Re: "Missing character" glyph- example

From: Peter_Constable@sil.org
Date: Thu Aug 01 2002 - 16:42:55 EDT


On 08/01/2002 02:34:17 PM Kenneth Whistler wrote:

>But if you insist on having a code point to stick directly in
>a sentence like that above, I'd take the cue from James Kass:
>
>> The missing glyph is the first glyph in any font. This is mapped to
>> U+0000 and the system correctly substitutes the glyph mapped to
>> U+0000 any time a font being used lacks an outline for a called
>> character.

I think James is mistaken on this point: the missing glyph *is* the first
glyph in any TTF, but it is *not* necessarily (probably not typically)
mapped from U+0000. For instance, in Times New Roman, Arial, Tahoma and
even James' own Code2000, the first entry in the cmap is for U+0020:

; TrueType v1.0 Dump Program - v1.60, Jul 10 1995, rrt, dra, gch, ddb, lcp
; Copyright (C) 1991 ZSoft Corporation. All rights reserved.
; Portions Copyright (C) 1991-1995 Microsoft Corporation. All rights
reserved.

; Dumping file 'code2000.ttf'

[snip]

                Which Means:
                   1. Char 0020 -> Index 3
                      Char 0021 -> Index 4

[snip]

On the other hand, not being explicitly mapped from a character means that
it is effectively implicitly mapped from a character. So,

>Thus, you have a reasonably good chance that if you try to
>purposefully display the character U+0000, you will get the
>missing glyph for the font in use. (Unless the application is
>filtering out NULL characters.)

is probably valid.

- Peter

---------------------------------------------------------------------------
Peter Constable

Non-Roman Script Initiative, SIL International
7500 W. Camp Wisdom Rd., Dallas, TX 75236, USA
Tel: +1 972 708 7485
E-mail: <peter_constable@sil.org>



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