Source/WebCore/page/ios/EventHandlerIOS.mm

/*
 * Copyright (C) 2006-2016 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 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 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. 
 */

#import "config.h"
#import "EventHandler.h"

#if PLATFORM(IOS_FAMILY)

#import "AXObjectCache.h"
#import "AutoscrollController.h"
#import "Chrome.h"
#import "ChromeClient.h"
#import "ContentChangeObserver.h"
#import "DataTransfer.h"
#import "DragState.h"
#import "FocusController.h"
#import "Frame.h"
#import "FrameView.h"
#import "KeyboardEvent.h"
#import "MouseEventWithHitTestResults.h"
#import "Page.h"
#import "Pasteboard.h"
#import "PlatformEventFactoryIOS.h"
#import "PlatformKeyboardEvent.h"
#import "RenderWidget.h"
#import "WAKView.h"
#import "WAKWindow.h"
#import "WebEvent.h"
#import <wtf/BlockObjCExceptions.h>
#import <wtf/NeverDestroyed.h>
#import <wtf/Noncopyable.h>
#import <wtf/SetForScope.h>

#if ENABLE(IOS_TOUCH_EVENTS)
#import <WebKitAdditions/EventHandlerIOSTouch.cpp>
#endif

namespace WebCore {

static RetainPtr<WebEvent>& currentEventSlot()
{
    static NeverDestroyed<RetainPtr<WebEvent>> event;
    return event;
}

WebEvent *EventHandler::currentEvent()
{
    return currentEventSlot().get();
}

class CurrentEventScope {
    WTF_MAKE_NONCOPYABLE(CurrentEventScope);
public:
    CurrentEventScope(WebEvent *);
    ~CurrentEventScope();

private:
    RetainPtr<WebEvent> m_savedCurrentEvent;
#ifndef NDEBUG
    RetainPtr<WebEvent> m_event;
#endif
};

inline CurrentEventScope::CurrentEventScope(WebEvent *event)
    : m_savedCurrentEvent(currentEventSlot())
#ifndef NDEBUG
    , m_event(event)
#endif
{
    currentEventSlot() = event;
}

inline CurrentEventScope::~CurrentEventScope()
{
    ASSERT(currentEventSlot() == m_event);
    currentEventSlot() = m_savedCurrentEvent;
}

bool EventHandler::wheelEvent(WebEvent *event)
{
    Page* page = m_frame.page();
    if (!page)
        return false;

    CurrentEventScope scope(event);

    bool eventWasHandled = handleWheelEvent(PlatformEventFactory::createPlatformWheelEvent(event));
    event.wasHandled = eventWasHandled;
    return eventWasHandled;
}

#if ENABLE(IOS_TOUCH_EVENTS)

bool EventHandler::dispatchSimulatedTouchEvent(IntPoint location)
{
    bool handled = handleTouchEvent(PlatformEventFactory::createPlatformSimulatedTouchEvent(PlatformEvent::TouchStart, location));
    handled |= handleTouchEvent(PlatformEventFactory::createPlatformSimulatedTouchEvent(PlatformEvent::TouchEnd, location));
    return handled;
}
    
void EventHandler::touchEvent(WebEvent *event)
{
    CurrentEventScope scope(event);

    event.wasHandled = handleTouchEvent(PlatformEventFactory::createPlatformTouchEvent(event));
}
#endif

bool EventHandler::tabsToAllFormControls(KeyboardEvent* event) const
{
    Page* page = m_frame.page();
    if (!page)
        return false;

    KeyboardUIMode keyboardUIMode = page->chrome().client().keyboardUIMode();
    bool handlingOptionTab = event && isKeyboardOptionTab(*event);

    // If tab-to-links is off, option-tab always highlights all controls.
    if ((keyboardUIMode & KeyboardAccessTabsToLinks) == 0 && handlingOptionTab)
        return true;

    // If system preferences say to include all controls, we always include all controls.
    if (keyboardUIMode & KeyboardAccessFull)
        return true;

    // Otherwise tab-to-links includes all controls, unless the sense is flipped via option-tab.
    if (keyboardUIMode & KeyboardAccessTabsToLinks)
        return !handlingOptionTab;

    return handlingOptionTab;
}

bool EventHandler::keyEvent(WebEvent *event)
{
    BEGIN_BLOCK_OBJC_EXCEPTIONS;

    ASSERT(event.type == WebEventKeyDown || event.type == WebEventKeyUp);

