Merge WebKit at r75315: Initial merge by git.

Change-Id: I570314b346ce101c935ed22a626b48c2af266b84

1 files changed, 852 insertions, 0 deletions

diff --git a/Source/WebCore/page/DragController.cpp b/Source/WebCore/page/DragController.cpp
new file mode 100644
index 0000000..d0e9a8c
--- /dev/null
+++ b/Source/WebCore/page/DragController.cpp
@@ -0,0 +1,852 @@
+/*
+ * Copyright (C) 2007, 2009, 2010 Apple Inc. All rights reserved.
+ *
+ * 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 "config.h"
+#include "DragController.h"
+
+#if ENABLE(DRAG_SUPPORT)
+#include "CSSStyleDeclaration.h"
+#include "Clipboard.h"
+#include "ClipboardAccessPolicy.h"
+#include "CachedResourceLoader.h"
+#include "Document.h"
+#include "DocumentFragment.h"
+#include "DragActions.h"
+#include "DragClient.h"
+#include "DragData.h"
+#include "Editor.h"
+#include "EditorClient.h"
+#include "Element.h"
+#include "EventHandler.h"
+#include "FloatRect.h"
+#include "Frame.h"
+#include "FrameLoader.h"
+#include "FrameView.h"
+#include "HTMLAnchorElement.h"
+#include "HTMLInputElement.h"
+#include "HTMLNames.h"
+#include "HitTestRequest.h"
+#include "HitTestResult.h"
+#include "Image.h"
+#include "MoveSelectionCommand.h"
+#include "Node.h"
+#include "Page.h"
+#include "PlatformKeyboardEvent.h"
+#include "RenderFileUploadControl.h"
+#include "RenderImage.h"
+#include "RenderLayer.h"
+#include "RenderView.h"
+#include "ReplaceSelectionCommand.h"
+#include "ResourceRequest.h"
+#include "SelectionController.h"
+#include "Settings.h"
+#include "Text.h"
+#include "TextEvent.h"
+#include "htmlediting.h"
+#include "markup.h"
+#include <wtf/CurrentTime.h>
+#include <wtf/RefPtr.h>
+
+namespace WebCore {
+
+static PlatformMouseEvent createMouseEvent(DragData* dragData)
+{
+    bool shiftKey, ctrlKey, altKey, metaKey;
+    shiftKey = ctrlKey = altKey = metaKey = false;
+    PlatformKeyboardEvent::getCurrentModifierState(shiftKey, ctrlKey, altKey, metaKey);
+    return PlatformMouseEvent(dragData->clientPosition(), dragData->globalPosition(),
+                              LeftButton, MouseEventMoved, 0, shiftKey, ctrlKey, altKey,
+                              metaKey, currentTime());
+}
+
+DragController::DragController(Page* page, DragClient* client)
+    : m_page(page)
+    , m_client(client)
+    , m_documentUnderMouse(0)
+    , m_dragInitiator(0)
+    , m_dragDestinationAction(DragDestinationActionNone)
+    , m_dragSourceAction(DragSourceActionNone)
+    , m_didInitiateDrag(false)
+    , m_isHandlingDrag(false)
+    , m_sourceDragOperation(DragOperationNone)
+{
+}
+
+DragController::~DragController()
+{
+    m_client->dragControllerDestroyed();
+}
+
+static PassRefPtr<DocumentFragment> documentFragmentFromDragData(DragData* dragData, RefPtr<Range> context,
+                                          bool allowPlainText, bool& chosePlainText)
+{
+    ASSERT(dragData);
+    chosePlainText = false;
+
+    Document* document = context->ownerDocument();
+    ASSERT(document);
+    if (document && dragData->containsCompatibleContent()) {
+        if (PassRefPtr<DocumentFragment> fragment = dragData->asFragment(document))
+            return fragment;
+
+        if (dragData->containsURL(DragData::DoNotConvertFilenames)) {
+            String title;
+            String url = dragData->asURL(DragData::DoNotConvertFilenames, &title);
+            if (!url.isEmpty()) {
+                RefPtr<HTMLAnchorElement> anchor = HTMLAnchorElement::create(document);
+                anchor->setHref(url);
+                if (title.isEmpty()) {
+                    // Try the plain text first because the url might be normalized or escaped.
