third_party/WebKit/Source/core/page/AutoscrollController.cpp - chromium/src - Git at Google

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights
  * reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2012 Digia Plc. and/or its subsidiary(-ies)
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "core/page/AutoscrollController.h"

 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/html/HTMLFrameOwnerElement.h"
 #include "core/input/EventHandler.h"
 #include "core/layout/HitTestResult.h"
 #include "core/layout/LayoutBox.h"
 #include "core/layout/LayoutListBox.h"
 #include "core/page/ChromeClient.h"
 #include "core/page/Page.h"
 #include "platform/wtf/Time.h"

 namespace blink {

 // Delay time in second for start autoscroll if pointer is in border edge of
 // scrollable element.
 static const TimeDelta kAutoscrollDelay = TimeDelta::FromSecondsD(0.2);

 AutoscrollController* AutoscrollController::Create(Page& page) {
   return new AutoscrollController(page);
 }

 AutoscrollController::AutoscrollController(Page& page)
     : page_(&page),
       autoscroll_layout_object_(nullptr),
       pressed_layout_object_(nullptr),
       autoscroll_type_(kNoAutoscroll),
       did_latch_for_middle_click_autoscroll_(false) {}

 DEFINE_TRACE(AutoscrollController) {
   visitor->Trace(page_);
 }

 bool AutoscrollController::AutoscrollInProgress() const {
   return autoscroll_type_ == kAutoscrollForSelection;
 }

 bool AutoscrollController::AutoscrollInProgress(
     const LayoutBox* layout_object) const {
   return autoscroll_layout_object_ == layout_object;
 }

 void AutoscrollController::StartAutoscrollForSelection(
     LayoutObject* layout_object) {
   // We don't want to trigger the autoscroll or the middleClickAutoscroll if
   // it's already active.
   if (autoscroll_type_ != kNoAutoscroll)
     return;
   LayoutBox* scrollable = LayoutBox::FindAutoscrollable(layout_object);
   if (!scrollable)
     scrollable =
         layout_object->IsListBox() ? ToLayoutListBox(layout_object) : nullptr;
   if (!scrollable)
     return;

   pressed_layout_object_ = layout_object && layout_object->IsBox()
                                ? ToLayoutBox(layout_object)
                                : nullptr;
   autoscroll_type_ = kAutoscrollForSelection;
   autoscroll_layout_object_ = scrollable;
   StartAutoscroll();
 }

 void AutoscrollController::StopAutoscroll() {
   if (pressed_layout_object_) {
     pressed_layout_object_->StopAutoscroll();
     pressed_layout_object_ = nullptr;
   }
   LayoutBox* scrollable = autoscroll_layout_object_;
   autoscroll_layout_object_ = nullptr;

   if (!scrollable)
     return;

   if (RuntimeEnabledFeatures::middleClickAutoscrollEnabled() &&
       MiddleClickAutoscrollInProgress()) {
     if (FrameView* view = scrollable->GetFrame()->View()) {
       view->SetCursor(PointerCursor());
     }
   }
   autoscroll_type_ = kNoAutoscroll;
 }

 void AutoscrollController::StopAutoscrollIfNeeded(LayoutObject* layout_object) {
   if (pressed_layout_object_ == layout_object)
     pressed_layout_object_ = nullptr;

   if (autoscroll_layout_object_ != layout_object)
     return;
   autoscroll_layout_object_ = nullptr;
   autoscroll_type_ = kNoAutoscroll;
 }

 void AutoscrollController::UpdateAutoscrollLayoutObject() {
   if (!autoscroll_layout_object_)
     return;

   LayoutObject* layout_object = autoscroll_layout_object_;

   if (RuntimeEnabledFeatures::middleClickAutoscrollEnabled()) {
     HitTestResult hit_test =
         layout_object->GetFrame()->GetEventHandler().HitTestResultAtPoint(
             middle_click_autoscroll_start_pos_,
             HitTestRequest::kReadOnly | HitTestRequest::kActive);

     if (Node* node_at_point = hit_test.InnerNode())
       layout_object = node_at_point->GetLayoutObject();
   }

   while (layout_object && !(layout_object->IsBox() &&
                             ToLayoutBox(layout_object)->CanAutoscroll()))
     layout_object = layout_object->Parent();

   autoscroll_layout_object_ = layout_object && layout_object->IsBox()
                                   ? ToLayoutBox(layout_object)
                                   : nullptr;