    CurrentEventScope scope(event);
    bool eventWasHandled = keyEvent(PlatformEventFactory::createPlatformKeyboardEvent(event));
    event.wasHandled = eventWasHandled;
    return eventWasHandled;

    END_BLOCK_OBJC_EXCEPTIONS;

    return false;
}

void EventHandler::focusDocumentView()
{
    Page* page = m_frame.page();
    if (!page)
        return;

    Ref<Frame> protectedFrame(m_frame);

    if (FrameView* frameView = m_frame.view()) {
        if (NSView *documentView = frameView->documentView())
            page->chrome().focusNSView(documentView);
    }

    page->focusController().setFocusedFrame(&m_frame);
}

bool EventHandler::passWidgetMouseDownEventToWidget(const MouseEventWithHitTestResults& event)
{
    // Figure out which view to send the event to.
    auto* target = event.targetNode() ? event.targetNode()->renderer() : nullptr;
    if (!is<RenderWidget>(target))
        return false;

    // Double-click events don't exist in Cocoa. Since passWidgetMouseDownEventToWidget() will
    // just pass currentEvent down to the widget, we don't want to call it for events that
    // don't correspond to Cocoa events. The mousedown/ups will have already been passed on as
    // part of the pressed/released handling.
    return passMouseDownEventToWidget(downcast<RenderWidget>(*target).widget());
}

bool EventHandler::passWidgetMouseDownEventToWidget(RenderWidget* renderWidget)
{
    return passMouseDownEventToWidget(renderWidget->widget());
}

static bool lastEventIsMouseUp()
{
    // Many AppKit widgets run their own event loops and consume events while the mouse is down.
    // When they finish, currentEvent is the mouseUp that they exited on. We need to update
    // the WebCore state with this mouseUp, which we never saw. This method lets us detect
    // that state. Handling this was critical when we used AppKit widgets for form elements.
    // It's not clear in what cases this is helpful now -- it's possible it can be removed. 

    BEGIN_BLOCK_OBJC_EXCEPTIONS;
    WebEvent *currentEventAfterHandlingMouseDown = [WAKWindow currentEvent];
    return currentEventAfterHandlingMouseDown
        && EventHandler::currentEvent() != currentEventAfterHandlingMouseDown
        && currentEventAfterHandlingMouseDown.type == WebEventMouseUp
        && currentEventAfterHandlingMouseDown.timestamp >= EventHandler::currentEvent().timestamp;
    END_BLOCK_OBJC_EXCEPTIONS;

    return false;
}

bool EventHandler::passMouseDownEventToWidget(Widget* pWidget)
{
    // FIXME: This function always returns true. It should be changed either to return
    // false in some cases or the return value should be removed.

    RefPtr<Widget> widget = pWidget;

    if (!widget) {
        LOG_ERROR("hit a RenderWidget without a corresponding Widget, means a frame is half-constructed");
        return true;
    }

    // In WebKit2 we will never have a native widget. Just return early and let the regular event handler machinery take care of
    // dispatching the event.
    if (!widget->platformWidget())
        return false;

    BEGIN_BLOCK_OBJC_EXCEPTIONS;

    NSView *nodeView = widget->platformWidget();
    ASSERT(nodeView);
    ASSERT([nodeView superview]);
    NSView *view = [nodeView hitTest:[[nodeView superview] convertPoint:currentEvent().locationInWindow fromView:nil]];
    if (!view) {
        // We probably hit the border of a RenderWidget
        return true;
    }

    Page* page = m_frame.page();
    if (!page)
        return true;

    if (page->chrome().client().firstResponder() != view) {
        // Normally [NSWindow sendEvent:] handles setting the first responder.
        // But in our case, the event was sent to the view representing the entire web page.
        if ([view acceptsFirstResponder] && [view needsPanelToBecomeKey])
            page->chrome().client().makeFirstResponder(view);
    }

    // We need to "defer loading" while tracking the mouse, because tearing down the
    // page while an AppKit control is tracking the mouse can cause a crash.

