获取当前鼠标下的元素，而不使用鼠标事件 [英] Get element currently under mouse without using mouse events

问题描述

WRT构建一个Firefox附加组件。

是否可以通过一些XPCOM或JavaScript方法获取鼠标下的元素？ （非js-ctypes，因为这需要操作系统的特殊性）

我想要检测当用户按下 Ctrl + Shift + M 。

现在我添加一个<$ c $当用户按下这个热键时，鼠标悬停在鼠标上，当鼠标移动时，鼠标可以在鼠标下，但是当鼠标按下热键组合。

解决方案

我只是通过源代码来获取（或存储并使其可用）的光标位置。我没有找到任何可以使用的东西（从Javascript，XPCOM或不）。我可能错过了一些... MXR 是你的朋友。

$ b $然而，如果你想避免 mousemove （这通常是一个好主意），你可以只查找最内层的元素，例如像这样。

  function getInnermostHovered（）{
 var n = document.querySelector（：hover）; 
 var nn; 
 while（n）{
 nn = n; 
 n = nn.querySelector（：hover）; 
} 
 return nn; 
 
  

（

虽然这是我认为的一个破解，但它似乎工作足够好大部分的时间，但如果元素通过 指针事件 。可能还有其他问题，我没有想到...

当然，当文档没有悬停的元素时，它可以不返回任何东西（例如，鼠标不是实际的在文件内）。

WRT building a Firefox Add-on.

Is it possible to get the element under the mouse via some XPCOM or javascript method? (non-js-ctypes please as that requires OS specificity)

I want to detect what is under the mouse when user presses Ctrl + Shift + M.

Right now I'm adding a mouseover listener to the document when the user presses this hotkey, so I can get the element under the mouse when he moves it, but not the element that was under the mouse exactly when he pressed the hotkey combination.

解决方案

I just looked through the source for code that gets (or stores and makes available) the cursor position. I didn't find anything one could use (from Javascript, XPCOM or not). I might have missed something... MXR is your friend.

However, if you want to avoid mousemove (and this is a good idea in general), you can just look for the innermost hovered element, e.g. like so.

function getInnermostHovered() {
    var n = document.querySelector(":hover");
    var nn;
    while (n) {
        nn = n;
        n = nn.querySelector(":hover");
    }
    return nn;
}

(fiddle demoing the principle)

While this is what I'd consider a hack, it seems to work good enough most of the time, but will fail if the element has mouse events disabled via pointer-events. There could be other issues I didn't think of...

Of course, this can return nothing when the document has no hovered element (e.g. the mouse is not actually within the document).

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