发现requestPointerLock只能在其他事件的响应函数中生效，直接在同步代码中执行和在requestAnimationFrame中执行都不生效，同时既没有报错也不会触发pointerlockerror事件。

请问requestPointerLock生效的条件究竟是什么？

下面是一个测试页面，requestPointerLock生效时鼠标会消失。

1 <!DOCTYPE html>
 2 <html lang="en">
 3 <head>
 4     <meta charset="UTF-8">
 5     <title>TestLock</title>
 6 </head>
 7 <body  oncontextmenu="return false;">
 8 <div style="width: 500px;height: 500px" id="div_test">
 9 
10 </div>
11 </body>
12 </html>
13 <script>
14 
15 
16     div_test=document.getElementById("div_test");
17     div_test.requestPointerLock = div_test.requestPointerLock || div_test.msRequestPointerLock || div_test.mozRequestPointerLock || div_test.webkitRequestPointerLock;
18 
19 
20     var pointerlockchange = function (event) {
21         
22         
23         var controlEnabled = (document.mozPointerLockElement === div_test || document.webkitPointerLockElement === div_test || document.msPointerLockElement === div_test || document.pointerLockElement === div_test);
24         if (!controlEnabled) {
25           
26             console.log("1");
27         } else {
28             console.log("2");
29         }
30         //}
31     };
32     document.addEventListener("pointerlockchange", pointerlockchange, false);
33     document.addEventListener("mspointerlockchange", pointerlockchange, false);
34     document.addEventListener("mozpointerlockchange", pointerlockchange, false);
35     document.addEventListener("webkitpointerlockchange", pointerlockchange, false);
36     document.addEventListener("pointerlockerror ", pointerlockchange, false);
37     function lock()
38     {
39         if (div_test.requestPointerLock) {
40             div_test.requestPointerLock();//但是如果这一句是在调试中运行的，就不能起作用了，因为光标在另一个页面中！！
41         }
42     }
43     lock();
44 
45     window.requestAnimFrame = (function() {
46         return window.requestAnimationFrame ||
47                 window.webkitRequestAnimationFrame ||
48                 window.mozRequestAnimationFrame ||
49                 window.oRequestAnimationFrame ||
50                 window.msRequestAnimationFrame ||
51                 function(/* function FrameRequestCallback */ callback, /* DOMElement Element */ element) {
52                     window.setTimeout(callback, 1000/60);
53                 };
54     })();
55     requestAnimFrame(lock);
56 
57     div_test.addEventListener("click", function(evt) {
58         
59         if(evt.button==2)//右键单击
60         {
61             lock();
62         }
63         else if(evt.button==0)
64         {
65             lock();
66         }
67     }, false);
68 
69 
70 </script>