Fonts in XFree86
原文链接http://www.xfree86.org/current/fonts.html作者：Juliusz Chroboczek, [email protected]
日期：17 November 2003
Table of Contents
1.Introduction
1.1. Two font systems
2. Installing fonts
2.1. Configuring Xft
2.2. Configuring the core X11 fonts system
3. Fonts included with XFree86
3.1. Standard bitmap fonts
3.2. The ClearlyU Unicode font family
3.3. Standard scalable fonts
3.4. The Bigelow & Holmes Luxi family
4. More about core fonts
4.1. Core fonts and internationalisation
4.2. Additional notes about scalable core fonts
5. Appendix: background and terminology
5.1. Characters and glyphs
5.2. Font files, fonts, and XLFD
5.3. Unicode
6. References 1.Introduction
This document describes the support for fonts in XFree86. Installing fonts is aimed at the casual user wishing to install fonts in XFree86; the rest of the document describes the font support in more detail.
We assume some familiarity with digital fonts. If anything is not clear to you, please consult Appendix: Background at the end of this document for background information.
1.1. Two font systems
XFree86 includes two font systems: the core X11 fonts system, which is present in all implementations of X11, and the Xft fonts system, which is not currently distributed with implementations of X11 that are not based on XFree86 but will hopefully be included by them in the future
The core X11 fonts system is directly derived from the fonts system included with X11R1 in 1987, which could only use monochrome bitmap fonts. Over the years, it has been more or less happily coerced into dealing with scalable fonts and rotated glyphs.
Xft was designed from the start to provide good support for scalable fonts, and do so efficiently. Unlike the core fonts system, it supports features such as anti-aliasing and sub-pixel rasterisation. Perhaps more importantly, it gives applications full control over the way glyphs are rendered, making fine typesetting and WYSIWIG display possible. Finally, it allows applications to use fonts that are not installed system-wide for displaying documents with embedded fonts.
Xft is not compatible with the core fonts system: usage of Xft requires making fairly extensive changes to toolkits (user-interface libraries). While XFree86 will continue to maintain the core fonts system, toolkit authors are encouraged to switch to Xft as soon as possible. 2. Installing fonts
This section explains how to configure both Xft and the core fonts system to access newly-installed fonts.
2.1. Configuring Xft
Xft has no configuration mechanism itself, rather it relies upon the fontconfig library to configure and customize fonts. That library is not specific to XFree86 or indeed on any particular font output mechanism. This discussion describes how fontconfig, rather than Xft, works.
2.1.1. Installing fonts in Xft
Fontconfig looks for fonts in a set of well-known directories that include all of XFree86's standard font directories (`/usr/X11R6/lib/X11/lib/fonts/*') by default) as well as a directory called `.fonts/' in the user's home directory. Installing a font for use by Xft applications is as simple as copying a font file into one of these directories.
$ cp lucbr.ttf ~/.fonts/
Fontconfig will notice the new font at the next opportunity and rebuild its list of fonts. If you want to trigger this update from the command line (for example in order to globally update the system-wide Fontconfig information), you may run the command `fc-cache'.
$ fc-cache
2.1.2. Fine-tuning Xft
Fontconfig's behaviour is controlled by a set of configuration files: a system-wide configuration file, `/etc/fonts/fonts.conf', and a user-specific file called `.fonts.conf' in the user's home directory (this can be overridden with the `FONTCONFIG_FILE' environment variable).
Every Fontconfig configuration file must start with the following boilerplate:
<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
In addition, every Fontconfig configuration file must end with the following line:
</fontconfig>
The default Fontconfig configuration file includes the directory `~/.fonts/' in the list of directories searched for font files, and this is where user-specific font files should be installed. In the unlikely case that a new font directory needs to be added, this can be done with the following syntax:
<dir>/usr/local/share/fonts/</dir>
Another useful option is the ability to disable anti-aliasing (font smoothing) for selected fonts. This can be done with the following syntax:
<match target="font">
<test qual="any" name="family">
<string>Lucida Console</string>
</test>
<edit name="antialias" mode="assign">
<bool>false</bool>
</edit>
</match>
Anti-aliasing can be disabled for all fonts by the following incantation:
<match target="font">
<edit name="antialias" mode="assign">
<bool>false</bool>
</edit>
</match>
Xft supports sub-pixel rasterisation on LCD displays. XFree86 should automatically enable this feature on laptops and when using an LCD monitor connected with a DVI cable; you can check whether this was done by typing
$ xdpyinfo -ext RENDER | grep sub-pixel
If this doesn't print anything, you will need to configure Render for your particular LCD hardware manually; this is done with the following syntax:
<match target="font">
<edit name="rgba" mode="assign">
<const>rgb</const>
</edit>
</match>
The string `rgb' within the `<const>'...`</const>' specifies the order of pixel components on your display, and should be changed to match your hardware; it can be one of `rgb (normal LCD screen), `bgr' (backwards LCD screen), `vrgb' (LCD screen rotated clockwise) or `vbgr' (LCD screen rotated counterclockwise).
2.1.3. Configuring applications
Because most current applications use the core fonts system by default, it is necessary to explicitly configure them to use Xft. How this is done depends on the application.
XTerm can be set to use Xft by using the `-fa' command line option or by setting the `XTerm*faceName' resource:
XTerm*faceName: Courier
or
$ xterm -fa "Courier"
For applications based on GTK+ 2.0 (including GNOME 2 applications), the environment variable `GDK_USE_XFT' should be set to `1':
$ export GDK_USE_XFT=1
GTK+ 2.2 uses Xft by default.
For KDE applications, you should select ``Anti-alias fonts'' in the ``Fonts'' panel of KDE's ``Control Center''. Note that this option is misnamed: it switches KDE to using Xft but doesn't enable anti-aliasing in case it was disabled by your Xft configuration file.
(What about Mozilla?)
