Fix SkTCopyOnFirstWrite copy semantics

The implicit SkTCopyOnFirstWrite copy-ctor and assignment operator are
incorrect: fObj must point to the local copy, not to the source copy
(when a copy has been made).

Add corrected explicit copy (and move) ctor + assignment operator.

Also add a get() helper to facilitate rawptr access.

Change-Id: Ie3983e12c04eae4f32c40e3e267618cf02008c20
Reviewed-on: https://skia-review.googlesource.com/120442
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>

1 files changed, 19 insertions, 2 deletions

diff --git a/include/core/SkTLazy.h b/include/core/SkTLazy.h
index 39ebdbef4a..a166f05a74 100644
--- a/include/core/SkTLazy.h
+++ b/include/core/SkTLazy.h
@@ -148,13 +148,28 @@ private:
 template <typename T>
 class SkTCopyOnFirstWrite {
 public:
-    SkTCopyOnFirstWrite(const T& initial) : fObj(&initial) {}
+    explicit SkTCopyOnFirstWrite(const T& initial) : fObj(&initial) {}
 
-    SkTCopyOnFirstWrite(const T* initial) : fObj(initial) {}
+    explicit SkTCopyOnFirstWrite(const T* initial) : fObj(initial) {}
 
     // Constructor for delayed initialization.
     SkTCopyOnFirstWrite() : fObj(nullptr) {}
 
+    SkTCopyOnFirstWrite(const SkTCopyOnFirstWrite&  that) { *this = that;            }
+    SkTCopyOnFirstWrite(      SkTCopyOnFirstWrite&& that) { *this = std::move(that); }
+
+    SkTCopyOnFirstWrite& operator=(const SkTCopyOnFirstWrite& that) {
+        fLazy = that.fLazy;
+        fObj  = fLazy.isValid() ? fLazy.get() : that.fObj;
+        return *this;
+    }
+
+    SkTCopyOnFirstWrite& operator=(SkTCopyOnFirstWrite&& that) {
+        fLazy = std::move(that.fLazy);
+        fObj  = fLazy.isValid() ? fLazy.get() : that.fObj;
+        return *this;
+    }
+
     // Should only be called once, and only if the default constructor was used.
     void init(const T& initial) {
         SkASSERT(nullptr == fObj);
@@ -174,6 +189,8 @@ public:
         return const_cast<T*>(fObj);
     }
 
+    const T* get() const { return fObj; }
+
     /**
      * Operators for treating this as though it were a const pointer.
      */