cairo-user-fonts.xml [plain text]
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<refentry id="cairo-User-Fonts">
<refmeta>
<refentrytitle role="top_of_page" id="cairo-User-Fonts.top_of_page">User Fonts</refentrytitle>
<manvolnum>3</manvolnum>
<refmiscinfo>
CAIRO Library
</refmiscinfo>
</refmeta>
<refnamediv>
<refname>User Fonts</refname>
<refpurpose>Font support with font data provided by the user</refpurpose>
</refnamediv>
<refsynopsisdiv id="cairo-User-Fonts.synopsis" role="synopsis">
<title role="synopsis.title">Synopsis</title>
<synopsis>#define <link linkend="CAIRO-HAS-USER-FONT:CAPS">CAIRO_HAS_USER_FONT</link>
<link linkend="cairo-status-t"><returnvalue>cairo_status_t</returnvalue></link> (<link linkend="cairo-user-scaled-font-init-func-t">*cairo_user_scaled_font_init_func_t</link>)
(<parameter><link linkend="cairo-scaled-font-t"><type>cairo_scaled_font_t</type></link> *scaled_font</parameter>,
<parameter><link linkend="cairo-t"><type>cairo_t</type></link> *cr</parameter>,
<parameter><link linkend="cairo-font-extents-t"><type>cairo_font_extents_t</type></link> *extents</parameter>);
<link linkend="cairo-status-t"><returnvalue>cairo_status_t</returnvalue></link> (<link linkend="cairo-user-scaled-font-render-glyph-func-t">*cairo_user_scaled_font_render_glyph_func_t</link>)
(<parameter><link linkend="cairo-scaled-font-t"><type>cairo_scaled_font_t</type></link> *scaled_font</parameter>,
<parameter><type>unsigned long </type> glyph</parameter>,
<parameter><link linkend="cairo-t"><type>cairo_t</type></link> *cr</parameter>,
<parameter><link linkend="cairo-text-extents-t"><type>cairo_text_extents_t</type></link> *extents</parameter>);
<link linkend="cairo-status-t"><returnvalue>cairo_status_t</returnvalue></link> (<link linkend="cairo-user-scaled-font-text-to-glyphs-func-t">*cairo_user_scaled_font_text_to_glyphs_func_t</link>)
(<parameter><link linkend="cairo-scaled-font-t"><type>cairo_scaled_font_t</type></link> *scaled_font</parameter>,
<parameter>const <link linkend="char"><type>char</type></link> *utf8</parameter>,
<parameter><link linkend="int"><type>int</type></link> utf8_len</parameter>,
<parameter><link linkend="cairo-glyph-t"><type>cairo_glyph_t</type></link> **glyphs</parameter>,
<parameter><link linkend="int"><type>int</type></link> *num_glyphs</parameter>,
<parameter><link linkend="cairo-text-cluster-t"><type>cairo_text_cluster_t</type></link> **clusters</parameter>,
<parameter><link linkend="int"><type>int</type></link> *num_clusters</parameter>,
<parameter><link linkend="cairo-text-cluster-flags-t"><type>cairo_text_cluster_flags_t</type></link> *cluster_flags</parameter>);
<link linkend="cairo-status-t"><returnvalue>cairo_status_t</returnvalue></link> (<link linkend="cairo-user-scaled-font-unicode-to-glyph-func-t">*cairo_user_scaled_font_unicode_to_glyph_func_t</link>)
(<parameter><link linkend="cairo-scaled-font-t"><type>cairo_scaled_font_t</type></link> *scaled_font</parameter>,
<parameter><type>unsigned long </type> unicode</parameter>,
<parameter>unsigned <link linkend="long"><type>long</type></link> *glyph_index</parameter>);
<link linkend="cairo-font-face-t"><returnvalue>cairo_font_face_t</returnvalue></link> * <link linkend="cairo-user-font-face-create">cairo_user_font_face_create</link> (<parameter><type>void</type></parameter>);
<link linkend="void"><returnvalue>void</returnvalue></link> <link linkend="cairo-user-font-face-set-init-func">cairo_user_font_face_set_init_func</link> (<parameter><link linkend="cairo-font-face-t"><type>cairo_font_face_t</type></link> *font_face</parameter>,
<parameter><link linkend="cairo-user-scaled-font-init-func-t"><type>cairo_user_scaled_font_init_func_t</type></link> init_func</parameter>);
<link linkend="cairo-user-scaled-font-init-func-t"><returnvalue>cairo_user_scaled_font_init_func_t</returnvalue></link> <link linkend="cairo-user-font-face-get-init-func">cairo_user_font_face_get_init_func</link>
(<parameter><link linkend="cairo-font-face-t"><type>cairo_font_face_t</type></link> *font_face</parameter>);
<link linkend="void"><returnvalue>void</returnvalue></link> <link linkend="cairo-user-font-face-set-render-glyph-func">cairo_user_font_face_set_render_glyph_func</link>
(<parameter><link linkend="cairo-font-face-t"><type>cairo_font_face_t</type></link> *font_face</parameter>,
<parameter><link linkend="cairo-user-scaled-font-render-glyph-func-t"><type>cairo_user_scaled_font_render_glyph_func_t</type></link> render_glyph_func</parameter>);
