Expand modulate, add, subtract, extract component glsl helpers.

src/gpu/gl/GrGLSL_impl.h

Index: src/gpu/gl/GrGLSL_impl.h
===================================================================
--- src/gpu/gl/GrGLSL_impl.h	(revision 0)
+++ src/gpu/gl/GrGLSL_impl.h	(revision 0)
@@ -0,0 +1,193 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrGLSL_impl_DEFINED
+#define GrGLSL_impl_DEFINED
+
+#include "SkString.h"
+
+namespace {
+template<int N>
+GrSLConstantVec return_const_vecf(GrSLConstantVec constVec, SkString* outAppend, bool omitAppend) {
+    GrAssert(kNone_GrSLConstantVec != constVec);
+    if (!omitAppend) {
+        if (kZeros_GrSLConstantVec == constVec) {
+            outAppend->append(GrGLSLZerosVecf(N));
+        } else {
+            outAppend->append(GrGLSLOnesVecf(N));
+        }
+    }
+    return constVec;
+}
+}
+
+template <int N>
+GrSLConstantVec GrGLSLModulatef(SkString* outAppend,
+                                const char* in0,
+                                const char* in1,
+                                GrSLConstantVec default0,
+                                GrSLConstantVec default1,
+                                bool omitIfConstVec) {
+    GrAssert(N > 0 && N <= 4);
+    GrAssert(NULL != outAppend);
+    
+    bool has0 = NULL != in0 && '\0' != *in0;
+    bool has1 = NULL != in1 && '\0' != *in1;
+    
+    GrAssert(has0 || kNone_GrSLConstantVec != default0);
+    GrAssert(has1 || kNone_GrSLConstantVec != default1);
+    
+    if (!has0 && !has1) {
+        GrAssert(kZeros_GrSLConstantVec == default0 || kOnes_GrSLConstantVec == default0);
+        GrAssert(kZeros_GrSLConstantVec == default1 || kOnes_GrSLConstantVec == default1);
+        if (kZeros_GrSLConstantVec == default0 || kZeros_GrSLConstantVec == default1) {
+            return return_const_vecf<N>(kZeros_GrSLConstantVec, outAppend, omitIfConstVec);
+        } else {
+            // both inputs are ones vectors
+            return return_const_vecf<N>(kOnes_GrSLConstantVec, outAppend, omitIfConstVec);
+        }
+    } else if (!has0) {
+        GrAssert(kZeros_GrSLConstantVec == default0 || kOnes_GrSLConstantVec == default0);
+        if (kZeros_GrSLConstantVec == default0) {
+            return return_const_vecf<N>(kZeros_GrSLConstantVec, outAppend, omitIfConstVec);
+        } else {
+            outAppend->appendf("%s(%s)", GrGLSLFloatVectorTypeString(N), in1);
+            return kNone_GrSLConstantVec;
+        }
+    } else if (!has1) {
+        GrAssert(kZeros_GrSLConstantVec == default1 || kOnes_GrSLConstantVec == default1);
+        if (kZeros_GrSLConstantVec == default1) {
+            return return_const_vecf<N>(kZeros_GrSLConstantVec, outAppend, omitIfConstVec);
+        } else {
+            outAppend->appendf("%s(%s)", GrGLSLFloatVectorTypeString(N), in0);
+            return kNone_GrSLConstantVec;
+        }
+    } else {
+        outAppend->appendf("%s((%s) * (%s))", GrGLSLFloatVectorTypeString(N), in0, in1);
+        return kNone_GrSLConstantVec;
+    }
+}
+
+template <int N>
+GrSLConstantVec GrGLSLAddf(SkString* outAppend,
+                           const char* in0,
+                           const char* in1,
+                           GrSLConstantVec default0,
+                           GrSLConstantVec default1,
+                           bool omitIfConstVec) {
+    GrAssert(N > 0 && N <= 4);
+    GrAssert(NULL != outAppend);
+    
+    bool has0 = NULL != in0 && '\0' != *in0;
+    bool has1 = NULL != in1 && '\0' != *in1;
+    
+    if (!has0 && !has1) {
+        GrAssert(kNone_GrSLConstantVec != default0);
+        GrAssert(kNone_GrSLConstantVec != default1);
+        int n = (kOnes_GrSLConstantVec == default0) + (kOnes_GrSLConstantVec == default1);
+        if (0 == n) {
+            return return_const_vecf<N>(kZeros_GrSLConstantVec, outAppend, omitIfConstVec);
+        } else if (1 == n) {
+            outAppend->append(GrGLSLOnesVecf(N));
