add zfast_lcd shader by popular demand

handheld/shaders/zfast_lcd.slang

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+#version 450
+
+/*
+    zfast_lcd_standard - A very simple LCD shader meant to be used at 1080p
+		on the raspberry pi 3.
+		
+    Copyright (C) 2017 Greg Hogan (SoltanGris42)
+    This program is free software; you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by the Free
+    Software Foundation; either version 2 of the License, or (at your option)
+    any later version.
+Notes:  This shader just does nearest neighbor scaling of the game and then
+		darkens the border pixels to imitate an LCD screen. You can change the
+		amount of darkening and the thickness of the borders.  You can also 
+		do basic gamma adjustment.
+		
+*/
+
+layout(push_constant) uniform Push
+{
+	vec4 SourceSize;
+	vec4 OriginalSize;
+	vec4 OutputSize;
+	uint FrameCount;
+	float BORDERMULT, GBAGAMMA;
+} params;
+
+#pragma parameter BORDERMULT "Border Multiplier" 14.0 -40.0 40.0 1.0
+#pragma parameter GBAGAMMA "GBA Gamma Hack" 1.0 0.0 1.0 1.0
+
+//For testing compilation 
+//#define FRAGMENT
+//#define VERTEX
+//#define GBAGAMMA 
+
+//Some drivers don't return black with texture coordinates out of bounds
+//SNES Classic is too slow to black these areas out when using fullscreen
+//overlays.  But you can uncomment the below to black them out if necessary
+
+#define BLACK_OUT_BORDER
+
+layout(std140, set = 0, binding = 0) uniform UBO
+{
+	mat4 MVP;
+} global;
+
+#pragma stage vertex
+layout(location = 0) in vec4 Position;
+layout(location = 1) in vec2 TexCoord;
+layout(location = 0) out vec2 vTexCoord;
+
+void main()
+{
+   gl_Position = global.MVP * Position;
+   vTexCoord = TexCoord;
+}
+
+#pragma stage fragment
+layout(location = 0) in vec2 vTexCoord;
+layout(location = 0) out vec4 FragColor;
+layout(set = 0, binding = 2) uniform sampler2D Source;
+
+void main()
+{
+	vec2 texcoordInPixels = vTexCoord.xy * params.SourceSize.xy;
+	vec2 centerCoord = floor(texcoordInPixels.xy)+vec2(0.5,0.5);
+	vec2 distFromCenter = abs(centerCoord - texcoordInPixels);
+
+	float Y = max(distFromCenter.x,(distFromCenter.y));
+
+	Y=Y*Y;
+	float YY = Y*Y;
+	float YYY = YY*Y;
+
+	float LineWeight = YY - 2.7*YYY;
+	LineWeight = 1.0 - params.BORDERMULT*LineWeight;
+
+	vec3 colour = texture(Source, params.SourceSize.zw*centerCoord).rgb*LineWeight;
+
+//#if defined(GBAGAMMA)
+//	//colour.rgb = pow(colour.rgb, vec3(1.35));
+//	colour.rgb*=0.6+0.4*(colour.rgb); //fake gamma because the pi is too slow!
+//#endif
+	if (params.GBAGAMMA > 0.5)
+		colour.rgb*=0.6+0.4*(colour.rgb); //fake gamma because the pi is too slow!
+		
+	FragColor = vec4(colour.rgb , 1.0);
+}

handheld/zfast-crt.slangp

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+shaders = 1
+
+shader0 = shaders/zfast_lcd.slang
+filter_linear0 = true