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<a href="#cogl-Offscreen-Buffers.synopsis" class="shortcut">Top</a>
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<a href="#cogl-Offscreen-Buffers.description" class="shortcut">Description</a>
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<div class="refentry">
<a name="cogl-Offscreen-Buffers"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2><span class="refentrytitle"><a name="cogl-Offscreen-Buffers.top_of_page"></a>Offscreen Buffers</span></h2>
<p>Offscreen Buffers — Functions for creating and manipulating offscreen
framebuffers.</p>
</td>
<td valign="top" align="right"></td>
</tr></table></div>
<div class="refsynopsisdiv">
<a name="cogl-Offscreen-Buffers.synopsis"></a><h2>Synopsis</h2>
<pre class="synopsis"><span class="returnvalue">CoglOffscreen</span> * <a class="link" href="cogl-Offscreen-Buffers.html#cogl-offscreen-new-with-texture" title="cogl_offscreen_new_with_texture ()">cogl_offscreen_new_with_texture</a> (<em class="parameter"><code><span class="type">CoglTexture</span> *texture</code></em>);
<span class="returnvalue">CoglOffscreen</span> * <a class="link" href="cogl-Offscreen-Buffers.html#cogl-offscreen-new-to-texture" title="cogl_offscreen_new_to_texture ()">cogl_offscreen_new_to_texture</a> (<em class="parameter"><code><span class="type">CoglTexture</span> *texture</code></em>);
<span class="returnvalue">CoglBool</span> <a class="link" href="cogl-Offscreen-Buffers.html#cogl-is-offscreen" title="cogl_is_offscreen ()">cogl_is_offscreen</a> (<em class="parameter"><code><span class="type">void</span> *object</code></em>);
<span class="returnvalue">void</span> <a class="link" href="cogl-Offscreen-Buffers.html#cogl-set-framebuffer" title="cogl_set_framebuffer ()">cogl_set_framebuffer</a> (<em class="parameter"><code><span class="type">CoglFramebuffer</span> *buffer</code></em>);
<span class="returnvalue">void</span> <a class="link" href="cogl-Offscreen-Buffers.html#cogl-push-framebuffer" title="cogl_push_framebuffer ()">cogl_push_framebuffer</a> (<em class="parameter"><code><span class="type">CoglFramebuffer</span> *buffer</code></em>);
<span class="returnvalue">void</span> <a class="link" href="cogl-Offscreen-Buffers.html#cogl-pop-framebuffer" title="cogl_pop_framebuffer ()">cogl_pop_framebuffer</a> (<em class="parameter"><code><span class="type">void</span></code></em>);
<span class="returnvalue">void</span> <a class="link" href="cogl-Offscreen-Buffers.html#cogl-set-draw-buffer" title="cogl_set_draw_buffer ()">cogl_set_draw_buffer</a> (<em class="parameter"><code><a class="link" href="cogl-General-API.html#CoglBufferTarget" title="enum CoglBufferTarget"><span class="type">CoglBufferTarget</span></a> target</code></em>,
<em class="parameter"><code><a class="link" href="cogl-General-API.html#CoglHandle" title="CoglHandle"><span class="type">CoglHandle</span></a> offscreen</code></em>);
<span class="returnvalue">void</span> <a class="link" href="cogl-Offscreen-Buffers.html#cogl-pop-draw-buffer" title="cogl_pop_draw_buffer ()">cogl_pop_draw_buffer</a> (<em class="parameter"><code><span class="type">void</span></code></em>);
<span class="returnvalue">void</span> <a class="link" href="cogl-Offscreen-Buffers.html#cogl-push-draw-buffer" title="cogl_push_draw_buffer ()">cogl_push_draw_buffer</a> (<em class="parameter"><code><span class="type">void</span></code></em>);
</pre>
</div>
<div class="refsect1">
<a name="cogl-Offscreen-Buffers.description"></a><h2>Description</h2>
<p>
Cogl allows creating and operating on offscreen framebuffers.
</p>
</div>
<div class="refsect1">
<a name="cogl-Offscreen-Buffers.details"></a><h2>Details</h2>
<div class="refsect2">
<a name="cogl-offscreen-new-with-texture"></a><h3>cogl_offscreen_new_with_texture ()</h3>
<pre class="programlisting"><span class="returnvalue">CoglOffscreen</span> * cogl_offscreen_new_with_texture (<em class="parameter"><code><span class="type">CoglTexture</span> *texture</code></em>);</pre>
<p>
This creates an offscreen framebuffer object using the given
<em class="parameter"><code>texture</code></em> as the primary color buffer. It doesn't just initialize
the contents of the offscreen buffer with the <em class="parameter"><code>texture</code></em>; they are
tightly bound so that drawing to the offscreen buffer effectively
updates the contents of the given texture. You don't need to
destroy the offscreen buffer before you can use the <em class="parameter"><code>texture</code></em> again.
