Implement Middle Click Autoscroll on all platforms not just Windows

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

 /*
  * 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.
@@ skipping 363 matching lines @@
         if (!parent)
             return WebInputEventResult::NotHandled;
 
         layoutObject = parent->layoutObject();
         if (!layoutObject || !layoutObject->isListBox())
             return WebInputEventResult::NotHandled;
     }
 
     m_mouseDownMayStartDrag = false;
 
-    if (m_mouseDownMayStartAutoscroll && !m_scrollManager->panScrollInProgress()) {
+    if (m_mouseDownMayStartAutoscroll && !m_scrollManager->middleClickAutoscrollInProgress()) {
         if (AutoscrollController* controller = m_scrollManager->autoscrollController()) {
             controller->startAutoscrollForSelection(layoutObject);
             m_mouseDownMayStartAutoscroll = false;
         }
     }
 
     selectionController().handleMouseDraggedEvent(event, m_mouseDownPos, m_dragStartPos, m_mousePressNode.get(), m_lastKnownMousePosition);
     return WebInputEventResult::HandledSystem;
 }
 
 void EventHandler::updateSelectionForMouseDrag()
 {
     selectionController().updateSelectionForMouseDrag(m_mousePressNode.get(), m_dragStartPos, m_lastKnownMousePosition);
 }
 
 // TODO(nzolghadr): Refactor the mouse related functions to MouseEventManager.
 WebInputEventResult EventHandler::handleMouseReleaseEvent(const MouseEventWithHitTestResults& event)
 {
     AutoscrollController* controller = m_scrollManager->autoscrollController();
     if (controller && controller->autoscrollInProgress())
         m_scrollManager->stopAutoscroll();
 
     return selectionController().handleMouseReleaseEvent(event, m_dragStartPos) ? WebInputEventResult::HandledSystem : WebInputEventResult::NotHandled;
 }
 
-#if OS(WIN)
-
-void EventHandler::startPanScrolling(LayoutObject* layoutObject)
+void EventHandler::startMiddleClickAutoscroll(LayoutObject* layoutObject)
 {
+    DCHECK(RuntimeEnabledFeatures::middleClickAutoscrollEnabled());
     if (!layoutObject->isBox())
         return;
     AutoscrollController* controller = m_scrollManager->autoscrollController();
     if (!controller)
         return;
-    controller->startPanScrolling(toLayoutBox(layoutObject), lastKnownMousePosition());
+    controller->startMiddleClickAutoscroll(toLayoutBox(layoutObject), lastKnownMousePosition());
     invalidateClick();
 }
 
-#endif // OS(WIN)
-
 HitTestResult EventHandler::hitTestResultAtPoint(const LayoutPoint& point, HitTestRequest::HitTestRequestType hitType, const LayoutSize& padding)
 {
     TRACE_EVENT0("blink", "EventHandler::hitTestResultAtPoint");
 
     ASSERT((hitType & HitTestRequest::ListBased) || padding.isEmpty());
 
     // We always send hitTestResultAtPoint to the main frame if we have one,
     // otherwise we might hit areas that are obscured by higher frames.
     if (m_frame->page()) {
         LocalFrame* mainFrame = m_frame->localFrameRoot();
@@ skipping 130 matching lines @@
 }
 
 OptionalCursor EventHandler::selectCursor(const HitTestResult& result)
 {
     if (m_scrollManager->inResizeMode())
         return NoCursorChange;
 
     Page* page = m_frame->page();
     if (!page)
         return NoCursorChange;
-    if (m_scrollManager->panScrollInProgress())
+    if (m_scrollManager->middleClickAutoscrollInProgress())
         return NoCursorChange;
 
     Node* node = result.innerPossiblyPseudoNode();
     if (!node)
         return selectAutoCursor(result, node, iBeamCursor());
 
