gecko-dev/dom/html/HTMLLabelElement.cpp

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/**
 * Implementation of HTML <label> elements.
 */
#include "HTMLLabelElement.h"
#include "mozilla/EventDispatcher.h"
#include "mozilla/MouseEvents.h"
#include "mozilla/dom/HTMLLabelElementBinding.h"
#include "nsFocusManager.h"
#include "nsIDOMMouseEvent.h"

// construction, destruction

NS_IMPL_NS_NEW_HTML_ELEMENT(Label)

namespace mozilla {
namespace dom {

HTMLLabelElement::~HTMLLabelElement()
{
}

JSObject*
HTMLLabelElement::WrapNode(JSContext *aCx)
{
  return HTMLLabelElementBinding::Wrap(aCx, this);
}

// nsISupports

NS_IMPL_ISUPPORTS_INHERITED(HTMLLabelElement, nsGenericHTMLFormElement,
                            nsIDOMHTMLLabelElement)

// nsIDOMHTMLLabelElement

NS_IMPL_ELEMENT_CLONE(HTMLLabelElement)

NS_IMETHODIMP
HTMLLabelElement::GetForm(nsIDOMHTMLFormElement** aForm)
{
  return nsGenericHTMLFormElement::GetForm(aForm);
}

NS_IMETHODIMP
HTMLLabelElement::GetControl(nsIDOMHTMLElement** aElement)
{
  nsCOMPtr<nsIDOMHTMLElement> element = do_QueryObject(GetLabeledElement());
  element.forget(aElement);
  return NS_OK;
}

NS_IMETHODIMP
HTMLLabelElement::SetHtmlFor(const nsAString& aHtmlFor)
{
  ErrorResult rv;
  SetHtmlFor(aHtmlFor, rv);
  return rv.ErrorCode();
}

NS_IMETHODIMP
HTMLLabelElement::GetHtmlFor(nsAString& aHtmlFor)
{
  nsString htmlFor;
  GetHtmlFor(htmlFor);
  aHtmlFor = htmlFor;
  return NS_OK;
}

void
HTMLLabelElement::Focus(ErrorResult& aError)
{
  // retarget the focus method at the for content
  nsIFocusManager* fm = nsFocusManager::GetFocusManager();
  if (fm) {
    nsCOMPtr<nsIDOMElement> elem = do_QueryObject(GetLabeledElement());
    if (elem)
      fm->SetFocus(elem, 0);
  }
}

static bool
EventTargetIn(WidgetEvent* aEvent, nsIContent* aChild, nsIContent* aStop)
{
  nsCOMPtr<nsIContent> c = do_QueryInterface(aEvent->target);
  nsIContent *content = c;
  while (content) {
    if (content == aChild) {
      return true;
    }

    if (content == aStop) {
      break;
    }

    content = content->GetParent();
  }
  return false;
}

nsresult
HTMLLabelElement::PostHandleEvent(EventChainPostVisitor& aVisitor)
{
  WidgetMouseEvent* mouseEvent = aVisitor.mEvent->AsMouseEvent();
  if (mHandlingEvent ||
      (!(mouseEvent && mouseEvent->IsLeftClickEvent()) &&
       aVisitor.mEvent->message != NS_MOUSE_BUTTON_DOWN) ||
      aVisitor.mEventStatus == nsEventStatus_eConsumeNoDefault ||
      !aVisitor.mPresContext ||
      // Don't handle the event if it's already been handled by another label
      aVisitor.mEvent->mFlags.mMultipleActionsPrevented) {
    return NS_OK;
  }

  // Strong ref because event dispatch is going to happen.
  nsRefPtr<Element> content = GetLabeledElement();

  if (content && !EventTargetIn(aVisitor.mEvent, content, this)) {
    mHandlingEvent = true;
    switch (aVisitor.mEvent->message) {
      case NS_MOUSE_BUTTON_DOWN:
        if (mouseEvent->button == WidgetMouseEvent::eLeftButton) {
          // We reset the mouse-down point on every event because there is
          // no guarantee we will reach the NS_MOUSE_CLICK code below.
          LayoutDeviceIntPoint* curPoint =
            new LayoutDeviceIntPoint(mouseEvent->refPoint);
          SetProperty(nsGkAtoms::labelMouseDownPtProperty,
                      static_cast<void*>(curPoint),
                      nsINode::DeleteProperty<LayoutDeviceIntPoint>);
        }
        break;

      case NS_MOUSE_CLICK:
        if (mouseEvent->IsLeftClickEvent()) {
          LayoutDeviceIntPoint* mouseDownPoint =
            static_cast<LayoutDeviceIntPoint*>(
              GetProperty(nsGkAtoms::labelMouseDownPtProperty));

          bool dragSelect = false;
          if (mouseDownPoint) {
            LayoutDeviceIntPoint dragDistance = *mouseDownPoint;
            DeleteProperty(nsGkAtoms::labelMouseDownPtProperty);