<link linkend="cairo-user-scaled-font-render-glyph-func-t"><returnvalue>cairo_user_scaled_font_render_glyph_func_t</returnvalue></link> <link linkend="cairo-user-font-face-get-render-glyph-func">cairo_user_font_face_get_render_glyph_func</link>
(<parameter><link linkend="cairo-font-face-t"><type>cairo_font_face_t</type></link> *font_face</parameter>);
<link linkend="void"><returnvalue>void</returnvalue></link> <link linkend="cairo-user-font-face-set-unicode-to-glyph-func">cairo_user_font_face_set_unicode_to_glyph_func</link>
(<parameter><link linkend="cairo-font-face-t"><type>cairo_font_face_t</type></link> *font_face</parameter>,
<parameter><link linkend="cairo-user-scaled-font-unicode-to-glyph-func-t"><type>cairo_user_scaled_font_unicode_to_glyph_func_t</type></link> unicode_to_glyph_func</parameter>);
<link linkend="cairo-user-scaled-font-unicode-to-glyph-func-t"><returnvalue>cairo_user_scaled_font_unicode_to_glyph_func_t</returnvalue></link> <link linkend="cairo-user-font-face-get-unicode-to-glyph-func">cairo_user_font_face_get_unicode_to_glyph_func</link>
(<parameter><link linkend="cairo-font-face-t"><type>cairo_font_face_t</type></link> *font_face</parameter>);
<link linkend="void"><returnvalue>void</returnvalue></link> <link linkend="cairo-user-font-face-set-text-to-glyphs-func">cairo_user_font_face_set_text_to_glyphs_func</link>
(<parameter><link linkend="cairo-font-face-t"><type>cairo_font_face_t</type></link> *font_face</parameter>,
<parameter><link linkend="cairo-user-scaled-font-text-to-glyphs-func-t"><type>cairo_user_scaled_font_text_to_glyphs_func_t</type></link> text_to_glyphs_func</parameter>);
<link linkend="cairo-user-scaled-font-text-to-glyphs-func-t"><returnvalue>cairo_user_scaled_font_text_to_glyphs_func_t</returnvalue></link> <link linkend="cairo-user-font-face-get-text-to-glyphs-func">cairo_user_font_face_get_text_to_glyphs_func</link>
(<parameter><link linkend="cairo-font-face-t"><type>cairo_font_face_t</type></link> *font_face</parameter>);
</synopsis>
</refsynopsisdiv>
<refsect1 id="cairo-User-Fonts.description" role="desc">
<title role="desc.title">Description</title>
<para>
The user-font feature allows the cairo user to provide drawings for glyphs
in a font. This is most useful in implementing fonts in non-standard
formats, like SVG fonts and Flash fonts, but can also be used by games and
other application to draw "funky" fonts.
</para>
</refsect1>
<refsect1 id="cairo-User-Fonts.details" role="details">
<title role="details.title">Details</title>
<refsect2 id="CAIRO-HAS-USER-FONT:CAPS" role="macro">
<title>CAIRO_HAS_USER_FONT</title>
<indexterm zone="CAIRO-HAS-USER-FONT:CAPS"><primary sortas="HAS_USER_FONT">CAIRO_HAS_USER_FONT</primary></indexterm>
<programlisting>#define CAIRO_HAS_USER_FONT 1
</programlisting>
<para>
Defined if the user font backend is available.
This macro can be used to conditionally compile backend-specific code.
The user font backend is always built in versions of cairo that support
this feature (1.8 and later).
</para>
<para>
<parameter>Since</parameter>: 1.8
</para></refsect2>
<refsect2 id="cairo-user-scaled-font-init-func-t" role="function" condition="since:1.8">
<title>cairo_user_scaled_font_init_func_t ()</title>
<indexterm zone="cairo-user-scaled-font-init-func-t" role="1.8"><primary sortas="user_scaled_font_init_func_t">cairo_user_scaled_font_init_func_t</primary></indexterm>
<programlisting><link linkend="cairo-status-t"><returnvalue>cairo_status_t</returnvalue></link> (*cairo_user_scaled_font_init_func_t)
(<parameter><link linkend="cairo-scaled-font-t"><type>cairo_scaled_font_t</type></link> *scaled_font</parameter>,
<parameter><link linkend="cairo-t"><type>cairo_t</type></link> *cr</parameter>,
<parameter><link linkend="cairo-font-extents-t"><type>cairo_font_extents_t</type></link> *extents</parameter>);</programlisting>
<para>
<link linkend="cairo-user-scaled-font-init-func-t"><type>cairo_user_scaled_font_init_func_t</type></link> is the type of function which is
called when a scaled-font needs to be created for a user font-face.
</para>
<para>
The cairo context <parameter>cr</parameter> is not used by the caller, but is prepared in font
space, similar to what the cairo contexts passed to the render_glyph
method will look like. The callback can use this context for extents
computation for example. After the callback is called, <parameter>cr</parameter> is checked
for any error status.
