[Jprogramming] unicode overstrike

[Dan Bron]

According to:

	http://www.alanwood.net/unicode/combining_diacritical_marks_for_symbols.html

the arrow combining characters are:

	   4 u: 16b20d4 + 0 1 2 3 13 22 26 27
	⃪⃮⃯⃔⃕⃖⃗⃡

However, according to:

	http://unicode.org/faq/char_combmark.html#12b

You need a font with specific support for a particular combined glyph in order to see it.  I don't understand why displays couldn't simply overlay the two primitive glyphs if the font lacks a specific combined glyph (similar to how they can italicize or bold or small-caps fonts that don't contain specific support for those typefaces), but that's just my ignorance.

Anyway, I downloaded the two "broad spectrum" fonts that link recommends (Doulos and Charis), and using either, when I issue:

	'A',.4 u: 16b20d4 + 0 1 2 3 13 22 26 27

I can see A properly composed with the latter two "COMBINING LEFT/RIGHT ARROW BELOW", but the other combinations result in A followed by an  empty rectangle, which is symptomatic of lacking font support, according to the Unicode FAQ link.

So there's no quick answer.  You need a Unicode font that supports these overstrikes, in addition to all the other requirements of a J font (for example, fixed-width, or making "control characters" visible, etc).  That is, assuming you are simply displaying these combined characters in the J session manager.  If you're e.g. writing them to a file or email, etc, you have more degrees of freedom (and error, of course -- you may have to instruct your clients to download and install a specific font).

-Dan

-----Original Message-----
From: programming-bounces at jsoftware.com [mailto:programming-bounces at jsoftware.com] On Behalf Of Brian Schott
Sent: Monday, March 08, 2010 1:52 PM
To: programming at jsoftware
Subject: [Jprogramming] unicode overstrike

	At the link below there is a statement, describing
how U+0061 and U+0332 together can be used to create the APL
symbol `a underbar` because U+0332 has the combining
characteristic which enables overstrikes in unicode.

http://unicode.org/book/ch12.pdf

	I want to overstrike alphabetic characters with
directional arrows such as the following ones, but cannot
see how to give these characters the combining
characteristic oversstriking would require. Is that
possible; I cannot find any existing combining characters
that suggest any directionality.

16b2190
16b2191
16b2192
16b2193

16b2196
16b2197
16b2198
16b2199

   4 u: 16b2190 + i. 10  NB. try this in J to see the arrows


--

(B=)
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm