302 lines
12 KiB
Plaintext
302 lines
12 KiB
Plaintext
/*
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* fontconfig/doc/fcformat.fncs
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*
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* Copyright © 2008 Behdad Esfahbod
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*
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* Permission to use, copy, modify, distribute, and sell this software and its
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* documentation for any purpose is hereby granted without fee, provided that
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* the above copyright notice appear in all copies and that both that
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* copyright notice and this permission notice appear in supporting
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* documentation, and that the name of Keith Packard not be used in
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* advertising or publicity pertaining to distribution of the software without
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* specific, written prior permission. Keith Packard makes no
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* representations about the suitability of this software for any purpose. It
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* is provided "as is" without express or implied warranty.
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*
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* THE AUTHOR(S) DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
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* INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
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* EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY SPECIAL, INDIRECT OR
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* CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
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* DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
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* TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
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* PERFORMANCE OF THIS SOFTWARE.
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*/
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@RET@ FcChar8 *
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@FUNC@ FcPatternFormat
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@TYPE1@ FcPattern * @ARG1@ pat
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@TYPE2@ const FcChar8 * @ARG2@ format
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@PURPOSE@ Format a pattern into a string according to a format specifier
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@DESC@
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Converts given pattern <parameter>pat</parameter> into text described by
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the format specifier <parameter>format</parameter>.
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The return value refers to newly allocated memory which should be freed by the
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caller using free(), or NULL if <parameter>format</parameter> is invalid.
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</para><para>
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The format is loosely modelled after printf-style format string.
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The format string is composed of zero or more directives: ordinary
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characters (not "%"), which are copied unchanged to the output stream;
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and tags which are interpreted to construct text from the pattern in a
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variety of ways (explained below).
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Special characters can be escaped
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using backslash. C-string style special characters like \n and \r are
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also supported (this is useful when the format string is not a C string
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literal).
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It is advisable to always escape curly braces that
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are meant to be copied to the output as ordinary characters.
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</para><para>
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Each tags is introduced by the character "%",
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followed by an optional minimum field width,
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followed by tag contents in curly braces ({}).
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If the minimum field width value is provided the tag
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will be expanded and the result padded to achieve the minimum width.
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If the minimum field width is positive, the padding will right-align
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the text. Negative field width will left-align.
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The rest of this section describes various supported tag contents
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and their expansion.
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</para><para>
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A <firstterm>simple</firstterm> tag
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is one where the content is an identifier. When simple
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tags are expanded, the named identifier will be looked up in
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<parameter>pattern</parameter> and the resulting list of values returned,
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joined together using comma. For example, to print the family name and style the
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pattern, use the format "%{family} %{style}\n". To extend the family column
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to forty characters use "%-40{family}%{style}\n".
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</para><para>
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Simple tags expand to list of all values for an element. To only choose
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one of the values, one can index using the syntax "%{elt[idx]}". For example,
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to get the first family name only, use "%{family[0]}".
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</para><para>
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If a simple tag ends with "=" and the element is found in the pattern, the
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name of the element followed by "=" will be output before the list of values.
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For example, "%{weight=}" may expand to the string "weight=80". Or to the empty
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string if <parameter>pattern</parameter> does not have weight set.
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</para><para>
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If a simple tag starts with ":" and the element is found in the pattern, ":"
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will be printed first. For example, combining this with the =, the format
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"%{:weight=}" may expand to ":weight=80" or to the empty string
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if <parameter>pattern</parameter> does not have weight set.
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</para><para>
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If a simple tag contains the string ":-", the rest of the the tag contents
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will be used as a default string. The default string is output if the element
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is not found in the pattern. For example, the format
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"%{:weight=:-123}" may expand to ":weight=80" or to the string
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":weight=123" if <parameter>pattern</parameter> does not have weight set.
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</para><para>
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A <firstterm>count</firstterm> tag
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is one that starts with the character "#" followed by an element
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name, and expands to the number of values for the element in the pattern.
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For example, "%{#family}" expands to the number of family names
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<parameter>pattern</parameter> has set, which may be zero.
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</para><para>
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A <firstterm>sub-expression</firstterm> tag
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is one that expands a sub-expression. The tag contents
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are the sub-expression to expand placed inside another set of curly braces.
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Sub-expression tags are useful for aligning an entire sub-expression, or to
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apply converters (explained later) on an entire sub-expression.
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For example, the format "%40{{%{family} %{style}}}" expands the sub-expression
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to construct the family name followed by the style, then takes the entire
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string and pads it on the left to be at least forty characters.
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</para><para>
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A <firstterm>filter-out</firstterm> tag
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is one starting with the character "-" followed by a
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comma-separated list of element names, followed by a sub-expression enclosed
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in curly braces. The sub-expression will be expanded but with a pattern that
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has the listed elements removed from it.
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For example, the format "%{-size,pixelsize{sub-expr}}" will expand "sub-expr"
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with <parameter>pattern</parameter> sans the size and pixelsize elements.
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</para><para>
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A <firstterm>filter-in</firstterm> tag
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is one starting with the character "+" followed by a
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comma-separated list of element names, followed by a sub-expression enclosed
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in curly braces. The sub-expression will be expanded but with a pattern that
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only has the listed elements from the surrounding pattern.
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For example, the format "%{+family,familylang{sub-expr}}" will expand "sub-expr"
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with a sub-pattern consisting only the family and family lang elements of
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<parameter>pattern</parameter>.
