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Next: <a href="Rendering-Engine.html#Rendering-Engine" accesskey="n" rel="next">Rendering Engine</a>, Previous: <a href="Framebuffers.html#Framebuffers" accesskey="p" rel="prev">Framebuffers</a>, Up: <a href="Graphics.html#Graphics" accesskey="u" rel="up">Graphics</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index.html#Index" title="Index" rel="index">Index</a>]</p>
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<a name="Viewports-1"></a>
<h4 class="subsection">2.3.9 Viewports</h4>
<p>A viewport represents a subset of the screen (or framebuffer). When
rendering a frame, the resulting image will only appear within that
viewport. These aren’t often needed, and Chickadee’s default viewport
occupies the entire screen, but there are certain situations where
they are useful. For example, a split-screen multiplayer game may
render to two different viewports, each occupying a different half of
the screen. For information about how to set the current viewport,
see <code>with-viewport</code> in <a href="Rendering-Engine.html#Rendering-Engine">Rendering Engine</a>.
</p>
<p>The <code>(chickadee render viewport)</code> module provides the following
API:
</p>
<dl>
<dt><a name="index-make_002dviewport"></a>Procedure: <strong>make-viewport</strong> <em>x y width height [#:clear-color] [#:clear-flags]</em></dt>
<dd>
<p>Create a viewport that covers an area of the window starting from
coordinates (<var>x</var>, <var>y</var>) and spanning <var>width</var> <code>x</code>
<var>height</var> pixels. Fill the viewport with <var>clear-color</var> when
clearing the screen. Clear the buffers denoted by the list of symbols
in <var>clear-flags</var>.
</p>
<p>Possible values for <var>clear-flags</var> are <var>color-buffer</var>,
<var>depth-buffer</var>, <var>accum-buffer</var>, and <var>stencil-buffer</var>.
</p></dd></dl>
<dl>
<dt><a name="index-viewport_003f"></a>Procedure: <strong>viewport?</strong> <em>obj</em></dt>
<dd><p>Return <code>#t</code> if <var>obj</var> is a viewport.
</p></dd></dl>
<dl>
<dt><a name="index-viewport_002dx"></a>Procedure: <strong>viewport-x</strong> <em>viewport</em></dt>
<dd><p>Return the left edge of <var>viewport</var>.
</p></dd></dl>
<dl>
<dt><a name="index-viewport_002dy"></a>Procedure: <strong>viewport-y</strong> <em>viewport</em></dt>
<dd><p>Return the bottom edge of <var>viewport</var>.
</p></dd></dl>
<dl>
<dt><a name="index-viewport_002dwidth"></a>Procedure: <strong>viewport-width</strong> <em>viewport</em></dt>
<dd><p>Return the width of <var>viewport</var>.
</p></dd></dl>
<dl>
<dt><a name="index-viewport_002dheight"></a>Procedure: <strong>viewport-height</strong> <em>viewport</em></dt>
<dd><p>Return the height of <var>viewport</var>.
</p></dd></dl>
<dl>
<dt><a name="index-viewport_002dclear_002dcolor"></a>Procedure: <strong>viewport-clear-color</strong> <em>viewport</em></dt>
<dd><p>Return the clear color for <var>viewport</var>.
</p></dd></dl>
<dl>
<dt><a name="index-viewport_002dclear_002dflags"></a>Procedure: <strong>viewport-clear-flags</strong> <em>viewport</em></dt>
<dd><p>Return the list of clear flags for <var>viewport</var>.
</p></dd></dl>
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