    // FIXME: In theory, WebCore now tolerates tear-down while tracking the
    // mouse. We should confirm that, and then remove the deferrsLoading
    // hack entirely.

    bool wasDeferringLoading = page->defersLoading();
    if (!wasDeferringLoading)
        page->setDefersLoading(true);

    ASSERT(!m_sendingEventToSubview);
    m_sendingEventToSubview = true;

    {
        WidgetHierarchyUpdatesSuspensionScope suspendWidgetHierarchyUpdates;
        [view mouseDown:currentEvent()];
    }

    m_sendingEventToSubview = false;
    
    if (!wasDeferringLoading)
        page->setDefersLoading(false);

    // Remember which view we sent the event to, so we can direct the release event properly.
    m_mouseDownView = view;
    m_mouseDownWasInSubframe = false;

    // Many AppKit widgets run their own event loops and consume events while the mouse is down.
    // When they finish, currentEvent is the mouseUp that they exited on.  We need to update
    // the EventHandler state with this mouseUp, which we never saw.
    // If this event isn't a mouseUp, we assume that the mouseUp will be coming later.  There
    // is a hole here if the widget consumes both the mouseUp and subsequent events.
    if (lastEventIsMouseUp())
        m_mousePressed = false;

    END_BLOCK_OBJC_EXCEPTIONS;

    return true;
}

// Note that this does the same kind of check as [target isDescendantOf:superview].
// There are two differences: This is a lot slower because it has to walk the whole
// tree, and this works in cases where the target has already been deallocated.
static bool findViewInSubviews(NSView *superview, NSView *target)
{
    BEGIN_BLOCK_OBJC_EXCEPTIONS;
    NSEnumerator *e = [[superview subviews] objectEnumerator];
    NSView *subview;
    while ((subview = [e nextObject])) {
        if (subview == target || findViewInSubviews(subview, target)) {
            return true;
        }
    }
    END_BLOCK_OBJC_EXCEPTIONS;

    return false;
}

NSView *EventHandler::mouseDownViewIfStillGood()
{
    // Since we have no way of tracking the lifetime of m_mouseDownView, we have to assume that
    // it could be deallocated already. We search for it in our subview tree; if we don't find
    // it, we set it to nil.
    NSView *mouseDownView = m_mouseDownView;
    if (!mouseDownView) {
        return nil;
    }
    FrameView* topFrameView = m_frame.view();
    NSView *topView = topFrameView ? topFrameView->platformWidget() : nil;
    if (!topView || !findViewInSubviews(topView, mouseDownView)) {
        m_mouseDownView = nil;
        return nil;
    }
    return mouseDownView;
}

bool EventHandler::eventActivatedView(const PlatformMouseEvent&) const
{
    return false;
}

bool EventHandler::eventLoopHandleMouseUp(const MouseEventWithHitTestResults&)
{
    NSView *view = mouseDownViewIfStillGood();
    if (!view)
        return false;

    if (!m_mouseDownWasInSubframe) {
        ASSERT(!m_sendingEventToSubview);
        m_sendingEventToSubview = true;
        BEGIN_BLOCK_OBJC_EXCEPTIONS;
        [view mouseUp:currentEvent()];
        END_BLOCK_OBJC_EXCEPTIONS;
        m_sendingEventToSubview = false;
    }
 
    return true;
}
    
bool EventHandler::passSubframeEventToSubframe(MouseEventWithHitTestResults& event, Frame* subframe, HitTestResult* hoveredNode)
{
    BEGIN_BLOCK_OBJC_EXCEPTIONS;

    WebEventType currentEventType = currentEvent().type;
    switch (currentEventType) {
    case WebEventMouseMoved: {
        // Since we're passing in currentNSEvent() here, we can call
        // handleMouseMoveEvent() directly, since the save/restore of
        // currentNSEvent() that mouseMoved() does would have no effect.
        ASSERT(!m_sendingEventToSubview);
        m_sendingEventToSubview = true;
        subframe->eventHandler().handleMouseMoveEvent(currentPlatformMouseEvent(), hoveredNode);
        m_sendingEventToSubview = false;
        return true;
    }
    case WebEventMouseDown: {
        auto* node = event.targetNode();
        if (!node)
            return false;
        auto* renderer = node->renderer();
        if (!is<RenderWidget>(renderer))
            return false;
        auto* widget = downcast<RenderWidget>(*renderer).widget();
        if (!widget || !widget->isFrameView())
            return false;
        if (!passWidgetMouseDownEventToWidget(downcast<RenderWidget>(renderer)))
            return false;
        m_mouseDownWasInSubframe = true;
        return true;
    }
    case WebEventMouseUp: {
        if (!m_mouseDownWasInSubframe)
            return false;
        ASSERT(!m_sendingEventToSubview);
        m_sendingEventToSubview = true;
        subframe->eventHandler().handleMouseReleaseEvent(currentPlatformMouseEvent());
        m_sendingEventToSubview = false;
        return true;
    }
    case WebEventKeyDown:
    case WebEventKeyUp:
    case WebEventScrollWheel:
    case WebEventTouchBegin:
    case WebEventTouchCancel:
    case WebEventTouchChange:
    case WebEventTouchEnd:
        return false;
    }
    END_BLOCK_OBJC_EXCEPTIONS;

    return false;
}

bool EventHandler::widgetDidHandleWheelEvent(const PlatformWheelEvent&, Widget& widget)
{
    BEGIN_BLOCK_OBJC_EXCEPTIONS;

