<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Hi David,<div><br><div><div>On 07/05/2015, at 9:26 AM, David Carlisle wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div><blockquote type="cite">The character itself, as bytes that is, is not wrong and users should be able to create these.<br></blockquote><blockquote type="cite">But preferably through macros that ensure that they come correctly paired.<br></blockquote><br>placing two character tokens representing a surrogate pair should not<br>though magically turn itself<br>into a single character. </div></blockquote><div><br></div><div>Agreed.</div><div>You don't know whether you want a single character until </div><div>you know what kind of output is being generated.</div><div>That need not be known on input.</div><br><blockquote type="cite"><div>The UTF-8 or ^^^^ encoding should refer to<br>the unicode code point not<br>to the UTF-16 encoding,<br></div></blockquote><div><br></div><div>No disagreement to this.</div><br><blockquote type="cite"><div><br>In the current versions ^^^^d835^^^^dc00 is two characters in luatex<br>and one character in xetex<br>as the implementation detail that xetex's underlying storage is mostly<br>UTF-16 is exposed. </div></blockquote><div><br></div><div>This seems to be premature of XeTeX then.</div><div>It seems to be making an assumption on how those bytes </div><div>will ultimately be used.</div><br><blockquote type="cite"><div>If it is<br>not possible to prevent ^^^ or utf8 encoded surrogate pairs combining<br>then it is better to<br>prevent them being formed.</div></blockquote><div><br></div><div>Hmm. </div><div>What if you have an entirely different purpose in mind for those bytes?</div><div>You still need to be able to create them and do further processing with them.</div><div><br></div><div>Maybe there should be a primitive that sets a flag controlling what</div><div>happens to surrogates' bytes on input?</div><div>It may well be that XeTeX's current behaviour is best for putting</div><div>content into PDF pages; but not best in other situations. So a macro</div><div>programmer should have a means to change this, when needed.</div><br><blockquote type="cite"><div><br>this is no different to XML where & #xd835;& #xdc00; always refers to<br>two (invalid) characters not<br>to & #x1d400;<br></div></blockquote><div><br></div><div>Seems fine to me.</div><div>If application software wants/needs to combine them, it can do so.</div><br><blockquote type="cite"><div><br>David<br></div></blockquote><br></div><div><br></div><div>Cheers,</div><div><br></div><div><span class="Apple-tab-span" style="white-space:pre"> </span>Ross</div><div><br></div><div><br></div><div>
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