WIP: Construct SPV2's scroll paint property tree

third_party/WebKit/Source/platform/graphics/paint/ScrollPaintPropertyNode.h

+// 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 ScrollPaintPropertyNode_h
+#define ScrollPaintPropertyNode_h
+
+#include "platform/PlatformExport.h"
+#include "platform/geometry/FloatSize.h"
+#include "platform/graphics/paint/TransformPaintPropertyNode.h"
+#include "wtf/PassRefPtr.h"
+#include "wtf/RefCounted.h"
+#include "wtf/RefPtr.h"
+
+#include <iosfwd>
+
+namespace blink {
+
+// A scroll node contains auxillary scrolling information about areas that
+// respond to user input and how far they can be scrolled. The actual scroll
+// offset is applied in an associated TransformPaintPropertyNode.
+class PLATFORM_EXPORT ScrollPaintPropertyNode : public RefCounted<ScrollPaintPropertyNode> {
+public:
+    static PassRefPtr<ScrollPaintPropertyNode> create(
+        PassRefPtr<const ScrollPaintPropertyNode> parent,
+        PassRefPtr<const TransformPaintPropertyNode> scrollOffsetTranslation,
+        const FloatSize& clip,
+        const FloatSize& bounds,
+        bool userScrollableHorizontal,
+        bool userScrollableVertical)
+    {
+        return adoptRef(new ScrollPaintPropertyNode(parent, scrollOffsetTranslation, clip, bounds, userScrollableHorizontal, userScrollableVertical));
+    }
+
+    void update(PassRefPtr<const ScrollPaintPropertyNode> parent, PassRefPtr<const TransformPaintPropertyNode> scrollOffsetTranslation, const FloatSize& clip, const FloatSize& bounds, bool userScrollableHorizontal, bool userScrollableVertical)
+    {
+        m_parent = parent;
+        DCHECK(scrollOffsetTranslation->matrix().isIdentityOr2DTranslation());
+        m_scrollOffsetTranslation = scrollOffsetTranslation;
+        m_clip = clip;
+        m_bounds = bounds;
+        m_userScrollableHorizontal = userScrollableHorizontal;
+        m_userScrollableVertical = userScrollableVertical;
+    }
+
+    const ScrollPaintPropertyNode* parent() const { return m_parent.get(); }
+
+    // Transform that the scroll is relative to.
+    const TransformPaintPropertyNode* scrollOffsetTranslation() const { return m_scrollOffsetTranslation.get(); }
+
+    // The clipped area that contains the scrolled content. In the common case
+    // this is the area that could respond to user input.
+    const FloatSize& clip() const { return m_clip; }
+
+    // The bounds of the content that is scrolled.
+    const FloatSize& bounds() const { return m_bounds; }
+
+    bool userScrollableHorizontal() const { return m_userScrollableHorizontal; }
+    bool userScrollableVertical() const { return m_userScrollableVertical; }
+
+private:
+    ScrollPaintPropertyNode(
+        PassRefPtr<const ScrollPaintPropertyNode> parent,
+        PassRefPtr<const TransformPaintPropertyNode> scrollOffsetTranslation,
+        FloatSize clip,
+        FloatSize bounds,
+        bool userScrollableHorizontal,
+        bool userScrollableVertical)
+        : m_parent(parent)
+        , m_scrollOffsetTranslation(scrollOffsetTranslation)
+        , m_clip(clip)
+        , m_bounds(bounds)
+        , m_userScrollableHorizontal(userScrollableHorizontal)
+        , m_userScrollableVertical(userScrollableVertical)
+    {
+        DCHECK(m_scrollOffsetTranslation->matrix().isIdentityOr2DTranslation());
+    }
+
+    RefPtr<const ScrollPaintPropertyNode> m_parent;
+    RefPtr<const TransformPaintPropertyNode> m_scrollOffsetTranslation;
+    FloatSize m_clip;
+    FloatSize m_bounds;
+    bool m_userScrollableHorizontal;
+    bool m_userScrollableVertical;
+    // TODO(pdr): Add main thread scrolling reasons.
+    // TODO(pdr): Add an offset for the clip and bounds to the transform.
+    // TODO(pdr): Add 2 bits for whether this is a viewport scroll node.
+    // TODO(pdr): Add a bit for whether this is affected by page scale.
+};
+
+// Redeclared here to avoid ODR issues.
+// See platform/testing/PaintPrinters.h.
+void PrintTo(const ScrollPaintPropertyNode&, std::ostream*);
+
+} // namespace blink
+
+#endif // ScrollPaintPropertyNode_h