+            return return_const_vecf<N>(kOnes_GrSLConstantVec, outAppend, omitIfConstVec);
+        } else {
+            GrAssert(2 == n);
+            outAppend->appendf("%s(2)", GrGLSLFloatVectorTypeString(N));
+            return kNone_GrSLConstantVec;
+        }
+    } else if (!has0) {
+        GrAssert(kNone_GrSLConstantVec != default0);
+        if (kZeros_GrSLConstantVec == default0) {
+            outAppend->appendf("%s(%s)", GrGLSLFloatVectorTypeString(N), in1);
+        } else {
+            outAppend->appendf("%s(%s) + %s",
+                               GrGLSLFloatVectorTypeString(N),
+                               in1,
+                               GrGLSLOnesVecf(N));
+        }
+        return kNone_GrSLConstantVec;
+    } else if (!has1) {
+        GrAssert(kNone_GrSLConstantVec != default1);
+        if (kZeros_GrSLConstantVec == default1) {
+            outAppend->appendf("%s(%s)", GrGLSLFloatVectorTypeString(N), in0);
+        } else {
+            outAppend->appendf("%s(%s) + %s",
+                               GrGLSLFloatVectorTypeString(N),
+                               in0,
+                               GrGLSLOnesVecf(N));
+        }
+        return kNone_GrSLConstantVec;
+    } else {
+        outAppend->appendf("(%s(%s) + %s(%s))",
+                           GrGLSLFloatVectorTypeString(N),
+                           in0,
+                           GrGLSLFloatVectorTypeString(N),
+                           in1);
+        return kNone_GrSLConstantVec;
+    }
+}
+
+template <int N>
+GrSLConstantVec GrGLSLSubtractf(SkString* outAppend,
+                                 const char* in0,
+                                 const char* in1,
+                                 GrSLConstantVec default0,
+                                 GrSLConstantVec default1,
+                                 bool omitIfConstVec) {
+    GrAssert(N > 0 && N <= 4);
+    GrAssert(NULL != outAppend);
+    
+    bool has0 = NULL != in0 && '\0' != *in0;
+    bool has1 = NULL != in1 && '\0' != *in1;
+    
+    if (!has0 && !has1) {
+        GrAssert(kNone_GrSLConstantVec != default0);
+        GrAssert(kNone_GrSLConstantVec != default1);
+        int n = (kOnes_GrSLConstantVec == default0) - (kOnes_GrSLConstantVec == default1);
+        if (-1 == n) {
+            outAppend->appendf("%s(-1)", GrGLSLFloatVectorTypeString(N));
+            return kNone_GrSLConstantVec;
+        } else if (0 == n) {
+            return return_const_vecf<N>(kZeros_GrSLConstantVec, outAppend, omitIfConstVec);
+        } else {
+            GrAssert(1 == n);
+            return return_const_vecf<N>(kOnes_GrSLConstantVec, outAppend, omitIfConstVec);
+        }
+    } else if (!has0) {
+        GrAssert(kNone_GrSLConstantVec != default0);
+        if (kZeros_GrSLConstantVec == default0) {
+            outAppend->appendf("-%s(%s)", GrGLSLFloatVectorTypeString(N), in1);
+        } else {
+            outAppend->appendf("%s - %s(%s)",
+                               GrGLSLOnesVecf(N),
+                               GrGLSLFloatVectorTypeString(N),
+                               in1);
+        }
+        return kNone_GrSLConstantVec;
+    } else if (!has1) {
+        GrAssert(kNone_GrSLConstantVec != default1);
+        if (kZeros_GrSLConstantVec == default1) {
+            outAppend->appendf("%s(%s)", GrGLSLFloatVectorTypeString(N), in0);
+        } else {
+            outAppend->appendf("%s(%s) - %s",
+                               GrGLSLFloatVectorTypeString(N),
+                               in0,
+                               GrGLSLOnesVecf(N));
+        }
+        return kNone_GrSLConstantVec;
+    } else {
+        outAppend->appendf("(%s(%s) - %s(%s))",
+                           GrGLSLFloatVectorTypeString(N),
+                           in0,
+                           GrGLSLFloatVectorTypeString(N),
+                           in1);
+        return kNone_GrSLConstantVec;
+    }
+}
+
+
+#endif