2.1.4. Troubleshooting
If some Xft-based applications don't seem to notice the changes you are making to your configuration files, they may be linked against the XFree86 4.2 version of Xft. In order to fix the problem, you should relink them against a current version of Xft; on most systems, it is enough to install the current version of the Xft and Fontconfig libraries.
If, for some reason, you cannot upgrade the shared libraries, please check the Xft(3) manual page included with XFree86 4.2 for the configuration mechanisms of the previous version of Xft.
2.2. Configuring the core X11 fonts system
Installing fonts in the core system is a two step process. First, you need to create a font directory that contains all the relevant font files as well as some index files. You then need to inform the X server of the existence of this new directory by including it in the font path.
2.2.1. Installing bitmap fonts
The XFree86 server can use bitmap fonts in both the cross-platform BDF format and the somewhat more efficient binary PCF format. (XFree86 also supports the obsolete SNF format.)
Bitmap fonts are normally distributed in the BDF format. Before installing such fonts, it is desirable (but not absolutely necessary) to convert the font files to the PCF format. This is done by using the command `bdftopcf', e.g.
$ bdftopcf courier12.bdf
You will then want to compress the resulting PCF font files:
$ gzip courier12.pcf
After the fonts have been converted, you should copy all the font files that you wish to make available into a arbitrary directory, say `/usr/local/share/fonts/bitmap/'. You should then create the index file `fonts.dir' by running the command `mkfontdir' (please see the mkfontdir(1) manual page for more information):
$ mkdir /usr/local/share/fonts/bitmap/
$ cp *.pcf.gz /usr/local/share/fonts/bitmap/
$ mkfontdir /usr/local/share/fonts/bitmap/
All that remains is to tell the X server about the existence of the new font directory; see Setting the server font path below.
2.2.2. Installing scalable fonts
The XFree86 server supports scalable fonts in four formats: Type 1, Speedo, TrueType and CIDFont. This section only applies to the former three; for information on CIDFonts, please see Installing CIDFonts later in this document.
Installing scalable fonts is very similar to installing bitmap fonts: you create a directory with the font files, and run `mkfontdir' to create an index file called `fonts.dir'.
There is, however, a big difference: `mkfontdir' cannot automatically recognise scalable font files. For that reason, you must first index all the font files in a file called `fonts.scale'. While this can be done by hand, it is best done by using the `mkfontscale' utility.
$ mkfontscale /usr/local/share/fonts/Type1/
$ mkfontdir /usr/local/share/fonts/Type1/
Under some circumstances, it may be necessary to modify the `fonts.scale' file generated by mkfontscale; for more information, please see the mkfontdir(1) and mkfontscale(1) manual pages and Core fonts and internationalisation later in this document.
2.2.3. Installing CID-keyed fonts
The CID-keyed font format was designed by Adobe Systems for fonts with large character sets. A CID-keyed font, or CIDFont for short, contains a collection of glyphs indexed by character ID (CID).
In order to map such glyphs to meaningful indices, Adobe provide a set of CMap files. The PostScript name of a font generated from a CIDFont consists of the name of the CIDFont and the name of the CMap separated by two dashes. For example, the font generated from the CIDFont `Munhwa-Regular' using the CMap `UniKS-UCS2-H' is called
Munhwa-Regular--UniKS-UCS2-H
The CIDFont code in XFree86 requires a very rigid directory structure. The main directory must be called `CID' (its location defaults to `/usr/X11R6/lib/X11/fonts/CID' but it may be located anywhere), and it should contain a subdirectory for every CID collection. Every subdirectory must contain subdirectories called CIDFont (containing the actual CIDFont files), CMap (containing all the needed CMaps), AFM (containing the font metric files) and CFM (initially empty). For example, in the case of the font Munhwa-Regular that uses the CID collection Adobe-Korea1-0, the directory structure should be as follows:
CID/Adobe-Korea1/CIDFont/Munhwa-Regular
CID/Adobe-Korea1/CMap/UniKS-UCS2-H
CID/Adobe-Korea1/AFM/Munhwa-Regular.afm
CID/Adobe-Korea1/CFM/
CID/fonts.dir
CID/fonts.scale
After creating this directory structure and copying the relevant files, you should create a `fonts.scale' file. This file has the same format as in the case of (non-CID) scalable fonts, except that its first column contains PostScript font names with the extension `.cid' appended rather than actual filenames:
1
Adobe-Korea1/Munhwa-Regular--UniKS-UCS2-H.cid \
-adobe-munhwa-medium-r-normal--0-0-0-0-p-0-iso10646-1
(both names on the same line). Running `mkfontdir' creates the `fonts.dir' file:
$ cd /usr/local/share/fonts/CID
$ mkfontdir
Finally, you should create the font metrics summary files in the directory `CFM' by running the command `mkcfm':
$ mkcfm /usr/local/share/fonts/CID
If no CFM files are available, the server will still be able to use the CID fonts but querying them will take a long time. You should run `mkcfm' again whenever a change is made to any of the CID-keyed fonts, or when the CID-keyed fonts are copied to a machine with a different architecture.
2.2.4. Setting the server's font path
The list of directories where the server looks for fonts is known as the font path. Informing the server of the existence of a new font directory consists of putting it on the font path.
The font path is an ordered list; if a client's request matches multiple fonts, the first one in the font path is the one that gets used. When matching fonts, the server makes two passes over the font path: during the first pass, it searches for an exact match; during the second, it searches for fonts suitable for scaling.
For best results, scalable fonts should appear in the font path before the bitmap fonts; this way, the server will prefer bitmap fonts to scalable fonts when an exact match is possible, but will avoid scaling bitmap fonts when a scalable font can be used. (The `:unscaled' hack, while still supported, should no longer be necessary in XFree86 4.0 and later.)
