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_posts/2015-12-30-Coolest-C-Preprocessor-Trick-of-the-Year.html
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_posts/2015-12-30-Coolest-C-Preprocessor-Trick-of-the-Year.html
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---
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layout: default
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title: 'Coolest C Preprocessor Trick of the Year'
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redirect_from:
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- /01451504315
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---
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<head>
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<title>Coolest C Preprocessor Trick of the Year</title>
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<link rel="stylesheet" href="https://media.unpythonic.net/css/bootstrap.min.css">
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<style>
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#mask {
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position: absolute;
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left: 0;
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top: 0;
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background-color: #000;
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opacity: 0.7;
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display: none;
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}
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#loading {
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position: fixed;
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left: 50%;
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top: 50%;
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width: 58px;
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height: 60px;
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background-color: black;
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background-image: url('https://media.unpythonic.net/img/loading.gif');
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opacity: 0.9;
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z-index: 20;
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display: none;
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border-radius: 4px;
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}
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#bigimg {
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position: fixed;
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top: 0;
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left: 0;
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width: 100%;
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height: 100%;
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display: none;
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}
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#maskouter {
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height: 100%;
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display: table;
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margin: 0 auto;
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}
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#maskinner {
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vertical-align: middle;
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display: table-cell;
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}
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#imgleft, #imgright {
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cursor: pointer;
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position: fixed;
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top: 50%;
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width: 64px;
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height: 64px;
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border-radius: 4px;
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background-color: black;
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z-index: 22;
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opacity: 0.7;
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}
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#imgleft {
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left: 0;
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background-image: url('https://media.unpythonic.net/img/prevbtn.png');
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}
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#imgleft.disabled, #imgright.disabled { display: none; }
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#imgright {
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right: 0;
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background-image: url('https://media.unpythonic.net/img/nextbtn.png');
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}
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#imgdesc {
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position: fixed;
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left: 64px;
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bottom: 0;
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background-color: #333;
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width: 100%;
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padding-top: 1em;
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padding-bottom: 1em;
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padding-left: 2em;
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border: 1px solid #555;
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border-bottom: 0;
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}
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#imgdesc .filename {
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color: #fff;
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font-weight: bold;
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}
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#imgdesc .description {
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color: #fff;
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padding-left: 1em;
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}
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#mask { z-index: 10990; }
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#loading { z-index: 10991; }
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#bigimg { z-index: 10992; }
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</style>
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<script type="text/javascript" src="https://media.unpythonic.net/js/jquery-1.6.4.min.js"></script>
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<script type="text/javascript" src="https://media.unpythonic.net/js/bootstrap-dropdown.js"></script>
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<script type="text/javascript" src="https://media.unpythonic.net/js/jquery.mousewheel.js"></script>
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<script type="text/javascript" src="https://media.unpythonic.net/js/jquery.ba-hashchange.min.js"></script>
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<script type="text/javascript" src="https://media.unpythonic.net/js/jquery.mobile.custom.min.js"></script>
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<script type="text/javascript" src="https://media.unpythonic.net/js/gallery.js"></script>
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<style><!--
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div.floatimageleft, div.floatimageright {
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border: 1px solid black;
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padding: 2px;
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margin: 1em;
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}
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div.floatimageleft { clear: left; float: left; }
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div.floatimageright { clear: right; float: right; }
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div.floatimageleft img, div.floatimageright img { border: 0px; }
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div.floatimageleft img.zoom, div.floatimageright img.zoom {
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padding: 4px;
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}
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--></style>
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<style><!--
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div.albumouter {
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margin-right: 1ex;
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margin-top: 1ex;
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vertical-align: baseline;
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display: -moz-inline-box;
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display: inline-block;
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text-decoration: none !important;
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}
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.album { display: block; clear: both; }
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.album a:link, .album a:hover, .album a:visited
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{ text-decoration: none; }
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.album a:hover { color: red; }
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.albumimage {
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display: block;
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padding-left: 2px; padding-right: 2px;
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padding-top: 3px; padding-bottom: 3px;
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background: #ececec;
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}
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.albumimage img.zoom {
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margin-left: 0px; margin-right: 0px;
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padding-top: 4px; padding-right: 4px; }
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.albumimage img { border: 0px;
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display: block; margin-left: auto; margin-right:auto
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}
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--></style>
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<!-- no summary found -->
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</head>
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<body>
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Probably everyone knew about this but me, but here goes anyway. (hat tip:
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<a href="https://github.com/google/angle/blob/master/util/shader_utils.h#L19">Google's ANGLE library</a>)
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<p>By suitably defining SHADER_SOURCE, you can write your shader program as
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though it was just inline source in your larger C(++) program:
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<pre>
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const char * fs = SHADER_SOURCE
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(
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precision mediump float;
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void main()
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{
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gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
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}
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);
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</pre>
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<p>The definition of SHADER_SOURCE is simple:
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<pre>
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#define SHADER_SOURCE(...) # __VA_ARGS__
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</pre>
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<p>This works as long as your shader is a valid sequence of preprocessor
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tokens. If you need to also use shader language directives like
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<tt>#version</tt>, you will need to write them as strings. But due to
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the way string catenation works, you can do
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<p><pre>
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const char * fs =
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"#version 100\n"
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SHADER_SOURCE(...);
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</pre>
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and keep most of the inline shader source outside of strings.
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<br><br><font size=-2>Entry first conceived on 30 December 2015, 19:38 UTC, last modified on 29 February 2016, 22:04 UTC</font>
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</body>
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</html>
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