Revert "Revert "Add Atlas Text interface for rendering SDF glyphs.""

This reverts commit 9c2202ffc22b4293b48a4edeafa1b5d2bab8bb83.

Bug: skia:
Change-Id: I482ddf74f8e40d3d0908c840ba5c6ff981ccefbd
Reviewed-on: https://skia-review.googlesource.com/73345
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>

2 files changed, 82 insertions, 3 deletions

diff --git a/src/core/SkArenaAlloc.h b/src/core/SkArenaAlloc.h
index 9e971610a6..2f23382ac1 100644
--- a/src/core/SkArenaAlloc.h
+++ b/src/core/SkArenaAlloc.h
@@ -5,8 +5,8 @@
  * found in the LICENSE file.
  */
 
-#ifndef SkFixedAlloc_DEFINED
-#define SkFixedAlloc_DEFINED
+#ifndef SkArenaAlloc_DEFINED
+#define SkArenaAlloc_DEFINED
 
 #include "SkRefCnt.h"
 #include "SkTFitsIn.h"
@@ -240,4 +240,4 @@ private:
     using INHERITED = SkArenaAlloc;
 };
 
-#endif//SkFixedAlloc_DEFINED
+#endif  // SkArenaAlloc_DEFINED
diff --git a/src/core/SkArenaAllocList.h b/src/core/SkArenaAllocList.h
new file mode 100644
index 0000000000..b4e442b0bd
--- /dev/null
+++ b/src/core/SkArenaAllocList.h
@@ -0,0 +1,79 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkArenaAllocList_DEFINED
+#define SkArenaAllocList_DEFINED
+
+#include "SkArenaAlloc.h"
+
+/**
+ * A singly linked list of Ts stored in a SkArenaAlloc. The arena rather than the list owns
+ * the elements. This supports forward iteration and range based for loops.
+ */
+template <typename T>
+class SkArenaAllocList {
+private:
+    struct Node;
+
+public:
+    SkArenaAllocList() = default;
+
+    void reset() { fHead = fTail = nullptr; }
+
+    template <typename... Args>
+    inline T& append(SkArenaAlloc* arena, Args... args);
+
+    class Iter {
+    public:
+        Iter() = default;
+        inline Iter& operator++();
+        T& operator*() const { return fCurr->fT; }
+        T* operator->() const { return &fCurr->fT; }
+        bool operator==(const Iter& that) const { return fCurr == that.fCurr; }
+        bool operator!=(const Iter& that) const { return !(*this == that); }
+
+    private:
+        friend class SkArenaAllocList;
+        explicit Iter(Node* node) : fCurr(node) {}
+        Node* fCurr = nullptr;
+    };
+
+    Iter begin() { return Iter(fHead); }
+    Iter end() { return Iter(); }
+    Iter tail() { return Iter(fTail); }
+
+private:
+    struct Node {
+        template <typename... Args>
+        Node(Args... args) : fT(std::forward<Args>(args)...) {}
+        T fT;
+        Node* fNext = nullptr;
+    };
+    Node* fHead = nullptr;
+    Node* fTail = nullptr;
+};
+
+template <typename T>
+template <typename... Args>
+T& SkArenaAllocList<T>::append(SkArenaAlloc* arena, Args... args) {
+    SkASSERT(!fHead == !fTail);
+    auto* n = arena->make<Node>(std::forward<Args>(args)...);
+    if (!fTail) {
+        fHead = fTail = n;
+    } else {
+        fTail = fTail->fNext = n;
+    }
+    return fTail->fT;
+}
+
+template <typename T>
+typename SkArenaAllocList<T>::Iter& SkArenaAllocList<T>::Iter::operator++() {
+    fCurr = fCurr->fNext;
+    return *this;
+}
+
+#endif