cc: Implement tile iteration order based on pyramid sequence. [old]

cc/base/pyramid_sequence.h

Index: cc/base/pyramid_sequence.h
diff --git a/cc/base/pyramid_sequence.h b/cc/base/pyramid_sequence.h
new file mode 100644
index 0000000000000000000000000000000000000000..dbfb74b3519ef1091a1f731c39e99e43951a0504
--- /dev/null
+++ b/cc/base/pyramid_sequence.h
@@ -0,0 +1,60 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CC_BASE_PYRAMID_SEQUENCE_H_
+#define CC_BASE_PYRAMID_SEQUENCE_H_
+
+#include "base/logging.h"
+#include "cc/base/cc_export.h"
+
+namespace cc {
+
+class CC_EXPORT PyramidSequence {

[vmpstr, 2016/06/16 18:28:58]

Can you put a comprehensive comment here explaining what this does?

+ public:
+  enum class Type : uint16_t {
+    FORWARD,
+    BACKWARD,
+    DIAGONAL_FORWARD,
+    DIAGONAL_BACKWARD
+  };
+
+  PyramidSequence(Type type, int start, int end, int levels);

[vmpstr, 2016/06/16 18:28:58]

This needs a comment to explain what each variable does

+  ~PyramidSequence();
+
+  int GetCurrent();

[vmpstr, 2016/06/16 18:28:58]

Name this better... GetCurrent what?

+  int GetCoverage();
+  bool within_bounds() { return within_bounds_; }

[vmpstr, 2016/06/16 18:28:58]

is_within_bounds

+  void Advance();
+
+ private:
+  typedef void (PyramidSequence::*InflateFn)();

[vmpstr, 2016/06/16 18:28:58]

using InflateFn = void (PyramidSequence::*)();

+  typedef bool (PyramidSequence::*IsWithinBoundsFn)();
+
+  void Init(Type type);
+  void Reset();
+
+  void InflateForward();
+  bool IsWithinBoundsForward();
+  void InflateBackward();
+  bool IsWithinBoundsBackward();
+  void InflateDiagonalForward();
+  bool IsWithinBoundsDiagonalForward();
+  void InflateDiagonalBackward();
+  bool IsWithinBoundsDiagonalBackward();
+
+  int start_;
+  int end_;
+  int levels_;
+  int levels_traversed_;
+  bool within_bounds_;
+  int current_;
+  int step_;
+
+  InflateFn inflater_;

[vmpstr, 2016/06/16 18:28:58]

I'd call this "inflate_" and "determine_within_bounds_" or something (like verbs
instead of nouns, but up to you)

+  IsWithinBoundsFn within_bounds_checker_;
+};
+
+}  // namespace cc
+
+#endif  // CC_BASE_PYRAMID_SEQUENCE_H_