463104 - elementFromPoint should take floating-point coords

Status: RESOLVED FIXED

(Core :: DOM: CSS Object Model, defect)

Description

[Boris Zbarsky [:bzbarsky]]

As things stand, elementFromPoint can lie about the element when something other than a DOM event is used to determine the point.  This could be fixed by changing to floating-point coords, which would allow sub-CSS-px points.

Comment 1

[Masatoshi Kimura [:emk]]

This method is no longer a Mozilla Extension. It's defined in CSSOM View working draft.
Per CSSOM View, elementFromPoint should take floating-point coordinates.
http://www.w3.org/TR/cssom-view/#the-documentview-interface
Moreover, getBoundingClientRect() already returns floating-point coordinates. Therefore
var rect = elem.getBoundingClientRect();
elem === document.elementFromPoint(rect.left, rect.top);
will return false incorrectly if the element has sub-CSS-px points.

Comment 2

[Masatoshi Kimura [:emk]]

Attachment: patch

changing elementFromPoint arguments to float

Comment 3

[Masatoshi Kimura [:emk]]

Attachment: patch v1.1

Forgotten to add a test file to Makefile.in

Comment 4

[Boris Zbarsky [:bzbarsky]]

Comment on attachment 436836 [details] [diff] [review]
patch v1.1

The test strings should be "a shouldn't be found" and "a should be found".  With that, r=bzbarsky.

Comment 5

[Masatoshi Kimura [:emk]]

Attachment: patch for checkin

Fixed test strings.
Carrying forward r+.

Comment 6

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

http://hg.mozilla.org/mozilla-central/rev/50b933e7db8e

Comment 7

[Robert O'Callahan (:roc) (email my personal email if necessary)]

The test had:
isnot(a, document.elementFromPoint(5.5, 5.5), "a should be found");
isnot(a, document.elementFromPoint(5.75, 5.75), "a should be found");

I believe these are incorrect, they should both return "a". I fixed that in bug 646757.

Comment 8

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Sorry, the original test lines were of course
isnot(a, document.elementFromPoint(5.5, 5.5), "a shouldn't be found");
isnot(a, document.elementFromPoint(5.75, 5.75), "a shouldn't be found");