Create SkLayerRasterizer w/o destroying Builder.

Add a new method to SkLayerRasterizer::Builder that creates a new
SkLayerRasterizer without destroying the Builder. Necessary to
continue to support Android's API.

Also fix a bug where creating a Builder and never calling
detachRasterizer results in not calling the destructor for any SkPaints
in the Builder.

Add tests.

BUG=b/13729784
R=reed@google.com, dominikg@chromium.org

Author: scroggo@google.com

Review URL: https://codereview.chromium.org/233673002

git-svn-id: http://skia.googlecode.com/svn/trunk@14139 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gyp/tests.gypi b/gyp/tests.gypi
index cf8e8ef..6fbcc03 100644
--- a/gyp/tests.gypi
+++ b/gyp/tests.gypi
@@ -102,6 +102,7 @@
     '../tests/JpegTest.cpp',
     '../tests/LListTest.cpp',
     '../tests/LayerDrawLooperTest.cpp',
+    '../tests/LayerRasterizerTest.cpp',
     '../tests/MD5Test.cpp',
     '../tests/MallocPixelRefTest.cpp',
     '../tests/MathTest.cpp',
diff --git a/include/effects/SkLayerRasterizer.h b/include/effects/SkLayerRasterizer.h
index fdfb179..fc21a7c 100644
--- a/include/effects/SkLayerRasterizer.h
+++ b/include/effects/SkLayerRasterizer.h
@@ -39,10 +39,26 @@
 
         /**
           *  Pass queue of layers on to newly created layer rasterizer and return it. The builder
-          *  cannot be used any more after calling this function.
+          *  *cannot* be used any more after calling this function.
+          *
+          *  The caller is responsible for calling unref() on the returned object.
           */
         SkLayerRasterizer* detachRasterizer();
 
+        /**
+          *  Create and return a new immutable SkLayerRasterizer that contains a shapshot of the
+          *  layers that were added to the Builder, without modifying the Builder. The Builder
+          *  *may* be used after calling this function. It will continue to hold any layers
+          *  previously added, so consecutive calls to this function will return identical objects,
+          *  and objects returned by future calls to this function contain all the layers in
+          *  previously returned objects.
+          *
+          *  Future calls to addLayer will not affect rasterizers previously returned by this call.
+          *
+          *  The caller is responsible for calling unref() on the returned object.
+          */
+        SkLayerRasterizer* snapshotRasterizer() const;
+
     private:
         SkDeque* fLayers;
     };
@@ -86,6 +102,8 @@
 
     static SkDeque* ReadLayers(SkReadBuffer& buffer);
 
+    friend class LayerRasterizerTester;
+
     typedef SkRasterizer INHERITED;
 };
 
diff --git a/src/effects/SkLayerRasterizer.cpp b/src/effects/SkLayerRasterizer.cpp
index e35c5e8..7143a3b 100644
--- a/src/effects/SkLayerRasterizer.cpp
+++ b/src/effects/SkLayerRasterizer.cpp
@@ -34,15 +34,20 @@
 {
 }
 
-SkLayerRasterizer::~SkLayerRasterizer() {
-    SkASSERT(fLayers);
-    SkDeque::F2BIter        iter(*fLayers);
+// Helper function to call destructors on SkPaints held by layers and delete layers.
+static void clean_up_layers(SkDeque* layers) {
+    SkDeque::F2BIter        iter(*layers);
     SkLayerRasterizer_Rec*  rec;
 
     while ((rec = (SkLayerRasterizer_Rec*)iter.next()) != NULL)
         rec->fPaint.~SkPaint();
 
-    SkDELETE(fLayers);
+    SkDELETE(layers);
+}
+
+SkLayerRasterizer::~SkLayerRasterizer() {
+    SkASSERT(fLayers);
+    clean_up_layers(const_cast<SkDeque*>(fLayers));
 }
 
