Add ToT WebGL conformance tests : part 9

conformance/ogles/GL2ExtensionTests/fwidth/fwidth_frag_ref.frag

Index: conformance/ogles/GL2ExtensionTests/fwidth/fwidth_frag_ref.frag
===================================================================
--- conformance/ogles/GL2ExtensionTests/fwidth/fwidth_frag_ref.frag	(revision 0)
+++ conformance/ogles/GL2ExtensionTests/fwidth/fwidth_frag_ref.frag	(working copy)
@@ -0,0 +1,64 @@
+
+/*
+** Copyright (c) 2012 The Khronos Group Inc.
+**
+** Permission is hereby granted, free of charge, to any person obtaining a
+** copy of this software and/or associated documentation files (the
+** "Materials"), to deal in the Materials without restriction, including
+** without limitation the rights to use, copy, modify, merge, publish,
+** distribute, sublicense, and/or sell copies of the Materials, and to
+** permit persons to whom the Materials are furnished to do so, subject to
+** the following conditions:
+**
+** The above copyright notice and this permission notice shall be included
+** in all copies or substantial portions of the Materials.
+**
+** THE MATERIALS ARE PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+** EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+** MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+** IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+** CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+** TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+** MATERIALS OR THE USE OR OTHER DEALINGS IN THE MATERIALS.
+*/
+
+
+#ifdef GL_ES
+#extension GL_OES_standard_derivatives : enable
+precision mediump float;
+#endif
+
+// setting a boundary for cases where screen sizes may exceed the precision
+// of the arithmetic used.
+#define SAFETY_BOUND 500.0
+
+// Macro to scale/bias the range of output.  If input is [-1.0, 1.0], maps to [0.5, 1.0]..  
+// Accounts for precision errors magnified by derivative operation.
+#define REDUCE_RANGE(A) ((A) + 3.0) / 4.0
+
+
+uniform float viewportwidth;
+uniform float viewportheight;
+
+varying vec2 vertXY;
+
+void main (void)
+{
+	const float M_PI = 3.14159265358979323846;
+	float func;
+
+	if( (gl_FragCoord.x < SAFETY_BOUND) && (gl_FragCoord.y < SAFETY_BOUND) )
+	{
+		// average of horizontal and vertical abs cosine waves with periods of 128 pixels
+
+#ifdef GL_OES_standard_derivatives
+		func = REDUCE_RANGE(0.5 * (abs(cos(fract(gl_FragCoord.x / 128.0) * (2.0 * M_PI))) + abs(cos(fract(gl_FragCoord.y / 128.0) * (2.0 * M_PI)))));
+#else
+    func = 0.5;
+#endif
+
+		gl_FragColor = vec4(func, func, func, 1.0);
+	}
+	else discard;
+}
+