   if (autoscroll_type_ != kNoAutoscroll && !autoscroll_layout_object_)
     autoscroll_type_ = kNoAutoscroll;
 }

 void AutoscrollController::UpdateDragAndDrop(Node* drop_target_node,
                                              const IntPoint& event_position,
                                              TimeTicks event_time) {
   if (!drop_target_node || !drop_target_node->GetLayoutObject()) {
     StopAutoscroll();
     return;
   }

   if (autoscroll_layout_object_ &&
       autoscroll_layout_object_->GetFrame() !=
           drop_target_node->GetLayoutObject()->GetFrame())
     return;

   drop_target_node->GetLayoutObject()
       ->GetFrameView()
       ->UpdateAllLifecyclePhasesExceptPaint();

   LayoutBox* scrollable =
       LayoutBox::FindAutoscrollable(drop_target_node->GetLayoutObject());
   if (!scrollable) {
     StopAutoscroll();
     return;
   }

   Page* page =
       scrollable->GetFrame() ? scrollable->GetFrame()->GetPage() : nullptr;
   if (!page) {
     StopAutoscroll();
     return;
   }

   IntSize offset = scrollable->CalculateAutoscrollDirection(event_position);
   if (offset.IsZero()) {
     StopAutoscroll();
     return;
   }

   drag_and_drop_autoscroll_reference_position_ = event_position + offset;

   if (autoscroll_type_ == kNoAutoscroll) {
     autoscroll_type_ = kAutoscrollForDragAndDrop;
     autoscroll_layout_object_ = scrollable;
     drag_and_drop_autoscroll_start_time_ = event_time;
     UseCounter::Count(page_->MainFrame(), UseCounter::kDragAndDropScrollStart);
     StartAutoscroll();
   } else if (autoscroll_layout_object_ != scrollable) {
     drag_and_drop_autoscroll_start_time_ = event_time;
     autoscroll_layout_object_ = scrollable;
   }
 }

 void AutoscrollController::HandleMouseReleaseForMiddleClickAutoscroll(
     LocalFrame* frame,
     const WebMouseEvent& mouse_event) {
   DCHECK(RuntimeEnabledFeatures::middleClickAutoscrollEnabled());
   if (!frame->IsMainFrame())
     return;
   switch (autoscroll_type_) {
     case kAutoscrollForMiddleClick:
       if (mouse_event.button == WebPointerProperties::Button::kMiddle)
         autoscroll_type_ = kAutoscrollForMiddleClickCanStop;
       break;
     case kAutoscrollForMiddleClickCanStop:
       StopAutoscroll();
       break;
     case kAutoscrollForDragAndDrop:
     case kAutoscrollForSelection:
     case kNoAutoscroll:
       // Nothing to do.
       break;
   }
 }

 bool AutoscrollController::MiddleClickAutoscrollInProgress() const {
   return autoscroll_type_ == kAutoscrollForMiddleClickCanStop ||
          autoscroll_type_ == kAutoscrollForMiddleClick;
 }

 void AutoscrollController::StartMiddleClickAutoscroll(
     LayoutBox* scrollable,
     const IntPoint& last_known_mouse_position) {
   DCHECK(RuntimeEnabledFeatures::middleClickAutoscrollEnabled());
   // We don't want to trigger the autoscroll or the middleClickAutoscroll if
   // it's already active.
   if (autoscroll_type_ != kNoAutoscroll)
     return;

   autoscroll_type_ = kAutoscrollForMiddleClick;
   autoscroll_layout_object_ = scrollable;
   middle_click_autoscroll_start_pos_ = last_known_mouse_position;
   did_latch_for_middle_click_autoscroll_ = false;

   UseCounter::Count(page_->MainFrame(),
                     UseCounter::kMiddleClickAutoscrollStart);
   StartAutoscroll();
 }

 static inline int AdjustedScrollDelta(int beginning_delta) {
   // This implemention matches Firefox's.
   // http://mxr.mozilla.org/firefox/source/toolkit/content/widgets/browser.xml#856.
   const int kSpeedReducer = 12;

   int adjusted_delta = beginning_delta / kSpeedReducer;
   if (adjusted_delta > 1) {
     adjusted_delta =
         static_cast<int>(adjusted_delta *
                          sqrt(static_cast<double>(adjusted_delta))) -
         1;
   } else if (adjusted_delta < -1) {
     adjusted_delta =
         static_cast<int>(adjusted_delta *
                          sqrt(static_cast<double>(-adjusted_delta))) +
         1;
   }

   return adjusted_delta;
 }

 static inline IntSize AdjustedScrollDelta(const IntSize& delta) {
   return IntSize(AdjustedScrollDelta(delta.Width()),
                  AdjustedScrollDelta(delta.Height()));
 }