</para>
<para>
The <parameter>extents</parameter> argument is where the user font sets the font extents for
<parameter>scaled_font</parameter>. It is in font space, which means that for most cases its
ascent and descent members should add to 1.0. <parameter>extents</parameter> is preset to
hold a value of 1.0 for ascent, height, and max_x_advance, and 0.0 for
descent and max_y_advance members.
</para>
<para>
The callback is optional. If not set, default font extents as described
in the previous paragraph will be used.
</para>
<para>
Note that <parameter>scaled_font</parameter> is not fully initialized at this
point and trying to use it for text operations in the callback will result
in deadlock.
</para><variablelist role="params">
<varlistentry><term><parameter>scaled_font</parameter> :</term>
<listitem><simpara>the scaled-font being created
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>cr</parameter> :</term>
<listitem><simpara>a cairo context, in font space
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>extents</parameter> :</term>
<listitem><simpara>font extents to fill in, in font space
</simpara></listitem></varlistentry>
<varlistentry><term><emphasis>Returns</emphasis> :</term><listitem><simpara> <link linkend="CAIRO-STATUS-SUCCESS:CAPS"><literal>CAIRO_STATUS_SUCCESS</literal></link> upon success, or an error status on error.
</simpara></listitem></varlistentry>
</variablelist><para role="since">Since 1.8</para></refsect2>
<refsect2 id="cairo-user-scaled-font-render-glyph-func-t" role="function" condition="since:1.8">
<title>cairo_user_scaled_font_render_glyph_func_t ()</title>
<indexterm zone="cairo-user-scaled-font-render-glyph-func-t" role="1.8"><primary sortas="user_scaled_font_render_glyph_func_t">cairo_user_scaled_font_render_glyph_func_t</primary></indexterm>
<programlisting><link linkend="cairo-status-t"><returnvalue>cairo_status_t</returnvalue></link> (*cairo_user_scaled_font_render_glyph_func_t)
(<parameter><link linkend="cairo-scaled-font-t"><type>cairo_scaled_font_t</type></link> *scaled_font</parameter>,
<parameter><type>unsigned long </type> glyph</parameter>,
<parameter><link linkend="cairo-t"><type>cairo_t</type></link> *cr</parameter>,
<parameter><link linkend="cairo-text-extents-t"><type>cairo_text_extents_t</type></link> *extents</parameter>);</programlisting>
<para>
<link linkend="cairo-user-scaled-font-render-glyph-func-t"><type>cairo_user_scaled_font_render_glyph_func_t</type></link> is the type of function which
is called when a user scaled-font needs to render a glyph.
</para>
<para>
The callback is mandatory, and expected to draw the glyph with code <parameter>glyph</parameter> to
the cairo context <parameter>cr</parameter>. <parameter>cr</parameter> is prepared such that the glyph drawing is done in
font space. That is, the matrix set on <parameter>cr</parameter> is the scale matrix of <parameter>scaled_font</parameter>,
The <parameter>extents</parameter> argument is where the user font sets the font extents for
<parameter>scaled_font</parameter>. However, if user prefers to draw in user space, they can
achieve that by changing the matrix on <parameter>cr</parameter>. All cairo rendering operations
to <parameter>cr</parameter> are permitted, however, the result is undefined if any source other
than the default source on <parameter>cr</parameter> is used. That means, glyph bitmaps should
be rendered using <link linkend="cairo-mask"><function>cairo_mask()</function></link> instead of <link linkend="cairo-paint"><function>cairo_paint()</function></link>.
</para>
<para>
Other non-default settings on <parameter>cr</parameter> include a font size of 1.0 (given that
it is set up to be in font space), and font options corresponding to
<parameter>scaled_font</parameter>.
</para>
<para>
The <parameter>extents</parameter> argument is preset to have <literal>x_bearing</literal>,
<literal>width</literal>, and <literal>y_advance</literal> of zero,
<literal>y_bearing</literal> set to <literal>-font_extents.ascent</literal>,
<literal>height</literal> to <literal>font_extents.ascent+font_extents.descent</literal>,
and <literal>x_advance</literal> to <literal>font_extents.max_x_advance</literal>.
The only field user needs to set in majority of cases is
<literal>x_advance</literal>.
If the <literal>width</literal> field is zero upon the callback returning
(which is its preset value), the glyph extents are automatically computed
based on the drawings done to <parameter>cr</parameter>. This is in most cases exactly what the
desired behavior is. However, if for any reason the callback sets the
extents, it must be ink extents, and include the extents of all drawing
done to <parameter>cr</parameter> in the callback.
</para><variablelist role="params">
<varlistentry><term><parameter>scaled_font</parameter> :</term>
<listitem><simpara>user scaled-font
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>glyph</parameter> :</term>
<listitem><simpara>glyph code to render
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>cr</parameter> :</term>
<listitem><simpara>cairo context to draw to, in font space
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>extents</parameter> :</term>
<listitem><simpara>glyph extents to fill in, in font space
</simpara></listitem></varlistentry>
<varlistentry><term><emphasis>Returns</emphasis> :</term><listitem><simpara> <link linkend="CAIRO-STATUS-SUCCESS:CAPS"><literal>CAIRO_STATUS_SUCCESS</literal></link> upon success, or
<link linkend="CAIRO-STATUS-USER-FONT-ERROR:CAPS"><literal>CAIRO_STATUS_USER_FONT_ERROR</literal></link> or any other error status on error.
