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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<title>Matrix Stacks: Cogl 2.0 Reference Manual</title>
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<a href="#" class="shortcut">Top</a><span id="nav_description">  <span class="dim">|</span> 
                  <a href="#cogl-2.0-experimental-Matrix-Stacks.description" class="shortcut">Description</a></span>
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<div class="refentry">
<a name="cogl-2.0-experimental-Matrix-Stacks"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2><span class="refentrytitle"><a name="cogl-2.0-experimental-Matrix-Stacks.top_of_page"></a>Matrix Stacks</span></h2>
<p>Matrix Stacks — Functions for efficiently tracking many
                    related transformations</p>
</td>
<td class="gallery_image" valign="top" align="right"></td>
</tr></table></div>
<div class="refsect1">
<a name="cogl-2.0-experimental-Matrix-Stacks.functions"></a><h2>Functions</h2>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="functions_return">
<col class="functions_name">
</colgroup>
<tbody>
<tr>
<td class="function_type">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="returnvalue">CoglMatrixStack</span></a> *
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-new" title="cogl_matrix_stack_new ()">cogl_matrix_stack_new</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-push" title="cogl_matrix_stack_push ()">cogl_matrix_stack_push</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-pop" title="cogl_matrix_stack_pop ()">cogl_matrix_stack_pop</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-load-identity" title="cogl_matrix_stack_load_identity ()">cogl_matrix_stack_load_identity</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-scale" title="cogl_matrix_stack_scale ()">cogl_matrix_stack_scale</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-translate" title="cogl_matrix_stack_translate ()">cogl_matrix_stack_translate</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-rotate" title="cogl_matrix_stack_rotate ()">cogl_matrix_stack_rotate</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-rotate-quaternion" title="cogl_matrix_stack_rotate_quaternion ()">cogl_matrix_stack_rotate_quaternion</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-rotate-euler" title="cogl_matrix_stack_rotate_euler ()">cogl_matrix_stack_rotate_euler</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-multiply" title="cogl_matrix_stack_multiply ()">cogl_matrix_stack_multiply</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-frustum" title="cogl_matrix_stack_frustum ()">cogl_matrix_stack_frustum</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-perspective" title="cogl_matrix_stack_perspective ()">cogl_matrix_stack_perspective</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-orthographic" title="cogl_matrix_stack_orthographic ()">cogl_matrix_stack_orthographic</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="cogl-2.0-experimental-Common-Types.html#CoglBool" title="CoglBool"><span class="returnvalue">CoglBool</span></a>
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-get-inverse" title="cogl_matrix_stack_get_inverse ()">cogl_matrix_stack_get_inverse</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="returnvalue">CoglMatrixEntry</span></a> *
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-get-entry" title="cogl_matrix_stack_get_entry ()">cogl_matrix_stack_get_entry</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="cogl-2.0-experimental-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="returnvalue">CoglMatrix</span></a> *
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-get" title="cogl_matrix_stack_get ()">cogl_matrix_stack_get</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="cogl-2.0-experimental-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="returnvalue">CoglMatrix</span></a> *
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-entry-get" title="cogl_matrix_entry_get ()">cogl_matrix_entry_get</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-set" title="cogl_matrix_stack_set ()">cogl_matrix_stack_set</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="cogl-2.0-experimental-Common-Types.html#CoglBool" title="CoglBool"><span class="returnvalue">CoglBool</span></a>
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-entry-calculate-translation" title="cogl_matrix_entry_calculate_translation ()">cogl_matrix_entry_calculate_translation</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="cogl-2.0-experimental-Common-Types.html#CoglBool" title="CoglBool"><span class="returnvalue">CoglBool</span></a>
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-entry-is-identity" title="cogl_matrix_entry_is_identity ()">cogl_matrix_entry_is_identity</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="cogl-2.0-experimental-Common-Types.html#CoglBool" title="CoglBool"><span class="returnvalue">CoglBool</span></a>
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-entry-equal" title="cogl_matrix_entry_equal ()">cogl_matrix_entry_equal</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="returnvalue">CoglMatrixEntry</span></a> *
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-entry-ref" title="cogl_matrix_entry_ref ()">cogl_matrix_entry_ref</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-entry-unref" title="cogl_matrix_entry_unref ()">cogl_matrix_entry_unref</a> <span class="c_punctuation">()</span>
</td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect1">
<a name="cogl-2.0-experimental-Matrix-Stacks.other"></a><h2>Types and Values</h2>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="name">
<col class="description">
</colgroup>
<tbody>
<tr>
<td class="datatype_keyword"> </td>
<td class="function_name"><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack">CoglMatrixStack</a></td>
</tr>
<tr>
<td class="datatype_keyword"> </td>
<td class="function_name"><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry">CoglMatrixEntry</a></td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect1">
<a name="cogl-2.0-experimental-Matrix-Stacks.description"></a><h2>Description</h2>
<p>Matrices can be used (for example) to describe the model-view
transforms of objects, texture transforms, and projective
transforms.</p>
<p>The <a class="link" href="cogl-2.0-experimental-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> api provides a good way to manipulate individual