    NSView* nodeView = widget.platformWidget();
    if (!nodeView) {
        // WK2 code path. No wheel events on iOS anyway.
        return false;
    }

    if (currentEvent().type != WebEventScrollWheel || m_sendingEventToSubview)
        return false;

    ASSERT(nodeView);
    ASSERT([nodeView superview]);
    NSView *view = [nodeView hitTest:[[nodeView superview] convertPoint:currentEvent().locationInWindow fromView:nil]];
    if (!view) {
        // We probably hit the border of a RenderWidget
        return false;
    }

    ASSERT(!m_sendingEventToSubview);
    m_sendingEventToSubview = true;
    [view scrollWheel:currentEvent()];
    m_sendingEventToSubview = false;
    return true;

    END_BLOCK_OBJC_EXCEPTIONS;
    return false;
}

void EventHandler::mouseDown(WebEvent *event)
{
    FrameView* v = m_frame.view();
    if (!v || m_sendingEventToSubview)
        return;

    BEGIN_BLOCK_OBJC_EXCEPTIONS;

    // FIXME: Why is this here? EventHandler::handleMousePressEvent() calls it.
    m_frame.loader().resetMultipleFormSubmissionProtection();

    m_mouseDownView = nil;

    CurrentEventScope scope(event);

    event.wasHandled = handleMousePressEvent(currentPlatformMouseEvent());

    END_BLOCK_OBJC_EXCEPTIONS;
}

void EventHandler::mouseUp(WebEvent *event)
{
    FrameView* v = m_frame.view();
    if (!v || m_sendingEventToSubview)
        return;

    BEGIN_BLOCK_OBJC_EXCEPTIONS;

    CurrentEventScope scope(event);

    event.wasHandled = handleMouseReleaseEvent(currentPlatformMouseEvent());

    m_mouseDownView = nil;

    END_BLOCK_OBJC_EXCEPTIONS;
}

void EventHandler::mouseMoved(WebEvent *event)
{
    // Reject a mouse moved if the button is down - screws up tracking during autoscroll
    // These happen because WebKit sometimes has to fake up moved events.
    if (!m_frame.document() || !m_frame.view() || m_mousePressed || m_sendingEventToSubview)
        return;

    BEGIN_BLOCK_OBJC_EXCEPTIONS;
    auto& document = *m_frame.document();
    // Ensure we start mouse move event dispatching on a clear tree.
    document.updateStyleIfNeeded();
    CurrentEventScope scope(event);
    {
        ContentChangeObserver::MouseMovedScope observingScope(document);
        event.wasHandled = mouseMoved(currentPlatformMouseEvent());
        // Run style recalc to be able to capture content changes as the result of the mouse move event.
        document.updateStyleIfNeeded();
        callOnMainThread([protectedFrame = makeRef(m_frame)] {
            if (auto* document = protectedFrame->document())
                document->page()->chrome().client().observedContentChange(*document->frame());
        });
    }

    END_BLOCK_OBJC_EXCEPTIONS;
}

static bool frameHasPlatformWidget(const Frame& frame)
{
    if (FrameView* frameView = frame.view()) {
        if (frameView->platformWidget())
            return true;
    }

    return false;
}

void EventHandler::dispatchSyntheticMouseOut(const PlatformMouseEvent& platformMouseEvent)
{
    updateMouseEventTargetNode(nullptr, platformMouseEvent, FireMouseOverOut::Yes);
}

void EventHandler::dispatchSyntheticMouseMove(const PlatformMouseEvent& platformMouseEvent)
{
    mouseMoved(platformMouseEvent);
}

bool EventHandler::passMousePressEventToSubframe(MouseEventWithHitTestResults& mev, Frame* subframe)
{
    // WebKit1 code path.
    if (frameHasPlatformWidget(m_frame))
        return passSubframeEventToSubframe(mev, subframe);