You may check the font path of the running server by typing the command
$ xset q
2.2.4.1. Temporary modification of the font path
The `xset' utility may be used to modify the font path for the current session. The font path is set with the command xset fp; a new element is added to the front with xset +fp, and added to the end with xset fp+. For example,
$ xset +fp /usr/local/fonts/Type1
$ xset fp+ /usr/local/fonts/bitmap
Conversely, an element may be removed from the front of the font path with `xset -fp', and removed from the end with `xset fp-'. You may reset the font path to its default value with `xset fp default'.
For more information, please consult the xset(1) manual page.
2.2.4.2. Permanent modification of the font path
The default font path (the one used just after server startup or after `xset fp default') is specified in the X server's `XF86Config' file. It is computed by appending all the directories mentioned in the `FontPath' entries of the `Files' section in the order in which they appear.
FontPath "/usr/local/fonts/Type1"
...
FontPath "/usr/local/fonts/bitmap"
For more information, please consult the XF86Config(5) manual page.
2.2.5. Troubleshooting
If you seem to be unable to use some of the fonts you have installed, the first thing to check is that the `fonts.dir' files are correct and that they are readable by the server (the X server usually runs as root, beware of NFS-mounted font directories). If this doesn't help, it is quite possible that you are trying to use a font in a format that is not supported by your server.
XFree86 supports the BDF, PCF, SNF, Type 1, Speedo, TrueType, OpenType and CIDFont font formats. However, not all XFree86 servers come with all the font backends configured in.
On most platforms, the XFree86 servers are modular: the font backends are included in modules that are loaded at runtime. The modules to be loaded are specified in the `XF86Config' file using the `Load' directive:
Load "type1"
If you have trouble installing fonts in a specific format, you may want to check the server's log file in order to see whether the relevant modules are properly loaded. The list of font modules distributed with XFree86 is as follows:
* "bitmap": bitmap fonts (`*.bdf', `*.pcf' and `*.snf');
* "freetype": TrueType fonts (`*.ttf' and `*.ttc'), OpenType fonts (`*.otf' and `*.otc') and Type 1 fonts (`*.pfa' and `*.pfb');
* "type1": alternate Type 1 backend (`*.pfa' and `*.pfb') and CIDFont backend;
* "xtt": alternate TrueType backend (`*.ttf' and `*.ttc');
* "speedo": Bitstream Speedo fonts (`*.spd').
Please note that the argument of the `Load' directive is case-sensitive. 3. Fonts included with XFree86
3.1. Standard bitmap fonts
The Sample Implementation of X11 (SI) comes with a large number of bitmap fonts, including the `fixed' family, and bitmap versions of Courier, Times, Helvetica and some members of the Lucida family. In the SI, these fonts are provided in the ISO 8859-1 encoding (ISO Latin Western-European).
In XFree86, a number of these fonts are provided in Unicode-encoded font files instead. At build time, these fonts are split into font files encoded according to legacy encodings, a process which allows us to provide the standard fonts in a number of regional encodings with no duplication of work.
For example, the font file
/usr/X11R6/lib/X11/fonts/misc/6x13.bdf
with XLFD
-misc-fixed-medium-r-semicondensed--13-120-75-75-c-60-iso10646-1
is a Unicode-encoded version of the standard `fixed' font with added support for the Latin, Greek, Cyrillic, Georgian, Armenian, IPA and other scripts plus numerous technical symbols. It contains over 2800 glyphs, covering all characters of ISO 8859 parts 1-5, 7-10, 13-15, as well as all European IBM and Microsoft code pages, KOI8, WGL4, and the repertoires of many other character sets.
This font is used at build time for generating the font files
6x13-ISO8859-1.bdf
6x13-ISO8859-2.bdf
...
6x13-ISO8859-15.bdf
6x13-KOI8-R.bdf
with respective XLFDs
-misc-fixed-medium-r-normal--13-120-75-75-c-60-iso8859-1
...
-misc-fixed-medium-r-normal--13-120-75-75-c-60-iso8859-15
-misc-fixed-medium-r-normal--13-120-75-75-c-60-koi8-r
The standard short name `fixed' is normally an alias for
-misc-fixed-medium-r-normal--13-120-75-75-c-60-iso8859-1
3.2. The ClearlyU Unicode font family
The ClearlyU family of fonts provides a set of 12 pt, 100 dpi proportional fonts with many of the glyphs needed for Unicode text. Together, the fonts contain approximately 7500 glyphs.
The main ClearlyU font has the XLFD
-mutt-clearlyu-medium-r-normal--17-120-100-100-p-101-iso10646-1
and resides in the font file
/usr/X11R6/lib/X11/fonts/misc/cu12.pcf.gz
Additional ClearlyU fonts include
-mutt-clearlyu alternate glyphs-medium-r-normal--17-120-100-100-p-91-iso10646-1
-mutt-clearlyu pua-medium-r-normal--17-120-100-100-p-111-iso10646-1
-mutt-clearlyu arabic extra-medium-r-normal--17-120-100-100-p-103-fontspecific-0
-mutt-clearlyu ligature-medium-r-normal--17-120-100-100-p-141-fontspecific-0
The Alternate Glyphs font contains additional glyph shapes that are needed for certain languages. A second alternate glyph font will be provided later for cases where a character has more than one commonly used alternate shape (e.g. the Urdu heh).
The PUA font contains extra glyphs that are useful for certain rendering purposes.
The Arabic Extra font contains the glyphs necessary for characters that don't have all of their possible shapes encoded in ISO 10646. The glyphs are roughly ordered according to the order of the characters in the ISO 10646 standard.
The Ligature font contains ligatures for various scripts that may be useful for improved presentation of text.
3.3. Standard scalable fonts
XFree86 includes all the scalable fonts distributed with X11R6.