matrices representing a single transformation but if you need to
track many-many such transformations for many objects that are
organized in a scenegraph for example then using a separate
<a class="link" href="cogl-2.0-experimental-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> for each object may not be the most efficient way.</p>
<p>A <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> enables applications to track lots of
transformations that are related to each other in some kind of
hierarchy.  In a scenegraph for example if you want to know how to
transform a particular node then you usually have to walk up
through the ancestors and accumulate their transforms before
finally applying the transform of the node itself. In this model
things are grouped together spatially according to their ancestry
and all siblings with the same parent share the same initial
transformation. The <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> API is suited to tracking lots
of transformations that fit this kind of model.</p>
<p>Compared to using the <a class="link" href="cogl-2.0-experimental-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> api directly to track many
related transforms, these can be some advantages to using a
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a>:</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">Faster equality comparisons of transformations</li>
<li class="listitem">Efficient comparisons of the differences between arbitrary
  transformations</li>
<li class="listitem">Avoid redundant arithmetic related to common transforms
  </li>
<li class="listitem">Can be more space efficient (not always though)</li>
</ul></div>
<p>For reference (to give an idea of when a <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> can
provide a space saving) a <a class="link" href="cogl-2.0-experimental-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> can be expected to take 72
bytes whereas a single <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a> in a <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> is
currently around 32 bytes on a 32bit CPU or 36 bytes on a 64bit
CPU. An entry is needed for each individual operation applied to
the stack (such as rotate, scale, translate) so if most of your
leaf node transformations only need one or two simple operations
relative to their parent then a matrix stack will likely take less
space than having a <a class="link" href="cogl-2.0-experimental-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> for each node.</p>
<p>Even without any space saving though the ability to perform fast
comparisons and avoid redundant arithmetic (especially sine and
cosine calculations for rotations) can make using a matrix stack
worthwhile.</p>
</div>
<div class="refsect1">
<a name="cogl-2.0-experimental-Matrix-Stacks.functions_details"></a><h2>Functions</h2>
<div class="refsect2">
<a name="cogl-matrix-stack-new"></a><h3>cogl_matrix_stack_new ()</h3>
<pre class="programlisting"><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="returnvalue">CoglMatrixStack</span></a> *
cogl_matrix_stack_new (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-The-Top-Level-Context.html#CoglContext" title="CoglContext"><span class="type">CoglContext</span></a> *ctx</code></em>);</pre>
<p>Allocates a new <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> that can be used to build up
transformations relating to objects in a scenegraph like hierarchy.
(See the description of <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> and <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a> for
more details of what a matrix stack is best suited for)</p>
<p>When a <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> is first allocated it is conceptually
positioned at the root of your scenegraph hierarchy. As you
traverse your scenegraph then you should call
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-push" title="cogl_matrix_stack_push ()"><code class="function">cogl_matrix_stack_push()</code></a> whenever you move down a level and
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-pop" title="cogl_matrix_stack_pop ()"><code class="function">cogl_matrix_stack_pop()</code></a> whenever you move back up a level towards
the root.</p>
<p>Once you have allocated a <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> you can get a reference
to the current transformation for the current position in the
hierarchy by calling <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-get-entry" title="cogl_matrix_stack_get_entry ()"><code class="function">cogl_matrix_stack_get_entry()</code></a>.</p>
<p>Once you have allocated a <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> you can apply operations
such as rotate, scale and translate to modify the current transform
for the current position in the hierarchy by calling
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-rotate" title="cogl_matrix_stack_rotate ()"><code class="function">cogl_matrix_stack_rotate()</code></a>, <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-scale" title="cogl_matrix_stack_scale ()"><code class="function">cogl_matrix_stack_scale()</code></a> and
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-translate" title="cogl_matrix_stack_translate ()"><code class="function">cogl_matrix_stack_translate()</code></a>.</p>
<div class="refsect3">
<a name="cogl-matrix-stack-new.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>ctx</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-The-Top-Level-Context.html#CoglContext" title="CoglContext"><span class="type">CoglContext</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<div class="refsect3">
<a name="cogl-matrix-stack-new.returns"></a><h4>Returns</h4>
<p> A newly allocated <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a>. </p>
<p><span class="annotation">[<acronym title="Free data after the code is done."><span class="acronym">transfer full</span></acronym>]</span></p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-stack-push"></a><h3>cogl_matrix_stack_push ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_stack_push (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> *stack</code></em>);</pre>
<p>Saves the current transform and starts a new transform that derives
from the current transform.</p>
<p>This is usually called while traversing a scenegraph whenever you