</p>
<p>
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Note</h3>This api only works with low-level <span class="type">CoglTexture</span> types such as
<span class="type">CoglTexture2D</span>, <span class="type">CoglTexture3D</span> and <span class="type">CoglTextureRectangle</span>, and not
with meta-texture types such as <span class="type">CoglTexture2DSliced</span>.</div>
<p>
</p>
<p>
The storage for the framebuffer is actually allocated lazily
so this function will never return <code class="literal">NULL</code> to indicate a runtime
error. This means it is still possible to configure the framebuffer
before it is really allocated.
</p>
<p>
Simple applications without full error handling can simply rely on
Cogl to lazily allocate the storage of framebuffers but you should
be aware that if Cogl encounters an error (such as running out of
GPU memory) then your application will simply abort with an error
message. If you need to be able to catch such exceptions at runtime
then you can explicitly allocate your framebuffer when you have
finished configuring it by calling <code class="function">cogl_framebuffer_allocate()</code> and
passing in a <span class="type">CoglError</span> argument to catch any exceptions.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>texture</code></em> :</span></p></td>
<td>A <span class="type">CoglTexture</span> pointer</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>a newly instantiated <span class="type">CoglOffscreen</span>
framebuffer. <span class="annotation">[<acronym title="Free data after the code is done."><span class="acronym">transfer full</span></acronym>]</span>
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-offscreen-new-to-texture"></a><h3>cogl_offscreen_new_to_texture ()</h3>
<pre class="programlisting"><span class="returnvalue">CoglOffscreen</span> * cogl_offscreen_new_to_texture (<em class="parameter"><code><span class="type">CoglTexture</span> *texture</code></em>);</pre>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Warning</h3>
<p><code class="literal">cogl_offscreen_new_to_texture</code> has been deprecated since version 1.16 and should not be used in newly-written code. Use cogl_offscreen_new_with_texture instead.</p>
</div>
<p>
This creates an offscreen buffer object using the given <em class="parameter"><code>texture</code></em> as the
primary color buffer. It doesn't just initialize the contents of the
offscreen buffer with the <em class="parameter"><code>texture</code></em>; they are tightly bound so that
drawing to the offscreen buffer effectivly updates the contents of the
given texture. You don't need to destroy the offscreen buffer before
you can use the <em class="parameter"><code>texture</code></em> again.
</p>
<p>
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Note</h3>This only works with low-level <span class="type">CoglTexture</span> types such as
<span class="type">CoglTexture2D</span>, <span class="type">CoglTexture3D</span> and <span class="type">CoglTextureRectangle</span>, and not
with meta-texture types such as <span class="type">CoglTexture2DSliced</span>.</div>
<p>
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>texture</code></em> :</span></p></td>
<td>A <span class="type">CoglTexture</span> pointer</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>a newly instantiated <span class="type">CoglOffscreen</span>
framebuffer or <code class="literal">NULL</code> if it wasn't possible to create the
buffer. <span class="annotation">[<acronym title="Free data after the code is done."><span class="acronym">transfer full</span></acronym>]</span>
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-is-offscreen"></a><h3>cogl_is_offscreen ()</h3>
<pre class="programlisting"><span class="returnvalue">CoglBool</span> cogl_is_offscreen (<em class="parameter"><code><span class="type">void</span> *object</code></em>);</pre>
<p>
Determines whether the given <a class="link" href="cogl-General-API.html#CoglObject" title="CoglObject"><span class="type">CoglObject</span></a> references an offscreen
framebuffer object.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>object</code></em> :</span></p></td>
<td>A pointer to a <a class="link" href="cogl-General-API.html#CoglObject" title="CoglObject"><span class="type">CoglObject</span></a>
</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>
<code class="literal">TRUE</code> if <em class="parameter"><code>object</code></em> is a <span class="type">CoglOffscreen</span> framebuffer,
<code class="literal">FALSE</code> otherwise</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-set-framebuffer"></a><h3>cogl_set_framebuffer ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> cogl_set_framebuffer (<em class="parameter"><code><span class="type">CoglFramebuffer</span> *buffer</code></em>);</pre>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Warning</h3>
<p><code class="literal">cogl_set_framebuffer</code> has been deprecated since version 1.16 and should not be used in newly-written code. The latest drawing apis take explicit
