Add ScrollManager class

Extract scrolling and resizing related logic
from EventHandler and put it in a dedicated
class.

BUG=615079

Review-Url: https://codereview.chromium.org/2010133003
Cr-Commit-Position: refs/heads/master@{#397485}

third_party/WebKit/Source/core/core.gypi

@@ -2804,6 +2804,8 @@
             'input/InputDeviceCapabilities.h',
             'input/PointerEventManager.cpp',
             'input/PointerEventManager.h',
+            'input/ScrollManager.cpp',
+            'input/ScrollManager.h',
             'input/TouchActionUtil.cpp',
             'input/TouchActionUtil.h',
             'input/TouchEventManager.cpp',

third_party/WebKit/Source/core/input/EventHandler.h

@@ -29,6 +29,7 @@
 #include "core/CoreExport.h"
 #include "core/events/TextEventInputType.h"
 #include "core/input/PointerEventManager.h"
+#include "core/input/ScrollManager.h"
 #include "core/layout/HitTestRequest.h"
 #include "core/page/DragActions.h"
 #include "core/page/EventWithHitTestResults.h"
@@ -47,14 +48,11 @@
 #include "wtf/HashMap.h"
 #include "wtf/HashTraits.h"
 #include "wtf/RefPtr.h"
-#include <deque>
 
 namespace blink {
 
-class AutoscrollController;
 class DataTransfer;
 class PaintLayer;
-class PaintLayerScrollableArea;
 class Document;
 class DragState;
 class Element;
@@ -79,7 +77,6 @@ class PlatformTouchEvent;
 class PlatformWheelEvent;
 class ScrollableArea;
 class Scrollbar;
-class ScrollState;
 class SelectionController;
 class TextEvent;
 class WheelEvent;
@@ -104,6 +101,11 @@ public:
     void startPanScrolling(LayoutObject*);
 #endif
 
+    // TODO(nzolghadr): Some of the APIs in this class only forward the action
+    // to the corresponding Manager class. We need to investigate whether it is
+    // better to expose the manager instance itself later or can the access to
+    // those APIs be more limited or removed.
+
     void stopAutoscroll();
 
     void dispatchFakeMouseMoveEventSoon();
@@ -235,9 +237,6 @@ private:
     WebInputEventResult handleGestureTap(const GestureEventWithHitTestResults&);
     WebInputEventResult handleGestureLongPress(const GestureEventWithHitTestResults&);
     WebInputEventResult handleGestureLongTap(const GestureEventWithHitTestResults&);
-    WebInputEventResult handleGestureScrollUpdate(const PlatformGestureEvent&);
-    WebInputEventResult handleGestureScrollBegin(const PlatformGestureEvent&);
-    void clearGestureScrollState();
 
     void updateGestureTargetNodeForMouseEvent(const GestureEventWithHitTestResults&);
 
@@ -257,54 +256,6 @@ private:
 
     ScrollableArea* associatedScrollableArea(const PaintLayer*) const;
 
-    // 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 = nullptr);
-
-    ScrollResult scrollBox(
-        LayoutBox*,
-        ScrollGranularity,
-        const FloatSize& delta,
-        const FloatPoint& position,
-        const FloatSize& velocity,
-        bool* wasRootScroller);
-
-    bool isRootScroller(const Node&) const;
-    void customizedScroll(const Node& startNode, ScrollState&);
-
     void invalidateClick();
 
     Node* updateMouseEventTargetNode(Node*, const PlatformMouseEvent&);
@@ -349,18 +300,10 @@ private:
 
     void updateLastScrollbarUnderMouse(Scrollbar*, bool);
 
-    void setFrameWasScrolledByUser();
-
     bool capturesDragging() const { return m_capturesDragging; }
 
     WebInputEventResult handleGestureShowPress();
 
-    bool handleScrollGestureOnResizer(Node*, const PlatformGestureEvent&);
-
-    WebInputEventResult passScrollGestureEventToWidget(const PlatformGestureEvent&, LayoutObject*);
-
-    AutoscrollController* autoscrollController() const;
-    bool panScrollInProgress() const;
     void setLastKnownMousePosition(const PlatformMouseEvent&);
 
     bool shouldTopControlsConsumeScroll(FloatSize) const;
@@ -401,8 +344,6 @@ private:
 
     bool m_svgPan;
 
-    Member<PaintLayerScrollableArea> m_resizeScrollableArea;
-
     Member<Node> m_capturingMouseEventsNode;
     bool m_eventHandlerWillResetCapturingMouseEventsNode;
 
@@ -420,8 +361,6 @@ private:
 
     Member<HTMLFrameSetElement> m_frameSetBeingResized;
 
-    LayoutSize m_offsetFromResizeCorner; // In the coords of m_resizeScrollableArea.
-
     bool m_mousePositionIsUnknown;
     // The last mouse movement position this frame has seen in root frame coordinates.
     IntPoint m_lastKnownMousePosition;
@@ -432,15 +371,7 @@ private:
     RefPtr<UserGestureToken> m_lastMouseDownUserGestureToken;
 
     PointerEventManager m_pointerEventManager;
-
-    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;
-    Member<Scrollbar> m_scrollbarHandlingScrollGesture;
+    ScrollManager m_scrollManager;
 
     double m_maxMouseMovedDuration;
 
@@ -449,15 +380,6 @@ private:
     Timer<EventHandler> m_activeIntervalTimer;
     double m_lastShowPressTimestamp;
     Member<Element> m_lastDeferredTapElement;
-
-    // Only used with the ScrollCustomization runtime enabled feature.
-    std::deque<int> m_currentScrollChain;
-    // 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;
 };
 
 } // namespace blink

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