traverse one level deeper. <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-pop" title="cogl_matrix_stack_pop ()"><code class="function">cogl_matrix_stack_pop()</code></a> can then be
called when going back up one layer to restore the previous
transform of an ancestor.</p>
<div class="refsect3">
<a name="cogl-matrix-stack-push.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>stack</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-stack-pop"></a><h3>cogl_matrix_stack_pop ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_stack_pop (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> *stack</code></em>);</pre>
<p>Restores the previous transform that was last saved by calling
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-push" title="cogl_matrix_stack_push ()"><code class="function">cogl_matrix_stack_push()</code></a>.</p>
<p>This is usually called while traversing a scenegraph whenever you
return up one level in the graph towards the root node.</p>
<div class="refsect3">
<a name="cogl-matrix-stack-pop.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>stack</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-stack-load-identity"></a><h3>cogl_matrix_stack_load_identity ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_stack_load_identity (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> *stack</code></em>);</pre>
<p>Resets the current matrix to the identity matrix.</p>
<div class="refsect3">
<a name="cogl-matrix-stack-load-identity.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>stack</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-stack-scale"></a><h3>cogl_matrix_stack_scale ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_stack_scale (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> *stack</code></em>,
                         <em class="parameter"><code><span class="type">float</span> x</code></em>,
                         <em class="parameter"><code><span class="type">float</span> y</code></em>,
                         <em class="parameter"><code><span class="type">float</span> z</code></em>);</pre>
<p>Multiplies the current matrix by one that scales the x, y and z
axes by the given values.</p>
<div class="refsect3">
<a name="cogl-matrix-stack-scale.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>stack</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>x</p></td>
<td class="parameter_description"><p>Amount to scale along the x-axis</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>y</p></td>
<td class="parameter_description"><p>Amount to scale along the y-axis</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>z</p></td>
<td class="parameter_description"><p>Amount to scale along the z-axis</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-stack-translate"></a><h3>cogl_matrix_stack_translate ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_stack_translate (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> *stack</code></em>,
                             <em class="parameter"><code><span class="type">float</span> x</code></em>,
                             <em class="parameter"><code><span class="type">float</span> y</code></em>,
                             <em class="parameter"><code><span class="type">float</span> z</code></em>);</pre>
<p>Multiplies the current matrix by one that translates along all
three axes according to the given values.</p>
<div class="refsect3">
<a name="cogl-matrix-stack-translate.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>stack</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>x</p></td>
<td class="parameter_description"><p>Distance to translate along the x-axis</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>y</p></td>
<td class="parameter_description"><p>Distance to translate along the y-axis</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>z</p></td>
<td class="parameter_description"><p>Distance to translate along the z-axis</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-stack-rotate"></a><h3>cogl_matrix_stack_rotate ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_stack_rotate (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> *stack</code></em>,
                          <em class="parameter"><code><span class="type">float</span> angle</code></em>,
                          <em class="parameter"><code><span class="type">float</span> x</code></em>,
                          <em class="parameter"><code><span class="type">float</span> y</code></em>,
                          <em class="parameter"><code><span class="type">float</span> z</code></em>);</pre>
<p>Multiplies the current matrix by one that rotates the around the
axis-vector specified by <em class="parameter"><code>x</code></em>
, <em class="parameter"><code>y</code></em>
 and <em class="parameter"><code>z</code></em>
. The rotation follows the
right-hand thumb rule so for example rotating by 10 degrees about
the axis-vector (0, 0, 1) causes a small counter-clockwise
rotation.</p>
<div class="refsect3">
<a name="cogl-matrix-stack-rotate.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>stack</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>angle</p></td>
<td class="parameter_description"><p>Angle in degrees to rotate.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>x</p></td>
<td class="parameter_description"><p>X-component of vertex to rotate around.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>y</p></td>
<td class="parameter_description"><p>Y-component of vertex to rotate around.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>z</p></td>
<td class="parameter_description"><p>Z-component of vertex to rotate around.</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-stack-rotate-quaternion"></a><h3>cogl_matrix_stack_rotate_quaternion ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_stack_rotate_quaternion (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> *stack</code></em>,
                                     <em class="parameter"><code>const <a class="link" href="cogl-2.0-experimental-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a> *quaternion</code></em>);</pre>
<p>Multiplies the current matrix by one that rotates according to the
rotation described by <em class="parameter"><code>quaternion</code></em>
.</p>
<div class="refsect3">