</simpara></listitem></varlistentry>
</variablelist><para role="since">Since 1.8</para></refsect2>
<refsect2 id="cairo-user-scaled-font-text-to-glyphs-func-t" role="function" condition="since:1.8">
<title>cairo_user_scaled_font_text_to_glyphs_func_t ()</title>
<indexterm zone="cairo-user-scaled-font-text-to-glyphs-func-t" role="1.8"><primary sortas="user_scaled_font_text_to_glyphs_func_t">cairo_user_scaled_font_text_to_glyphs_func_t</primary></indexterm>
<programlisting><link linkend="cairo-status-t"><returnvalue>cairo_status_t</returnvalue></link> (*cairo_user_scaled_font_text_to_glyphs_func_t)
(<parameter><link linkend="cairo-scaled-font-t"><type>cairo_scaled_font_t</type></link> *scaled_font</parameter>,
<parameter>const <link linkend="char"><type>char</type></link> *utf8</parameter>,
<parameter><link linkend="int"><type>int</type></link> utf8_len</parameter>,
<parameter><link linkend="cairo-glyph-t"><type>cairo_glyph_t</type></link> **glyphs</parameter>,
<parameter><link linkend="int"><type>int</type></link> *num_glyphs</parameter>,
<parameter><link linkend="cairo-text-cluster-t"><type>cairo_text_cluster_t</type></link> **clusters</parameter>,
<parameter><link linkend="int"><type>int</type></link> *num_clusters</parameter>,
<parameter><link linkend="cairo-text-cluster-flags-t"><type>cairo_text_cluster_flags_t</type></link> *cluster_flags</parameter>);</programlisting>
<para>
<link linkend="cairo-user-scaled-font-text-to-glyphs-func-t"><type>cairo_user_scaled_font_text_to_glyphs_func_t</type></link> is the type of function which
is called to convert input text to an array of glyphs. This is used by the
<link linkend="cairo-show-text"><function>cairo_show_text()</function></link> operation.
</para>
<para>
Using this callback the user-font has full control on glyphs and their
positions. That means, it allows for features like ligatures and kerning,
as well as complex <firstterm>shaping</firstterm> required for scripts like
Arabic and Indic.
</para>
<para>
The <parameter>num_glyphs</parameter> argument is preset to the number of glyph entries available
in the <parameter>glyphs</parameter> buffer. If the <parameter>glyphs</parameter> buffer is <link linkend="NULL:CAPS"><literal>NULL</literal></link>, the value of
<parameter>num_glyphs</parameter> will be zero. If the provided glyph array is too short for
the conversion (or for convenience), a new glyph array may be allocated
using <link linkend="cairo-glyph-allocate"><function>cairo_glyph_allocate()</function></link> and placed in <parameter>glyphs</parameter>. Upon return,
<parameter>num_glyphs</parameter> should contain the number of generated glyphs. If the value
<parameter>glyphs</parameter> points at has changed after the call, the caller will free the
allocated glyph array using <link linkend="cairo-glyph-free"><function>cairo_glyph_free()</function></link>.
The callback should populate the glyph indices and positions (in font space)
assuming that the text is to be shown at the origin.
</para>
<para>
If <parameter>clusters</parameter> is not <link linkend="NULL:CAPS"><literal>NULL</literal></link>, <parameter>num_clusters</parameter> and <parameter>cluster_flags</parameter> are also
non-<link linkend="NULL:CAPS"><literal>NULL</literal></link>, and cluster mapping should be computed. The semantics of how
cluster array allocation works is similar to the glyph array. That is,
if <parameter>clusters</parameter> initially points to a non-<link linkend="NULL:CAPS"><literal>NULL</literal></link> value, that array may be used
as a cluster buffer, and <parameter>num_clusters</parameter> points to the number of cluster
entries available there. If the provided cluster array is too short for
the conversion (or for convenience), a new cluster array may be allocated
using <link linkend="cairo-text-cluster-allocate"><function>cairo_text_cluster_allocate()</function></link> and placed in <parameter>clusters</parameter>. Upon return,
<parameter>num_clusters</parameter> should contain the number of generated clusters.
If the value <parameter>clusters</parameter> points at has changed after the call, the caller
will free the allocated cluster array using <link linkend="cairo-text-cluster-free"><function>cairo_text_cluster_free()</function></link>.
</para>
<para>
The callback is optional. If <parameter>num_glyphs</parameter> is negative upon
the callback returning or if the return value
is <link linkend="CAIRO-STATUS-USER-FONT-NOT-IMPLEMENTED:CAPS"><literal>CAIRO_STATUS_USER_FONT_NOT_IMPLEMENTED</literal></link>, the unicode_to_glyph callback
is tried. See <link linkend="cairo-user-scaled-font-unicode-to-glyph-func-t"><type>cairo_user_scaled_font_unicode_to_glyph_func_t</type></link>.