3.3.1. Standard Type 1 fonts
The IBM Courier set of fonts cover ISO 8859-1 and ISO 8859-2 as well as Adobe Standard Encoding. These fonts have XLFD
-adobe-courier-medium-*-*--0-0-0-0-m-0-*-*
and reside in the font files
/usr/X11R6/lib/X11/fonts/Type1/cour*.pfa
The Adobe Utopia set of fonts only cover ISO 8859-1 as well as Adobe Standard Encoding. These fonts have XLFD
-adobe-utopia-*-*-normal--0-0-0-0-p-0-iso8859-1
and reside in the font files
/usr/X11R6/lib/X11/fonts/Type1/UT*.pfa
Finally, XFree86 also comes with Type 1 versions of Bitstream Courier and Charter. These fonts have XLFD
-bitstream-courier-*-*-normal--0-0-0-0-m-0-iso8859-1
-bitstream-charter-*-*-normal--0-0-0-0-p-0-iso8859-1
and reside in the font files
/usr/X11R6/lib/X11/fonts/Type1/c*bt_.pfb
3.3.2. Standard Speedo fonts
XFree86 includes Speedo versions of the Bitstream Courier and Charter fonts. In order to use these fonts, you should ensure that your X server is loading the `Speedo' font backend; see Troubleshooting.
These fonts cover all of ISO 8859-1 and almost all of ISO 8859-2. They have XLFD name
-bitstream-courier-*-*-normal--0-0-0-0-m-0-*-*
-bitstream-charter-*-*-normal--0-0-0-0-p-0-*-*
and reside in the font files
/usr/X11R6/lib/X11/fonts/Speedo/font*.spd
3.4. The Bigelow & Holmes Luxi family
XFree86 includes the Luxi family of scalable fonts, in both TrueType and Type 1 format. This family consists of the fonts Luxi Serif, with XLFD
-b&h-luxi serif-medium-*-normal--*-*-*-*-p-*-*-*
Luxi Sans, with XLFD
-b&h-luxi sans-medium-*-normal--*-*-*-*-p-*-*-*
and Luxi Mono, with XLFD
-b&h-luxi mono-medium-*-normal--*-*-*-*-m-*-*-*
Each of these fonts comes Roman, oblique, bold and bold oblique variants The TrueType version have glyphs covering the basic ASCII Unicode range, the Latin 1 range, as well as the Extended Latin range and some additional punctuation characters. In particular, these fonts include all the glyphs needed for ISO 8859 parts 1, 2, 3, 4, 9, 13 and 15, as well as all the glyphs in the Adobe Standard encoding and the Windows 3.1 character set.
The glyph coverage of the Type 1 versions is somewhat reduced, and only covers ISO 8859 parts 1, 2 and 15 as well as the Adobe Standard encoding.
The Luxi fonts are original designs by Kris Holmes and Charles Bigelow. Luxi fonts include seriffed, sans serif, and monospaced styles, in roman and oblique, and normal and bold weights. The fonts share stem weight, x-height, capital height, ascent and descent, for graphical harmony.
The character width metrics of Luxi roman and bold fonts match those of core fonts bundled with popular operating and window systems.
The license terms for the Luxi fonts are included in the file `COPYRIGHT.BH', as well as in the License document.
Charles Bigelow and Kris Holmes from Bigelow and Holmes Inc. developed the Luxi typeface designs in Ikarus digital format.
URW++ Design and Development GmbH converted the Ikarus format fonts to TrueType and Type1 font programs and implemented the grid-fitting "hints" and kerning tables in the Luxi fonts.
For more information, please contact [email protected] or [email protected] , or consult the URW++ web site.
An earlier version of the Luxi fonts was made available under the name Lucidux. This name should no longer be used due to trademark uncertainties, and all traces of the Lucidux name have been removed from XFree86. up 4. More about core fonts
This section describes XFree86-specific enhancements to the core X11 fonts system.
4.1. Core fonts and internationalisation
The scalable font backends (Type 1, Speedo and TrueType) can automatically re-encode fonts to the encoding specified in the XLFD in `fonts.dir'. For example, a `fonts.dir' file can contain entries for the Type 1 Courier font such as
cour.pfa -adobe-courier-medium-r-normal--0-0-0-0-m-0-iso8859-1
cour.pfa -adobe-courier-medium-r-normal--0-0-0-0-m-0-iso8859-2
which will lead to the font being recoded to ISO 8859-1 and ISO 8859-2 respectively.
4.1.1. The fontenc layer
Three of the scalable backends (Type 1, Speedo, and the FreeType TrueType backend) use a common fontenc layer for font re-encoding. This allows these backends to share their encoding data, and allows simple configuration of new locales independently of font type.
Please note: the X-TrueType (X-TT) backend does not use the fontenc layer, but instead uses its own method for font reencoding. If you are only interested in X-TT you may want to skip to Using Symbol Fonts, as the intervening information does not apply to X-TT. X-TT itself is described in more detail in X-TrueType.
In the fontenc layer, an encoding is defined by a name (such as iso8859-1), possibly a number of aliases (alternate names), and an ordered collection of mappings. A mapping defines the way the encoding can be mapped into one of the target encodings known to fontenc; currently, these consist of Unicode, Adobe glyph names, and arbitrary TrueType ``cmap''s.
A number of encodings are hardwired into fontenc, and are therefore always available; the hardcoded encodings cannot easily be redefined. These include:
* iso10646-1: Unicode;
* iso8859-1: ISO Latin-1 (Western Europe);
* iso8859-2: ISO Latin-2 (Eastern Europe);
* iso8859-3: ISO Latin-3 (Southern Europe);
* iso8859-4: ISO Latin-4 (Northern Europe);
* iso8859-5: ISO Cyrillic;
* iso8859-6: ISO Arabic;
* iso8859-7: ISO Greek;
* iso8859-8: ISO Hebrew;
* iso8859-9: ISO Latin-5 (Turkish);
* iso8859-10: ISO Latin-6 (Nordic);
* iso8859-15: ISO Latin-9, or Latin-0 (Revised Western-European);
* koi8-r: KOI8 Russian;
* koi8-u: KOI8 Ukrainian (see RFC 2319);
* koi8-ru: KOI8 Russian/Ukrainian;
* koi8-uni: KOI8 ``Unified'' (Russian, Ukrainian, and Byelorussian);
* koi8-e: KOI8 ``European,'' ISO-IR-111, or ECMA-Cyrillic;
* microsoft-symbol and apple-roman: these are only likely to be useful with TrueType symbol fonts.
