Bug 169548 – Spec change: <img ismap> coordinates should be from image edge, not border edge

• Status: NEW
• Component: DOM

[Simon Pieters (:zcorpan)]

Demo: http://software.hixie.ch/utilities/js/live-dom-viewer/?saved=3800

Expect click on border in the top-left corner to get coordinates 0,0. WebKit measures from the border edge instead.

whatwg/html issue: https://github.com/whatwg/html/issues/438
whatwg/html change: https://github.com/whatwg/html/pull/529

web-platform-test: https://github.com/w3c/web-platform-tests/pull/5118

The test passes in Chromium and Gecko; fail in WebKit and Edge.

Comment from Travis (Edge) https://github.com/w3c/html/issues/492#issuecomment-285819148

> Definitely makes sense just to align with Chrome/Firefox on this...

[Chris Dumez]

Likely the code in appendServerMapMousePosition(). Looks like link has some extra logic there:
  // The origin (0,0) is at the upper left of the content area, inside the
  // padding and border.
  mapPoint -= toLayoutBox(layoutObject)->contentBoxOffset();

[Chris Dumez]

(In reply to comment #1)
> Likely the code in appendServerMapMousePosition(). Looks like link has some
> extra logic there:
>   // The origin (0,0) is at the upper left of the content area, inside the
>   // padding and border.
>   mapPoint -= toLayoutBox(layoutObject)->contentBoxOffset();

s/link/Blink

[Simon Pieters (:zcorpan)]

https://github.com/w3c/web-platform-tests/pull/5118 has now landed.