Extract "text align proc" functions as reusable classes

src/core/SkTextMapStateProc.h

+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkTextMapStateProc_DEFINED
+#define SkTextMapStateProc_DEFINED
+
+#include "SkPoint.h"
+#include "SkMatrix.h"
+
+class SkTextMapStateProc {
+public:
+    SkTextMapStateProc(const SkMatrix& matrix, SkScalar y, int scalarsPerPosition)
+        : fMatrix(matrix)
+        , fProc(matrix.getMapXYProc())
+        , fY(y)
+        , fScaleX(fMatrix.getScaleX())
+        , fTransX(fMatrix.getTranslateX()) {
+        SkASSERT(1 == scalarsPerPosition || 2 == scalarsPerPosition);
+        if (1 == scalarsPerPosition) {
+            unsigned mtype = fMatrix.getType();
+            if (mtype & (SkMatrix::kAffine_Mask | SkMatrix::kPerspective_Mask)) {
+                fMapCase = kX;
+            } else {
+                fY = SkScalarMul(y, fMatrix.getScaleY()) +
+                    fMatrix.getTranslateY();
+                if (mtype & SkMatrix::kScale_Mask) {
+                    fMapCase = kOnlyScaleX;
+                } else {
+                    fMapCase = kOnlyTransX;
+                }
+            }
+        } else {
+            fMapCase = kXY;
+        }
+    }
+
+    void operator()(const SkScalar pos[], SkPoint* loc) const;
+
+private:
+    const SkMatrix& fMatrix;
+    enum {
+        kXY,
+        kOnlyScaleX,
+        kOnlyTransX,
+        kX
+    } fMapCase;
+    const SkMatrix::MapXYProc fProc;
+    SkScalar fY; // Ignored by kXY case.
+    SkScalar fScaleX, fTransX; // These are only used by Only... cases.
+};
+
+inline void SkTextMapStateProc::operator()(const SkScalar pos[], SkPoint* loc) const {
+    switch(fMapCase) {
+    case kXY:
+        fProc(fMatrix, pos[0], pos[1], loc);
+        break;
+    case kOnlyScaleX:
+        loc->set(SkScalarMul(fScaleX, *pos) + fTransX, fY);
+        break;
+    case kOnlyTransX:
+        loc->set(*pos + fTransX, fY);
+        break;
+    default:
+        SkASSERT(false);
+    case kX:
+        fProc(fMatrix, *pos, fY, loc);
+        break;
+    }
+}
+
+#endif
+