+                    if (dragData->containsPlainText())
+                        title = dragData->asPlainText();
+                    if (title.isEmpty())
+                        title = url;
+                }
+                RefPtr<Node> anchorText = document->createTextNode(title);
+                ExceptionCode ec;
+                anchor->appendChild(anchorText, ec);
+                RefPtr<DocumentFragment> fragment = document->createDocumentFragment();
+                fragment->appendChild(anchor, ec);
+                return fragment.get();
+            }
+        }
+    }
+    if (allowPlainText && dragData->containsPlainText()) {
+        chosePlainText = true;
+        return createFragmentFromText(context.get(), dragData->asPlainText()).get();
+    }
+
+    return 0;
+}
+
+bool DragController::dragIsMove(SelectionController* selection)
+{
+    return m_documentUnderMouse == m_dragInitiator && selection->isContentEditable() && !isCopyKeyDown();
+}
+
+// FIXME: This method is poorly named.  We're just clearing the selection from the document this drag is exiting.
+void DragController::cancelDrag()
+{
+    m_page->dragCaretController()->clear();
+}
+
+void DragController::dragEnded()
+{
+    m_dragInitiator = 0;
+    m_didInitiateDrag = false;
+    m_page->dragCaretController()->clear();
+}
+
+DragOperation DragController::dragEntered(DragData* dragData)
+{
+    return dragEnteredOrUpdated(dragData);
+}
+
+void DragController::dragExited(DragData* dragData)
+{
+    ASSERT(dragData);
+    Frame* mainFrame = m_page->mainFrame();
+
+    if (RefPtr<FrameView> v = mainFrame->view()) {
+        ClipboardAccessPolicy policy = (!m_documentUnderMouse || m_documentUnderMouse->securityOrigin()->isLocal()) ? ClipboardReadable : ClipboardTypesReadable;
+        RefPtr<Clipboard> clipboard = Clipboard::create(policy, dragData, mainFrame);
+        clipboard->setSourceOperation(dragData->draggingSourceOperationMask());
+        mainFrame->eventHandler()->cancelDragAndDrop(createMouseEvent(dragData), clipboard.get());
+        clipboard->setAccessPolicy(ClipboardNumb);    // invalidate clipboard here for security
+    }
+    mouseMovedIntoDocument(0);
+}
+
+DragOperation DragController::dragUpdated(DragData* dragData)
+{
+    return dragEnteredOrUpdated(dragData);
+}
+
+bool DragController::performDrag(DragData* dragData)
+{
+    ASSERT(dragData);
+    m_documentUnderMouse = m_page->mainFrame()->documentAtPoint(dragData->clientPosition());
+    if (m_isHandlingDrag) {
+        ASSERT(m_dragDestinationAction & DragDestinationActionDHTML);
+        m_client->willPerformDragDestinationAction(DragDestinationActionDHTML, dragData);
+        RefPtr<Frame> mainFrame = m_page->mainFrame();
+        if (mainFrame->view()) {
+            // Sending an event can result in the destruction of the view and part.
+            RefPtr<Clipboard> clipboard = Clipboard::create(ClipboardReadable, dragData, mainFrame.get());
+            clipboard->setSourceOperation(dragData->draggingSourceOperationMask());
+            mainFrame->eventHandler()->performDragAndDrop(createMouseEvent(dragData), clipboard.get());
+            clipboard->setAccessPolicy(ClipboardNumb);    // invalidate clipboard here for security
+        }
+        m_documentUnderMouse = 0;
+        return true;
+    }
+
+    if ((m_dragDestinationAction & DragDestinationActionEdit) && concludeEditDrag(dragData)) {
+        m_documentUnderMouse = 0;
+        return true;
+    }
+
+    m_documentUnderMouse = 0;
+
+    if (operationForLoad(dragData) == DragOperationNone)
+        return false;
+
+    m_client->willPerformDragDestinationAction(DragDestinationActionLoad, dragData);
+    m_page->mainFrame()->loader()->load(ResourceRequest(dragData->asURL()), false);
+    return true;
+}
+
+void DragController::mouseMovedIntoDocument(Document* newDocument)
+{
+    if (m_documentUnderMouse == newDocument)
+        return;
+
+    // If we were over another document clear the selection
+    if (m_documentUnderMouse)
+        cancelDrag();
+    m_documentUnderMouse = newDocument;
+}
+
+DragOperation DragController::dragEnteredOrUpdated(DragData* dragData)
+{
+    ASSERT(dragData);
+    ASSERT(m_page->mainFrame()); // It is not possible in Mac WebKit to have a Page without a mainFrame()
+    mouseMovedIntoDocument(m_page->mainFrame()->documentAtPoint(dragData->clientPosition()));
+
+    m_dragDestinationAction = m_client->actionMaskForDrag(dragData);
+    if (m_dragDestinationAction == DragDestinationActionNone) {
+        cancelDrag(); // FIXME: Why not call mouseMovedIntoDocument(0)?