     LayoutObject* layoutObject = node->layoutObject();
     const ComputedStyle* style = layoutObject ? layoutObject->style() : nullptr;
 
     if (layoutObject) {
@@ skipping 209 matching lines @@
         // has been handled. See crbug.com/269917
         m_capturesDragging = subframe->eventHandler().capturesDragging();
         if (m_mousePressed && m_capturesDragging) {
             m_capturingMouseEventsNode = mev.innerNode();
             m_eventHandlerWillResetCapturingMouseEventsNode = true;
         }
         invalidateClick();
         return result;
     }
 
-#if OS(WIN)
-    // We store whether pan scrolling is in progress before calling stopAutoscroll()
-    // because it will set m_autoscrollType to NoAutoscroll on return.
-    bool isPanScrollInProgress = m_scrollManager->panScrollInProgress();
-    m_scrollManager->stopAutoscroll();
-    if (isPanScrollInProgress) {
-        // We invalidate the click when exiting pan scrolling so that we don't inadvertently navigate
-        // away from the current page (e.g. the click was on a hyperlink). See <rdar://problem/6095023>.
-        invalidateClick();
-        return WebInputEventResult::HandledSuppressed;
+    if (RuntimeEnabledFeatures::middleClickAutoscrollEnabled()) {
+        // We store whether middle click autoscroll is in progress before calling stopAutoscroll()
+        // because it will set m_autoscrollType to NoAutoscroll on return.
+        bool isMiddleClickAutoscrollInProgress = m_scrollManager->middleClickAutoscrollInProgress();
+        m_scrollManager->stopAutoscroll();
+        if (isMiddleClickAutoscrollInProgress) {
+            // We invalidate the click when exiting middle click auto scroll so that we don't inadvertently navigate
+            // away from the current page (e.g. the click was on a hyperlink). See <rdar://problem/6095023>.
+            invalidateClick();
+            return WebInputEventResult::HandledSuppressed;
+        }
     }
-#endif
 
     m_clickCount = mouseEvent.clickCount();
     m_clickNode = mev.innerNode()->isTextNode() ?  FlatTreeTraversal::parent(*mev.innerNode()) : mev.innerNode();
 
     if (!mouseEvent.fromTouch())
         m_frame->selection().setCaretBlinkingSuspended(true);
 
     WebInputEventResult eventResult = updatePointerTargetAndDispatchEvents(EventTypeNames::mousedown, mev.innerNode(), m_clickCount, mev.event());
 
     if (eventResult == WebInputEventResult::NotHandled && m_frame->view()) {
@@ skipping 250 matching lines @@
     if (!mouseEvent.fromTouch())
         m_frame->selection().setCaretBlinkingSuspended(false);
 
     std::unique_ptr<UserGestureIndicator> gestureIndicator;
 
     if (m_frame->localFrameRoot()->eventHandler().m_lastMouseDownUserGestureToken)
         gestureIndicator = wrapUnique(new UserGestureIndicator(m_frame->localFrameRoot()->eventHandler().m_lastMouseDownUserGestureToken.release()));
     else
         gestureIndicator = wrapUnique(new UserGestureIndicator(DefinitelyProcessingUserGesture));
 
-#if OS(WIN)
-    if (Page* page = m_frame->page())
-        page->autoscrollController().handleMouseReleaseForPanScrolling(m_frame, mouseEvent);
-#endif
+    if (RuntimeEnabledFeatures::middleClickAutoscrollEnabled()) {
+        if (Page* page = m_frame->page())
+            page->autoscrollController().handleMouseReleaseForMiddleClickAutoscroll(m_frame, mouseEvent);
+    }
 
     m_mousePressed = false;
     setLastKnownMousePosition(mouseEvent);
 
     if (m_svgPan) {
         m_svgPan = false;
         m_frame->document()->accessSVGExtensions().updatePan(m_frame->view()->rootFrameToContents(m_lastKnownMousePosition));
         return WebInputEventResult::HandledSuppressed;
     }
 
@@ skipping 1460 matching lines @@
 
 FrameHost* EventHandler::frameHost() const
 {
     if (!m_frame->page())
         return nullptr;
 
     return &m_frame->page()->frameHost();
 }
 
 } // namespace blink