有做任何不同的事情，只是暂时添加两个元素，使CSS3 3D变换样式应用于一些帧，然后我停止与它们交互

我们在这里看到的是Chrome报告，rAF的每一次发射（16ms）都会导致

动画帧发射x3

这种重复以及重复的速率单调地增加，直到页面刷新为止

您已经可以在第二个屏幕盖中看到锯齿斜率在最初从

动画帧激发

跳到

动画帧激发X3

后显著增加

过了一会儿，它跳到了

x21

：

看起来我的代码被额外运行了很多次，但所有额外的多次运行都只是浪费热量和计算

当我拍摄第三个屏幕时，我的Macbook热得很厉害。不久之后，在我能够将时间线拖到最后一位（大约8分钟）以查看

x

数字增加到什么之前，inspector窗口变得完全无响应，并且提示我的页面已无响应，必须终止

以下是页面中运行的全部代码：

// ============================================================================
// Copyright (c) 2013 Steven Lu

// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
// IN THE SOFTWARE.
// ============================================================================

// This is meant to be a true velocity verlet integrator, which means sending
// in for the force and torque a function (not a value). If the forces provided
// are evaluated at the current time step then I think we are left with plain
// old Euler integration.  This is a 3 DOF integrator that is meant for use
// with 2D rigid bodies, but it should be equally useful for modeling 3d point
// dynamics.

// this attempts to minimize memory waste by operating on state in-place.

function vel_verlet_3(state, acc, dt) {
  var x = state[0],
      y = state[1],
      z = state[2],
      vx = state[3],
      vy = state[4],
      vz = state[5],
      ax = state[6],
      ay = state[7],
      az = state[8],
      x1 = x + vx * dt + 0.5 * ax * dt * dt,
      y1 = y + vy * dt + 0.5 * ay * dt * dt,
      z1 = z + vz * dt + 0.5 * az * dt * dt,  // eqn 1
      a1 = acc(x1, y1, z1),
      ax1 = a1[0],
      ay1 = a1[1],
      az1 = a1[2];
  state[0] = x1;
  state[1] = y1;
  state[2] = z1;
  state[3] = vx + 0.5 * (ax + ax1) * dt,
  state[4] = vy + 0.5 * (ay + ay1) * dt,
  state[5] = vz + 0.5 * (az + az1) * dt; // eqn 2
  state[6] = ax1;
  state[7] = ay1;
  state[8] = az1;
}

// velocity indepedent acc --- shit this is gonna need to change soon
var acc = function(x, y, z) {
  return [0,0,0];
};
$("#lock").click(function() {
  var values = [Number($('#ax').val()), Number($('#ay').val()), Number($('#az').val())];
  acc = function() {
    return values;
  };
});

// Obtain the sin and cos from an angle.
// Allocate nothing.
function getRotation(angle, cs) {
  cs[0] = Math.cos(angle);
  cs[1] = Math.sin(angle);
}

// Provide the localpoint as [x,y].
// Allocate nothing.
function global(bodystate, localpoint, returnpoint) {
  getRotation(bodystate[2], returnpoint);
  // now returnpoint contains cosine+sine of angle.
  var px = bodystate[0], py = bodystate[1];
  var x = localpoint[0], y = localpoint[1];
  // console.log('global():', cs, [px, py], localpoint, 'with', [x,y]);
  // [ c -s px ]   [x]
  // [ s  c py ] * [y]
  //               [1]
  var c = returnpoint[0];
  var s = returnpoint[1];
  returnpoint[0] = c * x - s * y + px;
  returnpoint[1] = s * x + c * y + py;
}

function local(bodystate, globalpoint, returnpoint) {
  getRotation(bodystate[2], returnpoint);
  // now returnpoint contains cosine+sine of angle
  var px = bodystate[0], py = bodystate[1];
  var x = globalpoint[0], y = globalpoint[1];
  // console.log('local():', cs, [px, py], globalpoint, 'with', [x,y]);
  // [  c s ]   [x - px]
  // [ -s c ] * [y - py]
  var xx = x - px, yy = y - py;
  var c = returnpoint[0], s = returnpoint[1];
  returnpoint[0] = c * xx + s * yy;
  returnpoint[1] = -s * xx + c * yy;
}

var cumulativeOffset = function(element) {
  var top = 0, left = 0;
  do {
    top += element.offsetTop || 0;
    left += element.offsetLeft || 0;
    element = element.offsetParent;
  } while (element);
  return {
    top: top,
    left: left
  };
};