+        return DragOperationNone;
+    }
+
+    DragOperation operation = DragOperationNone;
+    bool handledByDocument = tryDocumentDrag(dragData, m_dragDestinationAction, operation);
+    if (!handledByDocument && (m_dragDestinationAction & DragDestinationActionLoad))
+        return operationForLoad(dragData);
+    return operation;
+}
+
+static HTMLInputElement* asFileInput(Node* node)
+{
+    ASSERT(node);
+
+    // The button for a FILE input is a sub element with no set input type
+    // In order to get around this problem we assume any non-FILE input element
+    // is this internal button, and try querying the shadow parent node.
+    if (node->hasTagName(HTMLNames::inputTag) && node->isShadowRoot() && !static_cast<HTMLInputElement*>(node)->isFileUpload())
+        node = node->shadowHost();
+
+    if (!node || !node->hasTagName(HTMLNames::inputTag))
+        return 0;
+
+    HTMLInputElement* inputElement = static_cast<HTMLInputElement*>(node);
+    if (!inputElement->isFileUpload())
+        return 0;
+
+    return inputElement;
+}
+
+// This can return null if an empty document is loaded.
+static Element* elementUnderMouse(Document* documentUnderMouse, const IntPoint& p)
+{
+    Frame* frame = documentUnderMouse->frame();
+    float zoomFactor = frame ? frame->pageZoomFactor() : 1;
+    IntPoint point = roundedIntPoint(FloatPoint(p.x() * zoomFactor, p.y() * zoomFactor));
+
+    HitTestRequest request(HitTestRequest::ReadOnly | HitTestRequest::Active);
+    HitTestResult result(point);
+    documentUnderMouse->renderView()->layer()->hitTest(request, result);
+
+    Node* n = result.innerNode();
+    while (n && !n->isElementNode())
+        n = n->parentNode();
+    if (n)
+        n = n->shadowAncestorNode();
+
+    return static_cast<Element*>(n);
+}
+
+bool DragController::tryDocumentDrag(DragData* dragData, DragDestinationAction actionMask, DragOperation& operation)
+{
+    ASSERT(dragData);
+
+    if (!m_documentUnderMouse)
+        return false;
+
+    if (m_dragInitiator && !m_documentUnderMouse->securityOrigin()->canReceiveDragData(m_dragInitiator->securityOrigin()))
+        return false;
+
+    m_isHandlingDrag = false;
+    if (actionMask & DragDestinationActionDHTML) {
+        m_isHandlingDrag = tryDHTMLDrag(dragData, operation);
+        // Do not continue if m_documentUnderMouse has been reset by tryDHTMLDrag.
+        // tryDHTMLDrag fires dragenter event. The event listener that listens
+        // to this event may create a nested message loop (open a modal dialog),
+        // which could process dragleave event and reset m_documentUnderMouse in
+        // dragExited.
+        if (!m_documentUnderMouse)
+            return false;
+    }
+
+    // It's unclear why this check is after tryDHTMLDrag.
+    // We send drag events in tryDHTMLDrag and that may be the reason.
+    RefPtr<FrameView> frameView = m_documentUnderMouse->view();
+    if (!frameView)
+        return false;
+
+    if (m_isHandlingDrag) {
+        m_page->dragCaretController()->clear();
+        return true;
+    } else if ((actionMask & DragDestinationActionEdit) && canProcessDrag(dragData)) {
+        if (dragData->containsColor()) {
+            operation = DragOperationGeneric;
+            return true;
+        }
+
+        IntPoint point = frameView->windowToContents(dragData->clientPosition());
+        Element* element = elementUnderMouse(m_documentUnderMouse.get(), point);
+        if (!element)
+            return false;
+        if (!asFileInput(element)) {
+            VisibleSelection dragCaret = m_documentUnderMouse->frame()->visiblePositionForPoint(point);
+            m_page->dragCaretController()->setSelection(dragCaret);
+        }
+
+        Frame* innerFrame = element->document()->frame();
+        operation = dragIsMove(innerFrame->selection()) ? DragOperationMove : DragOperationCopy;
+        return true;
+    }
+    // If we're not over an editable region, make sure we're clearing any prior drag cursor.