<a name="cogl-matrix-stack-rotate-quaternion.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>stack</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>quaternion</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Quaternions-(Rotations).html#CoglQuaternion" title="CoglQuaternion"><span class="type">CoglQuaternion</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-stack-rotate-euler"></a><h3>cogl_matrix_stack_rotate_euler ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_stack_rotate_euler (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> *stack</code></em>,
                                <em class="parameter"><code>const <a class="link" href="cogl-2.0-experimental-Eulers-(Rotations).html#CoglEuler" title="CoglEuler"><span class="type">CoglEuler</span></a> *euler</code></em>);</pre>
<p>Multiplies the current matrix by one that rotates according to the
rotation described by <em class="parameter"><code>euler</code></em>
.</p>
<div class="refsect3">
<a name="cogl-matrix-stack-rotate-euler.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>stack</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>euler</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Eulers-(Rotations).html#CoglEuler" title="CoglEuler"><span class="type">CoglEuler</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-stack-multiply"></a><h3>cogl_matrix_stack_multiply ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_stack_multiply (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> *stack</code></em>,
                            <em class="parameter"><code>const <a class="link" href="cogl-2.0-experimental-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *matrix</code></em>);</pre>
<p>Multiplies the current matrix by the given matrix.</p>
<div class="refsect3">
<a name="cogl-matrix-stack-multiply.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>stack</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>matrix</p></td>
<td class="parameter_description"><p>the matrix to multiply with the current model-view</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-stack-frustum"></a><h3>cogl_matrix_stack_frustum ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_stack_frustum (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> *stack</code></em>,
                           <em class="parameter"><code><span class="type">float</span> left</code></em>,
                           <em class="parameter"><code><span class="type">float</span> right</code></em>,
                           <em class="parameter"><code><span class="type">float</span> bottom</code></em>,
                           <em class="parameter"><code><span class="type">float</span> top</code></em>,
                           <em class="parameter"><code><span class="type">float</span> z_near</code></em>,
                           <em class="parameter"><code><span class="type">float</span> z_far</code></em>);</pre>
<p>Replaces the current matrix with a perspective matrix for a given
viewing frustum defined by 4 side clip planes that all cross
through the origin and 2 near and far clip planes.</p>
<div class="refsect3">
<a name="cogl-matrix-stack-frustum.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>stack</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>left</p></td>
<td class="parameter_description"><p>X position of the left clipping plane where it
intersects the near clipping plane</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>right</p></td>
<td class="parameter_description"><p>X position of the right clipping plane where it
intersects the near clipping plane</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>bottom</p></td>
<td class="parameter_description"><p>Y position of the bottom clipping plane where it
intersects the near clipping plane</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>top</p></td>
<td class="parameter_description"><p>Y position of the top clipping plane where it intersects
the near clipping plane</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>z_near</p></td>
<td class="parameter_description"><p>The distance to the near clipping plane (Must be positive)</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>z_far</p></td>
<td class="parameter_description"><p>The distance to the far clipping plane (Must be positive)</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-stack-perspective"></a><h3>cogl_matrix_stack_perspective ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_stack_perspective (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> *stack</code></em>,
                               <em class="parameter"><code><span class="type">float</span> fov_y</code></em>,
                               <em class="parameter"><code><span class="type">float</span> aspect</code></em>,
                               <em class="parameter"><code><span class="type">float</span> z_near</code></em>,
                               <em class="parameter"><code><span class="type">float</span> z_far</code></em>);</pre>
<p>Replaces the current matrix with a perspective matrix based on the
provided values.</p>
<div class="note">You should be careful not to have too great a <em class="parameter"><code>z_far</code></em> / <em class="parameter"><code>z_near</code></em>
ratio since that will reduce the effectiveness of depth testing
since there wont be enough precision to identify the depth of
objects near to each other.</div>
<div class="refsect3">
<a name="cogl-matrix-stack-perspective.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>stack</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>fov_y</p></td>
<td class="parameter_description"><p>Vertical field of view angle in degrees.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>aspect</p></td>
<td class="parameter_description"><p>The (width over height) aspect ratio for display</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>z_near</p></td>
<td class="parameter_description"><p>The distance to the near clipping plane (Must be positive,
and must not be 0)</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>z_far</p></td>
<td class="parameter_description"><p>The distance to the far clipping plane (Must be positive)</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-stack-orthographic"></a><h3>cogl_matrix_stack_orthographic ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_stack_orthographic (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> *stack</code></em>,
                                <em class="parameter"><code><span class="type">float</span> x_1</code></em>,
