[webkit-dev] JavaScript question: how to find out the position of a tooltip relative to the document body in a zoomed and scrolled page

Xiaomei Ji xji at chromium.org
Mon Oct 5 16:37:51 PDT 2009

I am trying to display a tooltip under the mouse when mouse stays at a
position long enough.
I am using "absolute" positioning, set the tooltip as the child of the
document.body, and set the style.left and style.top as event.clientX +
document.body.scrollLeft and event.clientY + documentbody.scrollTop.
Following is the related code:

tooltip.style.position = "absolute";
var x = event.clientX + document.body.scrollLeft;
var y = event.clientY + document.body.scrollTop;
tooltip.style.left = x + "px";
tooltip.style.top = y + "px";

But it does not work in a scrolled and zoomed page. (works fine in a
scrolled page without zooming  or zoomed page without scrolling).

I think the (x, y) need to be adjusted by pageZoomFactor.
But I did not find pageZoomFactor is exposed through JS.

I tried to change the position to be "fixed" and hide the tooltip
onMouseWheel/onMouseDown/onKeyDown event to comprise "fixed element does not
scroll with the rest of the document", but I still could not find the right
position value for the tooltip in case of scolled and zoomed page.

Anyone has any idea how should I position the tooltip correctly in JS? Does
pageZoomFactor has to be exposed in JS to make it work?

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