+    m_page->dragCaretController()->clear();
+    return false;
+}
+
+DragSourceAction DragController::delegateDragSourceAction(const IntPoint& windowPoint)
+{
+    m_dragSourceAction = m_client->dragSourceActionMaskForPoint(windowPoint);
+    return m_dragSourceAction;
+}
+
+DragOperation DragController::operationForLoad(DragData* dragData)
+{
+    ASSERT(dragData);
+    Document* doc = m_page->mainFrame()->documentAtPoint(dragData->clientPosition());
+    if (doc && (m_didInitiateDrag || doc->isPluginDocument() || (doc->frame() && doc->frame()->editor()->clientIsEditable())))
+        return DragOperationNone;
+    return dragOperation(dragData);
+}
+
+static bool setSelectionToDragCaret(Frame* frame, VisibleSelection& dragCaret, RefPtr<Range>& range, const IntPoint& point)
+{
+    frame->selection()->setSelection(dragCaret);
+    if (frame->selection()->isNone()) {
+        dragCaret = frame->visiblePositionForPoint(point);
+        frame->selection()->setSelection(dragCaret);
+        range = dragCaret.toNormalizedRange();
+    }
+    return !frame->selection()->isNone() && frame->selection()->isContentEditable();
+}
+
+bool DragController::dispatchTextInputEventFor(Frame* innerFrame, DragData* dragData)
+{
+    VisibleSelection dragCaret(m_page->dragCaretController()->selection());
+    String text = dragCaret.isContentRichlyEditable() ? "" : dragData->asPlainText();
+    Node* target = innerFrame->editor()->findEventTargetFrom(dragCaret);
+    ExceptionCode ec = 0;
+    return target->dispatchEvent(TextEvent::createForDrop(innerFrame->domWindow(), text), ec);
+}
+
+bool DragController::concludeEditDrag(DragData* dragData)
+{
+    ASSERT(dragData);
+    ASSERT(!m_isHandlingDrag);
+
+    if (!m_documentUnderMouse)
+        return false;
+
+    IntPoint point = m_documentUnderMouse->view()->windowToContents(dragData->clientPosition());
+    Element* element = elementUnderMouse(m_documentUnderMouse.get(), point);
+    if (!element)
+        return false;
+    Frame* innerFrame = element->ownerDocument()->frame();
+    ASSERT(innerFrame);
+
+    if (!dispatchTextInputEventFor(innerFrame, dragData))
+        return true;
+
+    if (dragData->containsColor()) {
+        Color color = dragData->asColor();
+        if (!color.isValid())
+            return false;
+        RefPtr<Range> innerRange = innerFrame->selection()->toNormalizedRange();
+        RefPtr<CSSStyleDeclaration> style = m_documentUnderMouse->createCSSStyleDeclaration();
+        ExceptionCode ec;
+        style->setProperty("color", color.name(), ec);
+        if (!innerFrame->editor()->shouldApplyStyle(style.get(), innerRange.get()))
+            return false;
+        m_client->willPerformDragDestinationAction(DragDestinationActionEdit, dragData);
+        innerFrame->editor()->applyStyle(style.get(), EditActionSetColor);
+        return true;
+    }
+
+    if (!m_page->dragController()->canProcessDrag(dragData)) {
+        m_page->dragCaretController()->clear();
+        return false;
+    }
+
+    if (HTMLInputElement* fileInput = asFileInput(element)) {
+        if (fileInput->disabled())
+            return false;
+
+        if (!dragData->containsFiles())
+            return false;
+
+        Vector<String> filenames;
+        dragData->asFilenames(filenames);
+        if (filenames.isEmpty())
+            return false;
+
+        // Ugly. For security none of the APIs available to us can set the input value
+        // on file inputs. Even forcing a change in HTMLInputElement doesn't work as
+        // RenderFileUploadControl clears the file when doing updateFromElement().
+        RenderFileUploadControl* renderer = toRenderFileUploadControl(fileInput->renderer());
+        if (!renderer)
+            return false;
+
+        renderer->receiveDroppedFiles(filenames);
+        return true;
+    }
+
+    VisibleSelection dragCaret(m_page->dragCaretController()->selection());
+    m_page->dragCaretController()->clear();
+    RefPtr<Range> range = dragCaret.toNormalizedRange();
+
+    // For range to be null a WebKit client must have done something bad while
+    // manually controlling drag behaviour
+    if (!range)
+        return false;
+    CachedResourceLoader* cachedResourceLoader = range->ownerDocument()->cachedResourceLoader();
+    cachedResourceLoader->setAllowStaleResources(true);
+    if (dragIsMove(innerFrame->selection()) || dragCaret.isContentRichlyEditable()) {
+        bool chosePlainText = false;
+        RefPtr<DocumentFragment> fragment = documentFragmentFromDragData(dragData, range, true, chosePlainText);
+        if (!fragment || !innerFrame->editor()->shouldInsertFragment(fragment, range, EditorInsertActionDropped)) {
+            cachedResourceLoader->setAllowStaleResources(false);
+            return false;
+        }
+
+        m_client->willPerformDragDestinationAction(DragDestinationActionEdit, dragData);
+        if (dragIsMove(innerFrame->selection())) {
+            // NSTextView behavior is to always smart delete on moving a selection,
+            // but only to smart insert if the selection granularity is word granularity.
