Although the symptoms of font problems show up in the context of Word <->
LibreOffice Writer, the situation is trickier than that. It is exacerbated by
failure to use standard Unicode code points, eliminating the possibility of
successful font substitutions, especially for symbols that don't vary that much
from one font to another and there is little danger of confusion.
1. AVAILABLE FONTS
Most office-productivity software products rely on the fonts installed on the
operating system, sharing those fonts with all software on the platform. It is
also the case that the installation of software products will install fonts,
optionally or automatically, for users on that computer. (Some fonts are only
licensed to be used with the product or platform on which the product is
installed.)
Users can also install an enormous variety of fonts of their own choosing,
whether licensed from a font foundry or obtained from one of the sources of
unrestricted fonts.
Example: Beside the fonts that are available on the platform directly, my main
Windows 7 desktop system has fonts installed by Microsoft Office 2010, Visual
Studio 2010, Photoshop Elements, Word Perfect X5 Standard, and LibreOffice
3.3.2, among others. All of these fonts are available to LibreOffice 3.3.2
Writer.
2. INTERCHANGING DOCUMENTS WITH FONT DEPENDENCIES
When fonts use essentially the same code points for the same characters, but
with differences in font-face design, there are techniques to substitute a
close kindred font when the specific font is not available to the consumer of a
document. This might create problems with metrics, but there are many fonts
that substitute well enough. Systems may provide automatic substitutions for
fonts that are not installed. Products also have ways to let users direct the
substitutions.
Example: In LibreOffice, the Tools | Options | LibreOffice | Fonts dialog
provides for substitutions. The Help topic indicates the range of capabilties.
Font substitutions don't work so well for decorative fonts and it is generally
not possible for symbol fonts that use special code pages (older systems) or
non-standard Unicode code points for their characters.
Some fonts don't provide substitutions very well at all. In particular, there
is no assured substitution for Unicode-based fonts that rely on code points in
the Unicode Private Use Area, U+E000 to U+F8FF.
Example: The Microsoft Symbol, Webdings, Wingdings, Wingdings2, and Wingdings 3
each use private-use code points in the same range: U+F020 to F0FF. U+F020 is
always a space character, but the other code points are not substitutable
characters among those fonts. Likewise, OpenSymbol uses some standard Unicode
code points but it also includes an extensive number of code points in the
private-use range U+E001 to U+E6A3. These do not correspond to the use of
private-use code points by Linux Libertine G (a Serif Unicode-based font) and
Linux Biolinum G (a Sans Serif Unicode-based font). None of these characters
that have private-use code points are substitutable among different symbol-only
or Unicode-based fonts.
A significant number of the characters defined in the Private Use Area also
have standard Unicode code points. The standard Unicode code points should
always be used instead if fonts that include them are available, such as Lucida
Sans Unicode and Cambria Math. Linux Biolinium G can also be used this way so
long as its Private Use Area characters are avoided.
Generally, the greatest fidelity is obtained if it can be arranged to have the
same font and font metrics installed on the computer system of the document
consumers as were used by the document producer and on which the document
depends.
For documents that use characters from the private use area of fonts available
to the document producer, the only prospect for successful interchange is if
the document consumer has a font that defines those very same characters at the
same code points of the private use area. This has to be accomplished by
private convention.
3. PROVIDING THE FONTS THAT A DOCUMENT DEPENDS ON
If the same software is used by the producer and consumer, there is no
difficulty when fonts consistently-supplied with the software, are used even if
the platforms are different.
If the font has a different source, or different software is being used, there
needs to be another way to provide the necessary font for use by the consumer.
There are two ways to do this:
- Using a document format that embeds the fonts
- Transferring font files to the other computer system
4. USING EMBEDDED FONTS IN AN INTERCHANGE DOCUMENT
A common method for ensuring that the consumer will view the document with
fidelity to the document that was produced is to export Adobe PDF documents.
These documents can carry embedded fonts and it is possible to arrange
production of bitmap versions of characters when the font is not embeddable.
Microsoft Word documents can also carry embedded fonts. This allows for
correct viewing by a recipient as well.
In general, having an embedded font in a document is not the same as having it
available for use in other documents. There are also barriers to using the
font in further collaborative editing of the same document. There are manual
workarounds that experts might employ, but those are probably too tedious for
anything but rare occasions.