                                <em class="parameter"><code><span class="type">float</span> y_1</code></em>,
                                <em class="parameter"><code><span class="type">float</span> x_2</code></em>,
                                <em class="parameter"><code><span class="type">float</span> y_2</code></em>,
                                <em class="parameter"><code><span class="type">float</span> near</code></em>,
                                <em class="parameter"><code><span class="type">float</span> far</code></em>);</pre>
<p>Replaces the current matrix with an orthographic projection matrix.</p>
<div class="refsect3">
<a name="cogl-matrix-stack-orthographic.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>stack</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>x_1</p></td>
<td class="parameter_description"><p>The x coordinate for the first vertical clipping plane</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>y_1</p></td>
<td class="parameter_description"><p>The y coordinate for the first horizontal clipping plane</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>x_2</p></td>
<td class="parameter_description"><p>The x coordinate for the second vertical clipping plane</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>y_2</p></td>
<td class="parameter_description"><p>The y coordinate for the second horizontal clipping plane</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>near</p></td>
<td class="parameter_description"><p>The <span class="emphasis"><em>distance</em></span> to the near clipping
plane (will be <span class="emphasis"><em>negative</em></span> if the plane is
behind the viewer)</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>far</p></td>
<td class="parameter_description"><p>The <span class="emphasis"><em>distance</em></span> to the far clipping
plane (will be <span class="emphasis"><em>negative</em></span> if the plane is
behind the viewer)</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-stack-get-inverse"></a><h3>cogl_matrix_stack_get_inverse ()</h3>
<pre class="programlisting"><a class="link" href="cogl-2.0-experimental-Common-Types.html#CoglBool" title="CoglBool"><span class="returnvalue">CoglBool</span></a>
cogl_matrix_stack_get_inverse (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> *stack</code></em>,
                               <em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *inverse</code></em>);</pre>
<p>Gets the inverse transform of the current matrix and uses it to
initialize a new <a class="link" href="cogl-2.0-experimental-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a>.</p>
<div class="refsect3">
<a name="cogl-matrix-stack-get-inverse.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>stack</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>inverse</p></td>
<td class="parameter_description"><p> The destination for a 4x4 inverse transformation matrix. </p></td>
<td class="parameter_annotations"><span class="annotation">[<acronym title="Parameter for returning results. Default is transfer full."><span class="acronym">out</span></acronym>]</span></td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="cogl-matrix-stack-get-inverse.returns"></a><h4>Returns</h4>
<p> <code class="literal">TRUE</code> if the inverse was successfully calculated or <code class="literal">FALSE</code>
for degenerate transformations that can't be inverted (in this case the
<em class="parameter"><code>inverse</code></em>
matrix will simply be initialized with the identity matrix)</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-stack-get-entry"></a><h3>cogl_matrix_stack_get_entry ()</h3>
<pre class="programlisting"><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="returnvalue">CoglMatrixEntry</span></a> *
cogl_matrix_stack_get_entry (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> *stack</code></em>);</pre>
<p>Gets a reference to the current transform represented by a
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a> pointer.</p>
<div class="note">The transform represented by a <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a> is
immutable.</div>
<div class="note">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a>s are reference counted using
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-entry-ref" title="cogl_matrix_entry_ref ()"><code class="function">cogl_matrix_entry_ref()</code></a> and <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-entry-unref" title="cogl_matrix_entry_unref ()"><code class="function">cogl_matrix_entry_unref()</code></a> and you
should call <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-entry-unref" title="cogl_matrix_entry_unref ()"><code class="function">cogl_matrix_entry_unref()</code></a> when you are finished with
and entry you get via <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-get-entry" title="cogl_matrix_stack_get_entry ()"><code class="function">cogl_matrix_stack_get_entry()</code></a>.</div>
<div class="refsect3">
<a name="cogl-matrix-stack-get-entry.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>stack</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<div class="refsect3">
<a name="cogl-matrix-stack-get-entry.returns"></a><h4>Returns</h4>
<p> A pointer to the <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a>
representing the current matrix stack transform. </p>
<p><span class="annotation">[<acronym title="Don't free data after the code is done."><span class="acronym">transfer none</span></acronym>]</span></p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-stack-get"></a><h3>cogl_matrix_stack_get ()</h3>
<pre class="programlisting"><a class="link" href="cogl-2.0-experimental-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="returnvalue">CoglMatrix</span></a> *
cogl_matrix_stack_get (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> *stack</code></em>,
                       <em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *matrix</code></em>);</pre>
<p>Resolves the current <em class="parameter"><code>stack</code></em>
 transform into a <a class="link" href="cogl-2.0-experimental-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> by
combining the operations that have been applied to build up the
current transform.</p>
<p>There are two possible ways that this function may return its
result depending on whether the stack is able to directly point
