cairo-recording.xml [plain text]
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<refentry id="cairo-Recording-Surfaces">
<refmeta>
<refentrytitle role="top_of_page" id="cairo-Recording-Surfaces.top_of_page">Recording Surfaces</refentrytitle>
<manvolnum>3</manvolnum>
<refmiscinfo>
CAIRO Library
</refmiscinfo>
</refmeta>
<refnamediv>
<refname>Recording Surfaces</refname>
<refpurpose>Records all drawing operations</refpurpose>
</refnamediv>
<refsynopsisdiv id="cairo-Recording-Surfaces.synopsis" role="synopsis">
<title role="synopsis.title">Synopsis</title>
<synopsis>#define <link linkend="CAIRO-HAS-RECORDING-SURFACE:CAPS">CAIRO_HAS_RECORDING_SURFACE</link>
<link linkend="cairo-surface-t"><returnvalue>cairo_surface_t</returnvalue></link> * <link linkend="cairo-recording-surface-create">cairo_recording_surface_create</link> (<parameter><link linkend="cairo-content-t"><type>cairo_content_t</type></link> content</parameter>,
<parameter>const <link linkend="cairo-rectangle-t"><type>cairo_rectangle_t</type></link> *extents</parameter>);
<link linkend="void"><returnvalue>void</returnvalue></link> <link linkend="cairo-recording-surface-ink-extents">cairo_recording_surface_ink_extents</link> (<parameter><link linkend="cairo-surface-t"><type>cairo_surface_t</type></link> *surface</parameter>,
<parameter><link linkend="double"><type>double</type></link> *x0</parameter>,
<parameter><link linkend="double"><type>double</type></link> *y0</parameter>,
<parameter><link linkend="double"><type>double</type></link> *width</parameter>,
<parameter><link linkend="double"><type>double</type></link> *height</parameter>);
</synopsis>
</refsynopsisdiv>
<refsect1 id="cairo-Recording-Surfaces.description" role="desc">
<title role="desc.title">Description</title>
<para>
A recording surface is a surface that records all drawing operations at
the highest level of the surface backend interface, (that is, the
level of paint, mask, stroke, fill, and show_text_glyphs). The recording
surface can then be "replayed" against any target surface by using it
as a source surface.
</para>
<para>
If you want to replay a surface so that the results in target will be
identical to the results that would have been obtained if the original
operations applied to the recording surface had instead been applied to the
target surface, you can use code like this:
<informalexample><programlisting>
cairo_t *cr;
cr = cairo_create (target);
cairo_set_source_surface (cr, recording_surface, 0.0, 0.0);
cairo_paint (cr);
cairo_destroy (cr);
</programlisting></informalexample>
</para>
<para>
A recording surface is logically unbounded, i.e. it has no implicit constraint
on the size of the drawing surface. However, in practice this is rarely
useful as you wish to replay against a particular target surface with
known bounds. For this case, it is more efficient to specify the target
extents to the recording surface upon creation.
</para>
<para>
The recording phase of the recording surface is careful to snapshot all
necessary objects (paths, patterns, etc.), in order to achieve
accurate replay. The efficiency of the recording surface could be
improved by improving the implementation of snapshot for the
various objects. For example, it would be nice to have a
copy-on-write implementation for _cairo_surface_snapshot.
</para>
</refsect1>
<refsect1 id="cairo-Recording-Surfaces.details" role="details">
<title role="details.title">Details</title>
<refsect2 id="CAIRO-HAS-RECORDING-SURFACE:CAPS" role="macro" condition="since:1.10">
<title>CAIRO_HAS_RECORDING_SURFACE</title>
<indexterm zone="CAIRO-HAS-RECORDING-SURFACE:CAPS" role="1.10"><primary sortas="HAS_RECORDING_SURFACE">CAIRO_HAS_RECORDING_SURFACE</primary></indexterm>
<programlisting>#define CAIRO_HAS_RECORDING_SURFACE 1
</programlisting>
<para>
Defined if the recording surface backend is available.
