Unicode of Death 2.0

Philippe Verdy via Unicode unicode at unicode.org
Thu Feb 15 12:58:10 CST 2018

That's probably not a bug of Unicode but of MacOS/iOS text renderers with
some fonts using advanced composition feature.

Similar bugs could as well the new advanced features added in Windows or
Android to support multicolored emojis, variable fonts, contextual glyph
transforms, style variants, or more font formats (not just OpenType); the
bug may also be in the graphic renderer (incorrect clipping when drawing
the glyph into the glyph cache, with buffer overflows possibly caused by
incorrectly computed splines), and it could be in the display driver (or in
the hardware accelerator having some limitations on the compelxity of
multipolygons to fill and to antialias), causing some infinite recursion
loop, or too deep recursion exhausting the stack limit;

Finally the bug could be in the OpenType hinting engine moving some points
outside the clipping area (the math theory may say that such plcement of a
point outside the clipping area may be impossible, but various mathematical
simplifcations and shortcuts are used to simplify or accelerate the
rendering, at the price of some quirks. Even the SVG standard (in constant
evolution) could be affected as well in its implementation.

There are tons of possible bugs here.

2018-02-15 18:21 GMT+01:00 James Kass via Unicode <unicode at unicode.org>:

> This article:
> https://techcrunch.com/2018/02/15/iphone-text-bomb-ios-
> mac-crash-apple/?ncid=mobilenavtrend
> The single Unicode symbol referred to in the article results from a
> string of Telugu characters.  The article doesn't list or display the
> characters, so Mac users can visit the above link.  A link in one of
> the comments leads to a page which does display the characters.
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