added support for discarding fragments

IIS.SLSharp/IIS.SLSharp.csproj

@@ -80,6 +80,7 @@
     <Compile Include="Shaders\ShaderDefinition.MatrixFunctions.cs" />
     <Compile Include="Shaders\ShaderDefinition.Noise.cs" />
     <Compile Include="Shaders\ShaderDefinition.Sampler.cs" />
+    <Compile Include="Shaders\ShaderDefinition.Special.cs" />
     <Compile Include="Shaders\ShaderDefinition.Texture.cs" />
     <Compile Include="Shaders\ShaderDefinition.Trigonometry.cs" />
     <Compile Include="Shaders\ShaderDefinition.UInt32Vector.cs" />

IIS.SLSharp/Shaders/ShaderDefinition.Special.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace IIS.SLSharp.Shaders
+{
+    public abstract partial class ShaderDefinition
+    {
+        /// <summary>
+        /// Discards the current fragment.
+        /// </summary>
+        protected internal static void Discard() { throw _invalidAccess; }
+    }
+}

IIS.SLSharp/Translation/GLSL/GlslVisitor.ShaderDef.cs

@@ -14,6 +14,8 @@ public GlslVisitor()
         {
             Handlers = new Dictionary<Expression<Action>, Func<MethodDefinition, InvocationExpression, StringBuilder>>(new HandlerComparer())
             {
+                { () => ShaderDefinition.Discard(), KeywordDiscard },
+
                 #region Trigonometry
 
                 { () => ShaderDefinition.Radians(_float), ToLower },
@@ -518,5 +520,10 @@ public GlslVisitor()
                 #endregion
             };
         }
+
+        private StringBuilder KeywordDiscard(MethodDefinition unused1, InvocationExpression unused2)
+        {
+            return new StringBuilder("discard");
+        }
     }
 }