The recording surface backend is always built in.
This macro was added for completeness in cairo 1.10.
</para><para role="since">Since 1.10</para></refsect2>
<refsect2 id="cairo-recording-surface-create" role="function" condition="since:1.10">
<title>cairo_recording_surface_create ()</title>
<indexterm zone="cairo-recording-surface-create" role="1.10"><primary sortas="recording_surface_create">cairo_recording_surface_create</primary></indexterm>
<programlisting><link linkend="cairo-surface-t"><returnvalue>cairo_surface_t</returnvalue></link> * cairo_recording_surface_create (<parameter><link linkend="cairo-content-t"><type>cairo_content_t</type></link> content</parameter>,
<parameter>const <link linkend="cairo-rectangle-t"><type>cairo_rectangle_t</type></link> *extents</parameter>);</programlisting>
<para>
Creates a recording-surface which can be used to record all drawing operations
at the highest level (that is, the level of paint, mask, stroke, fill
and show_text_glyphs). The recording surface can then be "replayed" against
any target surface by using it as a source to drawing operations.
</para>
<para>
The recording phase of the recording surface is careful to snapshot all
necessary objects (paths, patterns, etc.), in order to achieve
accurate replay.
</para><variablelist role="params">
<varlistentry><term><parameter>content</parameter> :</term>
<listitem><simpara>the content of the recording surface
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>extents</parameter> :</term>
<listitem><simpara>the extents to record in pixels, can be <link linkend="NULL:CAPS"><literal>NULL</literal></link> to record
unbounded operations.
</simpara></listitem></varlistentry>
<varlistentry><term><emphasis>Returns</emphasis> :</term><listitem><simpara> a pointer to the newly created surface. The caller
owns the surface and should call <link linkend="cairo-surface-destroy"><function>cairo_surface_destroy()</function></link> when done
with it.
</simpara></listitem></varlistentry>
</variablelist><para role="since">Since 1.10</para></refsect2>
<refsect2 id="cairo-recording-surface-ink-extents" role="function" condition="since:1.10">
<title>cairo_recording_surface_ink_extents ()</title>
<indexterm zone="cairo-recording-surface-ink-extents" role="1.10"><primary sortas="recording_surface_ink_extents">cairo_recording_surface_ink_extents</primary></indexterm>
<programlisting><link linkend="void"><returnvalue>void</returnvalue></link> cairo_recording_surface_ink_extents (<parameter><link linkend="cairo-surface-t"><type>cairo_surface_t</type></link> *surface</parameter>,
<parameter><link linkend="double"><type>double</type></link> *x0</parameter>,
<parameter><link linkend="double"><type>double</type></link> *y0</parameter>,
<parameter><link linkend="double"><type>double</type></link> *width</parameter>,
<parameter><link linkend="double"><type>double</type></link> *height</parameter>);</programlisting>
<para>
Measures the extents of the operations stored within the recording-surface.
This is useful to compute the required size of an image surface (or
equivalent) into which to replay the full sequence of drawing operations.
</para><variablelist role="params">
<varlistentry><term><parameter>surface</parameter> :</term>
<listitem><simpara>a <link linkend="cairo-recording-surface-t"><type>cairo_recording_surface_t</type></link>
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>x0</parameter> :</term>
<listitem><simpara>the x-coordinate of the top-left of the ink bounding box
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>y0</parameter> :</term>
<listitem><simpara>the y-coordinate of the top-left of the ink bounding box
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>width</parameter> :</term>
<listitem><simpara>the width of the ink bounding box
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>height</parameter> :</term>
<listitem><simpara>the height of the ink bounding box
</simpara></listitem></varlistentry>
</variablelist><para role="since">Since 1.10</para></refsect2>
</refsect1>
<refsect1 id="cairo-Recording-Surfaces.see-also">
<title>See Also</title>
<link linkend="cairo-surface-t"><type>cairo_surface_t</type></link>
</refsect1>
</refentry>