Also, if the collaborative interchange is between different products, embedded
fonts won't be enough. The odds of passing embedded fonts through a converter
are rather low at this point. The possibility of round-trip preservation of
embedded fonts by conversion in both directions is even more remote.
Example: ODF lacks an agreed means for embedding of fonts. Word saving of
documents with embedded fonts as ODF text documents loses the embedded fonts.
(If the receiving ODF consumer has the fonts, it will still work though.)
LibreOffice could provide font embedding as part of Save As Word format, but
the current converters do not provide that capability. Also, even with an
embedded font, it may be cumbersome to use that font in further editing of the
received document unless the embedded font can be installed on the receiving
system by some means.
5. TRANSFERRING FONTS TO ANOTHER COMPUTER SYSTEM
One way to transfer fonts is to install a software application that provides
them.
This is not so far-fetched. LibreOffice can be installed for free, with
minimum configuration, simply to obtain its unique fonts. It is not necessary
to run it. We just want to have a common set of fonts.
Another way is to package and transfer fonts for mutual installation and agreed
use. Fonts are not difficult to install. It is likely that the LibreOffice
fonts are more amenable to unrestricted transfer onto other computers. This
may be the only way of adding fonts into some controlled computer
configurations.
Round trip collaboration also requires agreement to use only fonts that are
arranged to be available on any of the computers and software products used
among the collaborators. Users will need to understand how to limit
themselves to use of mutually-available fonts and to avoid pitfalls such as
relying on characters in the Private Use Area instead of their standard Unicode
code-point positions when those are mutually supported.
The limitation to mutual agreed use is the tricky part, since it requires users
to be aware of and careful of the conditions that assure mutual success.
6. FOR LIBREOFFICE DEVELOPERS
It is unfortunate that there are so many uses of the Private Use Area at large
in the world. It would be valuable to avoid distributing more files that rely
on them. (The existing conflict between Open Symbol and Linux
Biolinum/Libertine G is amusing enough.)
a. It would be useful to update OpenSymbol to use the now-standard code
Unicode code points for those characters that were previously unavailable as
standard characters.
b. It would also be useful to document the usage of the Private Use Area by
fonts distributed with LibreOffice. A PDF that shows the code points and
character appearance would be an excellent way to make these known, so people
would be informed on the impact their usage has for interchange with other
systems and conversion to other formats.
c. It would be especially valuable to adjust the LibreOffice repertoire of
bullet symbols, especially those used by default, to avoid using code points in
the Private Use Area for those characters.
- Dennis
-----Original Message-----
From: Dennis E. Hamilton [mailto:[email protected]]
Sent: Friday, May 27, 2011 13:53
To: 'Deve'; '[email protected]'
Cc: 'LOffice Users List'
Subject: RE: [Libreoffice] Word doesn't see symbols - NEW PROBLEM
There's a new problem. I checked around for middle dots, centered dots, etc.
The SAFE one is U+22C5, the Middle Dot in the extensive Unicode block on
Mathematical Operators, from U+2200 to U+22FF.
The dots that I saw in OpenSymbol are these: U+E146, U+E468, U+E466, U+E58D,
and U+E584. My copy of the Unicode Standard 4.0 says that these are all
PRIVATE USE SYMBOLS. This Private Use Area has existed since at least Unicode
3.2 and is unchanged in Unicode 6.0. See <http://www.unicode.org/charts/>.
"These areas will never be defined by the Unicode Standard. These code points
can be freely used for characters of any purpose, but successful interchange
requires an agreement between sender and receiver on their interpretation."
Furthermore, the codes extending upward from U+E000 are intended for END-USER
assignment and the codes extending downward from U+F8FF are intended for
CORPORATE USE (including vendors, platform providers, etc.), the idea that the
chance of collision is reduced thereby. This is only a suggested convention,
however.
These depend on private agreements for having matching fonts or even being used
for visible characters. Something tells me you'll be hard-pressed to find
these in fonts on Windows unless you can send the OpenSymbol font to the
recipient.
[ ... ]
My recommendation is to use a defined Unicode character (and a font that
supports it) in preference to the same OpenSymbol character whenever possible.
- Dennis
[ ... ]
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