<span class="type">CoglFramebuffer</span> arguments so this stack of
framebuffers shouldn't be used anymore.</p>
</div>
<p>
This redirects all subsequent drawing to the specified framebuffer. This can
either be an offscreen buffer created with <a class="link" href="cogl-Offscreen-Buffers.html#cogl-offscreen-new-to-texture" title="cogl_offscreen_new_to_texture ()"><code class="function">cogl_offscreen_new_to_texture()</code></a>
or in the future it may be an onscreen framebuffers too.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody><tr>
<td><p><span class="term"><em class="parameter"><code>buffer</code></em> :</span></p></td>
<td>A <span class="type">CoglFramebuffer</span> object, either onscreen or offscreen.</td>
</tr></tbody>
</table></div>
<p class="since">Since 1.2</p>
</div>
<hr>
<div class="refsect2">
<a name="cogl-push-framebuffer"></a><h3>cogl_push_framebuffer ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> cogl_push_framebuffer (<em class="parameter"><code><span class="type">CoglFramebuffer</span> *buffer</code></em>);</pre>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Warning</h3>
<p><code class="literal">cogl_push_framebuffer</code> has been deprecated since version 1.16 and should not be used in newly-written code. The latest drawing apis take explicit
<span class="type">CoglFramebuffer</span> arguments so this stack of
framebuffers shouldn't be used anymore.</p>
</div>
<p>
Redirects all subsequent drawing to the specified framebuffer. This can
either be an offscreen buffer created with <a class="link" href="cogl-Offscreen-Buffers.html#cogl-offscreen-new-to-texture" title="cogl_offscreen_new_to_texture ()"><code class="function">cogl_offscreen_new_to_texture()</code></a>
or in the future it may be an onscreen framebuffer too.
</p>
<p>
You should understand that a framebuffer owns the following state:
</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">The projection matrix</li>
<li class="listitem">The modelview matrix stack</li>
<li class="listitem">The viewport</li>
<li class="listitem">The clip stack</li>
</ul></div>
<p>
So these items will automatically be saved and restored when you
push and pop between different framebuffers.
</p>
<p>
Also remember a newly allocated framebuffer will have an identity matrix for
the projection and modelview matrices which gives you a coordinate space
like OpenGL with (-1, -1) corresponding to the top left of the viewport,
(1, 1) corresponding to the bottom right and +z coming out towards the
viewer.
</p>
<p>
If you want to set up a coordinate space like Clutter does with (0, 0)
corresponding to the top left and (framebuffer_width, framebuffer_height)
corresponding to the bottom right you can do so like this:
</p>
<p>
</p>
<div class="informalexample"><pre class="programlisting">
static void
setup_viewport (unsigned int width,
unsigned int height,
float fovy,
float aspect,
float z_near,
float z_far)
{
float z_camera;
CoglMatrix projection_matrix;
CoglMatrix mv_matrix;
cogl_set_viewport (0, 0, width, height);
cogl_perspective (fovy, aspect, z_near, z_far);
cogl_get_projection_matrix (&projection_matrix);
z_camera = 0.5 * projection_matrix.xx;
cogl_matrix_init_identity (&mv_matrix);
cogl_matrix_translate (&mv_matrix, -0.5f, -0.5f, -z_camera);
cogl_matrix_scale (&mv_matrix, 1.0f / width, -1.0f / height, 1.0f / width);
cogl_matrix_translate (&mv_matrix, 0.0f, -1.0 * height, 0.0f);
cogl_set_modelview_matrix (&mv_matrix);
}
static void
my_init_framebuffer (ClutterStage *stage,
CoglFramebuffer *framebuffer,
unsigned int framebuffer_width,
unsigned int framebuffer_height)
{
ClutterPerspective perspective;
clutter_stage_get_perspective (stage, &perspective);
cogl_push_framebuffer (framebuffer);
setup_viewport (framebuffer_width,
framebuffer_height,
perspective.fovy,
perspective.aspect,
perspective.z_near,
perspective.z_far);
}
</pre></div>
<p>
</p>
<p>
The previous framebuffer can be restored by calling <a class="link" href="cogl-Offscreen-Buffers.html#cogl-pop-framebuffer" title="cogl_pop_framebuffer ()"><code class="function">cogl_pop_framebuffer()</code></a>
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody><tr>
<td><p><span class="term"><em class="parameter"><code>buffer</code></em> :</span></p></td>
<td>A <span class="type">CoglFramebuffer</span> object, either onscreen or offscreen.</td>
</tr></tbody>
</table></div>
<p class="since">Since 1.2</p>
</div>
<hr>
<div class="refsect2">
<a name="cogl-pop-framebuffer"></a><h3>cogl_pop_framebuffer ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> cogl_pop_framebuffer (<em class="parameter"><code><span class="type">void</span></code></em>);</pre>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Warning</h3>
<p><code class="literal">cogl_pop_framebuffer</code> has been deprecated since version 1.16 and should not be used in newly-written code. The latest drawing apis take explicit
<span class="type">CoglFramebuffer</span> arguments so this stack of
framebuffers shouldn't be used anymore.</p>
</div>
<p>
Restores the framebuffer that was previously at the top of the stack.
