MouseEvent-prototype-offsetX-offsetY.html seems to depend on non-spec-defined behavior

[bzbarsky]

The test is testing things like the offsetTop of an inline, but this is not actually defined in the CSS specification. Specifically, the relevant text in CSS 2.1, last I checked, is:

 10.6 Calculating heights and margins
   10.6.1 Inline, non-replaced elements
     The 'height' property does not apply. The height of the content area
     should be based on the font, but this specification does not specify how.

and I'm not aware of any later CSS specs that define the behavior.

Since the offsetTop depends on the interaction of the line-height and the heights of the inlines, it's not specified either.

The test should probably use a display: block target element instead.

@rniwa, thoughts? It looks like you wrote this test.

[bzbarsky]

Actually, we could probably stay with an inline if we set line-height: 1; font-family: Ahem on the my-host element. That should eliminate the browser rendering differences in terms of inline layout.

[rniwa]

Yeah, setting line-height and font-family sounds great to me. I wanted to add testing for inline elements but didn't realize it wasn't specified at all. I guess we could use display:block if we wanted to avoid depending on any unspec'ed behavior.

[bzbarsky]

No, browsers are still not interoperable even with the Ahem/line-height thing, looks like...