add SkCanvas::drawAtlas

include/core/SkRSXform.h

Index: include/core/SkRSXform.h
diff --git a/include/core/SkRSXform.h b/include/core/SkRSXform.h
new file mode 100644
index 0000000000000000000000000000000000000000..5dffdc25d954d00c42b4020c459a1f7a76c959f5
--- /dev/null
+++ b/include/core/SkRSXform.h
@@ -0,0 +1,49 @@
+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkRSXform_DEFINED
+#define SkRSXform_DEFINED
+
+#include "SkScalar.h"
+
+/**
+ *  A compressed form of a rotation+scale matrix.
+ *
+ *  [ fSCos     -fSSin    fTx ]
+ *  [ fSSin      fSCos    fTy ]
+ *  [     0          0      1 ]
+ */
+struct SkRSXform {
+    SkScalar    fSCos;
+    SkScalar    fSSin;
+    SkScalar    fTx;
+    SkScalar    fTy;
+
+    bool rectStaysRect() const {
+        return 0 == fSCos || 0 == fSSin;
+    }
+    
+    void setIdentity() {
+        fSCos = 1;
+        fSSin = fTx = fTy = 0;
+    }
+
+    void set(SkScalar scos, SkScalar ssin, SkScalar tx, SkScalar ty) {
+        fSCos = scos;
+        fSSin = ssin;
+        fTx = tx;
+        fTy = ty;
+    }
+
+    void toQuad(SkScalar width, SkScalar height, SkPoint quad[4]) const;
+    void toQuad(const SkSize& size, SkPoint quad[4]) const {
+        this->toQuad(size.width(), size.height(), quad);
+    }
+};
+
+#endif
+