Express (GLSL expression, possibly known value) pairs as a class

src/gpu/gl/GrGLSL.h

Index: src/gpu/gl/GrGLSL.h
diff --git a/src/gpu/gl/GrGLSL.h b/src/gpu/gl/GrGLSL.h
index b97e709aca39001b43757e0a1834e3ba9e856ac1..b48cecaef35f1f8e272ebd7decfbd1171a8b4f6e 100644
--- a/src/gpu/gl/GrGLSL.h
+++ b/src/gpu/gl/GrGLSL.h
@@ -11,10 +11,10 @@
 #include "gl/GrGLInterface.h"
 #include "GrColor.h"
 #include "GrTypesPriv.h"
+#include "SkString.h"
 
 class GrGLContextInfo;
 class GrGLShaderVar;
-class SkString;
 
 // Limited set of GLSL versions we build shaders for. Caller should round
 // down the GLSL version to one of these enums.
@@ -37,12 +37,6 @@ enum GrGLSLGeneration {
     k150_GrGLSLGeneration,
 };
 
-enum GrSLConstantVec {
-    kZeros_GrSLConstantVec,
-    kOnes_GrSLConstantVec,
-    kNone_GrSLConstantVec,
-};
-
 namespace {
 static inline int GrSLTypeToVecLength(GrSLType type) {
     static const int kVecLengths[] = {
@@ -59,20 +53,8 @@ static inline int GrSLTypeToVecLength(GrSLType type) {
     return kVecLengths[type];
 }
 
-static inline const char* GrGLSLOnesVecf(int count) {
-    static const char* kONESVEC[] = {"ERROR", "1.0", "vec2(1,1)",
-                                     "vec3(1,1,1)", "vec4(1,1,1,1)"};
-    SkASSERT(count >= 1 && count < (int)GR_ARRAY_COUNT(kONESVEC));
-    return kONESVEC[count];
 }
 
-static inline const char* GrGLSLZerosVecf(int count) {
-    static const char* kZEROSVEC[] = {"ERROR", "0.0", "vec2(0,0)",
-                                      "vec3(0,0,0)", "vec4(0,0,0,0)"};
-    SkASSERT(count >= 1 && count < (int)GR_ARRAY_COUNT(kZEROSVEC));
-    return kZEROSVEC[count];
-}
-}
 
 /**
  * Gets the most recent GLSL Generation compatible with the OpenGL context.
@@ -89,7 +71,7 @@ const char* GrGetGLSLVersionDecl(const GrGLContextInfo&);
 /**
  * Converts a GrSLType to a string containing the name of the equivalent GLSL type.
  */
-static const char* GrGLSLTypeString(GrSLType t) {
+inline const char* GrGLSLTypeString(GrSLType t) {

[bsalomon, 2013/10/02 13:20:26]

probably want both static and inline here, right?

[Kimmo Kinnunen, 2013/10/08 12:18:29]

Well, maybe from standpoint of being consistent with the rest of the header...

I just didn't see why there would need to have multiple versions of the same
function in different translation units?

Changed it to "static inline". (the code is dead anyway)

[bsalomon, 2013/10/08 14:45:27]

If it's dead let's remove it.

[Kimmo Kinnunen, 2013/10/09 13:39:59]

Sorry, mistook it for the other dead code. I removed the other dead code,
though.

I added "static inline" vs just "inline".

Just to verify: Using the "static inline" in this .h file will cause creation of
a new function for every .cpp file that uses the function "GrGLSLTypeString". Is
this really intended?

[bsalomon, 2013/10/09 19:53:31]

Hmm..  Perhaps not. Though, if the function really is always inlined then it
doesn't matter. Maybe we should consider making some of our "static inline"
functions just "inline" but there are many similar examples in Skia and if we
make the change it should be a broader migration.

     switch (t) {
         case kVoid_GrSLType:
             return "void";
@@ -113,12 +95,6 @@ static const char* GrGLSLTypeString(GrSLType t) {
     }
 }
 
-/** Return the type enum for a vector of floats of length n (1..4),
-    e.g. 1 -> "float", 2 -> "vec2", ... */
-static inline const char* GrGLSLFloatVectorTypeString(int n) {
-    return GrGLSLTypeString(GrSLFloatVectorType(n));
-}
-
 /** Return the GLSL swizzle operator for a homogenous component of a vector
     with the given number of coordinates, e.g. 2 -> ".y", 3 -> ".z" */
 const char* GrGLSLVectorHomogCoord(int count);
@@ -129,85 +105,131 @@ const char* GrGLSLVectorHomogCoord(GrSLType type);
 const char* GrGLSLVectorNonhomogCoords(int count);
 const char* GrGLSLVectorNonhomogCoords(GrSLType type);
 
