Keep the selection of the text field when changed by JS.

Source/core/page/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 561 matching lines @@
                 else
                     newSelection = VisibleSelection(start, pos);
             }
         } else
             newSelection.setExtent(pos);
 
         if (m_frame->selection().granularity() != CharacterGranularity) {
             granularity = m_frame->selection().granularity();
             newSelection.expandUsingGranularity(m_frame->selection().granularity());
         }
-    } else {
+    } else if (m_selectionInitiationState != ExtendedSelection) {
         newSelection = expandSelectionToRespectUserSelectAll(innerNode, VisibleSelection(visiblePos));
     }
 
     // Updating the selection is considered side-effect of the event and so it doesn't impact the handled state.
     updateSelectionForMouseDownDispatchingSelectStart(innerNode, newSelection, granularity);
     return false;
 }
 
 static inline bool canMouseDownStartSelect(Node* node)
 {
@@ skipping 47 matching lines @@
     if (singleClick)
         focusDocumentView();
 
     Node* innerNode = event.innerNode();
 
     m_mousePressNode = innerNode;
     m_dragStartPos = event.event().position();
 
     bool swallowEvent = false;
     m_mousePressed = true;
-    m_selectionInitiationState = HaveNotStartedSelection;
 
     if (event.event().clickCount() == 2)
         swallowEvent = handleMousePressEventDoubleClick(event);
     else if (event.event().clickCount() >= 3)
         swallowEvent = handleMousePressEventTripleClick(event);
     else
         swallowEvent = handleMousePressEventSingleClick(event);
 
     m_mouseDownMayStartAutoscroll = m_mouseDownMayStartSelect
         || (m_mousePressNode && m_mousePressNode->layoutBox() && m_mousePressNode->layoutBox()->canBeProgramaticallyScrolled());
@@ skipping 664 matching lines @@
             m_resizeScrollableArea->setInResizeMode(true);
             m_offsetFromResizeCorner = LayoutSize(m_resizeScrollableArea->offsetFromResizeCorner(p));
             invalidateClick();
             return true;
         }
     }
 
     m_frame->selection().setCaretBlinkingSuspended(true);
 
     bool swallowEvent = !dispatchMouseEvent(EventTypeNames::mousedown, mev.innerNode(), m_clickCount, mouseEvent, true);
+    // m_selectionInitiationState is initialized after dispatching mousedown event in order not to keep the selection by DOM APIs
+    // Because we can't give the user the chance to handle the selection by user action like dragging if we keep the selection in case of mousedown.
+    // FireFox also has the same behavior and it's more compatible with other browsers.
+    m_selectionInitiationState = HaveNotStartedSelection;
     HitTestResult hitTestResult = hitTestResultInFrame(m_frame, mouseEvent.position(), HitTestRequest::ReadOnly);
     swallowEvent = swallowEvent || handleMouseFocus(MouseEventWithHitTestResults(mouseEvent, hitTestResult));
     m_capturesDragging = !swallowEvent || mev.scrollbar();
 
     // If the hit testing originally determined the event was in a scrollbar, refetch the MouseEventWithHitTestResults
     // in case the scrollbar widget was destroyed when the mouse event was handled.
     if (mev.scrollbar()) {
         const bool wasLastScrollBar = mev.scrollbar() == m_lastScrollbarUnderMouse.get();
         HitTestRequest request(HitTestRequest::ReadOnly | HitTestRequest::Active);
         mev = m_frame->document()->prepareMouseEvent(request, documentPoint, mouseEvent);
@@ skipping 1000 matching lines @@
     IntPoint tappedPosition = gestureEvent.position();
 
     if (m_clickNode && m_clickNode->isTextNode())
         m_clickNode = NodeRenderingTraversal::parent(*m_clickNode);
 
