Add homogeneous point mapping to Matrix

src/core/SkMatrix.cpp

Index: src/core/SkMatrix.cpp
diff --git a/src/core/SkMatrix.cpp b/src/core/SkMatrix.cpp
index 36e735309bb4739bf66ead50fd2571dd8af75cf3..e5d48f022f43c6a0c86f8e706a998939dd6b3490 100644
--- a/src/core/SkMatrix.cpp
+++ b/src/core/SkMatrix.cpp
@@ -1218,7 +1218,7 @@ const SkMatrix::MapPtsProc SkMatrix::gMapPtsProcs[] = {
 };
 
 void SkMatrix::mapPoints(SkPoint dst[], const SkPoint src[], int count) const {
-    SkASSERT((dst && src && count > 0) || count == 0);
+    SkASSERT((dst && src && count > 0) || 0 == count);
     // no partial overlap
     SkASSERT(src == dst || SkAbs32((int32_t)(src - dst)) >= count);
 
@@ -1227,6 +1227,42 @@ void SkMatrix::mapPoints(SkPoint dst[], const SkPoint src[], int count) const {
 
 ///////////////////////////////////////////////////////////////////////////////
 
+void SkMatrix::mapHomogeneousPoints(SkScalar dst[], const SkScalar src[], int count) const {
+    SkASSERT((dst && src && count > 0) || 0 == count);
+    // no partial overlap
+    SkASSERT(src == dst || SkAbs32((int32_t)(src - dst)) >= 3*count);
+
+    if (count > 0) {
+        if (this->isIdentity()) {
+            memcpy(dst, src, 3*count*sizeof(SkScalar));
+            return;
+        }
+        do {
+            SkScalar sx = src[0];
+            SkScalar sy = src[1];
+            SkScalar sw = src[2];
+            src += 3;
+
+            SkScalar x = SkScalarMul(sx, fMat[kMScaleX]) +
+                         SkScalarMul(sy, fMat[kMSkewX]) +
+                         SkScalarMul(sw, fMat[kMTransX]);
+            SkScalar y = SkScalarMul(sx, fMat[kMSkewY]) +
+                         SkScalarMul(sy, fMat[kMScaleY]) +
+                         SkScalarMul(sw, fMat[kMTransY]);
+            SkScalar w = SkScalarMul(sx, fMat[kMPersp0]) +
+                         SkScalarMul(sy, fMat[kMPersp1]) +
+                         SkScalarMul(sw, fMat[kMPersp2]);
+
+            dst[0] = x;
+            dst[1] = y;
+            dst[2] = w;
+            dst += 3;
+        } while (--count);
+    }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
 void SkMatrix::mapVectors(SkPoint dst[], const SkPoint src[], int count) const {
     if (this->hasPerspective()) {
         SkPoint origin;