All subsequent drawing will be redirected to this framebuffer.
</p>
<p class="since">Since 1.2</p>
</div>
<hr>
<div class="refsect2">
<a name="cogl-set-draw-buffer"></a><h3>cogl_set_draw_buffer ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> cogl_set_draw_buffer (<em class="parameter"><code><a class="link" href="cogl-General-API.html#CoglBufferTarget" title="enum CoglBufferTarget"><span class="type">CoglBufferTarget</span></a> target</code></em>,
<em class="parameter"><code><a class="link" href="cogl-General-API.html#CoglHandle" title="CoglHandle"><span class="type">CoglHandle</span></a> offscreen</code></em>);</pre>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Warning</h3>
<p><code class="literal">cogl_set_draw_buffer</code> has been deprecated since version 1.16 and should not be used in newly-written code. The latest drawing apis take explicit
<span class="type">CoglFramebuffer</span> arguments so this stack of
framebuffers shouldn't be used anymore.</p>
</div>
<p>
Redirects all subsequent drawing to the specified framebuffer. This
can either be an offscreen buffer created with
<a class="link" href="cogl-Offscreen-Buffers.html#cogl-offscreen-new-to-texture" title="cogl_offscreen_new_to_texture ()"><code class="function">cogl_offscreen_new_to_texture()</code></a> or you can revert to your original
on screen window buffer.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>target</code></em> :</span></p></td>
<td>A <a class="link" href="cogl-General-API.html#CoglBufferTarget" title="enum CoglBufferTarget"><span class="type">CoglBufferTarget</span></a> that specifies what kind of framebuffer you
are setting as the render target.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>offscreen</code></em> :</span></p></td>
<td>If you are setting a framebuffer of type COGL_OFFSCREEN_BUFFER
then this is a CoglHandle for the offscreen buffer.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-pop-draw-buffer"></a><h3>cogl_pop_draw_buffer ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> cogl_pop_draw_buffer (<em class="parameter"><code><span class="type">void</span></code></em>);</pre>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Warning</h3>
<p><code class="literal">cogl_pop_draw_buffer</code> has been deprecated since version 1.16 and should not be used in newly-written code. The latest drawing apis take explicit
<span class="type">CoglFramebuffer</span> arguments so this stack of
framebuffers shouldn't be used anymore.</p>
</div>
<p>
Restore <a class="link" href="cogl-Offscreen-Buffers.html#cogl-set-draw-buffer" title="cogl_set_draw_buffer ()"><code class="function">cogl_set_draw_buffer()</code></a> state.
</p>
</div>
<hr>
<div class="refsect2">
<a name="cogl-push-draw-buffer"></a><h3>cogl_push_draw_buffer ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> cogl_push_draw_buffer (<em class="parameter"><code><span class="type">void</span></code></em>);</pre>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Warning</h3>
<p><code class="literal">cogl_push_draw_buffer</code> has been deprecated since version 1.16 and should not be used in newly-written code. The latest drawing apis take explicit
<span class="type">CoglFramebuffer</span> arguments so this stack of
framebuffers shouldn't be used anymore.</p>
</div>
<p>
Save <a class="link" href="cogl-Offscreen-Buffers.html#cogl-set-draw-buffer" title="cogl_set_draw_buffer ()"><code class="function">cogl_set_draw_buffer()</code></a> state.
</p>
</div>
</div>
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