Additional encodings can be added by defining encoding files. When a font encoding is requested that the fontenc layer doesn't know about, the backend checks the directory in which the font file resides (not necessarily the directory with fonts.dir!) for a file named `encodings.dir'. If found, this file is scanned for the requested encoding, and the relevant encoding definition file is read in. The `mkfontdir' utility, when invoked with the `-e' option followed by the name of a directory containing encoding files, can be used to automatically build `encodings.dir' files. Please see the mkfontdir(1) manual page for more details.
A number of encoding files for common encodings are included with XFree86. Information on writing new encoding files can be found in Format of encodings directory files and Format of encoding files later in this document.
4.1.2. Backend-specific notes about fontenc
4.1.2.1. The FreeType backend
For TrueType and OpenType fonts, the FreeType backend scans the mappings in order. Mappings with a target of PostScript are ignored; mappings with a TrueType or Unicode target are checked against all the cmaps in the file. The first applicable mapping is used.
For Type 1 fonts, the FreeType backend first searches for a mapping with a target of PostScript. If one is found, it is used. Otherwise, the backend searches for a mapping with target Unicode, which is then composed with a built-in table mapping codes to glyph names. Note that this table only covers part of the Unicode code points that have been assigned names by Adobe.
Specifying an encoding value of adobe-fontspecific for a Type 1 font disables the encoding mechanism. This is useful with symbol and incorrectly encoded fonts (see Incorrectly encoded fonts below).
If a suitable mapping is not found, the FreeType backend defaults to ISO 8859-1.
4.1.2.2. Type 1
The Type 1 backend behaves similarly to the FreeType backend with Type 1 fonts, except that it limits all encodings to 8-bit codes.
4.1.2.3. Speedo1
The Speedo backend searches for a mapping with a target of Unicode, and uses it if found. If none is found, the backend defaults to ISO 8859-1.
The Speedo backend limits all encodings to 8-bit codes.
4.1.3. Format of encoding directory files
In order to use a font in an encoding that the font backend does not know about, you need to have an `encodings.dir' file either in the same directory as the font file used or in a system-wide location (`/usr/X11R6/lib/X11/fonts/encodings/' by default).
The `encodings.dir' file has a similar format to `fonts.dir'. Its first line specifies the number of encodings, while every successive line has two columns, the name of the encoding, and the name of the encoding file; this can be relative to the current directory, or absolute. Every encoding name should agree with the encoding name defined in the encoding file. For example,
3
mulearabic-0 /usr/X11R6/lib/X11/fonts/encodings/mulearabic-0.enc
mulearabic-1 /usr/X11R6/lib/X11/fonts/encodings/mulearabic-1.enc
mulearabic-2 /usr/X11R6/lib/X11/fonts/encodings/mulearabic-2.enc
The name of an encoding must be specified in the encoding file's `STARTENCODING' or `ALIAS' line. It is not enough to create an `encodings.dir' entry.
If your platform supports it (it probably does), encoding files may be compressed or gzipped.
The `encoding.dir' files are best maintained by the `mkfontdir' utility. Please see the mkfontdir(1) manual page for more information.
4.1.4. Format of encoding files
The encoding files are ``free form,'' i.e. any string of whitespace is equivalent to a single space. Keywords are parsed in a non-case-sensitive manner, meaning that `size', `SIZE', and `SiZE' all parse as the same keyword; on the other hand, case is significant in glyph names.
Numbers can be written in decimal, as in `256', in hexadecimal, as in `0x100', or in octal, as in `0400'.
Comments are introduced by a hash sign `#'. A `#' may appear at any point in a line, and all characters following the `#' are ignored, up to the end of the line.
The encoding file starts with the definition of the name of the encoding, and possibly its alternate names (aliases):
STARTENCODING mulearabic-0
ALIAS arabic-0
The name of the encoding and its aliases should be suitable for use in an XLFD font name, and therefore contain exactly one dash `-'.
The encoding file may then optionally declare the size of the encoding. For a linear encoding (such as ISO 8859-1), the SIZE line specifies the maximum code plus one:
SIZE 0x2B
For a matrix encoding, it should specify two numbers. The first is the number of the last row plus one, the other, the highest column number plus one. In the case of `jisx0208.1990-0' (JIS X 0208(1990), double-byte encoding, high bit clear), it should be
SIZE 0x75 0x80
In the case of a matrix encoding, a `FIRSTINDEX' line may be included to specify the minimum glyph index in an encoding. The keyword `FIRSTINDEX' is followed by two integers, the minimum row number followed by the minimum column number:
FIRSTINDEX 0x20 0x20
In the case of a linear encoding, a `FIRSTINDEX' line is not very useful. If for some reason however you chose to include on, it should be followed by a single integer.
Note that in most font backends inclusion of a `FIRSTINDEX' line has the side effect of disabling default glyph generation, and this keyword should therefore be avoided unless absolutely necessary.
Codes outside the region defined by the `SIZE' and `FIRSTINDEX' lines are understood to be undefined. Encodings default to linear encoding with a size of 256 (0x100). This means that you must declare the size of all 16 bit encodings.
What follows is one or more mapping sections. A mapping section starts with a `STARTMAPPING' line stating the target of the mapping. The target may be one of:
* Unicode (ISO 10646):
STARTMAPPING unicode
* a given TrueType ``cmap'':
STARTMAPPING cmap 3 1
* PostScript glyph names:
STARTMAPPING postscript
Every line in a mapping section maps one from the encoding being defined to the target of the mapping. In mappings with a Unicode or TrueType mapping, codes are mapped to codes:
0x21 0x0660
0x22 0x0661
...