to an internal <a class="link" href="cogl-2.0-experimental-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> or whether the result needs to be
composed of multiple operations.</p>
<p>If an internal matrix contains the required result then this
function will directly return a pointer to that matrix, otherwise
if the function returns <code class="literal">NULL</code> then <em class="parameter"><code>matrix</code></em>
 will be initialized
to match the current transform of <em class="parameter"><code>stack</code></em>
.</p>
<div class="note">
<em class="parameter"><code>matrix</code></em> will be left untouched if a direct pointer is
returned.</div>
<div class="refsect3">
<a name="cogl-matrix-stack-get.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>stack</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>matrix</p></td>
<td class="parameter_description"><p> The potential destination for the current matrix. </p></td>
<td class="parameter_annotations"><span class="annotation">[<acronym title="Parameter for returning results. Default is transfer full."><span class="acronym">out</span></acronym>]</span></td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="cogl-matrix-stack-get.returns"></a><h4>Returns</h4>
<p> A direct pointer to the current transform or <code class="literal">NULL</code>
and in that case <em class="parameter"><code>matrix</code></em>
will be initialized with
the value of the current transform.</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-entry-get"></a><h3>cogl_matrix_entry_get ()</h3>
<pre class="programlisting"><a class="link" href="cogl-2.0-experimental-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="returnvalue">CoglMatrix</span></a> *
cogl_matrix_entry_get (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a> *entry</code></em>,
                       <em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *matrix</code></em>);</pre>
<p>Resolves the current <em class="parameter"><code>entry</code></em>
 transform into a <a class="link" href="cogl-2.0-experimental-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> by
combining the sequence of operations that have been applied to
build up the current transform.</p>
<p>There are two possible ways that this function may return its
result depending on whether it's possible to directly point
to an internal <a class="link" href="cogl-2.0-experimental-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> or whether the result needs to be
composed of multiple operations.</p>
<p>If an internal matrix contains the required result then this
function will directly return a pointer to that matrix, otherwise
if the function returns <code class="literal">NULL</code> then <em class="parameter"><code>matrix</code></em>
 will be initialized
to match the transform of <em class="parameter"><code>entry</code></em>
.</p>
<div class="note">
<em class="parameter"><code>matrix</code></em> will be left untouched if a direct pointer is
returned.</div>
<div class="refsect3">
<a name="cogl-matrix-entry-get.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>entry</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>matrix</p></td>
<td class="parameter_description"><p> The potential destination for the transform as
a matrix. </p></td>
<td class="parameter_annotations"><span class="annotation">[<acronym title="Parameter for returning results. Default is transfer full."><span class="acronym">out</span></acronym>]</span></td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="cogl-matrix-entry-get.returns"></a><h4>Returns</h4>
<p> A direct pointer to a <a class="link" href="cogl-2.0-experimental-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> transform or <code class="literal">NULL</code>
and in that case <em class="parameter"><code>matrix</code></em>
will be initialized with
the effective transform represented by <em class="parameter"><code>entry</code></em>
.</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-stack-set"></a><h3>cogl_matrix_stack_set ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_stack_set (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> *stack</code></em>,
                       <em class="parameter"><code>const <a class="link" href="cogl-2.0-experimental-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> *matrix</code></em>);</pre>
<p>Replaces the current <em class="parameter"><code>stack</code></em>
 matrix value with the value of <em class="parameter"><code>matrix</code></em>
.
This effectively discards any other operations that were applied
since the last time <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-push" title="cogl_matrix_stack_push ()"><code class="function">cogl_matrix_stack_push()</code></a> was called or since
the stack was initialized.</p>
<div class="refsect3">
<a name="cogl-matrix-stack-set.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>stack</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>matrix</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Matrices.html#CoglMatrix" title="CoglMatrix"><span class="type">CoglMatrix</span></a> replace the current matrix value with</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-entry-calculate-translation"></a><h3>cogl_matrix_entry_calculate_translation ()</h3>
<pre class="programlisting"><a class="link" href="cogl-2.0-experimental-Common-Types.html#CoglBool" title="CoglBool"><span class="returnvalue">CoglBool</span></a>
cogl_matrix_entry_calculate_translation
                               (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a> *entry0</code></em>,
                                <em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a> *entry1</code></em>,
                                <em class="parameter"><code><span class="type">float</span> *x</code></em>,
                                <em class="parameter"><code><span class="type">float</span> *y</code></em>,
                                <em class="parameter"><code><span class="type">float</span> *z</code></em>);</pre>
<p>Determines if the only difference between two transforms is a
translation and if so returns what the <em class="parameter"><code>x</code></em>
, <em class="parameter"><code>y</code></em>
, and <em class="parameter"><code>z</code></em>
 components of
the translation are.</p>
<p>If the difference between the two translations involves anything
other than a translation then the function returns <code class="literal">FALSE</code>.</p>
<div class="refsect3">