// helper to create/assign position debugger (handles a single point)
// offset here is a boundingclientrect offset and needs window.scrollXY correction
var hasDPOffsetRun = false;
var dpoff = false;
function debugPoint(position, id, color, offset) {
  if (offset) {
    position[0] += offset.left;
    position[1] += offset.top;
  }
  // if (position[0] >= 0) { console.log('debugPoint:', id, color, position); }
  var element = $('#point' + id);
  if (!element.length) {
    element = $('<div></div>')
    .attr('id', 'point' + id)
    .css({
          pointerEvents: 'none',
          position: 'absolute',
          backgroundColor: color,
          border: '#fff 1px solid',
          top: -2,
          left: -2,
          width: 2,
          height: 2,
          borderRadius: 300,
          boxShadow: '0 0 6px 0 ' + color
        });
    $('body').append(
        $('<div></div>')
        .addClass('debugpointcontainer')
        .css({
          position: 'absolute',
          top: 0,
          left: 0
        })
      .append(element)
    );
    if (!hasDPOffsetRun) {
      // determine the offset of the body-appended absolute element. body's margin
      // is the primary offender that tends to throw a wrench into our shit.
      var dpoffset = $('.debugpointcontainer')[0].getBoundingClientRect();
      dpoff = [dpoffset.left + window.scrollX, dpoffset.top + window.scrollY];
      hasDPOffsetRun = true;
    }
  }
  if (dpoff) {
    position[0] -= dpoff[0];
    position[1] -= dpoff[1];
  }
  // set position
  element[0].style.webkitTransform = 'translate3d(' + position[0] + 'px,' + position[1] + 'px,0)';
}

var elements_tracked = [];

/*
var globaleventhandler = function(event) {
  var t = event.target;
  if (false) { // t is a child of a tracked element...

  }
};

// when the library is loaded the global event handler for GRAB is not
// installed. It is lazily installed when GRAB_global is first called, and so
// if you only ever call GRAB then the document does not get any handlers
// attached to it.  This will remain unimplemented as it's not clear what the
// semantics for defining behavior are. It's much more straightforward to use
// the direct API
function GRAB_global(element, custom_behavior) {
  // this is the entry point that will initialize a grabbable element all state
  // for the element will be accessible through its __GRAB__ element through
  // the DOM, and the DOM is never accessed (other than through initial
  // assignment) by the code.

  // event handlers are attached to the document, so use GRAB_direct if your
  // webpage relies on preventing event bubbling.
  if (elements_tracked.indexOf(element) !== -1) {
    console.log('You tried to call GRAB() on an element more than once.',
                element, 'existing elements:', elements_tracked);
  }
  elements_tracked.push(element);
  if (elements_tracked.length === 1) { // this is the initial call
    document.addEventListener('touchstart', globaleventhandler, true);
    document.addEventListener('mousedown', globaleventhandler, true);
  }
}

// cleanup function cleans everything up, returning behavior to normal.
// may provide a boolean true argument to indicate that you want the CSS 3D
// transform value to be cleared
function GRAB_global_remove(cleartransform) {
  document.removeEventListener('touchstart', globaleventhandler, true);
  document.removeEventListener('mousedown', globaleventhandler, true);
}

