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I'm trying to design a font containing symbols for internal use in our organisation.

I've created a font using this tutorial, and I've assigned a symbol to the unicode position 0xF600. This lies within the 'Private use area', and doesn't appear to have any fonts which are supplying it.

I've created my font and installed it. I've tried with the font in either ~/Library/Fonts or /System/Library/Fonts.

If I insert this character () in TextEdit or any system text box I get either a box or some kind of mark contained within a box. Either way, not my character.

If I manually set the font to my font, the character is displayed.

However, I notice that other characters don't work like this. If I'm using Helvetica, and I insert a Chinese character, the symbol is taken from a different font which can display that glyph. So clearly there's a mechanism to fallback to a font which contains the character.

Are some fonts blessed by the system? How would I get my font to be the fallback?

EDIT: I've tried clearing the font cache with sudo atsutil databases -remove, didn't affect it.

EDIT 2: After poking around a bit and doing some reading, there's a font called LastResort.ttf that is the final fallback for all the unicode characters, there must be a precedence set somewhere in the system, so that that is always last. I wonder where that is...

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2 Answers 2

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OS X normally will not display a character in the Private Use Area unless you manually set the font in the app. I understand this is intentional, since every font could have a different glyph at the same PUA code point, and it only makes sense to display something when the user specifies the font.

I think it should also work when the right font is selected via CSS or other markup in a document being read.

Some earlier versions of OS X did not have this "feature" and did display PUA stuff. I don't know how they chose which font to use when more than one had something at the code point selected.

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  • Many thanks for your answer! I note however that there are a few symbols in the PUA that are displayed ordinarily (). Perhaps these are special cases?
    – joerick
    Commented Nov 29, 2012 at 9:13
  • @joerick Yes, I think there a couple fonts which don't obey the normal rule and do show up for some reason.
    – Tom Gewecke
    Commented Nov 29, 2012 at 13:28
  • Thanks! Got it working by putting my glyph at code point 0x10000, this is in the range 'Linear B Syllabary', which is currently empty. As long as a historical Greek font isn't installed in a future update I should be fine... !!
    – joerick
    Commented Nov 29, 2012 at 14:47
  • @joerick That should work fine, these days I think all apps should support characters in that higher Unicode plane. If one has a problem, you could probably find an empty spot lower down somewhere.
    – Tom Gewecke
    Commented Nov 29, 2012 at 16:16
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The character you show, of multiple horizontal lines, is San Francisco's 'notdef' character. That is the character that it shows when a requested glyph is not encoded in the font.

Other fonts may well have whatever character is being requested; or they may have a different notdef character, usually something in a box.

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    I think you may have glyph and character turned around here. The character being shown is f600, and what we see is the notdef glyph. It's the glyph displayed when no font has one for that code point, or when the OS ignores glyphs which fonts do have in the private use area. I suspect it looked differently in 2012 when posted than it does now.
    – Tom Gewecke
    Commented Nov 29, 2021 at 14:54

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