</para>
<para>
Note: While cairo does not impose any limitation on glyph indices,
some applications may assume that a glyph index fits in a 16-bit
unsigned integer. As such, it is advised that user-fonts keep their
glyphs in the 0 to 65535 range. Furthermore, some applications may
assume that glyph 0 is a special glyph-not-found glyph. User-fonts
are advised to use glyph 0 for such purposes and do not use that
glyph value for other purposes.
</para><variablelist role="params">
<varlistentry><term><parameter>scaled_font</parameter> :</term>
<listitem><simpara>the scaled-font being created
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>utf8</parameter> :</term>
<listitem><simpara>a string of text encoded in UTF-8
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>utf8_len</parameter> :</term>
<listitem><simpara>length of <parameter>utf8</parameter> in bytes
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>glyphs</parameter> :</term>
<listitem><simpara>pointer to array of glyphs to fill, in font space
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>num_glyphs</parameter> :</term>
<listitem><simpara>pointer to number of glyphs
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>clusters</parameter> :</term>
<listitem><simpara>pointer to array of cluster mapping information to fill, or <link linkend="NULL:CAPS"><literal>NULL</literal></link>
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>num_clusters</parameter> :</term>
<listitem><simpara>pointer to number of clusters
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>cluster_flags</parameter> :</term>
<listitem><simpara>pointer to location to store cluster flags corresponding to the
output <parameter>clusters</parameter>
</simpara></listitem></varlistentry>
<varlistentry><term><emphasis>Returns</emphasis> :</term><listitem><simpara> <link linkend="CAIRO-STATUS-SUCCESS:CAPS"><literal>CAIRO_STATUS_SUCCESS</literal></link> upon success,
<link linkend="CAIRO-STATUS-USER-FONT-NOT-IMPLEMENTED:CAPS"><literal>CAIRO_STATUS_USER_FONT_NOT_IMPLEMENTED</literal></link> if fallback options should be tried,
or <link linkend="CAIRO-STATUS-USER-FONT-ERROR:CAPS"><literal>CAIRO_STATUS_USER_FONT_ERROR</literal></link> or any other error status on error.
</simpara></listitem></varlistentry>
</variablelist><para role="since">Since 1.8</para></refsect2>
<refsect2 id="cairo-user-scaled-font-unicode-to-glyph-func-t" role="function" condition="since:1.8">
<title>cairo_user_scaled_font_unicode_to_glyph_func_t ()</title>
<indexterm zone="cairo-user-scaled-font-unicode-to-glyph-func-t" role="1.8"><primary sortas="user_scaled_font_unicode_to_glyph_func_t">cairo_user_scaled_font_unicode_to_glyph_func_t</primary></indexterm>
<programlisting><link linkend="cairo-status-t"><returnvalue>cairo_status_t</returnvalue></link> (*cairo_user_scaled_font_unicode_to_glyph_func_t)
(<parameter><link linkend="cairo-scaled-font-t"><type>cairo_scaled_font_t</type></link> *scaled_font</parameter>,
<parameter><type>unsigned long </type> unicode</parameter>,
<parameter>unsigned <link linkend="long"><type>long</type></link> *glyph_index</parameter>);</programlisting>
<para>
<link linkend="cairo-user-scaled-font-unicode-to-glyph-func-t"><type>cairo_user_scaled_font_unicode_to_glyph_func_t</type></link> is the type of function which
is called to convert an input Unicode character to a single glyph.
This is used by the <link linkend="cairo-show-text"><function>cairo_show_text()</function></link> operation.
</para>
<para>
This callback is used to provide the same functionality as the
text_to_glyphs callback does (see <link linkend="cairo-user-scaled-font-text-to-glyphs-func-t"><type>cairo_user_scaled_font_text_to_glyphs_func_t</type></link>)
but has much less control on the output,
in exchange for increased ease of use. The inherent assumption to using
this callback is that each character maps to one glyph, and that the
mapping is context independent. It also assumes that glyphs are positioned
according to their advance width. These mean no ligatures, kerning, or
complex scripts can be implemented using this callback.
</para>
<para>
The callback is optional, and only used if text_to_glyphs callback is not
set or fails to return glyphs. If this callback is not set or if it returns
<link linkend="CAIRO-STATUS-USER-FONT-NOT-IMPLEMENTED:CAPS"><literal>CAIRO_STATUS_USER_FONT_NOT_IMPLEMENTED</literal></link>, an identity mapping from Unicode
code-points to glyph indices is assumed.
</para>
<para>
Note: While cairo does not impose any limitation on glyph indices,
some applications may assume that a glyph index fits in a 16-bit
unsigned integer. As such, it is advised that user-fonts keep their
glyphs in the 0 to 65535 range. Furthermore, some applications may
assume that glyph 0 is a special glyph-not-found glyph. User-fonts
are advised to use glyph 0 for such purposes and do not use that
glyph value for other purposes.