*/

var mousedownelement = false;
var stop = false;
// there is only one mouse, and the only time when we need to handle release
// of pointer is when the one mouse is let go somewhere far away.
function GRAB(element, onfinish, center_of_mass) {
  // This version directly assigns the event handlers to the element
  // it is less efficient but more "portable" and self-contained, and also
  // potentially more friendly by using a regular event handler rather than
  // a capture event handler, so that you can customize the grabbing behavior
  // better and also more easily define it per element
  var offset = center_of_mass;
  var pageOffset = cumulativeOffset(element);
  var bcrOffset = element.getBoundingClientRect();
  bcrOffset = {
    left: bcrOffset.left + window.scrollX,
    right: bcrOffset.right + window.scrollX,
    top: bcrOffset.top + window.scrollY,
    bottom: bcrOffset.bottom + window.scrollY
  };
  if (!offset) {
    offset = [element.offsetWidth / 2, element.offsetHeight / 2];
  }
  var model = {
    state: [0, 0, 0, 0, 0, 0, 0, 0, 0],
    offset: offset,
    pageoffset: bcrOffset // remember, these values are pre-window.scroll[XY]-corrected
  };
  element.__GRAB__ = model;
  var eventhandlertouchstart = function(event) {
    // set
    var et0 = event.touches[0];
    model.anchor = [0,0];
    local(model.state, [et0.pageX - bcrOffset.left - offset[0], et0.pageY - bcrOffset.top - offset[1]], model.anchor);
    debugPoint([et0.pageX, et0.pageY], 1, 'red');
    event.preventDefault();
    requestAnimationFrame(step);
  };
  var eventhandlermousedown = function(event) {
    console.log('todo: reject right clicks');
    // console.log('a', document.body.scrollLeft);
    // set
    // model.anchor = [event.offsetX - offset[0], event.offsetY - offset[1]];
    model.anchor = [0,0];
    var globalwithoffset = [event.pageX - bcrOffset.left - offset[0], event.pageY - bcrOffset.top - offset[1]];
    local(model.state, globalwithoffset, model.anchor);
    debugPoint([event.pageX, event.pageY], 1, 'red');
    mousedownelement = element;
    requestAnimationFrame(step);
  };
  var eventhandlertouchend = function(event) {
    // clear
    model.anchor = false;
    requestAnimationFrame(step);
  };
  element.addEventListener('touchstart', eventhandlertouchstart, false);
  element.addEventListener('mousedown', eventhandlermousedown, false);
  element.addEventListener('touchend', eventhandlertouchend, false);
  elements_tracked.push(element);
  // assign some favorable properties to grabbable element.
  element.style.webkitTouchCallout = 'none';
  element.style.webkitUserSelect = 'none';
  // TODO: figure out the proper values for these
  element.style.MozUserSelect = 'none';
  element.style.msUserSelect = 'none';
  element.style.MsUserSelect = 'none';
}
document.addEventListener('mouseup', function() {
  if (mousedownelement) {
    mousedownelement.__GRAB__.anchor = false;
    mousedownelement = false;
    requestAnimationFrame(step);
  }
}, false);

function GRAB_remove(element, cleartransform) {}
// unimpld
function GRAB_remove_all(cleartransform) {}

GRAB($('#content2')[0]);

(function() {
  var requestAnimationFrame = window.mozRequestAnimationFrame ||
      window.webkitRequestAnimationFrame ||
      window.msRequestAnimationFrame ||
      window.requestAnimationFrame;
  window.requestAnimationFrame = requestAnimationFrame;
})();

var now = function() { return window.performance ? performance.now() : Date.now(); };
var lasttime = 0;
var abs = Math.abs;
var dt = 0;
var scratch0 = [0,0];
var scratch1 = [0,0]; // memory pool
var step = function(time) {
  dt = (time - lasttime) * 0.001;
  if (time < 1e12) {
    // highres timer
  } else {
    // ms since unix epoch
    if (dt > 1e9) {
      dt = 0;
    }
  }
  // console.log('dt: ' + dt);
  lasttime = time;
  var foundnotstopped = false;
  for (var i = 0; i < elements_tracked.length; ++i) {
    var e = elements_tracked[i];
    var data = e.__GRAB__;
    if (data.anchor) {
      global(data.state, data.anchor, scratch0);
      scratch1[0] = scratch0[0] + data.offset[0];
      scratch1[1] = scratch0[1] + data.offset[1];
      //console.log("output of global", point);
      debugPoint(scratch1,
                 0, 'blue', data.pageoffset);
    } else {
      scratch1[0] = -1000;
      scratch1[1] = -1000;
      debugPoint(scratch1, 0, 'blue');
    }
    // timestep is dynamic and based on reported time. clamped to 100ms.
    if (dt > 0.3) {
      //console.log('clamped from ' + dt + ' @' + now());
      dt = 0.3;
    }
    vel_verlet_3(data.state, acc, dt);
    e.style.webkitTransform = 'translate3d(' + data.state[0] + 'px,' + data.state[1] + 'px,0)' +
        'rotateZ(' + data.state[2] + 'rad)';
  }
  requestAnimationFrame(step);
};