As an abbreviation, it is possible to map a contiguous range of codes in a single line. A line consisting of three integers
<it/start/ <it/end/ <it/target/
is an abbreviation for the range of lines
start target
start+1 target+1
...
end target+end-start
For example, the line
0x2121 0x215F 0x8140
is an abbreviation for
0x2121 0x8140
0x2122 0x8141
...
0x215F 0x817E
Codes not listed are assumed to map through the identity (i.e. to the same numerical value). In order to override this default mapping, you may specify a range of codes to be undefined by using an `UNDEFINE' line:
UNDEFINE 0x00 0x2A
or, for a single code,
UNDEFINE 0x1234
PostScript mappings are different. Every line in a PostScript mapping maps a code to a glyph name
0x41 A
0x42 B
...
and codes not explicitly listed are undefined.
A mapping section ends with an ENDMAPPING line
ENDMAPPING
After all the mappings have been defined, the file ends with an ENDENCODING line
ENDENCODING
In order to make future extensions to the format possible, lines starting with an unknown keyword are silently ignored, as are mapping sections with an unknown target.
4.1.5. Using symbol fonts
Type 1 symbol fonts should be installed using the adobe-fontspecific encoding.
In an ideal world, all TrueType symbol fonts would be installed using one of the microsoft-symbol and apple-roman encodings. A number of symbol fonts, however, are not marked as such; such fonts should be installed using microsoft-cp1252, or, for older fonts, microsoft-win3.1.
In order to guarantee consistent results (especially between Type 1 and TrueType versions of the same font), it is possible to define a special encoding for a given font. This has already been done for the ZapfDingbats font; see the file `encodings/adobe-dingbats.enc'.
4.1.6. Hints about using badly encoded fonts
A number of text fonts are incorrectly encoded. Incorrect encoding is sometimes done by design, in order to make a font for an exotic script appear like an ordinary Western text font on systems which are not easily extended with new locale data. It is often the result of the font designer's laziness or incompetence; for some reason, most people seem to find it easier to invent idiosyncratic glyph names rather than follow the Adobe glyph list.
There are two ways of dealing with such fonts: using them with the encoding they were designed for, and creating an ad hoc encoding file.
4.1.6.1. Using fonts with the designer's encoding
In the case of Type 1 fonts, the font designer can specify a default encoding; this encoding is requested by using the `adobe-fontspecific' encoding in the XLFD name. Sometimes, the font designer omitted to specify a reasonable default encoding, in which case you should experiment with `adobe-standard', `iso8859-1', `microsoft-cp1252', and `microsoft-win3.1'. (The encoding `microsoft-symbol' doesn't make sense for Type 1 fonts).
TrueType fonts do not have a default encoding. However, most TrueType fonts are designed with either Microsoft or Apple platforms in mind, so one of `microsoft-symbol', `microsoft-cp1252', `microsoft-win3.1', or `apple-roman' should yield reasonable results.
4.1.6.2. Specifying an ad hoc encoding file
It is always possible to define an encoding file to put the glyphs in a font in any desired order. Again, see the `encodings/adobe-dingbats.enc' file to see how this is done.
4.1.6.3. Specifying font aliases
By following the directions above, you will find yourself with a number of fonts with unusual names --- with encodings such as `adobe-fontspecific', `microsoft-win3.1' etc. In order to use these fonts with standard applications, it may be useful to remap them to their proper names.
This is done by writing a `fonts.alias' file. The format of this file is very simple: it consists of a series of lines each mapping an alias name to a font name. A `fonts.alias' file might look as follows:
"-ogonki-alamakota-medium-r-normal--0-0-0-0-p-0-iso8859-2" \
"-ogonki-alamakota-medium-r-normal--0-0-0-0-p-0-adobe-fontspecific"
(both XLFD names on a single line). The syntax of the `fonts.alias' file is more precisely described in the mkfontdir(1) manual page.
4.2. Additional notes about scalable core fonts
The FreeType (libfreetype-xtt2) backend (module `freetype', formerly known as xfsft) is able to deal with both TrueType and Type 1 fonts. This puts it in conflict with the X-TT and Type 1 backends respectively.
If both the FreeType and the Type 1 backends are loaded, the FreeType backend will be used for Type 1 fonts. If both the FreeType and X-TT backends are loaded, X-TT will be used for TrueType fonts.
4.2.1. About the FreeType backend
The FreeType (libfreetype-xtt2) backend (formerly xfsft) is a backend based on version 2 of the FreeType library (see the FreeType web site) and has the X-TT functionalities for CJKV support provided by the After X-TT Project (see the After X-TT Project web site). The FreeType module has support for the ``fontenc'' style of internationalisation (see The fontenc layer). This backend supports TrueType font files (`*.ttf'), OpenType font files (`*.otf'), TrueType Collections (`*.ttc'), OpenType Collections (`*.otc') and Type 1 font files (`*.pfa' and `*.pfb').
In order to access the faces in a TrueType Collection file, the face number must be specified in the fonts.dir file before the filename, within a pair of colons, or by setting the 'fn' TTCap option. For example,
:1:mincho.ttc -misc-pmincho-medium-r-normal--0-0-0-0-p-0-jisx0208.1990-0
refers to face 1 in the `mincho.ttc' TrueType Collection file.
