[whatwg] Control over selection direction

[Aryeh Gregor]

On Sun, Jan 16, 2011 at 3:51 PM, Ryosuke Niwa <rniwa at webkit.org> wrote:
> Does it make sense to add selectionBase and selectionExtent instead of
> exposing direction?  That seems to match better with DOM selection for which
> we have baseNode, baseOffset, extentNode, and extentOffset.

Yes, but it's more redundant.  The exposed properties would no longer
be orthogonal -- changing one would have to change the others, and
it's not intuitively obvious in some cases how they should change.
E.g., suppose selectionAnchor == 5, selectionFocus == 8, so the
selection is forward.  Now I set selectionStart = 4.  Does this give
me selectionAnchor == 4 and selectionFocus == 8 (so it's the same as
changing selectionAnchor), or does it give selectionAnchor == 8 and
selectionFocus == 4 (changing direction to backwards because I
extended backwards), or maybe selectionAnchor == 5 and selectionFocus
== 4 (behaving like extend())?

If we just have a boolean, it's unambiguous: the properties are all
logically separate.  We don't want to emulate the DOM selection API,
IMO -- it's ridiculously complex for minimal functionality gain, even
accounting for the fact that it has to deal with nodes as well as
offsets.  Save authors the pain, if they only have to deal with text
fields.