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[docs] Add a Cairo integration section

This commit is contained in:
Matthias Clasen 2022-12-29 09:57:56 -05:00 committed by Behdad Esfahbod
parent 89bd7f64ae
commit 2c2121784a
1 changed files with 43 additions and 1 deletions
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docs/usermanual-integration.xml
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@ -309,6 +309,48 @@
</para>
</section>
<section id="integration-cairo">
<title>Cairo integration</title>
<para>
Cairo is a 2D graphics library that is frequently used together
with GTK and Pango. Cairo supports rendering text using FreeType, or
by using callback-based 'user fonts'.
</para>
<para>
HarfBuzz provides integration points with cairo for fonts as well as
for buffers. To use the Cairo-integration API, link against libharfbuzz-cairo,
and include the <filename>hb-cairo.h</filename> header. For easy buildsystem
integration, HarfBuzz comes with a <filename>harfbuzz-cairo.pc</filename>
pkg-config file.
</para>
<para>
To create a <type>cairo_scaled_font_t</type> font from a HarfBuzz
<type>hb_font_t</type>, you can use <function>hb_cairo_font_face_create_for_font()</function>
or <function>hb_cairo_font_face_create_for_face()</function>. The former API
applies variations and synthetic slant from the <type>hb_font_t</type> when
rendering, the latter takes them from the <type>cairo_font_options_t</type>
that were passed when creating the <type>cairo_scaled_font_t</type>.
</para>
<para>
The Cairo fonts created in this way make use of Cairo's user-font facilities.
They can be used to render on any Cairo context, and provide full support for
font rendering features, including color. One current limitation of the
implementation is that it does not support hinting for glyph outlines.
</para>
<para>
When using color fonts with this API, the color palette index is taken from
the <type>cairo_font_options_t</type> (with new enough Cairo), and the foreground
color is extracted from the source of the Cairo context.
</para>
<para>
To render the results of shaping a piece of text, use
<function>hb_cairo_glyphs_from_buffer()</function> to obtain the glyphs in
a form that can be passed to <function>cairo_show_text_glyphs()</function> or
<function>cairo_show_glyphs()</function>.
</para>
</section>
<section id="integration-uniscribe">
<title>Uniscribe integration</title>
<para>