Determine the layoutobject of middleClickAutoscroll by the scroll direction.

third_party/WebKit/Source/core/page/AutoscrollController.cpp

 /*
  * 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:
@@ skipping 13 matching lines @@
  * 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 "wtf/CurrentTime.h"
 
 namespace blink {
 
 // Delay time in second for start autoscroll if pointer is in border edge of
 // scrollable element.
 static double autoscrollDelay = 0.2;
 
 AutoscrollController* AutoscrollController::create(Page& page) {
   return new AutoscrollController(page);
 }
 
 AutoscrollController::AutoscrollController(Page& page)
     : m_page(&page),
       m_autoscrollLayoutObject(nullptr),
       m_pressedLayoutObject(nullptr),
       m_autoscrollType(NoAutoscroll),
-      m_dragAndDropAutoscrollStartTime(0) {}
+      m_dragAndDropAutoscrollStartTime(0),
+      m_middleClickAutoscrolled(false) {}
 
 DEFINE_TRACE(AutoscrollController) {
   visitor->trace(m_page);
 }
 
 bool AutoscrollController::autoscrollInProgress() const {
   return m_autoscrollType == AutoscrollForSelection;
 }
 
 bool AutoscrollController::autoscrollInProgress(
@@ skipping 159 matching lines @@
     const IntPoint& lastKnownMousePosition) {
   DCHECK(RuntimeEnabledFeatures::middleClickAutoscrollEnabled());
   // We don't want to trigger the autoscroll or the middleClickAutoscroll if
   // it's already active.
   if (m_autoscrollType != NoAutoscroll)
     return;
 
   m_autoscrollType = AutoscrollForMiddleClick;
   m_autoscrollLayoutObject = scrollable;
   m_middleClickAutoscrollStartPos = lastKnownMousePosition;
+  m_middleClickAutoscrolled = false;
 
   UseCounter::count(m_page->mainFrame(),
                     UseCounter::MiddleClickAutoscrollStart);
   startAutoscroll();
 }
 
+static inline int adjustedScrollDelta(int beginningDelta) {
+  // This implemention matches Firefox's.
+  // http://mxr.mozilla.org/firefox/source/toolkit/content/widgets/browser.xml#856.
+  const int speedReducer = 12;
+
+  int adjustedDelta = beginningDelta / speedReducer;
+  if (adjustedDelta > 1) {
+    adjustedDelta = static_cast<int>(adjustedDelta *
+                                     sqrt(static_cast<double>(adjustedDelta))) -
+                    1;
+  } else if (adjustedDelta < -1) {
+    adjustedDelta =
+        static_cast<int>(adjustedDelta *
+                         sqrt(static_cast<double>(-adjustedDelta))) +
+        1;
+  }
+
+  return adjustedDelta;
+}
+
+static inline IntSize adjustedScrollDelta(const IntSize& delta) {
+  return IntSize(adjustedScrollDelta(delta.width()),
+                 adjustedScrollDelta(delta.height()));
+}
+
+FloatSize AutoscrollController::calculateAutoscrollDelta() {
+  LocalFrame* frame = m_autoscrollLayoutObject->frame();
+  if (!frame)
+    return FloatSize();
+
+  IntPoint lastKnownMousePosition =
+      frame->eventHandler().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 previousMousePosition;
+  if (lastKnownMousePosition.x() < 0 || lastKnownMousePosition.y() < 0)
+    lastKnownMousePosition = previousMousePosition;
+  else
+    previousMousePosition = lastKnownMousePosition;
+
+  IntSize delta = lastKnownMousePosition - m_middleClickAutoscrollStartPos;
+
+  // at the center we let the space for the icon.
+  if (abs(delta.width()) <= noMiddleClickAutoscrollRadius)
+    delta.setWidth(0);
+  if (abs(delta.height()) <= noMiddleClickAutoscrollRadius)
+    delta.setHeight(0);
+  return FloatSize(adjustedScrollDelta(delta));
+}
+
 void AutoscrollController::animate(double) {
   if (!m_autoscrollLayoutObject || !m_autoscrollLayoutObject->frame()) {
     stopAutoscroll();
     return;
   }
 
   EventHandler& eventHandler =
       m_autoscrollLayoutObject->frame()->eventHandler();
   IntSize offset = m_autoscrollLayoutObject->calculateAutoscrollDirection(
       eventHandler.lastKnownMousePosition());
@@ skipping 19 matching lines @@
     case AutoscrollForMiddleClickCanStop:
     case AutoscrollForMiddleClick:
       DCHECK(RuntimeEnabledFeatures::middleClickAutoscrollEnabled());
       if (!middleClickAutoscrollInProgress()) {
         stopAutoscroll();
         return;
       }
       if (FrameView* view = m_autoscrollLayoutObject->frame()->view())
         updateMiddleClickAutoscrollState(view,
                                          eventHandler.lastKnownMousePosition());
-      m_autoscrollLayoutObject->middleClickAutoscroll(
-          m_middleClickAutoscrollStartPos);
+      FloatSize delta = calculateAutoscrollDelta();
+      if (delta.isZero())
+        break;
+      ScrollResult result =
+          m_autoscrollLayoutObject->scroll(ScrollByPixel, delta);
+      LayoutObject* layoutObject = m_autoscrollLayoutObject;
+      while (!m_middleClickAutoscrolled && !result.didScroll()) {
+        if (layoutObject->node() && layoutObject->node()->isDocumentNode()) {
+          Element* owner = toDocument(layoutObject->node())->localOwner();
+          layoutObject = owner ? owner->layoutObject() : nullptr;
+        } else {
+          layoutObject = layoutObject->parent();
+        }
+        if (!layoutObject) {
+          break;
+        }
+        if (layoutObject && layoutObject->isBox() &&
+            toLayoutBox(layoutObject)->canBeScrolledAndHasScrollableArea())
+          result = toLayoutBox(layoutObject)->scroll(ScrollByPixel, delta);
+      }
+      if (result.didScroll()) {
+        m_middleClickAutoscrolled = true;

[bokan, 2016/11/11 19:48:46]

This variable would be more descriptive as m_didLatchForMiddleClickAutoscroll

+        m_autoscrollLayoutObject = toLayoutBox(layoutObject);
+      }
       break;
   }
   if (m_autoscrollType != NoAutoscroll && m_autoscrollLayoutObject)
     m_page->chromeClient().scheduleAnimation(
         m_autoscrollLayoutObject->frame()->view());
 }
 
 void AutoscrollController::startAutoscroll() {
   m_page->chromeClient().scheduleAnimation(
       m_autoscrollLayoutObject->frame()->view());
@@ skipping 35 matching lines @@
   } else if (east) {
     view->setCursor(eastPanningCursor());
   } else if (west) {
     view->setCursor(westPanningCursor());
   } else {
     view->setCursor(middlePanningCursor());
   }
 }
 
 }  // namespace blink