</para><variablelist role="params">
<varlistentry><term><parameter>scaled_font</parameter> :</term>
<listitem><simpara>the scaled-font being created
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>unicode</parameter> :</term>
<listitem><simpara>input unicode character code-point
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>glyph_index</parameter> :</term>
<listitem><simpara>output glyph index
</simpara></listitem></varlistentry>
<varlistentry><term><emphasis>Returns</emphasis> :</term><listitem><simpara> <link linkend="CAIRO-STATUS-SUCCESS:CAPS"><literal>CAIRO_STATUS_SUCCESS</literal></link> upon success,
<link linkend="CAIRO-STATUS-USER-FONT-NOT-IMPLEMENTED:CAPS"><literal>CAIRO_STATUS_USER_FONT_NOT_IMPLEMENTED</literal></link> if fallback options should be tried,
or <link linkend="CAIRO-STATUS-USER-FONT-ERROR:CAPS"><literal>CAIRO_STATUS_USER_FONT_ERROR</literal></link> or any other error status on error.
</simpara></listitem></varlistentry>
</variablelist><para role="since">Since 1.8</para></refsect2>
<refsect2 id="cairo-user-font-face-create" role="function" condition="since:1.8">
<title>cairo_user_font_face_create ()</title>
<indexterm zone="cairo-user-font-face-create" role="1.8"><primary sortas="user_font_face_create">cairo_user_font_face_create</primary></indexterm>
<programlisting><link linkend="cairo-font-face-t"><returnvalue>cairo_font_face_t</returnvalue></link> * cairo_user_font_face_create (<parameter><type>void</type></parameter>);</programlisting>
<para>
Creates a new user font-face.
</para>
<para>
Use the setter functions to associate callbacks with the returned
user font. The only mandatory callback is render_glyph.
</para>
<para>
After the font-face is created, the user can attach arbitrary data
(the actual font data) to it using <link linkend="cairo-font-face-set-user-data"><function>cairo_font_face_set_user_data()</function></link>
and access it from the user-font callbacks by using
<link linkend="cairo-scaled-font-get-font-face"><function>cairo_scaled_font_get_font_face()</function></link> followed by
<link linkend="cairo-font-face-get-user-data"><function>cairo_font_face_get_user_data()</function></link>.
</para><variablelist role="params">
<varlistentry><term><emphasis>Returns</emphasis> :</term><listitem><simpara> a newly created <link linkend="cairo-font-face-t"><type>cairo_font_face_t</type></link>. Free with
<link linkend="cairo-font-face-destroy"><function>cairo_font_face_destroy()</function></link> when you are done using it.
</simpara></listitem></varlistentry>
</variablelist><para role="since">Since 1.8</para></refsect2>
<refsect2 id="cairo-user-font-face-set-init-func" role="function" condition="since:1.8">
<title>cairo_user_font_face_set_init_func ()</title>
<indexterm zone="cairo-user-font-face-set-init-func" role="1.8"><primary sortas="user_font_face_set_init_func">cairo_user_font_face_set_init_func</primary></indexterm>
<programlisting><link linkend="void"><returnvalue>void</returnvalue></link> cairo_user_font_face_set_init_func (<parameter><link linkend="cairo-font-face-t"><type>cairo_font_face_t</type></link> *font_face</parameter>,
<parameter><link linkend="cairo-user-scaled-font-init-func-t"><type>cairo_user_scaled_font_init_func_t</type></link> init_func</parameter>);</programlisting>
<para>
Sets the scaled-font initialization function of a user-font.
See <link linkend="cairo-user-scaled-font-init-func-t"><type>cairo_user_scaled_font_init_func_t</type></link> for details of how the callback
works.
</para>
<para>
The font-face should not be immutable or a <link linkend="CAIRO-STATUS-USER-FONT-IMMUTABLE:CAPS"><literal>CAIRO_STATUS_USER_FONT_IMMUTABLE</literal></link>
error will occur. A user font-face is immutable as soon as a scaled-font
is created from it.
</para><variablelist role="params">
<varlistentry><term><parameter>font_face</parameter> :</term>
<listitem><simpara>A user font face
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>init_func</parameter> :</term>
<listitem><simpara>The init callback, or <link linkend="NULL:CAPS"><literal>NULL</literal></link>
</simpara></listitem></varlistentry>
</variablelist><para role="since">Since 1.8</para></refsect2>
<refsect2 id="cairo-user-font-face-get-init-func" role="function" condition="since:1.8">
<title>cairo_user_font_face_get_init_func ()</title>
<indexterm zone="cairo-user-font-face-get-init-func" role="1.8"><primary sortas="user_font_face_get_init_func">cairo_user_font_face_get_init_func</primary></indexterm>
<programlisting><link linkend="cairo-user-scaled-font-init-func-t"><returnvalue>cairo_user_scaled_font_init_func_t</returnvalue></link> cairo_user_font_face_get_init_func
(<parameter><link linkend="cairo-font-face-t"><type>cairo_font_face_t</type></link> *font_face</parameter>);</programlisting>
<para>
Gets the scaled-font initialization function of a user-font.
</para><variablelist role="params">
<varlistentry><term><parameter>font_face</parameter> :</term>
<listitem><simpara>A user font face
</simpara></listitem></varlistentry>
<varlistentry><term><emphasis>Returns</emphasis> :</term><listitem><simpara> The init callback of <parameter>font_face</parameter>
or <link linkend="NULL:CAPS"><literal>NULL</literal></link> if none set or an error has occurred.
