Re: [cssom-view] Range.getClientRects() when the range contains part of a grapheme cluster

On Sun, Apr 10, 2016 at 2:05 PM, Koji Ishii <kojiishi@gmail.com> wrote:

> On Sat, Apr 9, 2016 at 10:28 PM, Xidorn Quan <quanxunzhen@gmail.com>
> wrote:
>
>> On Sat, Apr 9, 2016 at 1:11 AM, Simon Pieters <simonp@opera.com> wrote:
>>
>>> On Thu, 07 Apr 2016 13:29:34 +0200, Koji Ishii <kojiishi@gmail.com>
>>> wrote:
>>>
>>> We recently figured out that the spec[1] isn't clear when the range
>>>> contains part of a grapheme cluster. Our behavior for the case was
>>>> recently
>>>> changed due to some other improvements, which lead to a discussion of
>>>> the
>>>> right behavior of getClientRects() and getBoundingClientRect().
>>>>
>>>> Could we define cases such as:
>>>> 1. What to do when the range contains part of a grapheme cluster.
>>>> 2. What to do when the range contains part of a surrogate pair.
>>>>
>>>
>>> I think these two should cover the whole grapheme cluster.
>>>
>>
>> In my opinion, a range should never contain only part of a surrogate
>> pair. I'd suggest that browsers should force the range to be either cover
>> the whole pair, or none of the parts. Containing part of surrogate pair
>> makes no sense to me.
>>
>
> Agreed, I wish us to define when and how.
>
> 1. var range = document.createRange();
> 2. range.setStart(node, 0);
> 3. range.setEnd(node, 1);
> 4. var rects = range.getClientRects();
>
> When the first code unit of the node is part of a grapheme cluster, when
> do we extend the range? I can think 3 options:
>
> a. Range is always adjusted to cover grapheme cluster, so at step 3.
> b. Adjusted when particular operations are invoked, so at step 4.
> c. Adjusted when particular operations are invoked, at step 4 internally,
> but does not change the range itself.
>
> I prefer option b at this moment, but I'm fine with option c if that looks
> more useful. I'm not a big fan of option a because it's expensive.
>

I was not talking about grapheme cluster, because that's hard... I think
allowing range to contain only part of a grapheme cluster may make sense
for some use cases, unlike surrogate pair, so probably c for grapheme
cluster is sensible.

- Xidorn