Implement link selection on alt+mouse drag.

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 392 matching lines @@
 
     m_frame->document()->updateLayoutIgnorePendingStylesheets();
 
     if (FrameView* frameView = m_frame->view()) {
         if (frameView->isPointInScrollbarCorner(event.event().position()))
             return WebInputEventResult::NotHandled;
     }
 
     bool singleClick = event.event().clickCount() <= 1;
 
-    m_mouseDownMayStartDrag = singleClick;
+    m_mouseDownMayStartDrag = singleClick && !mayBeLinkSelection(event);
 
     selectionController().handleMousePressEvent(event);
 
     m_mouseDown = event.event();
 
     if (m_frame->document()->isSVGDocument() && m_frame->document()->accessSVGExtensions().zoomAndPanEnabled()) {
         if (event.event().shiftKey() && singleClick) {
             m_svgPan = true;
             m_frame->document()->accessSVGExtensions().startPan(m_frame->view()->rootFrameToContents(event.event().position()));
             return WebInputEventResult::HandledSystem;
@@ skipping 520 matching lines @@
     case CURSOR_WEBKIT_GRABBING:
         return grabbingCursor();
     }
     return pointerCursor();
 }
 
 OptionalCursor EventHandler::selectAutoCursor(const HitTestResult& result, Node* node, const Cursor& iBeam)
 {
     bool editable = (node && node->hasEditableStyle());
 
-    if (useHandCursor(node, result.isOverLink()))
+    const bool isOverLink = !selectionController().mouseDownMayStartSelect() && result.isOverLink();

[kotenkov, 2016/03/09 17:27:59]

This is needed so that there is a beam cursor when we have started the link
selection.

+    if (useHandCursor(node, isOverLink))
         return handCursor();
 
     bool inResizer = false;
     LayoutObject* layoutObject = node ? node->layoutObject() : nullptr;
     if (layoutObject && m_frame->view()) {
         PaintLayer* layer = layoutObject->enclosingLayer();
         inResizer = layer->scrollableArea() && layer->scrollableArea()->isPointInResizeControl(result.roundedPointInMainFrame(), ResizerForPointer);
     }
 
     // During selection, use an I-beam no matter what we're over.
@@ skipping 403 matching lines @@
         mouseEvent.getModifiers());
 
     bool contextMenuEvent = mouseEvent.button() == RightButton;
 #if OS(MACOSX)
     // FIXME: The Mac port achieves the same behavior by checking whether the context menu is currently open in WebPage::mouseEvent(). Consider merging the implementations.
     if (mouseEvent.button() == LeftButton && mouseEvent.getModifiers() & PlatformEvent::CtrlKey)
         contextMenuEvent = true;
 #endif
 
     WebInputEventResult clickEventResult = WebInputEventResult::NotHandled;
-    if (m_clickCount > 0 && !contextMenuEvent && mev.innerNode() && m_clickNode && mev.innerNode()->canParticipateInFlatTree() && m_clickNode->canParticipateInFlatTree()) {
+    const bool shouldDispatchClickEvent = m_clickCount > 0
+        && !contextMenuEvent
+        && mev.innerNode() && m_clickNode
+        && mev.innerNode()->canParticipateInFlatTree() && m_clickNode->canParticipateInFlatTree()
+        && !(selectionController().hasExtendedSelection() && mayBeLinkSelection(mev));

[kotenkov, 2016/03/09 17:27:59]

This is needed so that no click event is sent when we select a part of a link.

+    if (shouldDispatchClickEvent) {
         // Updates distribution because a 'mouseup' event listener can make the
         // tree dirty at dispatchMouseEvent() invocation above.
         // Unless distribution is updated, commonAncestor would hit ASSERT.
         // Both m_clickNode and mev.innerNode() don't need to be updated
         // because commonAncestor() will exit early if their documents are different.
         m_clickNode->updateDistribution();
         if (Node* clickTargetNode = mev.innerNode()->commonAncestor(
             *m_clickNode, parentForClickEvent)) {
 
             // Dispatch mouseup directly w/o calling updateMouseEventTargetNode
@@ skipping 2626 matching lines @@
 PlatformEvent::Modifiers EventHandler::accessKeyModifiers()
 {
 #if OS(MACOSX)
     return static_cast<PlatformEvent::Modifiers>(PlatformEvent::CtrlKey | PlatformEvent::AltKey);
 #else
     return PlatformEvent::AltKey;
 #endif
 }
 
 } // namespace blink