Add ScrollManager class

third_party/WebKit/Source/core/input/ScrollManager.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 ScrollManager_h
+#define ScrollManager_h
+
+#include "core/CoreExport.h"
+#include "core/page/EventWithHitTestResults.h"
+#include "platform/PlatformEvent.h"
+#include "platform/geometry/LayoutSize.h"
+#include "platform/heap/Handle.h"
+#include "platform/heap/Visitor.h"
+#include "platform/scroll/ScrollTypes.h"
+#include "public/platform/WebInputEventResult.h"
+#include "wtf/Allocator.h"
+#include <deque>
+
+namespace blink {
+
+class AutoscrollController;
+class FloatPoint;
+class FrameHost;
+class LayoutBox;
+class LayoutObject;
+class LocalFrame;
+class PaintLayer;
+class PaintLayerScrollableArea;
+class PlatformGestureEvent;
+class Scrollbar;
+class ScrollState;
+
+// This class takes care of scrolling and resizing and the related states. The
+// user action that causes scrolling or resizing is determined in other *Manager
+// classes and they call into this class for doing the work.
+class CORE_EXPORT ScrollManager {
+    WTF_MAKE_NONCOPYABLE(ScrollManager);
+    DISALLOW_NEW();
+public:
+    explicit ScrollManager(LocalFrame*);
+    ~ScrollManager();
+    DECLARE_TRACE();
+
+    void clear();
+
+    bool panScrollInProgress() const;
+    AutoscrollController* autoscrollController() const;
+    void stopAutoscroll();
+
+    // Performs a chaining scroll, within a *single* frame, starting from a
+    // given node and optionally stopping on a given node.
+    // granularity - The units that the  scroll delta parameter is in.
+    // delta - The delta to scroll by, in the units of the granularity param
+    //         (e.g. pixels, lines, pages, etc.). These are in a physical
+    //         direction. i.e. Positive is down and right.
+    // position - Where the scroll originated from (e.g. touch location).
+    // velocity - The velocity of the scroll in the case of fling gestures.
+    // startNode - The node to start the scroll chaining from.
+    // stopNode - On input, if non-null, the node at which we should stop
+    //            chaining. On output, if provided and a node was scrolled,
+    //            stopNode will point to that node.
+    // consumed - [OUT] Whether the scroll was consumed. This is different than
+    //            ScrollResult.didScroll since we might not have scrolled but
+    //            have reached the stopNode and thus don't want to continue
+    //            chaining the scroll.
+    ScrollResult physicalScroll(
+        ScrollGranularity,
+        const FloatSize& delta,
+        const FloatPoint& position,
+        const FloatSize& velocity,
+        Node* startNode,
+        Node** stopNode,
+        bool* consumed);
+
+    // Performs a chaining logical scroll, within a *single* frame, starting
+    // from either a provided starting node or a default based on the focused or
+    // most recently clicked node, falling back to the frame.
+    // Returns true if the scroll was consumed.
+    // direction - The logical direction to scroll in. This will be converted to
+    //             a physical direction for each LayoutBox we try to scroll
+    //             based on that box's writing mode.
+    // granularity - The units that the  scroll delta parameter is in.
+    // startNode - Optional. If provided, start chaining from the given node.
+    //             If not, use the current focus or last clicked node.
+    bool logicalScroll(ScrollDirection, ScrollGranularity, Node* startNode, Node* mousePressNode);
+
+    // Performs a logical scroll that chains, crossing frames, starting from
+    // the given node or a reasonable default (focus/last clicked).
+    bool bubblingScroll(ScrollDirection, ScrollGranularity, Node* startingNode, Node* mousePressNode);
+
+    void setFrameWasScrolledByUser();
+
+
+    // TODO(crbug.com/616491): Consider moving all gesture related functions to
+    // another class.
+
+    // Handle the provided scroll gesture event, propagating down to child frames as necessary.
+    WebInputEventResult handleGestureScrollEvent(const PlatformGestureEvent&);
+
+    WebInputEventResult handleGestureScrollEnd(const PlatformGestureEvent&);
+
+    bool isScrollbarHandlingGestures() const;
+
+    // Returns true if the gesture event should be handled in ScrollManager.
+    bool canHandleGestureEvent(const GestureEventWithHitTestResults&);
+
+    // These functions are related to |m_resizeScrollableArea|.
+    bool inResizeMode() const;
+    void resize(const PlatformEvent&);
+    // Clears |m_resizeScrollableArea|. if |shouldNotBeNull| is true this
+    // function DCHECKs to make sure that variable is indeed not null.
+    void clearResizeScrollableArea(bool shouldNotBeNull);
+    void setResizeScrollableArea(PaintLayer*, IntPoint);
+
+private:
+
+    WebInputEventResult handleGestureScrollUpdate(const PlatformGestureEvent&);
+    WebInputEventResult handleGestureScrollBegin(const PlatformGestureEvent&);
+
+    WebInputEventResult passScrollGestureEventToWidget(const PlatformGestureEvent&, LayoutObject*);
+
+    void clearGestureScrollState();
+
+    void customizedScroll(const Node& startNode, ScrollState&);
+
+    ScrollResult scrollBox(
+        LayoutBox*,
+        ScrollGranularity,
+        const FloatSize& delta,
+        const FloatPoint& position,
+        const FloatSize& velocity,
+        bool* wasRootScroller);
+
+    FrameHost* frameHost() const;
+
+    bool isRootScroller(const Node&) const;
+
+    bool handleScrollGestureOnResizer(Node*, const PlatformGestureEvent&);
+
+
+    // NOTE: If adding a new field to this class please ensure that it is
+    // cleared in |ScrollManager::clear()|.
+
+    const Member<LocalFrame> m_frame;
+
+    // Only used with the ScrollCustomization runtime enabled feature.
+    std::deque<int> m_currentScrollChain;
+
+    Member<Node> m_scrollGestureHandlingNode;
+
+    bool m_lastGestureScrollOverWidget;
+
+    // The most recent element to scroll natively during this scroll
+    // sequence. Null if no native element has scrolled this scroll
+    // sequence, or if the most recent element to scroll used scroll
+    // customization.
+    Member<Node> m_previousGestureScrolledNode;
+
+    // True iff some of the delta has been consumed for the current
+    // scroll sequence in this frame, or any child frames. Only used
+    // with ScrollCustomization. If some delta has been consumed, a
+    // scroll which shouldn't propagate can't cause any element to
+    // scroll other than the |m_previousGestureScrolledNode|.
+    bool m_deltaConsumedForScrollSequence;
+
+    Member<Scrollbar> m_scrollbarHandlingScrollGesture;
+
+    Member<PaintLayerScrollableArea> m_resizeScrollableArea;
+
+    LayoutSize m_offsetFromResizeCorner; // In the coords of m_resizeScrollableArea.
+
+};
+
+} // namespace blink
+
+#endif // ScrollManager_h