 FloatSize AutoscrollController::CalculateAutoscrollDelta() {
   LocalFrame* frame = autoscroll_layout_object_->GetFrame();
   if (!frame)
     return FloatSize();

   IntPoint last_known_mouse_position =
       frame->GetEventHandler().LastKnownMousePosition();

   // We need to check if the last known mouse position is out of the window.
   // When the mouse is out of the window, the position is incoherent
   static IntPoint previous_mouse_position;
   if (last_known_mouse_position.X() < 0 || last_known_mouse_position.Y() < 0)
     last_known_mouse_position = previous_mouse_position;
   else
     previous_mouse_position = last_known_mouse_position;

   IntSize delta =
       last_known_mouse_position - middle_click_autoscroll_start_pos_;

   // at the center we let the space for the icon.
   if (abs(delta.Width()) <= kNoMiddleClickAutoscrollRadius)
     delta.SetWidth(0);
   if (abs(delta.Height()) <= kNoMiddleClickAutoscrollRadius)
     delta.SetHeight(0);
   return FloatSize(AdjustedScrollDelta(delta));
 }

 void AutoscrollController::Animate(double) {
   if (!autoscroll_layout_object_ || !autoscroll_layout_object_->GetFrame()) {
     StopAutoscroll();
     return;
   }

   EventHandler& event_handler =
       autoscroll_layout_object_->GetFrame()->GetEventHandler();
   IntSize offset = autoscroll_layout_object_->CalculateAutoscrollDirection(
       event_handler.LastKnownMousePosition());
   IntPoint selection_point = event_handler.LastKnownMousePosition() + offset;
   switch (autoscroll_type_) {
     case kAutoscrollForDragAndDrop:
       if ((TimeTicks::Now() - drag_and_drop_autoscroll_start_time_) >
           kAutoscrollDelay)
         autoscroll_layout_object_->Autoscroll(
             drag_and_drop_autoscroll_reference_position_);
       break;
     case kAutoscrollForSelection:
       if (!event_handler.MousePressed()) {
         StopAutoscroll();
         return;
       }
       event_handler.UpdateSelectionForMouseDrag();
       autoscroll_layout_object_->Autoscroll(selection_point);
       break;
     case kNoAutoscroll:
       break;
     case kAutoscrollForMiddleClickCanStop:
     case kAutoscrollForMiddleClick:
       DCHECK(RuntimeEnabledFeatures::middleClickAutoscrollEnabled());
       if (!MiddleClickAutoscrollInProgress()) {
         StopAutoscroll();
         return;
       }
       if (FrameView* view = autoscroll_layout_object_->GetFrame()->View())
         UpdateMiddleClickAutoscrollState(
             view, event_handler.LastKnownMousePosition());
       FloatSize delta = CalculateAutoscrollDelta();
       if (delta.IsZero())
         break;
       ScrollResult result =
           autoscroll_layout_object_->Scroll(kScrollByPixel, delta);
       LayoutObject* layout_object = autoscroll_layout_object_;
       while (!did_latch_for_middle_click_autoscroll_ && !result.DidScroll()) {
         if (layout_object->GetNode() &&
             layout_object->GetNode()->IsDocumentNode()) {
           Element* owner = ToDocument(layout_object->GetNode())->LocalOwner();
           layout_object = owner ? owner->GetLayoutObject() : nullptr;
         } else {
           layout_object = layout_object->Parent();
         }
         if (!layout_object) {
           break;
         }
         if (layout_object && layout_object->IsBox() &&
             ToLayoutBox(layout_object)->CanBeScrolledAndHasScrollableArea())
           result = ToLayoutBox(layout_object)->Scroll(kScrollByPixel, delta);
       }
       if (result.DidScroll()) {
         did_latch_for_middle_click_autoscroll_ = true;
         autoscroll_layout_object_ = ToLayoutBox(layout_object);
       }
       break;
   }
   if (autoscroll_type_ != kNoAutoscroll && autoscroll_layout_object_) {
     page_->GetChromeClient().ScheduleAnimation(
         autoscroll_layout_object_->GetFrame()->View());
   }
 }