-/**
-  * Produces a string that is the result of modulating two inputs. The inputs must be vecN or
-  * float. The result is always a vecN. The inputs may be expressions, not just identifier names.
-  * Either can be NULL or "" in which case the default params control whether a vector of ones or
-  * zeros. It is an error to pass kNone for default<i> if in<i> is NULL or "". Note that when the
-  * function determines that the result is a zeros or ones vec then any expression represented by
-  * or in1 will not be emitted (side effects won't occur). The return value indicates whether a
-  * known zeros or ones vector resulted. The output can be suppressed when known vector is produced
-  * by passing true for omitIfConstVec.
-  */
-template <int N>
-GrSLConstantVec GrGLSLModulatef(SkString* outAppend,
-                                const char* in0,
-                                const char* in1,
-                                GrSLConstantVec default0 = kOnes_GrSLConstantVec,
-                                GrSLConstantVec default1 = kOnes_GrSLConstantVec,
-                                bool omitIfConstVec = false);
-
-/**
- * Produces a string that is the result of adding two inputs. The inputs must be vecN or
- * float. The result is always a vecN. The inputs may be expressions, not just identifier names.
- * Either can be NULL or "" in which case the default params control whether a vector of ones or
- * zeros. It is an error to pass kNone for default<i> if in<i> is NULL or "". Note that when the
- * function determines that the result is a zeros or ones vec then any expression represented by
- * or in1 will not be emitted (side effects won't occur). The return value indicates whether a
- * known zeros or ones vector resulted. The output can be suppressed when known vector is produced
- * by passing true for omitIfConstVec.
+/** A class representing GLSL expression.
+ * The instance can be a variable name, expression or vecN(0) or vecN(1). Does simple constant
+ * folding with help of 1 and 0.
  */
 template <int N>
-GrSLConstantVec GrGLSLAddf(SkString* outAppend,
-                           const char* in0,
-                           const char* in1,
-                           GrSLConstantVec default0 = kZeros_GrSLConstantVec,
-                           GrSLConstantVec default1 = kZeros_GrSLConstantVec,
-                           bool omitIfConstVec = false);
+class GrGLSLExpr {
+public:
+    GrGLSLExpr()
+        : fType(kFullExpr_ExprType) {
+        // The only constructor that is allowed to build an empty expression.
+        SkASSERT(!isValid());

[bsalomon, 2013/10/02 13:20:26]

this->isValid()

several more below

[Kimmo Kinnunen, 2013/10/08 12:18:29]

Done.

+    }
 
-/**
- * Produces a string that is the result of subtracting two inputs. The inputs must be vecN or
- * float. The result is always a vecN. The inputs may be expressions, not just identifier names.
- * Either can be NULL or "" in which case the default params control whether a vector of ones or
- * zeros. It is an error to pass kNone for default<i> if in<i> is NULL or "". Note that when the
- * function determines that the result is a zeros or ones vec then any expression represented by
- * or in1 will not be emitted (side effects won't occur). The return value indicates whether a
- * known zeros or ones vector resulted. The output can be suppressed when known vector is produced
- * by passing true for omitIfConstVec.
- */
-template <int N>
-GrSLConstantVec GrGLSLSubtractf(SkString* outAppend,
-                                const char* in0,
-                                const char* in1,
-                                GrSLConstantVec default0 = kZeros_GrSLConstantVec,
-                                GrSLConstantVec default1 = kZeros_GrSLConstantVec,
-                                bool omitIfConstVec = false);
+    explicit GrGLSLExpr(int v) {

[bsalomon, 2013/10/02 13:20:26]

Comment that this replicates the int to all components?

[Kimmo Kinnunen, 2013/10/08 12:18:29]

Done.

+        if (v == 0) {
+            fType = kZeros_ExprType;
+        } else if (v == 1) {
+            fType = kOnes_ExprType;
+        } else {
+            fType = kFullExpr_ExprType;
+            fExpr.appendf(castIntStr(), v);

[bsalomon, 2013/10/02 13:20:26]

this->castIntStr()

[Kimmo Kinnunen, 2013/10/08 12:18:29]

Done.

+        }
+    }
 
-/**
- * Does an inplace mul, *=, of vec4VarName by mulFactor. If mulFactorDefault is not kNone then
- * mulFactor may be either "" or NULL. In this case either nothing will be appended (kOnes) or an
- * assignment of vec(0,0,0,0) will be appended (kZeros). The assignment is prepended by tabCnt tabs.
- * A semicolon and newline are added after the assignment. (TODO: Remove tabCnt when we auto-insert
- * tabs to GrGLEffect-generated lines.) If a zeros vec is assigned then the return value is
- * kZeros, otherwise kNone.
- */
-GrSLConstantVec GrGLSLMulVarBy4f(SkString* outAppend,
-                                 int tabCnt,
-                                 const char* vec4VarName,
-                                 const char* mulFactor,
-                                 GrSLConstantVec mulFactorDefault = kOnes_GrSLConstantVec);
+    // Argument expr is a simple expression or a parenthesized expression.
+    GrGLSLExpr(const char expr[]) {
+        if (NULL == expr) {  // TODO: remove this once effects input Exprs.
+            fType = kOnes_ExprType;
+        } else {
+            fType = kFullExpr_ExprType;
+            fExpr = expr;
+        }
+        SkASSERT(isValid());
+    }
+
+    // Argument expr is a simple expression or a parenthesized expression.
+    GrGLSLExpr(const SkString& expr) {
+        if (expr.isEmpty()) {  // TODO: remove this once effects input Exprs.
+            fType = kOnes_ExprType;
+        } else {
+            fType = kFullExpr_ExprType;
+            fExpr = expr;
+        }
+        SkASSERT(isValid());
+    }
+
+    /** Given an expression of vecM, cast it to vecN. */

[bsalomon, 2013/10/02 13:20:26]

Document what happens if N > M?

