New full Unicode for ES6 idea

Brendan Eich brendan at mozilla.org
Sun Feb 19 11:58:38 PST 2012


Brendan Eich wrote:
> My R2 resolution is not specific to any engine, but I have hopes it 
> can be accepted. It is concrete enough to help overcome 
> large-yet-vague doubts about implementation impact (at least IMHO). 
> Recall that document.domain setting may have to split a merged 
> same-origin window/frame graph, at any time. Again implementation 
> solutions vary, but this suggests cross-window mediation can be 
> interposed lazily.
>
> Another point: HTML5 WindowProxy (vs. Window, the global object on the 
> scope chain) exists to solve navigation-away-from-same-origin security 
> problems. Any JS that passes strings from one window to another must 
> be using a WindowProxy to reference the other. There's a mediation 
> point too.

IOW, whether there' s a heap/compartment per global is not critical (but 
if there is, then strings are already copied and could be transcoded as 
to their meta-data distinguishing non-BMP+UTF16-aka-full-Unicode from 
bad-ol'-90s-UCS2). The cross-window mediation via WindowProxy is.

The flag bits I mentioned could be combined: 1 flag bit for both 
non-BMP-chars-in-this-string-*and*-full-Unicode-BRS-setting-in-effect-for-its-global.

/be


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