gecko-dev/dom/events/JSEventHandler.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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/. */
#include "nsJSUtils.h"
#include "nsString.h"
#include "nsIScriptContext.h"
#include "nsIScriptGlobalObject.h"
#include "nsVariant.h"
#include "nsGkAtoms.h"
#include "xpcpublic.h"
#include "nsJSEnvironment.h"
#include "nsDOMJSUtils.h"
#include "mozilla/ContentEvents.h"
#include "mozilla/CycleCollectedJSContext.h"
#include "mozilla/HoldDropJSObjects.h"
#include "mozilla/JSEventHandler.h"
#include "mozilla/Likely.h"
#include "mozilla/dom/BeforeUnloadEvent.h"
#include "mozilla/dom/ErrorEvent.h"
#include "mozilla/dom/WorkerPrivate.h"

namespace mozilla {

using namespace dom;

JSEventHandler::JSEventHandler(EventTarget* aTarget, nsAtom* aType,
                               const TypedEventHandler& aTypedHandler)
    : mTarget(aTarget), mEventName(aType), mTypedHandler(aTypedHandler) {
  // Note, we call HoldJSObjects to get CanSkip called before CC.
  HoldJSObjects(this);
}

JSEventHandler::~JSEventHandler() {
  NS_ASSERTION(!mTarget, "Should have called Disconnect()!");
  DropJSObjects(this);
}

NS_IMPL_CYCLE_COLLECTION_CLASS(JSEventHandler)

NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(JSEventHandler)
  tmp->mTypedHandler.ForgetHandler();
NS_IMPL_CYCLE_COLLECTION_UNLINK_END
NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INTERNAL(JSEventHandler)
  if (MOZ_UNLIKELY(cb.WantDebugInfo()) && tmp->mEventName) {
    nsAutoCString name;
    name.AppendLiteral("JSEventHandler handlerName=");
    name.Append(
        NS_ConvertUTF16toUTF8(nsDependentAtomString(tmp->mEventName)).get());
    cb.DescribeRefCountedNode(tmp->mRefCnt.get(), name.get());
  } else {
    NS_IMPL_CYCLE_COLLECTION_DESCRIBE(JSEventHandler, tmp->mRefCnt.get())
  }
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_RAWPTR(mTypedHandler.Ptr())
NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END

NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_BEGIN(JSEventHandler)
  if (tmp->IsBlackForCC()) {
    return true;
  }
  // If we have a target, it is the one which has tmp as onfoo handler.
  if (tmp->mTarget) {
    nsXPCOMCycleCollectionParticipant* cp = nullptr;
    CallQueryInterface(tmp->mTarget, &cp);
    nsISupports* canonical = nullptr;
    tmp->mTarget->QueryInterface(NS_GET_IID(nsCycleCollectionISupports),
                                 reinterpret_cast<void**>(&canonical));
    // Usually CanSkip ends up unmarking the event listeners of mTarget,
    // so tmp may become black.
    if (cp && canonical && cp->CanSkip(canonical, true)) {
      return tmp->IsBlackForCC();
    }
  }
NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_END

NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_IN_CC_BEGIN(JSEventHandler)
  return tmp->IsBlackForCC();
NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_IN_CC_END

NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_THIS_BEGIN(JSEventHandler)
  return tmp->IsBlackForCC();
NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_THIS_END

NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(JSEventHandler)
  NS_INTERFACE_MAP_ENTRY(nsIDOMEventListener)
  NS_INTERFACE_MAP_ENTRY(nsISupports)
  NS_INTERFACE_MAP_ENTRY(JSEventHandler)
NS_INTERFACE_MAP_END

NS_IMPL_CYCLE_COLLECTING_ADDREF(JSEventHandler)
NS_IMPL_CYCLE_COLLECTING_RELEASE(JSEventHandler)

bool JSEventHandler::IsBlackForCC() {
  // We can claim to be black if all the things we reference are
  // effectively black already.
  return !mTypedHandler.HasEventHandler() ||
         mTypedHandler.Ptr()->IsBlackForCC();
}

nsresult JSEventHandler::HandleEvent(Event* aEvent) {
  nsCOMPtr<EventTarget> target = mTarget;
  if (!target || !mTypedHandler.HasEventHandler() ||
      !GetTypedEventHandler().Ptr()->CallbackPreserveColor()) {
    return NS_ERROR_FAILURE;
  }