<a name="cogl-matrix-entry-calculate-translation.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>entry0</p></td>
<td class="parameter_description"><p>The first reference transform</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>entry1</p></td>
<td class="parameter_description"><p>A second reference transform</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>x</p></td>
<td class="parameter_description"><p> The destination for the x-component of the translation. </p></td>
<td class="parameter_annotations"><span class="annotation">[<acronym title="Parameter for returning results. Default is transfer full."><span class="acronym">out</span></acronym>]</span></td>
</tr>
<tr>
<td class="parameter_name"><p>y</p></td>
<td class="parameter_description"><p> The destination for the y-component of the translation. </p></td>
<td class="parameter_annotations"><span class="annotation">[<acronym title="Parameter for returning results. Default is transfer full."><span class="acronym">out</span></acronym>]</span></td>
</tr>
<tr>
<td class="parameter_name"><p>z</p></td>
<td class="parameter_description"><p> The destination for the z-component of the translation. </p></td>
<td class="parameter_annotations"><span class="annotation">[<acronym title="Parameter for returning results. Default is transfer full."><span class="acronym">out</span></acronym>]</span></td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="cogl-matrix-entry-calculate-translation.returns"></a><h4>Returns</h4>
<p> <code class="literal">TRUE</code> if the only difference between the transform of
<em class="parameter"><code>entry0</code></em>
and the transform of <em class="parameter"><code>entry1</code></em>
is a translation,
otherwise <code class="literal">FALSE</code>.</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-entry-is-identity"></a><h3>cogl_matrix_entry_is_identity ()</h3>
<pre class="programlisting"><a class="link" href="cogl-2.0-experimental-Common-Types.html#CoglBool" title="CoglBool"><span class="returnvalue">CoglBool</span></a>
cogl_matrix_entry_is_identity (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a> *entry</code></em>);</pre>
<p>Determines whether <em class="parameter"><code>entry</code></em>
 is known to represent an identity
transform.</p>
<p>If this returns <code class="literal">TRUE</code> then the entry is definitely the identity
matrix. If it returns <code class="literal">FALSE</code> it may or may not be the identity
matrix but no expensive comparison is performed to verify it.</p>
<div class="refsect3">
<a name="cogl-matrix-entry-is-identity.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>entry</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<div class="refsect3">
<a name="cogl-matrix-entry-is-identity.returns"></a><h4>Returns</h4>
<p> <code class="literal">TRUE</code> if <em class="parameter"><code>entry</code></em>
is definitely an identity transform,
otherwise <code class="literal">FALSE</code>.</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-entry-equal"></a><h3>cogl_matrix_entry_equal ()</h3>
<pre class="programlisting"><a class="link" href="cogl-2.0-experimental-Common-Types.html#CoglBool" title="CoglBool"><span class="returnvalue">CoglBool</span></a>
cogl_matrix_entry_equal (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a> *entry0</code></em>,
                         <em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a> *entry1</code></em>);</pre>
<p>Compares two arbitrary <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a> transforms for equality
returning <code class="literal">TRUE</code> if they are equal or <code class="literal">FALSE</code> otherwise.</p>
<div class="note">In many cases it is unnecessary to use this api and instead
direct pointer comparisons of entries are good enough and much
cheaper too.</div>
<div class="refsect3">
<a name="cogl-matrix-entry-equal.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>entry0</p></td>
<td class="parameter_description"><p>The first <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a> to compare</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>entry1</p></td>
<td class="parameter_description"><p>A second <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a> to compare</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="cogl-matrix-entry-equal.returns"></a><h4>Returns</h4>
<p> <code class="literal">TRUE</code> if <em class="parameter"><code>entry0</code></em>
represents the same transform as
<em class="parameter"><code>entry1</code></em>
, otherwise <code class="literal">FALSE</code>.</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-entry-ref"></a><h3>cogl_matrix_entry_ref ()</h3>
<pre class="programlisting"><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="returnvalue">CoglMatrixEntry</span></a> *
cogl_matrix_entry_ref (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a> *entry</code></em>);</pre>
<p>Takes a reference on the given <em class="parameter"><code>entry</code></em>
 to ensure the <em class="parameter"><code>entry</code></em>
 stays
alive and remains valid. When you are finished with the <em class="parameter"><code>entry</code></em>
 then
you should call <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-entry-unref" title="cogl_matrix_entry_unref ()"><code class="function">cogl_matrix_entry_unref()</code></a>.</p>
<p>It is an error to pass an <em class="parameter"><code>entry</code></em>
 pointer to <a class="link" href="cogl-2.0-experimental-The-Object-Interface.html#cogl-object-ref" title="cogl_object_ref ()"><code class="function">cogl_object_ref()</code></a> and
<a class="link" href="cogl-2.0-experimental-The-Object-Interface.html#cogl-object-unref" title="cogl_object_unref ()"><code class="function">cogl_object_unref()</code></a></p>
<div class="refsect3">
<a name="cogl-matrix-entry-ref.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>entry</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-matrix-entry-unref"></a><h3>cogl_matrix_entry_unref ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_matrix_entry_unref (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a> *entry</code></em>);</pre>
<p>Releases a reference on <em class="parameter"><code>entry</code></em>
 either taken by calling
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-entry-unref" title="cogl_matrix_entry_unref ()"><code class="function">cogl_matrix_entry_unref()</code></a> or to release the reference given when