+            bool smartDelete = innerFrame->editor()->smartInsertDeleteEnabled();
+            bool smartInsert = smartDelete && innerFrame->selection()->granularity() == WordGranularity && dragData->canSmartReplace();
+            applyCommand(MoveSelectionCommand::create(fragment, dragCaret.base(), smartInsert, smartDelete));
+        } else {
+            if (setSelectionToDragCaret(innerFrame, dragCaret, range, point))
+                applyCommand(ReplaceSelectionCommand::create(m_documentUnderMouse.get(), fragment, true, dragData->canSmartReplace(), chosePlainText));
+        }
+    } else {
+        String text = dragData->asPlainText();
+        if (text.isEmpty() || !innerFrame->editor()->shouldInsertText(text, range.get(), EditorInsertActionDropped)) {
+            cachedResourceLoader->setAllowStaleResources(false);
+            return false;
+        }
+
+        m_client->willPerformDragDestinationAction(DragDestinationActionEdit, dragData);
+        if (setSelectionToDragCaret(innerFrame, dragCaret, range, point))
+            applyCommand(ReplaceSelectionCommand::create(m_documentUnderMouse.get(), createFragmentFromText(range.get(), text), true, false, true));
+    }
+    cachedResourceLoader->setAllowStaleResources(false);
+
+    return true;
+}
+
+bool DragController::canProcessDrag(DragData* dragData)
+{
+    ASSERT(dragData);
+
+    if (!dragData->containsCompatibleContent())
+        return false;
+
+    IntPoint point = m_page->mainFrame()->view()->windowToContents(dragData->clientPosition());
+    HitTestResult result = HitTestResult(point);
+    if (!m_page->mainFrame()->contentRenderer())
+        return false;
+
+    result = m_page->mainFrame()->eventHandler()->hitTestResultAtPoint(point, true);
+
+    if (!result.innerNonSharedNode())
+        return false;
+
+    if (dragData->containsFiles() && asFileInput(result.innerNonSharedNode()))
+        return true;
+
+    if (!result.innerNonSharedNode()->isContentEditable())
+        return false;
+
+    if (m_didInitiateDrag && m_documentUnderMouse == m_dragInitiator && result.isSelected())
+        return false;
+
+    return true;
+}
+
+static DragOperation defaultOperationForDrag(DragOperation srcOpMask)
+{
+    // This is designed to match IE's operation fallback for the case where
+    // the page calls preventDefault() in a drag event but doesn't set dropEffect.
+    if (srcOpMask == DragOperationEvery)
+        return DragOperationCopy;
+    if (srcOpMask == DragOperationNone)
+        return DragOperationNone;
+    if (srcOpMask & DragOperationMove || srcOpMask & DragOperationGeneric)
+        return DragOperationMove;
+    if (srcOpMask & DragOperationCopy)
+        return DragOperationCopy;
+    if (srcOpMask & DragOperationLink)
+        return DragOperationLink;
+    
+    // FIXME: Does IE really return "generic" even if no operations were allowed by the source?
+    return DragOperationGeneric;
+}
+
+bool DragController::tryDHTMLDrag(DragData* dragData, DragOperation& operation)
+{
+    ASSERT(dragData);
+    ASSERT(m_documentUnderMouse);
+    RefPtr<Frame> mainFrame = m_page->mainFrame();
+    RefPtr<FrameView> viewProtector = mainFrame->view();
+    if (!viewProtector)
+        return false;
+
+    ClipboardAccessPolicy policy = m_documentUnderMouse->securityOrigin()->isLocal() ? ClipboardReadable : ClipboardTypesReadable;
+    RefPtr<Clipboard> clipboard = Clipboard::create(policy, dragData, mainFrame.get());
+    DragOperation srcOpMask = dragData->draggingSourceOperationMask();
+    clipboard->setSourceOperation(srcOpMask);
+
+    PlatformMouseEvent event = createMouseEvent(dragData);
+    if (!mainFrame->eventHandler()->updateDragAndDrop(event, clipboard.get())) {
+        clipboard->setAccessPolicy(ClipboardNumb);    // invalidate clipboard here for security
+        return false;
+    }
+
+    operation = clipboard->destinationOperation();
+    if (clipboard->dropEffectIsUninitialized())
+        operation = defaultOperationForDrag(srcOpMask);
+    else if (!(srcOpMask & operation)) {
+        // The element picked an operation which is not supported by the source
+        operation = DragOperationNone;
+    }
+
+    clipboard->setAccessPolicy(ClipboardNumb);    // invalidate clipboard here for security
+    return true;
+}
+