</simpara></listitem></varlistentry>
</variablelist><para role="since">Since 1.8</para></refsect2>
<refsect2 id="cairo-user-font-face-set-render-glyph-func" role="function" condition="since:1.8">
<title>cairo_user_font_face_set_render_glyph_func ()</title>
<indexterm zone="cairo-user-font-face-set-render-glyph-func" role="1.8"><primary sortas="user_font_face_set_render_glyph_func">cairo_user_font_face_set_render_glyph_func</primary></indexterm>
<programlisting><link linkend="void"><returnvalue>void</returnvalue></link> cairo_user_font_face_set_render_glyph_func
(<parameter><link linkend="cairo-font-face-t"><type>cairo_font_face_t</type></link> *font_face</parameter>,
<parameter><link linkend="cairo-user-scaled-font-render-glyph-func-t"><type>cairo_user_scaled_font_render_glyph_func_t</type></link> render_glyph_func</parameter>);</programlisting>
<para>
Sets the glyph rendering function of a user-font.
See <link linkend="cairo-user-scaled-font-render-glyph-func-t"><type>cairo_user_scaled_font_render_glyph_func_t</type></link> for details of how the callback
works.
</para>
<para>
The font-face should not be immutable or a <link linkend="CAIRO-STATUS-USER-FONT-IMMUTABLE:CAPS"><literal>CAIRO_STATUS_USER_FONT_IMMUTABLE</literal></link>
error will occur. A user font-face is immutable as soon as a scaled-font
is created from it.
</para>
<para>
The render_glyph callback is the only mandatory callback of a user-font.
If the callback is <link linkend="NULL:CAPS"><literal>NULL</literal></link> and a glyph is tried to be rendered using
<parameter>font_face</parameter>, a <link linkend="CAIRO-STATUS-USER-FONT-ERROR:CAPS"><literal>CAIRO_STATUS_USER_FONT_ERROR</literal></link> will occur.
</para><variablelist role="params">
<varlistentry><term><parameter>font_face</parameter> :</term>
<listitem><simpara>A user font face
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>render_glyph_func</parameter> :</term>
<listitem><simpara>The render_glyph callback, or <link linkend="NULL:CAPS"><literal>NULL</literal></link>
</simpara></listitem></varlistentry>
</variablelist><para role="since">Since 1.8</para></refsect2>
<refsect2 id="cairo-user-font-face-get-render-glyph-func" role="function" condition="since:1.8">
<title>cairo_user_font_face_get_render_glyph_func ()</title>
<indexterm zone="cairo-user-font-face-get-render-glyph-func" role="1.8"><primary sortas="user_font_face_get_render_glyph_func">cairo_user_font_face_get_render_glyph_func</primary></indexterm>
<programlisting><link linkend="cairo-user-scaled-font-render-glyph-func-t"><returnvalue>cairo_user_scaled_font_render_glyph_func_t</returnvalue></link> cairo_user_font_face_get_render_glyph_func
(<parameter><link linkend="cairo-font-face-t"><type>cairo_font_face_t</type></link> *font_face</parameter>);</programlisting>
<para>
Gets the glyph rendering function of a user-font.
</para><variablelist role="params">
<varlistentry><term><parameter>font_face</parameter> :</term>
<listitem><simpara>A user font face
</simpara></listitem></varlistentry>
<varlistentry><term><emphasis>Returns</emphasis> :</term><listitem><simpara> The render_glyph callback of <parameter>font_face</parameter>
or <link linkend="NULL:CAPS"><literal>NULL</literal></link> if none set or an error has occurred.
</simpara></listitem></varlistentry>
</variablelist><para role="since">Since 1.8</para></refsect2>
<refsect2 id="cairo-user-font-face-set-unicode-to-glyph-func" role="function" condition="since:1.8">
<title>cairo_user_font_face_set_unicode_to_glyph_func ()</title>
<indexterm zone="cairo-user-font-face-set-unicode-to-glyph-func" role="1.8"><primary sortas="user_font_face_set_unicode_to_glyph_func">cairo_user_font_face_set_unicode_to_glyph_func</primary></indexterm>
<programlisting><link linkend="void"><returnvalue>void</returnvalue></link> cairo_user_font_face_set_unicode_to_glyph_func
(<parameter><link linkend="cairo-font-face-t"><type>cairo_font_face_t</type></link> *font_face</parameter>,
<parameter><link linkend="cairo-user-scaled-font-unicode-to-glyph-func-t"><type>cairo_user_scaled_font_unicode_to_glyph_func_t</type></link> unicode_to_glyph_func</parameter>);</programlisting>
<para>
Sets the unicode-to-glyph conversion function of a user-font.
See <link linkend="cairo-user-scaled-font-unicode-to-glyph-func-t"><type>cairo_user_scaled_font_unicode_to_glyph_func_t</type></link> for details of how the callback
works.
</para>
<para>
The font-face should not be immutable or a <link linkend="CAIRO-STATUS-USER-FONT-IMMUTABLE:CAPS"><literal>CAIRO_STATUS_USER_FONT_IMMUTABLE</literal></link>
error will occur. A user font-face is immutable as soon as a scaled-font
is created from it.