    // WebKit2 code path.
    subframe->eventHandler().handleMousePressEvent(mev.event());
    return true;
}

bool EventHandler::passMouseMoveEventToSubframe(MouseEventWithHitTestResults& mev, Frame* subframe, HitTestResult* hoveredNode)
{
    // WebKit1 code path.
    if (frameHasPlatformWidget(m_frame))
        return passSubframeEventToSubframe(mev, subframe, hoveredNode);

    subframe->eventHandler().handleMouseMoveEvent(mev.event(), hoveredNode);
    return true;
}

bool EventHandler::passMouseReleaseEventToSubframe(MouseEventWithHitTestResults& mev, Frame* subframe)
{
    // WebKit1 code path.
    if (frameHasPlatformWidget(m_frame))
        return passSubframeEventToSubframe(mev, subframe);

    // WebKit2 code path.
    subframe->eventHandler().handleMouseReleaseEvent(mev.event());
    return true;
}

OptionSet<PlatformEvent::Modifier> EventHandler::accessKeyModifiers()
{
    // Control+Option key combinations are usually unused on Mac OS X, but not when VoiceOver is enabled.
    // So, we use Control in this case, even though it conflicts with Emacs-style key bindings.
    // See <https://bugs.webkit.org/show_bug.cgi?id=21107> for more detail.
    if (AXObjectCache::accessibilityEnhancedUserInterfaceEnabled())
        return PlatformEvent::Modifier::ControlKey;

    return { PlatformEvent::Modifier::ControlKey, PlatformEvent::Modifier::AltKey };
}

PlatformMouseEvent EventHandler::currentPlatformMouseEvent() const
{
    return PlatformEventFactory::createPlatformMouseEvent(currentEvent());
}
    
void EventHandler::startSelectionAutoscroll(RenderObject* renderer, const FloatPoint& positionInWindow)
{
    Ref<Frame> protectedFrame(m_frame);

    m_targetAutoscrollPositionInWindow = protectedFrame->view()->contentsToView(roundedIntPoint(positionInWindow));
    
    m_isAutoscrolling = true;
    m_autoscrollController->startAutoscrollForSelection(renderer);
}

void EventHandler::cancelSelectionAutoscroll()
{
    m_isAutoscrolling = false;
    m_autoscrollController->stopAutoscrollTimer();
}

static IntSize autoscrollAdjustmentFactorForScreenBoundaries(const IntPoint& contentPosition, const FloatRect& unobscuredContentRect, float zoomFactor)
{
    // If the window is at the edge of the screen, and the touch position is also at that edge of the screen,
    // we need to adjust the autoscroll amount in order for the user to be able to autoscroll in that direction.
    // We can pretend that the touch position is slightly beyond the edge of the screen, and then autoscrolling
    // will occur as expected. This function figures out just how much to adjust the autoscroll amount by
    // in order to get autoscrolling to feel natural in this situation.
    
    IntSize adjustmentFactor;
    
#define EDGE_DISTANCE_THRESHOLD 100

    CGSize edgeDistanceThreshold = CGSizeMake(EDGE_DISTANCE_THRESHOLD / zoomFactor, EDGE_DISTANCE_THRESHOLD / zoomFactor);
    
    float screenLeftEdge = unobscuredContentRect.x();
    float insetScreenLeftEdge = screenLeftEdge + edgeDistanceThreshold.width;
    float screenRightEdge = unobscuredContentRect.maxX();
    float insetScreenRightEdge = screenRightEdge - edgeDistanceThreshold.width;
    if (contentPosition.x() >= screenLeftEdge && contentPosition.x() < insetScreenLeftEdge) {
        float distanceFromEdge = contentPosition.x() - screenLeftEdge - edgeDistanceThreshold.width;
        if (distanceFromEdge < 0)
            adjustmentFactor.setWidth(-edgeDistanceThreshold.width);
    } else if (contentPosition.x() >= insetScreenRightEdge && contentPosition.x() < screenRightEdge) {
        float distanceFromEdge = edgeDistanceThreshold.width - (screenRightEdge - contentPosition.x());
        if (distanceFromEdge > 0)
            adjustmentFactor.setWidth(edgeDistanceThreshold.width);
    }
    
    float screenTopEdge = unobscuredContentRect.y();
    float insetScreenTopEdge = screenTopEdge + edgeDistanceThreshold.height;
    float screenBottomEdge = unobscuredContentRect.maxY();
    float insetScreenBottomEdge = screenBottomEdge - edgeDistanceThreshold.height;
    