+bool DragController::mayStartDragAtEventLocation(const Frame* frame, const IntPoint& framePos, Node* node)
+{
+    ASSERT(frame);
+    ASSERT(frame->settings());
+
+    if (!frame->view() || !frame->contentRenderer())
+        return false;
+
+    HitTestResult mouseDownTarget = HitTestResult(framePos);
+
+    mouseDownTarget = frame->eventHandler()->hitTestResultAtPoint(framePos, true);
+    if (node)
+        mouseDownTarget.setInnerNonSharedNode(node);
+
+    if (mouseDownTarget.image()
+        && !mouseDownTarget.absoluteImageURL().isEmpty()
+        && frame->settings()->loadsImagesAutomatically()
+        && m_dragSourceAction & DragSourceActionImage)
+        return true;
+
+    if (!mouseDownTarget.absoluteLinkURL().isEmpty()
+        && m_dragSourceAction & DragSourceActionLink
+        && mouseDownTarget.isLiveLink()
+        && mouseDownTarget.URLElement()->renderer() && mouseDownTarget.URLElement()->renderer()->style()->userDrag() != DRAG_NONE)
+        return true;
+
+    if (mouseDownTarget.isSelected()
+        && m_dragSourceAction & DragSourceActionSelection)
+        return true;
+
+    return false;
+}
+
+static CachedImage* getCachedImage(Element* element)
+{
+    ASSERT(element);
+    RenderObject* renderer = element->renderer();
+    if (!renderer || !renderer->isImage())
+        return 0;
+    RenderImage* image = toRenderImage(renderer);
+    return image->cachedImage();
+}
+
+static Image* getImage(Element* element)
+{
+    ASSERT(element);
+    CachedImage* cachedImage = getCachedImage(element);
+    return (cachedImage && !cachedImage->errorOccurred()) ?
+        cachedImage->image() : 0;
+}
+
+static void prepareClipboardForImageDrag(Frame* src, Clipboard* clipboard, Element* node, const KURL& linkURL, const KURL& imageURL, const String& label)
+{
+    RefPtr<Range> range = src->document()->createRange();
+    ExceptionCode ec = 0;
+    range->selectNode(node, ec);
+    ASSERT(!ec);
+    src->selection()->setSelection(VisibleSelection(range.get(), DOWNSTREAM));
+    clipboard->declareAndWriteDragImage(node, !linkURL.isEmpty() ? linkURL : imageURL, label, src);
+}
+
+static IntPoint dragLocForDHTMLDrag(const IntPoint& mouseDraggedPoint, const IntPoint& dragOrigin, const IntPoint& dragImageOffset, bool isLinkImage)
+{
+    // dragImageOffset is the cursor position relative to the lower-left corner of the image.
+#if PLATFORM(MAC)
+    // We add in the Y dimension because we are a flipped view, so adding moves the image down.
+    const int yOffset = dragImageOffset.y();
+#else
+    const int yOffset = -dragImageOffset.y();
+#endif
+
+    if (isLinkImage)
+        return IntPoint(mouseDraggedPoint.x() - dragImageOffset.x(), mouseDraggedPoint.y() + yOffset);
+
+    return IntPoint(dragOrigin.x() - dragImageOffset.x(), dragOrigin.y() + yOffset);
+}
+
+static IntPoint dragLocForSelectionDrag(Frame* src)
+{
+    IntRect draggingRect = enclosingIntRect(src->selection()->bounds());
+    int xpos = draggingRect.right();
+    xpos = draggingRect.x() < xpos ? draggingRect.x() : xpos;
+    int ypos = draggingRect.bottom();
+#if PLATFORM(MAC)
+    // Deal with flipped coordinates on Mac
+    ypos = draggingRect.y() > ypos ? draggingRect.y() : ypos;
+#else
+    ypos = draggingRect.y() < ypos ? draggingRect.y() : ypos;
+#endif
+    return IntPoint(xpos, ypos);
+}
+
+bool DragController::startDrag(Frame* src, Clipboard* clipboard, DragOperation srcOp, const PlatformMouseEvent& dragEvent, const IntPoint& dragOrigin, bool isDHTMLDrag)
+{
+    ASSERT(src);
+    ASSERT(clipboard);
+
+    if (!src->view() || !src->contentRenderer())
+        return false;
+
+    HitTestResult dragSource = HitTestResult(dragOrigin);
+    dragSource = src->eventHandler()->hitTestResultAtPoint(dragOrigin, true);
+    KURL linkURL = dragSource.absoluteLinkURL();
+    KURL imageURL = dragSource.absoluteImageURL();
+    bool isSelected = dragSource.isSelected();
+
+    IntPoint mouseDraggedPoint = src->view()->windowToContents(dragEvent.pos());
+
+    m_draggingImageURL = KURL();
+    m_sourceDragOperation = srcOp;
+
+    DragImageRef dragImage = 0;
+    IntPoint dragLoc(0, 0);
+    IntPoint dragImageOffset(0, 0);
+
+    if (isDHTMLDrag)
+        dragImage = clipboard->createDragImage(dragImageOffset);
+    else {
+        // This drag operation is not a DHTML drag and may go outside the WebView.
