Blink-side contiguous allocation of display items.

Source/platform/graphics/paint/DisplayItems.h

-// Copyright 2015 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 DisplayItems_h
-#define DisplayItems_h
-
-#include "platform/PlatformExport.h"
-#include "platform/graphics/paint/DisplayItem.h"
-#include "platform/graphics/paint/DrawingDisplayItem.h"
-#include "wtf/Forward.h"
-#include "wtf/Noncopyable.h"
-#include "wtf/OwnPtr.h"
-#include "wtf/Vector.h"
-
-#include <iterator>
-
-class GraphicsContext;
-class SkPicture;
-
-namespace blink {
-
-// Encapsulates logic for dealing with a simple list of display items, as
-// opposed to DisplayItemList, which also manages the logic required for caching
-// and updating them.
-//
-// This is presently implemented on top of a vector of pointers, but the
-// implementation is intended to change in the future.
-class PLATFORM_EXPORT DisplayItems {
-    WTF_MAKE_NONCOPYABLE(DisplayItems);
-public:
-    // Holds a handle to an individual item, and provides restricted access to
-    // it. This limits what needs to be exposed by later implementations.
-    class PLATFORM_EXPORT ItemHandle {
-    public:
-        // Returns true if there is no item, because it was removed from the
-        // list for checking of cached items.
-        // TODO(jbroman): Clarify the purpose of this.
-        bool isGone() const { return !m_ptr; }
-
-        DisplayItemClient client() const { return m_ptr->client(); }
-        DisplayItem::Type type() const { return m_ptr->type(); }
-        DisplayItem::Id id() const { return m_ptr->id(); }
-
-        bool isBegin() const { return m_ptr->isBegin(); }
-        bool drawsContent() const { return m_ptr->drawsContent(); }
-        bool skippedCache() const { return m_ptr->skippedCache(); }
-
-        void appendToWebDisplayItemList(WebDisplayItemList* list) const
-        {
-            m_ptr->appendToWebDisplayItemList(list);
-        }
-
-        const SkPicture* picture() const
-        {
-            ASSERT_WITH_SECURITY_IMPLICATION(DisplayItem::isDrawingType(type()));
-            return static_cast<DrawingDisplayItem*>(m_ptr)->picture();
-        }
-
-#if ENABLE(ASSERT)
-        DrawingDisplayItem::UnderInvalidationCheckingMode underInvalidationCheckingMode() const
-        {
-            ASSERT_WITH_SECURITY_IMPLICATION(DisplayItem::isDrawingType(type()));
-            return static_cast<DrawingDisplayItem*>(m_ptr)->underInvalidationCheckingMode();
-        }
-#endif
-
-#ifndef NDEBUG
-        String asDebugString() const { return m_ptr->asDebugString(); }
-        void dumpPropertiesAsDebugString(StringBuilder& builder) const { m_ptr->dumpPropertiesAsDebugString(builder); }
-#endif
-
-        void replay(GraphicsContext& context) const { m_ptr->replay(context); }
-
-    private:
-        ItemHandle() : m_ptr(nullptr) { }
-        explicit ItemHandle(DisplayItem* ptr) : m_ptr(ptr) { }
-
-        DisplayItem* m_ptr;
-        friend class DisplayItems;
-    };
-
-    // Input iterators over the display items.
-    class Iterator : public std::iterator<std::input_iterator_tag, const ItemHandle> {
-    public:
-        const ItemHandle& operator*() const { m_handle = ItemHandle(m_iterator->get()); return m_handle; }
-        const ItemHandle* operator->() const { return &operator*(); }
-        Iterator& operator++() { ++m_iterator; return *this; }
-        Iterator operator++(int) { Iterator tmp(*this); operator++(); return tmp; }
-        bool operator==(const Iterator& other) const { return m_iterator == other.m_iterator; }
-        bool operator!=(const Iterator& other) const { return !(*this == other); }
-    private:
-        using InternalIterator = Vector<OwnPtr<DisplayItem>>::iterator;
-        Iterator(const InternalIterator& it) : m_iterator(it) { }
-        InternalIterator m_iterator;
-        mutable ItemHandle m_handle;
-        friend class DisplayItems;
-        friend class ConstIterator;
-    };
-    class ConstIterator : public std::iterator<std::input_iterator_tag, const ItemHandle> {
-    public:
-        ConstIterator(const Iterator& it) : m_iterator(it.m_iterator) { }
-        const ItemHandle& operator*() const { m_handle = ItemHandle(m_iterator->get()); return m_handle; }
-        const ItemHandle* operator->() const { return &operator*(); }
-        ConstIterator& operator++() { ++m_iterator; return *this; }
-        ConstIterator operator++(int) { ConstIterator tmp(*this); operator++(); return tmp; }
-        bool operator==(const ConstIterator& other) const { return m_iterator == other.m_iterator; }
-        bool operator!=(const ConstIterator& other) const { return !(*this == other); }
-    private:
-        using InternalIterator = Vector<OwnPtr<DisplayItem>>::const_iterator;
-        ConstIterator(const InternalIterator& it) : m_iterator(it) { }
-        InternalIterator m_iterator;
-        mutable ItemHandle m_handle;
-        friend class DisplayItems;
-    };
-
-    DisplayItems();
-    ~DisplayItems();
-
-    bool isEmpty() const { return m_items.isEmpty(); }
-    size_t size() const { return m_items.size(); }
-
-    // Random access may not remain O(1) in the future.
-    ItemHandle operator[](size_t index) const { return ItemHandle(m_items[index].get()); }
-    Iterator iteratorAt(size_t index) { return Iterator(m_items.begin() + index); }
-    ConstIterator iteratorAt(size_t index) const { return ConstIterator(m_items.begin() + index); }
-    size_t indexForIterator(const Iterator& it) const { return it.m_iterator - m_items.begin(); }
-    size_t indexForIterator(const ConstIterator& it) const { return it.m_iterator - m_items.begin(); }
-
-    // Input iteration, however, should remain cheap.
-    Iterator begin() { return Iterator(m_items.begin()); }
-    Iterator end() { return Iterator(m_items.end()); }
-    ConstIterator begin() const { return ConstIterator(m_items.begin()); }
-    ConstIterator end() const { return ConstIterator(m_items.end()); }
-
-    // Access to the end of the list should also be fast.
-    ItemHandle last() const { return ItemHandle(m_items.last().get()); }
-
-    // TODO(jbroman): Replace this with something that doesn't first require
-    // heap allocation.
-    void append(PassOwnPtr<DisplayItem>);
-
-    // Appends by moving from another list. The item in the list it's being
-    // removed from will become "gone" in this process, but can still be safely
-    // destroyed.
-    void appendByMoving(const Iterator&);
-
-    void removeLast();
-    void clear();
-
-    // TODO(jbroman): Is swap the right primitive?
-    void swap(DisplayItems&);
-
-    // TODO(jbroman): This abstraction is odd and it would be nice to explain it
-    // more clearly.
-    void setGone(const Iterator&);
-
-private:
-    Vector<OwnPtr<DisplayItem>> m_items;
-};
-
-} // namespace blink
-
-#endif // DisplayItems_h