calling <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-get-entry" title="cogl_matrix_stack_get_entry ()"><code class="function">cogl_matrix_stack_get_entry()</code></a>.</p>
<div class="refsect3">
<a name="cogl-matrix-entry-unref.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>entry</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a></p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
</div>
</div>
<div class="refsect1">
<a name="cogl-2.0-experimental-Matrix-Stacks.other_details"></a><h2>Types and Values</h2>
<div class="refsect2">
<a name="CoglMatrixStack"></a><h3>CoglMatrixStack</h3>
<pre class="programlisting">typedef struct _CoglMatrixStack CoglMatrixStack;</pre>
<p>Tracks your current position within a hierarchy and lets you build
up a graph of transformations as you traverse through a hierarchy
such as a scenegraph.</p>
<p>A <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> always maintains a reference to a single
transformation at any point in time, representing the
transformation at the current position in the hierarchy. You can
get a reference to the current transformation by calling
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-get-entry" title="cogl_matrix_stack_get_entry ()"><code class="function">cogl_matrix_stack_get_entry()</code></a>.</p>
<p>When a <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> is first created with
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-new" title="cogl_matrix_stack_new ()"><code class="function">cogl_matrix_stack_new()</code></a> then it is conceptually positioned at the
root of your hierarchy and the current transformation simply
represents an identity transformation.</p>
<p>As you traverse your object hierarchy (your scenegraph) then you
should call <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-push" title="cogl_matrix_stack_push ()"><code class="function">cogl_matrix_stack_push()</code></a> whenever you move down one
level and call <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-pop" title="cogl_matrix_stack_pop ()"><code class="function">cogl_matrix_stack_pop()</code></a> whenever you move back up
one level towards the root.</p>
<p>At any time you can apply a set of operations, such as "rotate",
"scale", "translate" on top of the current transformation of a
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> using functions such as
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-rotate" title="cogl_matrix_stack_rotate ()"><code class="function">cogl_matrix_stack_rotate()</code></a>, <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-scale" title="cogl_matrix_stack_scale ()"><code class="function">cogl_matrix_stack_scale()</code></a> and
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-translate" title="cogl_matrix_stack_translate ()"><code class="function">cogl_matrix_stack_translate()</code></a>. These operations will derive a new
current transformation and will never affect a transformation
that you have referenced using <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-get-entry" title="cogl_matrix_stack_get_entry ()"><code class="function">cogl_matrix_stack_get_entry()</code></a>.</p>
<p>Internally applying operations to a <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> builds up a
graph of <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a> structures which each represent a single
immutable transform.</p>
</div>
<hr>
<div class="refsect2">
<a name="CoglMatrixEntry"></a><h3>CoglMatrixEntry</h3>
<pre class="programlisting">typedef struct _CoglMatrixEntry CoglMatrixEntry;</pre>
<p>Represents a single immutable transformation that was retrieved
from a <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> using <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-stack-get-entry" title="cogl_matrix_stack_get_entry ()"><code class="function">cogl_matrix_stack_get_entry()</code></a>.</p>
<p>Internally a <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a> represents a single matrix
operation (such as "rotate", "scale", "translate") which is applied
to the transform of a single parent entry.</p>
<p>Using the <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> api effectively builds up a graph of
these immutable <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a> structures whereby operations
that can be shared between multiple transformations will result
in shared <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a> nodes in the graph.</p>
<p>When a <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> is first created it references one
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a> that represents a single "load identity"
operation. This serves as the root entry and all operations
that are then applied to the stack will extend the graph
starting from this root "load identity" entry.</p>
<p>Given the typical usage model for a <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixStack" title="CoglMatrixStack"><span class="type">CoglMatrixStack</span></a> and the way
the entries are built up while traversing a scenegraph then in most
cases where an application is interested in comparing two
transformations for equality then it is enough to simply compare
two <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a> pointers directly. Technically this can lead
to false negatives that could be identified with a deeper
comparison but often these false negatives are unlikely and
don't matter anyway so this enables extremely cheap comparisons.</p>
<div class="note">
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#CoglMatrixEntry" title="CoglMatrixEntry"><span class="type">CoglMatrixEntry</span></a>s are reference counted using
<a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-entry-ref" title="cogl_matrix_entry_ref ()"><code class="function">cogl_matrix_entry_ref()</code></a> and <a class="link" href="cogl-2.0-experimental-Matrix-Stacks.html#cogl-matrix-entry-unref" title="cogl_matrix_entry_unref ()"><code class="function">cogl_matrix_entry_unref()</code></a> not with
<a class="link" href="cogl-2.0-experimental-The-Object-Interface.html#cogl-object-ref" title="cogl_object_ref ()"><code class="function">cogl_object_ref()</code></a> and <a class="link" href="cogl-2.0-experimental-The-Object-Interface.html#cogl-object-unref" title="cogl_object_unref ()"><code class="function">cogl_object_unref()</code></a>.</div>
</div>
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