+        // We provide a default set of allowed drag operations that follows from:
+        // http://trac.webkit.org/browser/trunk/WebKit/mac/WebView/WebHTMLView.mm?rev=48526#L3430
+        m_sourceDragOperation = (DragOperation)(DragOperationGeneric | DragOperationCopy);
+    }
+
+    // We allow DHTML/JS to set the drag image, even if its a link, image or text we're dragging.
+    // This is in the spirit of the IE API, which allows overriding of pasteboard data and DragOp.
+    if (dragImage) {
+        dragLoc = dragLocForDHTMLDrag(mouseDraggedPoint, dragOrigin, dragImageOffset, !linkURL.isEmpty());
+        m_dragOffset = dragImageOffset;
+    }
+
+    bool startedDrag = true; // optimism - we almost always manage to start the drag
+
+    Node* node = dragSource.innerNonSharedNode();
+
+    Image* image = getImage(static_cast<Element*>(node));
+    if (!imageURL.isEmpty() && node && node->isElementNode() && image
+            && (m_dragSourceAction & DragSourceActionImage)) {
+        // We shouldn't be starting a drag for an image that can't provide an extension.
+        // This is an early detection for problems encountered later upon drop.
+        ASSERT(!image->filenameExtension().isEmpty());
+        Element* element = static_cast<Element*>(node);
+        if (!clipboard->hasData()) {
+            m_draggingImageURL = imageURL;
+            prepareClipboardForImageDrag(src, clipboard, element, linkURL, imageURL, dragSource.altDisplayString());
+        }
+
+        m_client->willPerformDragSourceAction(DragSourceActionImage, dragOrigin, clipboard);
+
+        if (!dragImage) {
+            IntRect imageRect = dragSource.imageRect();
+            imageRect.setLocation(m_page->mainFrame()->view()->windowToContents(src->view()->contentsToWindow(imageRect.location())));
+            doImageDrag(element, dragOrigin, dragSource.imageRect(), clipboard, src, m_dragOffset);
+        } else
+            // DHTML defined drag image
+            doSystemDrag(dragImage, dragLoc, dragOrigin, clipboard, src, false);
+
+    } else if (!linkURL.isEmpty() && (m_dragSourceAction & DragSourceActionLink)) {
+        if (!clipboard->hasData())
+            // Simplify whitespace so the title put on the clipboard resembles what the user sees
+            // on the web page. This includes replacing newlines with spaces.
+            clipboard->writeURL(linkURL, dragSource.textContent().simplifyWhiteSpace(), src);
+
+        if (src->selection()->isCaret() && src->selection()->isContentEditable()) {
+            // a user can initiate a drag on a link without having any text
+            // selected.  In this case, we should expand the selection to
+            // the enclosing anchor element
+            Position pos = src->selection()->base();
+            Node* node = enclosingAnchorElement(pos);
+            if (node)
+                src->selection()->setSelection(VisibleSelection::selectionFromContentsOfNode(node));
+        }
+
+        m_client->willPerformDragSourceAction(DragSourceActionLink, dragOrigin, clipboard);
+        if (!dragImage) {
+            dragImage = m_client->createDragImageForLink(linkURL, dragSource.textContent(), src);
+            IntSize size = dragImageSize(dragImage);
+            m_dragOffset = IntPoint(-size.width() / 2, -LinkDragBorderInset);
+            dragLoc = IntPoint(mouseDraggedPoint.x() + m_dragOffset.x(), mouseDraggedPoint.y() + m_dragOffset.y());
+        }
+        doSystemDrag(dragImage, dragLoc, mouseDraggedPoint, clipboard, src, true);
+    } else if (isSelected && (m_dragSourceAction & DragSourceActionSelection)) {
+        if (!clipboard->hasData()) {
+            if (isNodeInTextFormControl(src->selection()->start().node()))
+                clipboard->writePlainText(src->editor()->selectedText());
+            else {
+                RefPtr<Range> selectionRange = src->selection()->toNormalizedRange();
+                ASSERT(selectionRange);
+
+                clipboard->writeRange(selectionRange.get(), src);
+            }
+        }
+        m_client->willPerformDragSourceAction(DragSourceActionSelection, dragOrigin, clipboard);
+        if (!dragImage) {
+            dragImage = createDragImageForSelection(src);
+            dragLoc = dragLocForSelectionDrag(src);
+            m_dragOffset = IntPoint((int)(dragOrigin.x() - dragLoc.x()), (int)(dragOrigin.y() - dragLoc.y()));
+        }
+        doSystemDrag(dragImage, dragLoc, dragOrigin, clipboard, src, false);
+    } else if (isDHTMLDrag) {
+        ASSERT(m_dragSourceAction & DragSourceActionDHTML);
+        m_client->willPerformDragSourceAction(DragSourceActionDHTML, dragOrigin, clipboard);
+        doSystemDrag(dragImage, dragLoc, dragOrigin, clipboard, src, false);
+    } else {
+        // Only way I know to get here is if to get here is if the original element clicked on in the mousedown is no longer
+        // under the mousedown point, so linkURL, imageURL and isSelected are all false/empty.