 #ifdef SK_SUPPORT_LEGACY_LAYERRASTERIZER_API
@@ -194,7 +199,9 @@
 
 SkLayerRasterizer::Builder::~Builder()
 {
-    SkDELETE(fLayers);
+    if (fLayers != NULL) {
+        clean_up_layers(fLayers);
+    }
 }
 
 void SkLayerRasterizer::Builder::addLayer(const SkPaint& paint, SkScalar dx,
@@ -211,3 +218,20 @@
     fLayers = NULL;
     return rasterizer;
 }
+
+SkLayerRasterizer* SkLayerRasterizer::Builder::snapshotRasterizer() const {
+    SkDeque* layers = SkNEW_ARGS(SkDeque, (sizeof(SkLayerRasterizer_Rec), fLayers->count()));
+    SkDeque::F2BIter                iter(*fLayers);
+    const SkLayerRasterizer_Rec*    recOrig;
+    SkDEBUGCODE(int                 count = 0;)
+    while ((recOrig = static_cast<SkLayerRasterizer_Rec*>(iter.next())) != NULL) {
+        SkDEBUGCODE(count++);
+        SkLayerRasterizer_Rec* recCopy = static_cast<SkLayerRasterizer_Rec*>(layers->push_back());
+        SkNEW_PLACEMENT_ARGS(&recCopy->fPaint, SkPaint, (recOrig->fPaint));
+        recCopy->fOffset = recOrig->fOffset;
+    }
+    SkASSERT(fLayers->count() == count);
+    SkASSERT(layers->count() == count);
+    SkLayerRasterizer* rasterizer = SkNEW_ARGS(SkLayerRasterizer, (layers));
+    return rasterizer;
+}
diff --git a/tests/LayerRasterizerTest.cpp b/tests/LayerRasterizerTest.cpp
new file mode 100644
index 0000000..b393525
--- /dev/null
+++ b/tests/LayerRasterizerTest.cpp
@@ -0,0 +1,138 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkDeque.h"
+#include "SkLayerRasterizer.h"
+#include "SkPaint.h"
+#include "SkRasterizer.h"
+#include "Test.h"
+
+class SkReadBuffer;
+
+// Dummy class to place on a paint just to ensure the paint's destructor
+// is called.
+// ONLY to be used by LayerRasterizer_destructor, since other tests may
+// be run in a separate thread, and this class is not threadsafe.
+class DummyRasterizer : public SkRasterizer {
+public:
+    DummyRasterizer()
+        : INHERITED()
+    {
+        // Not threadsafe. Only used in one thread.
+        gCount++;
+    }
+
+    ~DummyRasterizer() {
+        // Not threadsafe. Only used in one thread.
+        gCount--;
+    }
+
+    static int GetCount() { return gCount; }
+
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(DummyRasterizer)
+
+private:
+    DummyRasterizer(SkReadBuffer&) {}
+
+    static int gCount;
+
+    typedef SkRasterizer INHERITED;
+};
+
+int DummyRasterizer::gCount;
+
+// Check to make sure that the SkPaint in the layer has its destructor called.
+DEF_TEST(LayerRasterizer_destructor, reporter) {
+    {
+        SkPaint paint;
+        paint.setRasterizer(SkNEW(DummyRasterizer))->unref();
+        REPORTER_ASSERT(reporter, DummyRasterizer::GetCount() == 1);
+
+        SkLayerRasterizer::Builder builder;
+        builder.addLayer(paint);
+    }
+    REPORTER_ASSERT(reporter, DummyRasterizer::GetCount() == 0);
+}
+
+class LayerRasterizerTester {
+public:
+    static int CountLayers(const SkLayerRasterizer& layerRasterizer) {
+        return layerRasterizer.fLayers->count();
+    }
+
+    static const SkDeque& GetLayers(const SkLayerRasterizer& layerRasterizer) {
+        return *layerRasterizer.fLayers;
+    }
+};
