1446300 - Implement updated uniformized input/textarea cursor position processing

Status: NEW

(Core :: DOM: Editor, enhancement, P3)

Description

[Domenic Denicola]

Spec change: https://github.com/whatwg/html/pull/3472
Tests: http://w3c-test.org/html/semantics/forms/textfieldselection/selection-start-end-extra.html

Note that these tests do not include many ways to change the value that are only possible manually, e.g. copy and paste or user input. See https://github.com/whatwg/html/issues/2424#issuecomment-286580627 and https://github.com/whatwg/html/issues/2424#issuecomment-286605947 for a more exhaustive list.

Comment 1

[Boris Zbarsky [:bzbarsky]]

Implementation notes:

1) There is a history of web compat problems when we change this stuff, so we need to be pretty careful.
2) Comparing Firefox, Chrome, and Safari on
   http://w3c-test.org/html/semantics/forms/textfieldselection/selection-start-end-extra.html shows
   that there's horrible interop so there may be some flexibility here.  That said, there is no
   guarantee that changing behavior even to the same one as one of the other browsers won't cause
   compat problems.