    if (contentPosition.y() >= screenTopEdge && contentPosition.y() < insetScreenTopEdge) {
        float distanceFromEdge = contentPosition.y() - screenTopEdge - edgeDistanceThreshold.height;
        if (distanceFromEdge < 0)
            adjustmentFactor.setHeight(-edgeDistanceThreshold.height);
    } else if (contentPosition.y() >= insetScreenBottomEdge && contentPosition.y() < screenBottomEdge) {
        float distanceFromEdge = edgeDistanceThreshold.height - (screenBottomEdge - contentPosition.y());
        if (distanceFromEdge > 0)
            adjustmentFactor.setHeight(edgeDistanceThreshold.height);
    }
    
    return adjustmentFactor;
}
    
IntPoint EventHandler::targetPositionInWindowForSelectionAutoscroll() const
{
    Ref<Frame> protectedFrame(m_frame);
    
    FloatRect unobscuredContentRect = protectedFrame->view()->unobscuredContentRect();
    
    // Manually need to convert viewToContents, as it will be skipped because delegatedScrolling is on iOS
    IntPoint contentPosition = protectedFrame->view()->viewToContents(protectedFrame->view()->convertFromContainingWindow(m_targetAutoscrollPositionInWindow));
    IntSize adjustPosition = autoscrollAdjustmentFactorForScreenBoundaries(contentPosition, unobscuredContentRect, protectedFrame->page()->pageScaleFactor());
    return contentPosition + adjustPosition;
}
    
bool EventHandler::shouldUpdateAutoscroll()
{
    return m_isAutoscrolling;
}

#if ENABLE(DRAG_SUPPORT)

bool EventHandler::eventLoopHandleMouseDragged(const MouseEventWithHitTestResults&)
{
    return false;
}

bool EventHandler::tryToBeginDragAtPoint(const IntPoint& clientPosition, const IntPoint&)
{
    Ref<Frame> protectedFrame(m_frame);

    auto* document = m_frame.document();
    if (!document)
        return false;

    SetForScope<bool> shouldAllowMouseDownToStartDrag { m_shouldAllowMouseDownToStartDrag, true };

    document->updateLayoutIgnorePendingStylesheets();

    FloatPoint adjustedClientPositionAsFloatPoint(clientPosition);
    protectedFrame->nodeRespondingToClickEvents(clientPosition, adjustedClientPositionAsFloatPoint);
    IntPoint adjustedClientPosition = roundedIntPoint(adjustedClientPositionAsFloatPoint);
    IntPoint adjustedGlobalPosition = protectedFrame->view()->windowToContents(adjustedClientPosition);

    PlatformMouseEvent syntheticMousePressEvent(adjustedClientPosition, adjustedGlobalPosition, LeftButton, PlatformEvent::MousePressed, 1, false, false, false, false, WallTime::now(), 0, NoTap);
    PlatformMouseEvent syntheticMouseMoveEvent(adjustedClientPosition, adjustedGlobalPosition, LeftButton, PlatformEvent::MouseMoved, 0, false, false, false, false, WallTime::now(), 0, NoTap);

    HitTestRequest request(HitTestRequest::Active | HitTestRequest::DisallowUserAgentShadowContent);
    auto documentPoint = protectedFrame->view() ? protectedFrame->view()->windowToContents(syntheticMouseMoveEvent.position()) : syntheticMouseMoveEvent.position();
    auto hitTestedMouseEvent = document->prepareMouseEvent(request, documentPoint, syntheticMouseMoveEvent);

    RefPtr<Frame> subframe = subframeForHitTestResult(hitTestedMouseEvent);
    if (subframe && subframe->eventHandler().tryToBeginDragAtPoint(adjustedClientPosition, adjustedGlobalPosition))
        return true;

    if (!eventMayStartDrag(syntheticMousePressEvent))
        return false;

    handleMousePressEvent(syntheticMousePressEvent);
    bool handledDrag = m_mouseDownMayStartDrag && handleMouseDraggedEvent(hitTestedMouseEvent, DontCheckDragHysteresis);
    // Reset this bit to prevent autoscrolling from updating the selection with the last mouse location.
    m_mouseDownMayStartSelect = false;
    return handledDrag;
}

bool EventHandler::supportsSelectionUpdatesOnMouseDrag() const
{
    return false;
}

bool EventHandler::shouldAllowMouseDownToStartDrag() const
{
    return m_shouldAllowMouseDownToStartDrag;
}

#endif // ENABLE(DRAG_SUPPORT)

}

#endif // PLATFORM(IOS_FAMILY)