+
+// MUST stay in sync with definition of SkLayerRasterizer_Rec in SkLayerRasterizer.cpp.
+struct SkLayerRasterizer_Rec {
+    SkPaint     fPaint;
+    SkVector    fOffset;
+};
+
+static bool equals(const SkLayerRasterizer_Rec& rec1, const SkLayerRasterizer_Rec& rec2) {
+    return rec1.fPaint == rec2.fPaint && rec1.fOffset == rec2.fOffset;
+}
+
+DEF_TEST(LayerRasterizer_copy, reporter) {
+    SkLayerRasterizer::Builder builder;
+    SkPaint paint;
+    // Create a bunch of paints with different flags.
+    for (uint32_t flags = 0x01; flags < SkPaint::kAllFlags; flags <<= 1) {
+        paint.setFlags(flags);
+        builder.addLayer(paint, flags, flags);
+    }
+
+    // Create a layer rasterizer with all the existing layers.
+    SkAutoTUnref<SkLayerRasterizer> firstCopy(builder.snapshotRasterizer());
+
+    // Add one more layer.
+    paint.setFlags(SkPaint::kAllFlags);
+    builder.addLayer(paint);
+
+    SkAutoTUnref<SkLayerRasterizer> oneLarger(builder.snapshotRasterizer());
+    SkAutoTUnref<SkLayerRasterizer> detached(builder.detachRasterizer());
+
+    // Check the counts for consistency.
+    const int largerCount = LayerRasterizerTester::CountLayers(*oneLarger.get());
+    const int smallerCount = LayerRasterizerTester::CountLayers(*firstCopy.get());
+    REPORTER_ASSERT(reporter, largerCount == LayerRasterizerTester::CountLayers(*detached.get()));
+    REPORTER_ASSERT(reporter, smallerCount == largerCount - 1);
+
+    const SkLayerRasterizer_Rec* recFirstCopy = NULL;
+    const SkLayerRasterizer_Rec* recOneLarger = NULL;
+    const SkLayerRasterizer_Rec* recDetached = NULL;
+
+    const SkDeque& layersFirstCopy = LayerRasterizerTester::GetLayers(*firstCopy.get());
+    const SkDeque& layersOneLarger = LayerRasterizerTester::GetLayers(*oneLarger.get());
+    const SkDeque& layersDetached = LayerRasterizerTester::GetLayers(*detached.get());
+
+    // Ensure that our version of SkLayerRasterizer_Rec is the same as the one in
+    // SkLayerRasterizer.cpp - or at least the same size. If the order were switched, we
+    // would fail the test elsewhere.
+    REPORTER_ASSERT(reporter, layersFirstCopy.elemSize() == sizeof(SkLayerRasterizer_Rec));
+    REPORTER_ASSERT(reporter, layersOneLarger.elemSize() == sizeof(SkLayerRasterizer_Rec));
+    REPORTER_ASSERT(reporter, layersDetached.elemSize() == sizeof(SkLayerRasterizer_Rec));
+
+    SkDeque::F2BIter iterFirstCopy(layersFirstCopy);
+    SkDeque::F2BIter iterOneLarger(layersOneLarger);
+    SkDeque::F2BIter iterDetached(layersDetached);
+
+    for (int i = 0; i < largerCount; ++i) {
+        recFirstCopy = static_cast<const SkLayerRasterizer_Rec*>(iterFirstCopy.next());
+        recOneLarger = static_cast<const SkLayerRasterizer_Rec*>(iterOneLarger.next());
+        recDetached  = static_cast<const SkLayerRasterizer_Rec*>(iterDetached.next());
+
+        REPORTER_ASSERT(reporter, equals(*recOneLarger, *recDetached));
+        if (smallerCount == i) {
+            REPORTER_ASSERT(reporter, recFirstCopy == NULL);
+        } else {
+            REPORTER_ASSERT(reporter, equals(*recFirstCopy, *recOneLarger));
+        }
+    }
+}