 void AutoscrollController::StartAutoscroll() {
   page_->GetChromeClient().ScheduleAnimation(
       autoscroll_layout_object_->GetFrame()->View());
 }

 void AutoscrollController::UpdateMiddleClickAutoscrollState(
     FrameView* view,
     const IntPoint& last_known_mouse_position) {
   DCHECK(RuntimeEnabledFeatures::middleClickAutoscrollEnabled());
   // At the original click location we draw a 4 arrowed icon. Over this icon
   // there won't be any scroll, So don't change the cursor over this area.
   bool east = middle_click_autoscroll_start_pos_.X() <
               (last_known_mouse_position.X() - kNoMiddleClickAutoscrollRadius);
   bool west = middle_click_autoscroll_start_pos_.X() >
               (last_known_mouse_position.X() + kNoMiddleClickAutoscrollRadius);
   bool north = middle_click_autoscroll_start_pos_.Y() >
                (last_known_mouse_position.Y() + kNoMiddleClickAutoscrollRadius);
   bool south = middle_click_autoscroll_start_pos_.Y() <
                (last_known_mouse_position.Y() - kNoMiddleClickAutoscrollRadius);

   if (autoscroll_type_ == kAutoscrollForMiddleClick &&
       (east || west || north || south))
     autoscroll_type_ = kAutoscrollForMiddleClickCanStop;

   if (north) {
     if (east)
       view->SetCursor(NorthEastPanningCursor());
     else if (west)
       view->SetCursor(NorthWestPanningCursor());
     else
       view->SetCursor(NorthPanningCursor());
   } else if (south) {
     if (east)
       view->SetCursor(SouthEastPanningCursor());
     else if (west)
       view->SetCursor(SouthWestPanningCursor());
     else
       view->SetCursor(SouthPanningCursor());
   } else if (east) {
     view->SetCursor(EastPanningCursor());
   } else if (west) {
     view->SetCursor(WestPanningCursor());
   } else {
     view->SetCursor(MiddlePanningCursor());
   }
 }

 }  // namespace blink
	/*
	* Copyright (C) 2013 Google Inc. All rights reserved.
	* Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights
	* reserved.
	* Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
	* Copyright (C) 2012 Digia Plc. and/or its subsidiary(-ies)
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
	* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
	* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE COMPUTER, INC. OR
	* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
	* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
	* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
	* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
	* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "core/page/AutoscrollController.h"

	#include "core/frame/FrameView.h"
	#include "core/frame/LocalFrame.h"
	#include "core/html/HTMLFrameOwnerElement.h"
	#include "core/input/EventHandler.h"
	#include "core/layout/HitTestResult.h"
	#include "core/layout/LayoutBox.h"
	#include "core/layout/LayoutListBox.h"
	#include "core/page/ChromeClient.h"
	#include "core/page/Page.h"
	#include "platform/wtf/Time.h"

	namespace blink {

	// Delay time in second for start autoscroll if pointer is in border edge of
	// scrollable element.
	static const TimeDelta kAutoscrollDelay = TimeDelta::FromSecondsD(0.2);

	AutoscrollController* AutoscrollController::Create(Page& page) {
	return new AutoscrollController(page);
	}

	AutoscrollController::AutoscrollController(Page& page)
	: page_(&page),
	autoscroll_layout_object_(nullptr),
	pressed_layout_object_(nullptr),
	autoscroll_type_(kNoAutoscroll),
	did_latch_for_middle_click_autoscroll_(false) {}

	DEFINE_TRACE(AutoscrollController) {
	visitor->Trace(page_);
	}

	bool AutoscrollController::AutoscrollInProgress() const {
	return autoscroll_type_ == kAutoscrollForSelection;
	}

	bool AutoscrollController::AutoscrollInProgress(
	const LayoutBox* layout_object) const {
	return autoscroll_layout_object_ == layout_object;
	}

	void AutoscrollController::StartAutoscrollForSelection(
	LayoutObject* layout_object) {
	// We don't want to trigger the autoscroll or the middleClickAutoscroll if
	// it's already active.
	if (autoscroll_type_ != kNoAutoscroll)
	return;
	LayoutBox* scrollable = LayoutBox::FindAutoscrollable(layout_object);
	if (!scrollable)
	scrollable =
	layout_object->IsListBox() ? ToLayoutListBox(layout_object) : nullptr;
	if (!scrollable)
	return;