  bool isMainThread = aEvent->IsMainThreadEvent();
  bool isChromeHandler =
      isMainThread
          ? nsContentUtils::ObjectPrincipal(
                GetTypedEventHandler().Ptr()->CallbackGlobalOrNull()) ==
                nsContentUtils::GetSystemPrincipal()
          : mozilla::dom::IsCurrentThreadRunningChromeWorker();

  if (mTypedHandler.Type() == TypedEventHandler::eOnError) {
    MOZ_ASSERT_IF(mEventName, mEventName == nsGkAtoms::onerror);

    nsString errorMsg, file;
    EventOrString msgOrEvent;
    Optional<nsAString> fileName;
    Optional<uint32_t> lineNumber;
    Optional<uint32_t> columnNumber;
    Optional<JS::Handle<JS::Value>> error;

    NS_ENSURE_TRUE(aEvent, NS_ERROR_UNEXPECTED);
    ErrorEvent* scriptEvent = aEvent->AsErrorEvent();
    if (scriptEvent) {
      scriptEvent->GetMessage(errorMsg);
      msgOrEvent.SetAsString().ShareOrDependUpon(errorMsg);

      scriptEvent->GetFilename(file);
      fileName = &file;

      lineNumber.Construct();
      lineNumber.Value() = scriptEvent->Lineno();

      columnNumber.Construct();
      columnNumber.Value() = scriptEvent->Colno();

      error.Construct(RootingCx());
      scriptEvent->GetError(&error.Value());
    } else {
      msgOrEvent.SetAsEvent() = aEvent;
    }

    RefPtr<OnErrorEventHandlerNonNull> handler =
        mTypedHandler.OnErrorEventHandler();
    ErrorResult rv;
    JS::Rooted<JS::Value> retval(RootingCx());
    handler->Call(target, msgOrEvent, fileName, lineNumber, columnNumber, error,
                  &retval, rv);
    if (rv.Failed()) {
      return rv.StealNSResult();
    }

    if (retval.isBoolean() && retval.toBoolean() == bool(scriptEvent)) {
      aEvent->PreventDefaultInternal(isChromeHandler);
    }
    return NS_OK;
  }

  if (mTypedHandler.Type() == TypedEventHandler::eOnBeforeUnload) {
    MOZ_ASSERT(mEventName == nsGkAtoms::onbeforeunload);

    RefPtr<OnBeforeUnloadEventHandlerNonNull> handler =
        mTypedHandler.OnBeforeUnloadEventHandler();
    ErrorResult rv;
    nsString retval;
    handler->Call(target, *aEvent, retval, rv);
    if (rv.Failed()) {
      return rv.StealNSResult();
    }

    BeforeUnloadEvent* beforeUnload = aEvent->AsBeforeUnloadEvent();
    NS_ENSURE_STATE(beforeUnload);

    if (!DOMStringIsNull(retval)) {
      aEvent->PreventDefaultInternal(isChromeHandler);

      nsAutoString text;
      beforeUnload->GetReturnValue(text);

      // Set the text in the beforeUnload event as long as it wasn't
      // already set (through event.returnValue, which takes
      // precedence over a value returned from a JS function in IE)
      if (text.IsEmpty()) {
        beforeUnload->SetReturnValue(retval);
      }
    }

    return NS_OK;
  }

  MOZ_ASSERT(mTypedHandler.Type() == TypedEventHandler::eNormal);
  ErrorResult rv;
  RefPtr<EventHandlerNonNull> handler = mTypedHandler.NormalEventHandler();
  JS::Rooted<JS::Value> retval(RootingCx());
  handler->Call(target, *aEvent, &retval, rv);
  if (rv.Failed()) {
    return rv.StealNSResult();
  }

  // If the handler returned false, then prevent default.
  if (retval.isBoolean() && !retval.toBoolean()) {
    aEvent->PreventDefaultInternal(isChromeHandler);
  }

  return NS_OK;
}

}  // namespace mozilla

using namespace mozilla;

/*
 * Factory functions
 */

nsresult NS_NewJSEventHandler(mozilla::dom::EventTarget* aTarget,
                              nsAtom* aEventType,
                              const TypedEventHandler& aTypedHandler,
                              JSEventHandler** aReturn) {
  NS_ENSURE_ARG(aEventType || !NS_IsMainThread());
  JSEventHandler* it = new JSEventHandler(aTarget, aEventType, aTypedHandler);
  NS_ADDREF(*aReturn = it);

  return NS_OK;
}