[Kimmo Kinnunen, 2013/10/08 12:18:29]

...

+    template<int M>
+    static GrGLSLExpr<N> VectorCast(const GrGLSLExpr<M>&);
+
+    bool isOnes() const { return fType == kOnes_ExprType; }
+    bool isZeros() const { return fType == kZeros_ExprType; }
+
+    template<int M>

[bsalomon, 2013/10/02 13:20:26]

Maybe a comment here about how a vecN and vecM are combined?

[Kimmo Kinnunen, 2013/10/08 12:18:29]

.. I see what you mean, good point. Changed the interface to not need the
hand-waving..

+    GrGLSLExpr<N> operator*(const GrGLSLExpr<M>& other) const;
+    template<int M>
+    GrGLSLExpr<N> operator+(const GrGLSLExpr<M>& other) const;
+    template<int M>
+    GrGLSLExpr<N> operator-(const GrGLSLExpr<M>& other) const;
+
+    /**

[bsalomon, 2013/10/02 15:18:04]

Maybe we ought to go ahead and have r() g() and b()?

[Kimmo Kinnunen, 2013/10/08 12:18:29]

Well, they'd be dead code... 

I didn't add them yet. If you feel they're a must, I can of course do it.

[bsalomon, 2013/10/08 14:45:27]

No, I just assume if we start really using this a lot in effects and what not
they will be needed. I'm ok if it's just a() but it'd be really weird to say
have r() and a() but not g() and b().

+     * Given an expression that evaluates to a GLSL vecN, extract alpha
+     * component. Valid only for expressions of dimensions 4.
+     */
+    GrGLSLExpr<1> a() const;
+
+    const char* c_str() const {
+        if (kZeros_ExprType == fType) {
+            return this->zerosStr();
+        } else if (kOnes_ExprType == fType) {
+            return this->onesStr();
+        }
+        SkASSERT(!fExpr.isEmpty()); // Empty expressions should not be used.
+        return fExpr.c_str();
+    }
+
+private:
+    GrGLSLExpr(const char format[], const char in0[])
+        : fType(kFullExpr_ExprType) {
+        fExpr.appendf(format, in0);
+    }
+
+    GrGLSLExpr(const char format[], const char in0[], const char in1[])
+        : fType(kFullExpr_ExprType) {
+        fExpr.appendf(format, in0, in1);
+    }
+
+    GrGLSLExpr(const char format[], const char in0[], const char in1)
+        : fType(kFullExpr_ExprType) {
+        fExpr.appendf(format, in0, in1);
+    }
+
+    bool isValid() const {
+        return kFullExpr_ExprType != fType || !fExpr.isEmpty();
+    }
+
+    static const char* zerosStr();
+    static const char* onesStr();
+    static const char* extractAlphaStr();
+    static const char* castStr();
+    static const char* castIntStr();
+
+    SkString fExpr;
+    enum ExprType {
+        kZeros_ExprType,
+        kOnes_ExprType,
+        kFullExpr_ExprType,
+    };
+    ExprType fType;
+
+    template <int> friend class GrGLSLExpr;
+};
+
+// Support for common case of (1 - expr.a()).
+template<int N>
+GrGLSLExpr<N> operator-(int a, const GrGLSLExpr<N>& b) {
+    return GrGLSLExpr<N>(a) - b;
+}
 
 /**
- * Given an expression that evaluates to a GLSL vec4, extract a component. If expr is NULL or ""
- * the value of defaultExpr is used. It is an error to pass an empty expr and have set defaultExpr
- * to kNone. The return value indicates whether the value is known to be 0 or 1. If omitIfConst is
- * set then nothing is appended when the return is not kNone.
+ * Does an inplace mul, *=, of vec4VarName by mulFactor.
+ * A semicolon and newline are added after the assignment.
  */
-GrSLConstantVec GrGLSLGetComponent4f(SkString* outAppend,
-                                     const char* expr,
-                                     GrColorComponentFlags component,
-                                     GrSLConstantVec defaultExpr = kNone_GrSLConstantVec,
-                                     bool omitIfConst = false);
+void GrGLSLMulVarBy4f(SkString* outAppend, unsigned tabCnt,
+                      const char* vec4VarName, const GrGLSLExpr<4>& mulFactor);
 
 #include "GrGLSL_impl.h"