<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> </head> <body><div class="auto-created-dir-div" dir="auto" style="unicode-bidi: embed;"><style>p{margin:0}</style>Hello John<div><p><br></p><p>Thank you for your helpful reply.</p><p><br></p><p>Best regards,</p><p><br></p><p>William Overington</p><p><br></p><p>Saturday 15 October 2022</p><p><br></p><p><br></p><br><blockquote style="margin: 0px auto; padding: 0px 2em; border-left: 2px solid rgb(0, 173, 229);"><br><br><span style="white-space: pre-wrap;">------ Original Message ------</span><br><span style="white-space: pre-wrap;">From: "John Hudson" <john@tiro.ca></span><br><span style="white-space: pre-wrap;">To: mpeg-otspec@lists.aau.at</span><br><span style="white-space: pre-wrap;">Sent: Friday, 2022 Oct 14 At 23:33</span><br><span style="white-space: pre-wrap;">Subject: Re: [MPEG-OTSPEC] Is it valid to use a GSUB sequence with a leading ZWJ character please?</span><br><br><span style="white-space: pre-wrap;"> </span><div class="moz-cite-prefix" style="white-space: pre-wrap;">I don’t see any reason why beginning a GSUB input sequence with ZWJ should not be valid, but that isn’t the same thing as implying that you might not run into problems in particular OTL implementations.</div><span style="white-space: pre-wrap;"> </span><div class="moz-cite-prefix" style="white-space: pre-wrap;"><br> </div><span style="white-space: pre-wrap;"> </span><div class="moz-cite-prefix" style="white-space: pre-wrap;">ZWJ and other formatting control characters with representative glyphs — properly only displayed in editing environments, not in text presentation — should be available to GSUB, but then suppressed from the resulting glyph string for GPOS and display purposes. That behaviour is mostly reliable in complex script shaping engines, but it is possible that the path emoji take in some environments may run into unexpected issues with some part of this procedure.<br> </div><span style="white-space: pre-wrap;"> </span><div class="moz-cite-prefix" style="white-space: pre-wrap;"><br> </div><span style="white-space: pre-wrap;"> </span><div class="moz-cite-prefix" style="white-space: pre-wrap;">JH<br> </div></blockquote></div></div></body></html>