The new FreeType backend supports the extended `fonts.dir' syntax introduced by X-TrueType with a number of options, collectively known as `TTCap'. A `TTCap' entry follows the general syntax
option=value:
and should be specified before the filename. The new FreeType almost perfectly supports TTCap options that are compatible with X-TT 1.4. The Automatic Italic (`ai'), Double Strike (`ds') and Bounding box Width (`bw') options are indispensable in CJKV. For example,
mincho.ttc -misc-mincho-medium-r-normal--0-0-0-0-c-0-jisx0208.1990-0
ds=y:mincho.ttc -misc-mincho-bold-r-normal--0-0-0-0-c-0-jisx0208.1990-0
ai=0.2:mincho.ttc -misc-mincho-medium-i-normal--0-0-0-0-c-0-jisx0208.1990-0
ds=y:ai=0.2:mincho.ttc -misc-mincho-bold-i-normal--0-0-0-0-c-0-jisx0208.1990-0
bw=0.5:mincho.ttc -misc-mincho-medium-r-normal--0-0-0-0-c-0-jisx0201.1976-0
bw=0.5:ds=y:mincho.ttc -misc-mincho-bold-r-normal--0-0-0-0-c-0-jisx0201.1976-0
bw=0.5:ai=0.2:mincho.ttc -misc-mincho-medium-i-normal--0-0-0-0-c-0-jisx0201.1976-0
bw=0.5:ds=y:ai=0.2:mincho.ttc -misc-mincho-bold-i-normal--0-0-0-0-c-0-jisx0201.1976-0
setup the complete combination of jisx0208 and jisx0201 using mincho.ttc only. More information on the TTCap syntax is found on the After X-TT Project page.
The FreeType backend uses the fontenc layer in order to support recoding of fonts; this was described in The fontenc layer and especially FreeType-specific notes about fontenc earlier in this document.
4.2.2. About the X-TrueType TrueType backend
The `X-TrueType' backend is a backend based on version 1 of the FreeType library. X-TrueType doesn't use the `fontenc' layer for managing font encodings, but instead uses its own database of encodings.
Since the functionalities for CJKV support introduced by X-TT have been merged into the new FreeType backend, the X-TT backend will be removed from XFree86's tree near the future. Therefore, the use of FreeType backend is preferred over the X-TT backend.
General information on X-TrueType may be found at the After X-TT Project page.
4.2.3. Delayed glyph rasterisation
When loading a proportional fonts which contain a huge number of glyphs, the old FreeType delayed glyph rasterisation until the time at which the glyph was first used. The new FreeType (libfreetype-xtt2) has an improved `very lazy' metric calculation method to speed up the process when loading TrueType or OpenType fonts. Although the X-TT module also has this method, the "vl=y" TTCap option must be set if you want to use it. This is the default method for FreeType when it loads multi-byte fonts. Even if you use a unicode font which has tens of thousands of glyphs, this delay will not be worrisome as long as you use the new FreeType backend -- its `very lazy' method is super-fast.
The maximum error of bitmap position using `very lazy' method is 1 pixel, and is the same as that of a character-cell spacing. When the X-TT backend is used with the `vl=y' option, a chipped bitmap is displayed with certain fonts. However, the new FreeType backend has minimal problem with this, since it corrects left- and right-side bearings using `italicAngle' in the TrueType/OpenType post table, and does automatic correction of bitmap positions when rasterisation so that chipped bitmaps are not displayed. Nevertheless if you don't want to use the `very lazy' method when using multi-bytes fonts, set `vl=n' in the TTCap option to disable it:
vl=n:luxirr.ttf -b&h-Luxi Serif-medium-r-normal--0-0-0-0-p-0-iso10646-1
Of course, both backends also support an optimisation for character-cell fonts (fonts with all glyph metrics equal, or terminal fonts). A font with an XLFD specifying a character-cell spacing `c', as in
-misc-mincho-medium-r-normal--0-0-0-0-c-0-jisx0208.1990-0
or
fs=c:mincho.ttc -misc-mincho-medium-r-normal--0-0-0-0-p-0-jisx0208.1990-0
will not compute the metric for each glyph, but instead trust the font to be a character-cell font. You are encouraged to make use of this optimisation when useful, but be warned that not all monospaced fonts are character-cell fonts. 5. Appendix: background and terminology
5.1. Characters and glyphs
A computer text-processing system inputs keystrokes and outputs glyphs, small pictures that are assembled on paper or on a computer screen. Keystrokes and glyphs do not, in general, coincide: for example, if the system does generate ligatures, then to the sequence of two keystrokes <f><i> will typically correspond a single glyph. Similarly, if the system shapes Arabic glyphs in a vaguely reasonable manner, then multiple different glyphs may correspond to a single keystroke.
The complex transformation rules from keystrokes to glyphs are usually factored into two simpler transformations, from keystrokes to characters and from characters to glyphs. You may want to think of characters as the basic unit of text that is stored e.g. in the buffer of your text editor. While the definition of a character is intrinsically application-specific, a number of standardised collections of characters have been defined.
A coded character set is a set of characters together with a mapping from integer codes --- known as codepoints --- to characters. Examples of coded character sets include US-ASCII, ISO 8859-1, KOI8-R, and JIS X 0208(1990).
A coded character set need not use 8 bit integers to index c
5.2. Font files, fonts, and XLFD
Traditionally, typographers speak about typefaces and founts. A typeface is a particular style or design, such as Times Italic, while a fount is a molten-lead incarnation of a given typeface at a given size.
Digital fonts come in font files. A font file contains the information necessary for generating glyphs of a given typeface, and applications using font files may access glyph information in an arbitrary order.
Digital fonts may consist of bitmap data, in which case they are said to be bitmap fonts. They may also consist of a mathematical description of glyph shapes, in which case they are said to be scalable fonts. Common formats for scalable font files are Type 1 (sometimes incorrectly called ATM fonts or PostScript fonts), TrueType and Speedo.
The glyph data in a digital font needs to be indexed somehow. How this is done depends on the font file format. In the case of Type 1 fonts, glyphs are identified by glyph names. In the case of TrueType fonts, glyphs are indexed by integers corresponding to one of a number of indexing schemes (usually Unicode --- see below).
The X11 core fonts system uses the data in a font file to generate font instances, which are collections of glyphs at a given size indexed according to a given encoding.
