Will I run into any issues if I don't include all the glyphs from a codepage (i.e skipping ∏∑√∂)?

Diana Ovezea
Diana Ovezea Posts: 14
in Technique and Theory
I have a client that wants to reduce font file size. I would like to get rid of characters like ΔΩμπ£¥∏∑√∂µ. Most of these characters are included in the MacOS Roman or Windows 1252 codepages. I have some vague memory that says "that it's not allowed to remove those or the font might have issues being recognized on older systems". 

Will I run into any issues if a web font doesn't include those characters? Or a otf font in Windows Office? 
Thanks in advance!
Diana
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Comments

  • John Savard
    John Savard Posts: 1,126
    No, lots of fonts only include certain characters from a given Unicode code page.
  • John Hudson
    John Hudson Posts: 3,186
    edited July 2021
    There are potential issues on systems that use algorithms to identify whether a fonts supports a language. Such algorithms may only check whether the OS/2 table flags for a given codepage associated with the language is set, but may also check for certain characters to be present in the cmap table. You can lie about codepage support in the OS/2 flag settings, i.e. claim support even if some characters are missing, but I try to avoid doing that.

    I would be wary about not including £ and ¥ since those are major currency symbols, but most of the others you identify could be left out simply by not aiming to support the Mac Roman codepage but instead just targeting Windows CP1252.
  • James Puckett
    James Puckett Posts: 1,992
    Few designers put ΔΩμπ∏∑√∂µ into their fonts and they work fine. £¥ shouldn’t be omitted if it’s for an editorial project where they might come up, but if it’s just for headlines on a site for an American company it probably doesn’t matter.
  • Andreas Stötzner
    Andreas Stötzner Posts: 792
    An old theme. Remind, you’ll never know who will be using your font for what. It happens very quickly that a measurement expression like 5µm or the simple notation of a sum ∑ is required. In the time you think about it and write about here, you have drawn the glyphs and are out of the conundrum.
  • Jasper de Waard
    Jasper de Waard Posts: 639
    Andreas Stötzner said:
    An old theme. Remind, you’ll never know who will be using your font for what. It happens very quickly that a measurement expression like 5µm or the simple notation of a sum ∑ is required. In the time you think about it and write about here, you have drawn the glyphs and are out of the conundrum.
    The point was to reduce file size though...

    What about including the glyphs but keeping them empty?
  • André G. Isaak
    André G. Isaak Posts: 632
    Jasper de Waard said:
    What about including the glyphs but keeping them empty?
    Please don't do that. A .notdef symbol clearly indicates that a symbol is missing, whereas a blank glyph can easily be missed when reviewing text.
  • Matthijs Herzberg
    Matthijs Herzberg Posts: 154
    I also think it really depends on the font. Your average workhorse should definitely include the lesser-used glyphs, but if we're talking about a wild display face, it is incredibly unlikely that a user will ever need a differential or whatever.
  • Michael Rafailyk
    Michael Rafailyk Posts: 146
    edited August 2021
    Disabling autohinting will also reduce the file size. But it depends on the font too.
  • Diana Ovezea
    Diana Ovezea Posts: 14
    Andreas Stötzner said:
    An old theme. Remind, you’ll never know who will be using your font for what. It happens very quickly that a measurement expression like 5µm or the simple notation of a sum ∑ is required. In the time you think about it and write about here, you have drawn the glyphs and are out of the conundrum.
    I am very aware of that. In this case, the glyphs I want to skip will surely not be used by my client (hence my wish to exclude them), but I am inquiring if I run into technical issues for skipping them.

    I thought about inserting a simple notdef inside those glyphs (a notdef drawing has less contours than those real glyphs, so it is less file size in the end).

    And we definitely need PS (auto)hinting. I'm just thinking about the best subsetting practices. 
  • Paul van der Laan
    Paul van der Laan Posts: 242
    From our experience you can safely leave out the glyphs in question without any technical issues. No need to insert a .notdef.
  • Thomas Phinney
    Thomas Phinney Posts: 2,883
    edited August 2021
    Diana Ovezea said:
    I thought about inserting a simple notdef inside those glyphs (a notdef drawing has less contours than those real glyphs, so it is less file size in the end).
    I have difficulty imagining any situation in which inserting additional notdefs into normal character slots in the font would be a good idea. Doing so stymies the ability of the app or OS to tell if a character is supported.

    For example, InDesign will normally display missing characters using a notdef—plus a bright pink highlight. Users who quite reasonably expect that highlight will be confused and might just miss the notdef if they don’t realize you have changed the rules.

    Yes, SOME app or environment may expect certain characters. As you already have them, your best solution for such cases is… include those characters. But as noted, these are mostly not particularly critical or general-use, except the currency symbols.

    Plus, unless your font is extremely unusual, the notdef won’t take up that much less space than the glyphs. Increment and product are definitely going to be smaller with the actual glyph!
  • Rob Barba
    Rob Barba Posts: 86
    edited August 2021
    Honestly, I say it depends.  If it's going to be used in special context or fonts where it might benefit, don't get rid of them.  But chances are, a display font isn't going to have much use for them.  For example, I've been removing ₧ and ʼn from my fonts as of late as they're pretty much confined to the dustbin of history nowadays.  Thus, it's beneficial to look at other glyphs you can kill off as needed. 
    In fact, if you're going to remove those characters, look at some of the other characters that might benefit your use by adding them instead: ℠, ₿, ₹, etc.
  • Georg Seifert
    Georg Seifert Posts: 674
    I have seen some fonts that wouldn’t install on windows because of some missing glyphs. Never had problems with webfont. 
    But if it is for a client it is easy to verify. Just send them the font and let them test. 
  • Erwin Denissen
    Erwin Denissen Posts: 300
    You can leave out as many glyphs as you want. Even a font with just one character will install just fine in Windows. The file size is 544 bytes, as discussed here:

  • RichardW
    RichardW Posts: 100
    I left the normally unused punctuation and logogram characters out from a Tai Tham font, and a program (probably LibreOffice) refused to use the font because they were missing.  That justifies the use of a variant .notdef glyph to fill in the omissions.  I don't know whether present day LibreOffice has this behaviour, which was observed on Linux.
  • Peter Constable
    Peter Constable Posts: 208
    John Savard said:
    No, lots of fonts only include certain characters from a given Unicode code page.

    Terminological nit: Unicode doesn't have code pages. It might be more accurate to say that Unicode is a code page, though "code page" is generally not used in relation to Unicode, unless you're talking about the legacy mess it replaced.

    Unicode does have blocks. But it's not necessarily good to think of blocks as chunks to be supported all or none.

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