	pressed_layout_object_ = layout_object && layout_object->IsBox()
	? ToLayoutBox(layout_object)
	: nullptr;
	autoscroll_type_ = kAutoscrollForSelection;
	autoscroll_layout_object_ = scrollable;
	StartAutoscroll();
	}

	void AutoscrollController::StopAutoscroll() {
	if (pressed_layout_object_) {
	pressed_layout_object_->StopAutoscroll();
	pressed_layout_object_ = nullptr;
	}
	LayoutBox* scrollable = autoscroll_layout_object_;
	autoscroll_layout_object_ = nullptr;

	if (!scrollable)
	return;

	if (RuntimeEnabledFeatures::middleClickAutoscrollEnabled() &&
	MiddleClickAutoscrollInProgress()) {
	if (FrameView* view = scrollable->GetFrame()->View()) {
	view->SetCursor(PointerCursor());
	}
	}
	autoscroll_type_ = kNoAutoscroll;
	}

	void AutoscrollController::StopAutoscrollIfNeeded(LayoutObject* layout_object) {
	if (pressed_layout_object_ == layout_object)
	pressed_layout_object_ = nullptr;

	if (autoscroll_layout_object_ != layout_object)
	return;
	autoscroll_layout_object_ = nullptr;
	autoscroll_type_ = kNoAutoscroll;
	}

	void AutoscrollController::UpdateAutoscrollLayoutObject() {
	if (!autoscroll_layout_object_)
	return;

	LayoutObject* layout_object = autoscroll_layout_object_;

	if (RuntimeEnabledFeatures::middleClickAutoscrollEnabled()) {
	HitTestResult hit_test =
	layout_object->GetFrame()->GetEventHandler().HitTestResultAtPoint(
	middle_click_autoscroll_start_pos_,
	HitTestRequest::kReadOnly \| HitTestRequest::kActive);

	if (Node* node_at_point = hit_test.InnerNode())
	layout_object = node_at_point->GetLayoutObject();
	}

	while (layout_object && !(layout_object->IsBox() &&
	ToLayoutBox(layout_object)->CanAutoscroll()))
	layout_object = layout_object->Parent();

	autoscroll_layout_object_ = layout_object && layout_object->IsBox()
	? ToLayoutBox(layout_object)
	: nullptr;

	if (autoscroll_type_ != kNoAutoscroll && !autoscroll_layout_object_)
	autoscroll_type_ = kNoAutoscroll;
	}

	void AutoscrollController::UpdateDragAndDrop(Node* drop_target_node,
	const IntPoint& event_position,
	TimeTicks event_time) {
	if (!drop_target_node \|\| !drop_target_node->GetLayoutObject()) {
	StopAutoscroll();
	return;
	}

	if (autoscroll_layout_object_ &&
	autoscroll_layout_object_->GetFrame() !=
	drop_target_node->GetLayoutObject()->GetFrame())
	return;

	drop_target_node->GetLayoutObject()
	->GetFrameView()
	->UpdateAllLifecyclePhasesExceptPaint();

	LayoutBox* scrollable =
	LayoutBox::FindAutoscrollable(drop_target_node->GetLayoutObject());
	if (!scrollable) {
	StopAutoscroll();
	return;
	}

	Page* page =
	scrollable->GetFrame() ? scrollable->GetFrame()->GetPage() : nullptr;
	if (!page) {
	StopAutoscroll();
	return;
	}

	IntSize offset = scrollable->CalculateAutoscrollDirection(event_position);
	if (offset.IsZero()) {
	StopAutoscroll();
	return;
	}

	drag_and_drop_autoscroll_reference_position_ = event_position + offset;

	if (autoscroll_type_ == kNoAutoscroll) {
	autoscroll_type_ = kAutoscrollForDragAndDrop;
	autoscroll_layout_object_ = scrollable;
	drag_and_drop_autoscroll_start_time_ = event_time;
	UseCounter::Count(page_->MainFrame(), UseCounter::kDragAndDropScrollStart);
	StartAutoscroll();
	} else if (autoscroll_layout_object_ != scrollable) {
	drag_and_drop_autoscroll_start_time_ = event_time;
	autoscroll_layout_object_ = scrollable;
	}
	}