X11 core font instances are usually specified using a notation known as the X Logical Font Description (XLFD). An XLFD starts with a dash `-', and consists of fourteen fields separated by dashes, for example:
-adobe-courier-medium-r-normal--12-120-75-75-m-70-iso8859-1
Or particular interest are the last two fields `iso8859-1', which specify the font instance's encoding.
A scalable font is specified by an XLFD which contains zeroes instead of some fields:
-adobe-courier-medium-r-normal--0-0-0-0-m-0-iso8859-1
X11 font instances may also be specified by short name. Unlike an XLFD, a short name has no structure and is simply a conventional name for a font instance. Two short names are of particular interest, as the server will not start if font instances with these names cannot be opened. These are `fixed', which specifies the fallback font to use when the requested font cannot be opened, and `cursor', which specifies the set of glyphs to be used by the mouse pointer.
Short names are usually implemented as aliases to XLFDs; the standard `fixed' and `cursor' aliases are defined in
/usr/X11R6/lib/X11/font/misc/fonts.alias
5.3. Unicode
Unicode (http://www.unicode.org) is a coded character set with the goal of uniquely identifying all characters for all scripts, current and historical. While Unicode was explicitly not designed as a glyph encoding scheme, it is often possible to use it as such.
Unicode is an open character set, meaning that codepoint assignments may be added to Unicode at any time (once specified, though, an assignment can never be changed). For this reason, a Unicode font will be sparse, meaning that it only defines glyphs for a subset of the character registry of Unicode.
The Unicode standard is defined in parallel with the international standard ISO 10646. Assignments in the two standards are always equivalent, and we often use the terms Unicode and ISO 10646 interchangeably.
When used in the X11 core fonts system, Unicode-encoded fonts should have the last two fields of their XLFD set to `iso10646-1'. 6. References
XFree86 comes with extensive documentation in the form of manual pages and typeset documents. Before installing fonts, you really should read the fontconfig(3) and mkfontdir(1) manual pages; other manual pages of interest include X(7), Xserver(1), xset(1), Xft(3), xlsfonts(1) and showfont(1). In addition, you may want to read the X Logical Font Description document, by Jim Flowers, which is provided in the file `xc/doc/xlfd.PS.Z'.
The latest released version of the XFree86 documentation (including this document and all manual pages) is available as current XFree86 documentation.
The comp.fonts FAQ, which is unfortunately no longer being maintained, contains a wealth of information about digital fonts.
Xft and Fontconfig are described on Keith Packard's Fontconfig site.
The xfsft home page has been superseded by this document, and is now obsolete; you may however still find some of the information that it contains useful. Joerg Pommnitz' xfsft page is the canonical source for the `ttmkfdir' utility, which is the ancestor of mkfontscale.
The author's software pages might or might not contain related scribbles and development versions of software.
The documentation of X-TrueType is available from the After X-TT Project page.
A number of East-Asian CIDFonts are available from O'Reilly's FTP site.
While the Unicode consortium site may be of interest, you are more likely to find what you need in Markus Kuhn's UTF-8 and Unicode FAQ.
The IANA RFC documents, available from a number of sites throughout the world, often provide interesting information about character set issues; see for example RFC 373. 大家最好还是看原文，我拷贝来的时候没怎么排版。
可能有的人要问，你为什么要拷贝过来，而不是直接给链接呢
因为我以前贴过很多次，怀疑根本没人去看，这样洋洋大观一把或许会吸引人看。
可能有人要要问，全是英文的，我英文不好，能不能给汉语的
我是没功夫翻译，不知道会不会有人有。我的意见是，这个世界上很多东西都是英文的，毕竟人家先进。我以前也不喜欢读英文文档，后来我发现，要真正理解LINUX，必须掌握好英文这个工具。其实在其它很多地方也一样，英文是个必备工具。
可能有人要问为什么贴这篇文章
希望大家能了解字体的原理，而不是每次新的发行版出来后就去找或者等待“美化包”，可能有意想不到的损失不说，还受制于人。应该自己动手制作字体或者“借”字体就可以搞定，像wxz8和cnhnln那样。
可能有人要问，我实在看不懂怎么办
我的意见是，再看一遍或者很多遍，再google相关资料，总会看懂的。 一些参考链接：
Xft - the X Font library
The Next XFree86 Wars: XFT2 vs STSF
XFree86 Font De-uglification HOWTO 大家平时所说的美化，无非就是使用PP的TrueType字体。
个人推荐的“美化”参考：
另类美好方法（通过制作字体来达到目的）
修改ttf字体实现中文粗斜体
XFree86这两种字体系统以及后面还将提到的字体服务器（如Redhat的XFS）都不太成熟，对汉字的粗体、粗斜体支持的不好，当然可以通过打firefly的补丁或者等它们成熟来搞定这些问题（:mrgreen: ），但是我觉得还是wxz8的另类方法比较好。 请斑竹授精 :mrgreen:
我感觉TrueType没有位图字体显示快，特别是当添加的字体很多的时候 请斑竹授精 :mrgreen:
我感觉TrueType没有位图字体显示快，特别是当添加的字体很多的时候
准！
这个我还没有觉出来 拜托，还有X Font Servers这篇也该进精华区的，否则我要介绍的内容就不完整了。
当然我可能有理解错误的地方，希望大家来完善。
“授之以鱼不如授之以渔”一直是我提倡的思想。
也希望这两篇文章能使这里变成寻求字体下载地址的地方，而不是个“美化”来“美化”去的地方，也希望众多新手不再成为别人练习SHELL编程的工具。 :mrgreen: 拜托，还有X Font Servers这篇也该进精华区的，否则我要介绍的内容就不完整了。
当然我可能有理解错误的地方，希望大家来完善。
“授之以鱼不如授之以渔”一直是我提倡的思想。
也希望这两篇文章能使这里变成寻求字体下载地址的地方，而不是个“美化”来“美化”去的地方，也希望众多新手不再成为别人练习SHELL编程的工具。 :mrgreen:
精华le！
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