+        startedDrag = false;
+    }
+
+    if (dragImage)
+        deleteDragImage(dragImage);
+    return startedDrag;
+}
+
+void DragController::doImageDrag(Element* element, const IntPoint& dragOrigin, const IntRect& rect, Clipboard* clipboard, Frame* frame, IntPoint& dragImageOffset)
+{
+    IntPoint mouseDownPoint = dragOrigin;
+    DragImageRef dragImage;
+    IntPoint origin;
+
+    Image* image = getImage(element);
+    if (image && image->size().height() * image->size().width() <= MaxOriginalImageArea
+        && (dragImage = createDragImageFromImage(image))) {
+        IntSize originalSize = rect.size();
+        origin = rect.location();
+
+        dragImage = fitDragImageToMaxSize(dragImage, rect.size(), maxDragImageSize());
+        dragImage = dissolveDragImageToFraction(dragImage, DragImageAlpha);
+        IntSize newSize = dragImageSize(dragImage);
+
+        // Properly orient the drag image and orient it differently if it's smaller than the original
+        float scale = newSize.width() / (float)originalSize.width();
+        float dx = origin.x() - mouseDownPoint.x();
+        dx *= scale;
+        origin.setX((int)(dx + 0.5));
+#if PLATFORM(MAC)
+        //Compensate for accursed flipped coordinates in cocoa
+        origin.setY(origin.y() + originalSize.height());
+#endif
+        float dy = origin.y() - mouseDownPoint.y();
+        dy *= scale;
+        origin.setY((int)(dy + 0.5));
+    } else {
+        dragImage = createDragImageIconForCachedImage(getCachedImage(element));
+        if (dragImage)
+            origin = IntPoint(DragIconRightInset - dragImageSize(dragImage).width(), DragIconBottomInset);
+    }
+
+    dragImageOffset.setX(mouseDownPoint.x() + origin.x());
+    dragImageOffset.setY(mouseDownPoint.y() + origin.y());
+    doSystemDrag(dragImage, dragImageOffset, dragOrigin, clipboard, frame, false);
+
+    deleteDragImage(dragImage);
+}
+
+void DragController::doSystemDrag(DragImageRef image, const IntPoint& dragLoc, const IntPoint& eventPos, Clipboard* clipboard, Frame* frame, bool forLink)
+{
+    m_didInitiateDrag = true;
+    m_dragInitiator = frame->document();
+    // Protect this frame and view, as a load may occur mid drag and attempt to unload this frame
+    RefPtr<Frame> frameProtector = m_page->mainFrame();
+    RefPtr<FrameView> viewProtector = frameProtector->view();
+    m_client->startDrag(image, viewProtector->windowToContents(frame->view()->contentsToWindow(dragLoc)),
+        viewProtector->windowToContents(frame->view()->contentsToWindow(eventPos)), clipboard, frameProtector.get(), forLink);
+
+    cleanupAfterSystemDrag();
+}
+
+// Manual drag caret manipulation
+void DragController::placeDragCaret(const IntPoint& windowPoint)
+{
+    mouseMovedIntoDocument(m_page->mainFrame()->documentAtPoint(windowPoint));
+    if (!m_documentUnderMouse)
+        return;
+    Frame* frame = m_documentUnderMouse->frame();
+    FrameView* frameView = frame->view();
+    if (!frameView)
+        return;
+    IntPoint framePoint = frameView->windowToContents(windowPoint);
+    VisibleSelection dragCaret(frame->visiblePositionForPoint(framePoint));
+    m_page->dragCaretController()->setSelection(dragCaret);
+}
+
+} // namespace WebCore
+
+#endif // ENABLE(DRAG_SUPPORT)