requestAnimationFrame(step);

这基本上会注销调用我的rAF例程（

step（）

函数）的所有时间

当它正常运行时，它大约每16.7毫秒记录一次时间

我明白了：

这清楚地表明它正在使用相同的时间输入参数运行

step（）

至少22次，就像时间线试图告诉我的那样

---

所以我敢说，互联网，你敢告诉我这是故意的行为。：）

我为创建了动画，还创建了requestAnimationFrame（）一致性检查器

支持将requestAnimationFrame（）自动同步到计算机显示器刷新率（即使不是60Hz）的web浏览器列表列在。。。这意味着在75Hz的监视器上，如果网页当前位于前台，并且CPU/图形性能允许，则requestAnimationFrame（）现在在受支持的浏览器上每秒调用75次

• Chrome 30的某个版本有一个令人讨厌的requestAnimationFrame（）错误：
• 而且Chrome32Beta似乎正在（再次）制造一些动画流动性缺陷。

Chrome29和Chrome31运行良好，Chrome30的更新版本也一样。幸运的是，据我所知，Chrome33金丝雀似乎更全面地解决了我所看到的问题。它运行动画更加流畅，无需对requestAnimationFrame（）进行不必要的调用

---

此外，我还注意到电源管理（CPU减速/节流太过节省电池电量）会严重影响requestAnimationFrame（）的回调速率。。。它表现为在帧渲染时间中向上/向下出现奇怪的尖峰（）

我认为您有问题，因为您调用了

requestAnimationFrame（步骤）mousedown

和

mouseup

事件上的code>。因为您的

step（）

函数也（应该）调用

requestAnimationFrame（步骤）

您基本上会为每个

mousedown

和

mouseup

事件启动新的“动画循环”，因为您从未停止它们，所以它们会累积

我可以看到，您还可以在代码末尾启动“动画循环”。如果要在鼠标事件发生时立即重画，应将绘图移出

step（）

函数，并直接从鼠标事件处理程序调用该函数

就像这样：

function redraw() { 
  // drawing logic
}
function onmousedown() {
  // ...
  redraw()
}
function onmouseup() {
  // ...
  redraw()
}

function step() {
  redraw();
  requestAnimationFrame(step);
}
requestAnimationFrame(step);

---

+但是我觉得如果问题的长度稍微长一点，人们会对它更感兴趣shorter@Onaseriousnote我接受了一些建议，这可能很有意思：我不认为这与每次刷新时运行rAF回调多次的完全错误行为有什么关系。无论如何，在rAF像setTimeout一样防弹之前，似乎还有很多工作要做。是的，您的伪代码示例是管理rAF渲染循环正确方法的一个很好的升华，事实上，通过鼠标单击启动额外的渲染“线程”是错误的，它会导致一种很难解决的情况。。。我需要重新审视这段代码，并找出这是否是我遇到的问题中的一个重要因素。

window.rafbuf = [];
var step = function(time) {
  window.rafbuf.push(time);

function redraw() { 
  // drawing logic
}
function onmousedown() {
  // ...
  redraw()
}
function onmouseup() {
  // ...
  redraw()
}

function step() {
  redraw();
  requestAnimationFrame(step);
}
requestAnimationFrame(step);