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</para><para>
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A <firstterm>conditional</firstterm> tag
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is one starting with the character "?" followed by a
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comma-separated list of element conditions, followed by two sub-expression
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enclosed in curly braces. An element condition can be an element name,
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in which case it tests whether the element is defined in pattern, or
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the character "!" followed by an element name, in which case the test
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is negated. The conditional passes if all the element conditions pass.
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The tag expands the first sub-expression if the conditional passes, and
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expands the second sub-expression otherwise.
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For example, the format "%{?size,dpi,!pixelsize{pass}{fail}}" will expand
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to "pass" if <parameter>pattern</parameter> has size and dpi elements but
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no pixelsize element, and to "fail" otherwise.
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</para><para>
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An <firstterm>enumerate</firstterm> tag
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is one starting with the string "[]" followed by a
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comma-separated list of element names, followed by a sub-expression enclosed
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in curly braces. The list of values for the named elements are walked in
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parallel and the sub-expression expanded each time with a pattern just having
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a single value for those elements, starting from the first value and
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continuing as long as any of those elements has a value.
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For example, the format "%{[]family,familylang{%{family} (%{familylang})\n}}"
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will expand the pattern "%{family} (%{familylang})\n" with a pattern
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having only the first value of the family and familylang elemtns, then expands
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it with the second values, then the third, etc.
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</para><para>
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As a special case, if an enumerate tag has only one element, and that element
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has only one value in the pattern, and that value is of type FcLangSet, the
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individual languages in the language set are enumerated.
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</para><para>
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A <firstterm>builtin</firstterm> tag
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is one starting with the character "=" followed by a builtin
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name. The following builtins are defined:
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<variablelist>
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<varlistentry><term>
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unparse
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</term><listitem><para>
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Expands to the result of calling FcNameUnparse() on the pattern.
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</para></listitem></varlistentry>
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<varlistentry><term>
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fcmatch
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</term><listitem><para>
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Expands to the output of the default output format of the fc-match
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command on the pattern, without the final newline.
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</para></listitem></varlistentry>
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<varlistentry><term>
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fclist
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</term><listitem><para>
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Expands to the output of the default output format of the fc-list
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command on the pattern, without the final newline.
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</para></listitem></varlistentry>
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<varlistentry><term>
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pkgkit
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</term><listitem><para>
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Expands to the list of PackageKit font() tags for the pattern.
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Currently this includes tags for each family name, and each language
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from the pattern, enumerated and sanitized into a set of tags terminated
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by newline. Package management systems can use these tags to tag their
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packages accordingly.
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</para></listitem></varlistentry>
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</variablelist>
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For example, the format "%{+family,style{%{=unparse}}}\n" will expand
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to an unparsed name containing only the family and style element values
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from <parameter>pattern</parameter>.
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</para><para>
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The contents of any tag can be followed by a set of zero or more
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<firstterm>converter</firstterm>s. A converter is specified by the
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character "|" followed by the converter name and arguments. The
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following converters are defined:
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<variablelist>
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<varlistentry><term>
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basename
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</term><listitem><para>
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Replaces text with the results of calling FcStrBasename() on it.
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</para></listitem></varlistentry>
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<varlistentry><term>
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dirname
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</term><listitem><para>
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Replaces text with the results of calling FcStrDirname() on it.
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</para></listitem></varlistentry>
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<varlistentry><term>
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downcase
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</term><listitem><para>
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Replaces text with the results of calling FcStrDowncase() on it.
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</para></listitem></varlistentry>
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<varlistentry><term>
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shescape
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</term><listitem><para>
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Escapes text for one level of shell expansion.
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(Escapes single-quotes, also encloses text in single-quotes.)
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</para></listitem></varlistentry>
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<varlistentry><term>
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cescape
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</term><listitem><para>
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Escapes text such that it can be used as part of a C string literal.
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(Escapes backslash and double-quotes.)
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</para></listitem></varlistentry>
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<varlistentry><term>
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xmlescape
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</term><listitem><para>
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Escapes text such that it can be used in XML and HTML.
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(Escapes less-than, greater-than, and ampersand.)
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</para></listitem></varlistentry>
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<varlistentry><term>
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delete(<parameter>chars</parameter>)
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</term><listitem><para>
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Deletes all occurrences of each of the characters in <parameter>chars</parameter>
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from the text.
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FIXME: This converter is not UTF-8 aware yet.
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</para></listitem></varlistentry>
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<varlistentry><term>
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escape(<parameter>chars</parameter>)
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</term><listitem><para>
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Escapes all occurrences of each of the characters in <parameter>chars</parameter>
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by prepending it by the first character in <parameter>chars</parameter>.
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FIXME: This converter is not UTF-8 aware yet.
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</para></listitem></varlistentry>
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<varlistentry><term>
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translate(<parameter>from</parameter>,<parameter>to</parameter>)
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</term><listitem><para>
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Translates all occurrences of each of the characters in <parameter>from</parameter>
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by replacing them with their corresponding character in <parameter>to</parameter>.
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If <parameter>to</parameter> has fewer characters than
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<parameter>from</parameter>, it will be extended by repeating its last
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character.
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FIXME: This converter is not UTF-8 aware yet.
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</para></listitem></varlistentry>
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</variablelist>
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For example, the format "%{family|downcase|delete( )}\n" will expand
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to the values of the family element in <parameter>pattern</parameter>,
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lower-cased and with spaces removed.
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@@
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