	void AutoscrollController::HandleMouseReleaseForMiddleClickAutoscroll(
	LocalFrame* frame,
	const WebMouseEvent& mouse_event) {
	DCHECK(RuntimeEnabledFeatures::middleClickAutoscrollEnabled());
	if (!frame->IsMainFrame())
	return;
	switch (autoscroll_type_) {
	case kAutoscrollForMiddleClick:
	if (mouse_event.button == WebPointerProperties::Button::kMiddle)
	autoscroll_type_ = kAutoscrollForMiddleClickCanStop;
	break;
	case kAutoscrollForMiddleClickCanStop:
	StopAutoscroll();
	break;
	case kAutoscrollForDragAndDrop:
	case kAutoscrollForSelection:
	case kNoAutoscroll:
	// Nothing to do.
	break;
	}
	}

	bool AutoscrollController::MiddleClickAutoscrollInProgress() const {
	return autoscroll_type_ == kAutoscrollForMiddleClickCanStop \|\|
	autoscroll_type_ == kAutoscrollForMiddleClick;
	}

	void AutoscrollController::StartMiddleClickAutoscroll(
	LayoutBox* scrollable,
	const IntPoint& last_known_mouse_position) {
	DCHECK(RuntimeEnabledFeatures::middleClickAutoscrollEnabled());
	// We don't want to trigger the autoscroll or the middleClickAutoscroll if
	// it's already active.
	if (autoscroll_type_ != kNoAutoscroll)
	return;

	autoscroll_type_ = kAutoscrollForMiddleClick;
	autoscroll_layout_object_ = scrollable;
	middle_click_autoscroll_start_pos_ = last_known_mouse_position;
	did_latch_for_middle_click_autoscroll_ = false;

	UseCounter::Count(page_->MainFrame(),
	UseCounter::kMiddleClickAutoscrollStart);
	StartAutoscroll();
	}

	static inline int AdjustedScrollDelta(int beginning_delta) {
	// This implemention matches Firefox's.
	// http://mxr.mozilla.org/firefox/source/toolkit/content/widgets/browser.xml#856.
	const int kSpeedReducer = 12;

	int adjusted_delta = beginning_delta / kSpeedReducer;
	if (adjusted_delta > 1) {
	adjusted_delta =
	static_cast<int>(adjusted_delta *
	sqrt(static_cast<double>(adjusted_delta))) -
	1;
	} else if (adjusted_delta < -1) {
	adjusted_delta =
	static_cast<int>(adjusted_delta *
	sqrt(static_cast<double>(-adjusted_delta))) +
	1;
	}

	return adjusted_delta;
	}

	static inline IntSize AdjustedScrollDelta(const IntSize& delta) {
	return IntSize(AdjustedScrollDelta(delta.Width()),
	AdjustedScrollDelta(delta.Height()));
	}

	FloatSize AutoscrollController::CalculateAutoscrollDelta() {
	LocalFrame* frame = autoscroll_layout_object_->GetFrame();
	if (!frame)
	return FloatSize();

	IntPoint last_known_mouse_position =
	frame->GetEventHandler().LastKnownMousePosition();

	// We need to check if the last known mouse position is out of the window.
	// When the mouse is out of the window, the position is incoherent
	static IntPoint previous_mouse_position;
	if (last_known_mouse_position.X() < 0 \|\| last_known_mouse_position.Y() < 0)
	last_known_mouse_position = previous_mouse_position;
	else
	previous_mouse_position = last_known_mouse_position;

	IntSize delta =
	last_known_mouse_position - middle_click_autoscroll_start_pos_;

	// at the center we let the space for the icon.
	if (abs(delta.Width()) <= kNoMiddleClickAutoscrollRadius)
	delta.SetWidth(0);
	if (abs(delta.Height()) <= kNoMiddleClickAutoscrollRadius)
	delta.SetHeight(0);
	return FloatSize(AdjustedScrollDelta(delta));
	}

	void AutoscrollController::Animate(double) {
	if (!autoscroll_layout_object_ \|\| !autoscroll_layout_object_->GetFrame()) {
	StopAutoscroll();
	return;
	}