            dragDistance -= mouseEvent->refPoint;
            const int CLICK_DISTANCE = 2;
            dragSelect = dragDistance.x > CLICK_DISTANCE ||
                         dragDistance.x < -CLICK_DISTANCE ||
                         dragDistance.y > CLICK_DISTANCE ||
                         dragDistance.y < -CLICK_DISTANCE;
          }
          // Don't click the for-content if we did drag-select text or if we
          // have a kbd modifier (which adjusts a selection).
          if (dragSelect || mouseEvent->IsShift() || mouseEvent->IsControl() ||
              mouseEvent->IsAlt() || mouseEvent->IsMeta()) {
            break;
          }
          // Only set focus on the first click of multiple clicks to prevent
          // to prevent immediate de-focus.
          if (mouseEvent->clickCount <= 1) {
            nsIFocusManager* fm = nsFocusManager::GetFocusManager();
            if (fm) {
              // Use FLAG_BYMOVEFOCUS here so that the label is scrolled to.
              // Also, within HTMLInputElement::PostHandleEvent, inputs will
              // be selected only when focused via a key or when the navigation
              // flag is used and we want to select the text on label clicks as
              // well.
              nsCOMPtr<nsIDOMElement> elem = do_QueryInterface(content);
              fm->SetFocus(elem, nsIFocusManager::FLAG_BYMOVEFOCUS);
            }
          }
          // Dispatch a new click event to |content|
          //    (For compatibility with IE, we do only left click.  If
          //    we wanted to interpret the HTML spec very narrowly, we
          //    would do nothing.  If we wanted to do something
          //    sensible, we might send more events through like
          //    this.)  See bug 7554, bug 49897, and bug 96813.
          nsEventStatus status = aVisitor.mEventStatus;
          // Ok to use aVisitor.mEvent as parameter because DispatchClickEvent
          // will actually create a new event.
          EventFlags eventFlags;
          eventFlags.mMultipleActionsPrevented = true;
          DispatchClickEvent(aVisitor.mPresContext, mouseEvent,
                             content, false, &eventFlags, &status);
          // Do we care about the status this returned?  I don't think we do...
          // Don't run another <label> off of this click
          mouseEvent->mFlags.mMultipleActionsPrevented = true;
        }
        break;
    }
    mHandlingEvent = false;
  }
  return NS_OK;
}

nsresult
HTMLLabelElement::Reset()
{
  return NS_OK;
}

NS_IMETHODIMP
HTMLLabelElement::SubmitNamesValues(nsFormSubmission* aFormSubmission)
{
  return NS_OK;
}

void
HTMLLabelElement::PerformAccesskey(bool aKeyCausesActivation,
                                   bool aIsTrustedEvent)
{
  if (!aKeyCausesActivation) {
    nsRefPtr<Element> element = GetLabeledElement();
    if (element)
      element->PerformAccesskey(aKeyCausesActivation, aIsTrustedEvent);
  } else {
    nsPresContext *presContext = GetPresContext(eForUncomposedDoc);
    if (!presContext)
      return;

    // Click on it if the users prefs indicate to do so.
    WidgetMouseEvent event(aIsTrustedEvent, NS_MOUSE_CLICK,
                           nullptr, WidgetMouseEvent::eReal);
    event.inputSource = nsIDOMMouseEvent::MOZ_SOURCE_KEYBOARD;

    nsAutoPopupStatePusher popupStatePusher(aIsTrustedEvent ?
                                            openAllowed : openAbused);

    EventDispatcher::Dispatch(static_cast<nsIContent*>(this), presContext,
                              &event);
  }
}

nsGenericHTMLElement*
HTMLLabelElement::GetLabeledElement() const
{
  nsAutoString elementId;

  if (!GetAttr(kNameSpaceID_None, nsGkAtoms::_for, elementId)) {
    // No @for, so we are a label for our first form control element.
    // Do a depth-first traversal to look for the first form control element.
    return GetFirstLabelableDescendant();
  }

  // We have a @for. The id has to be linked to an element in the same document
  // and this element should be a labelable form control.
  //XXXsmaug It is unclear how this should work in case the element is in
  //         Shadow DOM.
  //         See https://www.w3.org/Bugs/Public/show_bug.cgi?id=26365.
  nsIDocument* doc = GetUncomposedDoc();
  if (!doc) {
    return nullptr;
  }

  Element* element = doc->GetElementById(elementId);
  if (element && element->IsLabelable()) {
    return static_cast<nsGenericHTMLElement*>(element);
  }

  return nullptr;
}

nsGenericHTMLElement*
HTMLLabelElement::GetFirstLabelableDescendant() const
{
  for (nsIContent* cur = nsINode::GetFirstChild(); cur;
       cur = cur->GetNextNode(this)) {
    Element* element = cur->IsElement() ? cur->AsElement() : nullptr;
    if (element && element->IsLabelable()) {
      return static_cast<nsGenericHTMLElement*>(element);
    }
  }

  return nullptr;
}

} // namespace dom
} // namespace mozilla