为什么这个重绘/回流黑客工作？ [英] Why does this repaint/reflow hack work?

问题描述

有时我们必须强制重绘/回流浏览器来呈现某些状态。例如：

  window.onload = function（）{setTimeout ）{document.getElementById（gradient_text）。innerHTML =bar;}，500）;}  

  #gradient_div {background：linear-gradient（＃000000，＃ffffff）; -webkit-background-clip：text; -webkit-text-fill-color：transparent;}  

  < div id =gradient_div> < p id =gradient_textonload =update> Foo< / p>< / div>  

< gradient_text元素，拒绝可视地将其文本更新为bar。在某些情况下，它足以触发同步重绘，如下所示：

  ... 
 setTimeout {
 var elem = document.getElementById（gradient_text）; 
 //同步力重绘hack 
 elem.innerHTML =bar; 
 elem.style.display =' none'; 
 elem.style.display ='block'; 
}，500）; 
 ... 
  

但是，这不起作用。显然，它需要异步hack：

  window.onload = function {setTimeout（function（）{var elem = document.getElementById（gradient_text）; elem.innerHTML =bar; // async force repaint hack var display = elem.style.display; elem.style.display ='none '; setTimeout（function（）{elem.style.display = display}，50）;}，500）;}  

  #gradient_div {background：linear-gradient（＃000000，＃ffffff）; -webkit-background-clip：text; -webkit-text-fill-color：transparent;}  

  < div id =gradient_div> < p id =gradient_textonload =update> Foo< / p>< / div>  

浏览器引擎以这种方式表现？

解决方案

从我的评论，应该可以很容易地从任何浏览器测试：

我添加了一些混合混合模式效果，所以Firefox应该渲染类似于Chrome在这里假设的东西。

  window.onload = document.getElementById（gradient_text）。innerHTML =bar;  

  / *＃gradient_div {background：linear-gradient（＃000000，＃ffffff） ; -webkit-background-clip：text; -webkit-text-fill-color：transparent;} * // *更新以显示类似的文本填充效果在Firefox * /＃gradient_div {background：linear-gradient（＃000000，＃ffffff）;}＃gradient_text {background：白色; mix-blend-mode：screen}  

 < div id =gradient_div> < p id =gradient_text> Foo< / p>< / div>  

Sometimes we have to force repaint/reflow for the browser to render certain states. For instance:

window.onload = function () {
  setTimeout(function(){
    document.getElementById("gradient_text").innerHTML = "bar";
  }, 500);
}

#gradient_div {
  background: linear-gradient(#000000,#ffffff);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

<div id="gradient_div">
  <p id="gradient_text" onload="update">
    Foo
  </p>
</div>

The "gradient_text" element, refuses to visually update its text to "bar". In some cases, it's enough to trigger a synchronous repaint like so:

...
setTimeout(function(){
  var elem = document.getElementById("gradient_text");
  // sync force repaint hack
  elem.innerHTML="bar";
  elem.style.display = 'none';
  elem.style.display = 'block';
}, 500);
...

However, this does not work. Apparently, it requires an asynchronous hack:

window.onload = function () {
  setTimeout(function(){
    var elem = document.getElementById("gradient_text");
    elem.innerHTML = "bar";
    // async force repaint hack
    var display = elem.style.display;
    elem.style.display = 'none';
    setTimeout(function(){
      elem.style.display = display
    }, 50);
  }, 500);
}

#gradient_div {
  background: linear-gradient(#000000,#ffffff);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

<div id="gradient_div">
  <p id="gradient_text" onload="update">
    Foo
  </p>
</div>

What's causing the browser engine to behave this way? Mostly interested in Webkit/Blink.

解决方案

From my comment, should make it easy to test from any browser :

I added some mix-blend-mode effect so Firefox should render something similar to what Chrome is suppose to here .

window.onload = document.getElementById("gradient_text").innerHTML = "bar";

/*#gradient_div {
  background: linear-gradient(#000000,#ffffff);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}
*/
/* UPDATE to show similar text-fill effect in Firefox */
#gradient_div {
  background: linear-gradient(#000000,#ffffff);
}
#gradient_text {
  background:white;
  mix-blend-mode:screen
}

<div id="gradient_div">
  <p id="gradient_text">
    Foo
   </p>
</div>

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