	EventHandler& event_handler =
	autoscroll_layout_object_->GetFrame()->GetEventHandler();
	IntSize offset = autoscroll_layout_object_->CalculateAutoscrollDirection(
	event_handler.LastKnownMousePosition());
	IntPoint selection_point = event_handler.LastKnownMousePosition() + offset;
	switch (autoscroll_type_) {
	case kAutoscrollForDragAndDrop:
	if ((TimeTicks::Now() - drag_and_drop_autoscroll_start_time_) >
	kAutoscrollDelay)
	autoscroll_layout_object_->Autoscroll(
	drag_and_drop_autoscroll_reference_position_);
	break;
	case kAutoscrollForSelection:
	if (!event_handler.MousePressed()) {
	StopAutoscroll();
	return;
	}
	event_handler.UpdateSelectionForMouseDrag();
	autoscroll_layout_object_->Autoscroll(selection_point);
	break;
	case kNoAutoscroll:
	break;
	case kAutoscrollForMiddleClickCanStop:
	case kAutoscrollForMiddleClick:
	DCHECK(RuntimeEnabledFeatures::middleClickAutoscrollEnabled());
	if (!MiddleClickAutoscrollInProgress()) {
	StopAutoscroll();
	return;
	}
	if (FrameView* view = autoscroll_layout_object_->GetFrame()->View())
	UpdateMiddleClickAutoscrollState(
	view, event_handler.LastKnownMousePosition());
	FloatSize delta = CalculateAutoscrollDelta();
	if (delta.IsZero())
	break;
	ScrollResult result =
	autoscroll_layout_object_->Scroll(kScrollByPixel, delta);
	LayoutObject* layout_object = autoscroll_layout_object_;
	while (!did_latch_for_middle_click_autoscroll_ && !result.DidScroll()) {
	if (layout_object->GetNode() &&
	layout_object->GetNode()->IsDocumentNode()) {
	Element* owner = ToDocument(layout_object->GetNode())->LocalOwner();
	layout_object = owner ? owner->GetLayoutObject() : nullptr;
	} else {
	layout_object = layout_object->Parent();
	}
	if (!layout_object) {
	break;
	}
	if (layout_object && layout_object->IsBox() &&
	ToLayoutBox(layout_object)->CanBeScrolledAndHasScrollableArea())
	result = ToLayoutBox(layout_object)->Scroll(kScrollByPixel, delta);
	}
	if (result.DidScroll()) {
	did_latch_for_middle_click_autoscroll_ = true;
	autoscroll_layout_object_ = ToLayoutBox(layout_object);
	}
	break;
	}
	if (autoscroll_type_ != kNoAutoscroll && autoscroll_layout_object_) {
	page_->GetChromeClient().ScheduleAnimation(
	autoscroll_layout_object_->GetFrame()->View());
	}
	}

	void AutoscrollController::StartAutoscroll() {
	page_->GetChromeClient().ScheduleAnimation(
	autoscroll_layout_object_->GetFrame()->View());
	}

	void AutoscrollController::UpdateMiddleClickAutoscrollState(
	FrameView* view,
	const IntPoint& last_known_mouse_position) {
	DCHECK(RuntimeEnabledFeatures::middleClickAutoscrollEnabled());
	// At the original click location we draw a 4 arrowed icon. Over this icon
	// there won't be any scroll, So don't change the cursor over this area.
	bool east = middle_click_autoscroll_start_pos_.X() <
	(last_known_mouse_position.X() - kNoMiddleClickAutoscrollRadius);
	bool west = middle_click_autoscroll_start_pos_.X() >
	(last_known_mouse_position.X() + kNoMiddleClickAutoscrollRadius);
	bool north = middle_click_autoscroll_start_pos_.Y() >
	(last_known_mouse_position.Y() + kNoMiddleClickAutoscrollRadius);
	bool south = middle_click_autoscroll_start_pos_.Y() <
	(last_known_mouse_position.Y() - kNoMiddleClickAutoscrollRadius);

	if (autoscroll_type_ == kAutoscrollForMiddleClick &&
	(east \|\| west \|\| north \|\| south))
	autoscroll_type_ = kAutoscrollForMiddleClickCanStop;

	if (north) {
	if (east)
	view->SetCursor(NorthEastPanningCursor());
	else if (west)
	view->SetCursor(NorthWestPanningCursor());
	else
	view->SetCursor(NorthPanningCursor());
	} else if (south) {
	if (east)
	view->SetCursor(SouthEastPanningCursor());
	else if (west)
	view->SetCursor(SouthWestPanningCursor());
	else
	view->SetCursor(SouthPanningCursor());
	} else if (east) {
	view->SetCursor(EastPanningCursor());
	} else if (west) {
	view->SetCursor(WestPanningCursor());
	} else {
	view->SetCursor(MiddlePanningCursor());
	}
	}

	} // namespace blink