     PlatformMouseEvent fakeMouseDown(gestureEvent.position(), gestureEvent.globalPosition(),
         LeftButton, PlatformEvent::MousePressed, gestureEvent.tapCount(),
         static_cast<PlatformEvent::Modifiers>(modifiers | PlatformEvent::LeftButtonDown),
         PlatformMouseEvent::FromTouch,  gestureEvent.timestamp());
     bool swallowMouseDownEvent = !dispatchMouseEvent(EventTypeNames::mousedown, currentHitTest.innerNode(), gestureEvent.tapCount(), fakeMouseDown, true);
+    m_selectionInitiationState = HaveNotStartedSelection;
     if (!swallowMouseDownEvent)
         swallowMouseDownEvent = handleMouseFocus(MouseEventWithHitTestResults(fakeMouseDown, currentHitTest));
     if (!swallowMouseDownEvent)
         swallowMouseDownEvent = handleMousePressEvent(MouseEventWithHitTestResults(fakeMouseDown, currentHitTest));
 
     // FIXME: Use a hit-test cache to avoid unnecessary hit tests. http://crbug.com/398920
     if (currentHitTest.innerNode()) {
         LocalFrame* mainFrame = m_frame->localFrameRoot();
         if (mainFrame && mainFrame->view())
             mainFrame->view()->updateLayoutAndStyleIfNeededRecursive();
@@ skipping 754 matching lines @@
 }
 
 void EventHandler::notifyElementActivated()
 {
     // Since another element has been set to active, stop current timer and clear reference.
     if (m_activeIntervalTimer.isActive())
         m_activeIntervalTimer.stop();
     m_lastDeferredTapElement = nullptr;
 }
 
+void EventHandler::notifySelectionChanged()

[yosin_UTC9, 2015/04/10 02:06:09]

It is better to move selection handling code in EventHandler to FrameSeleciton,
or new class SelectionController. I feel strange that FrameSelection needs to
notify about selection change to EventHandler.

[Miyoung Shin(g), 2015/04/22 15:32:37]

I've tried to move the code related to the selection from EventHandler to
SelectionHandler.
I'm looking forward to getting your feedback.

[yosin_UTC9, 2015/04/28 01:59:54]

Yes, I'm thinking to have a SelectionHandler class. Although, we need to use
better name other than SelectionHandler, or SelectionController.

+{
+    if (m_frame->selection().isRange())
+        m_selectionInitiationState = ExtendedSelection;

[yosin_UTC9, 2015/04/10 02:06:09]

|m_selectionInitiationState| is no longer represent initiation state. It seems
it represent current state of selection, but enum fields aren't reflected it.

[Miyoung Shin(g), 2015/04/22 15:32:37]

I've changed |m_selectionInitiationState| to |m_selectionState| to be explicit.
Could you explain "enum fields aren't reflected it" that you mentioned in more
detail ?

[yosin_UTC9, 2015/04/28 01:59:54]

I mean |PlacedCaret| and |ExtendSelection| are state after modification rather
than initial state. If we name to |m_selectionState|, I'm OK.

+    else if (m_frame->selection().isCaret())
+        m_selectionInitiationState = PlacedCaret;
+    else
+        m_selectionInitiationState = HaveNotStartedSelection;
+}
+
 bool EventHandler::handleAccessKey(const PlatformKeyboardEvent& evt)
 {
     // FIXME: Ignoring the state of Shift key is what neither IE nor Firefox do.
     // IE matches lower and upper case access keys regardless of Shift key state - but if both upper and
     // lower case variants are present in a document, the correct element is matched based on Shift key state.
     // Firefox only matches an access key if Shift is not pressed, and does that case-insensitively.
     ASSERT(!(accessKeyModifiers() & PlatformEvent::ShiftKey));
     if ((evt.modifiers() & ~PlatformEvent::ShiftKey) != accessKeyModifiers())
         return false;
     String key = evt.unmodifiedText();
@@ skipping 855 matching lines @@
 unsigned EventHandler::accessKeyModifiers()
 {
 #if OS(MACOSX)
     return PlatformEvent::CtrlKey | PlatformEvent::AltKey;
 #else
     return PlatformEvent::AltKey;
 #endif
 }
 
 } // namespace blink