</para><variablelist role="params">
<varlistentry><term><parameter>font_face</parameter> :</term>
<listitem><simpara>A user font face
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>unicode_to_glyph_func</parameter> :</term>
<listitem><simpara>The unicode_to_glyph callback, or <link linkend="NULL:CAPS"><literal>NULL</literal></link>
</simpara></listitem></varlistentry>
</variablelist><para role="since">Since 1.8</para></refsect2>
<refsect2 id="cairo-user-font-face-get-unicode-to-glyph-func" role="function" condition="since:1.8">
<title>cairo_user_font_face_get_unicode_to_glyph_func ()</title>
<indexterm zone="cairo-user-font-face-get-unicode-to-glyph-func" role="1.8"><primary sortas="user_font_face_get_unicode_to_glyph_func">cairo_user_font_face_get_unicode_to_glyph_func</primary></indexterm>
<programlisting><link linkend="cairo-user-scaled-font-unicode-to-glyph-func-t"><returnvalue>cairo_user_scaled_font_unicode_to_glyph_func_t</returnvalue></link> cairo_user_font_face_get_unicode_to_glyph_func
(<parameter><link linkend="cairo-font-face-t"><type>cairo_font_face_t</type></link> *font_face</parameter>);</programlisting>
<para>
Gets the unicode-to-glyph conversion function of a user-font.
</para><variablelist role="params">
<varlistentry><term><parameter>font_face</parameter> :</term>
<listitem><simpara>A user font face
</simpara></listitem></varlistentry>
<varlistentry><term><emphasis>Returns</emphasis> :</term><listitem><simpara> The unicode_to_glyph callback of <parameter>font_face</parameter>
or <link linkend="NULL:CAPS"><literal>NULL</literal></link> if none set or an error occurred.
</simpara></listitem></varlistentry>
</variablelist><para role="since">Since 1.8</para></refsect2>
<refsect2 id="cairo-user-font-face-set-text-to-glyphs-func" role="function" condition="since:1.8">
<title>cairo_user_font_face_set_text_to_glyphs_func ()</title>
<indexterm zone="cairo-user-font-face-set-text-to-glyphs-func" role="1.8"><primary sortas="user_font_face_set_text_to_glyphs_func">cairo_user_font_face_set_text_to_glyphs_func</primary></indexterm>
<programlisting><link linkend="void"><returnvalue>void</returnvalue></link> cairo_user_font_face_set_text_to_glyphs_func
(<parameter><link linkend="cairo-font-face-t"><type>cairo_font_face_t</type></link> *font_face</parameter>,
<parameter><link linkend="cairo-user-scaled-font-text-to-glyphs-func-t"><type>cairo_user_scaled_font_text_to_glyphs_func_t</type></link> text_to_glyphs_func</parameter>);</programlisting>
<para>
Sets th text-to-glyphs conversion function of a user-font.
See <link linkend="cairo-user-scaled-font-text-to-glyphs-func-t"><type>cairo_user_scaled_font_text_to_glyphs_func_t</type></link> for details of how the callback
works.
</para>
<para>
The font-face should not be immutable or a <link linkend="CAIRO-STATUS-USER-FONT-IMMUTABLE:CAPS"><literal>CAIRO_STATUS_USER_FONT_IMMUTABLE</literal></link>
error will occur. A user font-face is immutable as soon as a scaled-font
is created from it.
</para><variablelist role="params">
<varlistentry><term><parameter>font_face</parameter> :</term>
<listitem><simpara>A user font face
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>text_to_glyphs_func</parameter> :</term>
<listitem><simpara>The text_to_glyphs callback, or <link linkend="NULL:CAPS"><literal>NULL</literal></link>
</simpara></listitem></varlistentry>
</variablelist><para role="since">Since 1.8</para></refsect2>
<refsect2 id="cairo-user-font-face-get-text-to-glyphs-func" role="function" condition="since:1.8">
<title>cairo_user_font_face_get_text_to_glyphs_func ()</title>
<indexterm zone="cairo-user-font-face-get-text-to-glyphs-func" role="1.8"><primary sortas="user_font_face_get_text_to_glyphs_func">cairo_user_font_face_get_text_to_glyphs_func</primary></indexterm>
<programlisting><link linkend="cairo-user-scaled-font-text-to-glyphs-func-t"><returnvalue>cairo_user_scaled_font_text_to_glyphs_func_t</returnvalue></link> cairo_user_font_face_get_text_to_glyphs_func
(<parameter><link linkend="cairo-font-face-t"><type>cairo_font_face_t</type></link> *font_face</parameter>);</programlisting>
<para>
Gets the text-to-glyphs conversion function of a user-font.
</para><variablelist role="params">
<varlistentry><term><parameter>font_face</parameter> :</term>
<listitem><simpara>A user font face
</simpara></listitem></varlistentry>
<varlistentry><term><emphasis>Returns</emphasis> :</term><listitem><simpara> The text_to_glyphs callback of <parameter>font_face</parameter>
or <link linkend="NULL:CAPS"><literal>NULL</literal></link> if none set or an error occurred.
</simpara></listitem></varlistentry>
</variablelist><para role="since">Since 1.8</para></refsect2>
</refsect1>
</refentry>