widget/IMEData.h
author Dorel Luca <dluca@mozilla.com>
Mon, 04 Dec 2017 18:01:09 +0200
changeset 394844 58fec9a96e269a57cc6f84bfe3a6dc6800acd955
parent 393189 4503ee61c1b3771139c27648ebeaecfd55b68326
child 395657 f6ef04a022f3c5aa861e438298302a989308369e
permissions -rw-r--r--
Backed out 7 changesets (bug 1377007) for failing build bustage on Linux pgo and faling Cpp's jsapi-tests r=backout on a CLOSED TREE Backed out changeset 9428a4ed7dec (bug 1377007) Backed out changeset 4407b43a8aff (bug 1377007) Backed out changeset 65a37a7f78a5 (bug 1377007) Backed out changeset 276fe6d9b716 (bug 1377007) Backed out changeset 1de46e60ffba (bug 1377007) Backed out changeset 893e303e17ec (bug 1377007) Backed out changeset 081a241e25d4 (bug 1377007)

/* -*- Mode: C++; tab-width: 40; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* 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/. */

#ifndef mozilla_widget_IMEData_h_
#define mozilla_widget_IMEData_h_

#include "nsPoint.h"
#include "nsRect.h"
#include "nsStringGlue.h"
#include "nsXULAppAPI.h"
#include "Units.h"

class nsIWidget;

namespace mozilla {

class WritingMode;

namespace widget {

/**
 * Preference for receiving IME updates
 *
 * If mWantUpdates is not NOTIFY_NOTHING, nsTextStateManager will observe text
 * change and/or selection change and call nsIWidget::NotifyIME() with
 * NOTIFY_IME_OF_SELECTION_CHANGE and/or NOTIFY_IME_OF_TEXT_CHANGE.
 * Please note that the text change observing cost is very expensive especially
 * on an HTML editor has focus.
 * If the IME implementation on a particular platform doesn't care about
 * NOTIFY_IME_OF_SELECTION_CHANGE and/or NOTIFY_IME_OF_TEXT_CHANGE,
 * they should set mWantUpdates to NOTIFY_NOTHING to avoid the cost.
 * If the IME implementation needs notifications even while our process is
 * deactive, it should also set NOTIFY_DURING_DEACTIVE.
 */
struct IMENotificationRequests final
{
  typedef uint8_t Notifications;

  enum : Notifications
  {
    NOTIFY_NOTHING                       = 0,
    NOTIFY_TEXT_CHANGE                   = 1 << 1,
    NOTIFY_POSITION_CHANGE               = 1 << 2,
    // NOTIFY_MOUSE_BUTTON_EVENT_ON_CHAR is used when mouse button is pressed
    // or released on a character in the focused editor.  The notification is
    // notified to IME as a mouse event.  If it's consumed by IME, NotifyIME()
    // returns NS_SUCCESS_EVENT_CONSUMED.  Otherwise, it returns NS_OK if it's
    // handled without any error.
    NOTIFY_MOUSE_BUTTON_EVENT_ON_CHAR    = 1 << 3,
    // NOTE: NOTIFY_DURING_DEACTIVE isn't supported in environments where two
    //       or more compositions are possible.  E.g., Mac and Linux (GTK).
    NOTIFY_DURING_DEACTIVE               = 1 << 7,

    NOTIFY_ALL = NOTIFY_TEXT_CHANGE |
                 NOTIFY_POSITION_CHANGE |
                 NOTIFY_MOUSE_BUTTON_EVENT_ON_CHAR,
  };

  IMENotificationRequests()
    : mWantUpdates(NOTIFY_NOTHING)
  {
  }

  explicit IMENotificationRequests(Notifications aWantUpdates)
    : mWantUpdates(aWantUpdates)
  {
  }

  IMENotificationRequests operator|(const IMENotificationRequests& aOther) const
  {
    return IMENotificationRequests(aOther.mWantUpdates | mWantUpdates);
  }
  IMENotificationRequests& operator|=(const IMENotificationRequests& aOther)
  {
    mWantUpdates |= aOther.mWantUpdates;
    return *this;
  }
  bool operator==(const IMENotificationRequests& aOther) const
  {
    return mWantUpdates == aOther.mWantUpdates;
  }

  bool WantTextChange() const
  {
    return !!(mWantUpdates & NOTIFY_TEXT_CHANGE);
  }

  bool WantPositionChanged() const
  {
    return !!(mWantUpdates & NOTIFY_POSITION_CHANGE);
  }

  bool WantChanges() const
  {
    return WantTextChange();
  }

  bool WantMouseButtonEventOnChar() const
  {
    return !!(mWantUpdates & NOTIFY_MOUSE_BUTTON_EVENT_ON_CHAR);
  }

  bool WantDuringDeactive() const
  {
    return !!(mWantUpdates & NOTIFY_DURING_DEACTIVE);
  }

  Notifications mWantUpdates;
};

/**
 * Contains IMEStatus plus information about the current
 * input context that the IME can use as hints if desired.
 */

struct IMEState final
{
  /**
   * IME enabled states, the mEnabled value of
   * SetInputContext()/GetInputContext() should be one value of following
   * values.
   *
   * WARNING: If you change these values, you also need to edit:
   *   nsIDOMWindowUtils.idl
   *   nsContentUtils::GetWidgetStatusFromIMEStatus
   */
  enum Enabled
  {
    /**
     * 'Disabled' means the user cannot use IME. So, the IME open state should
     * be 'closed' during 'disabled'.
     */
    DISABLED,
    /**
     * 'Enabled' means the user can use IME.
     */
    ENABLED,
    /**
     * 'Password' state is a special case for the password editors.
     * E.g., on mac, the password editors should disable the non-Roman
     * keyboard layouts at getting focus. Thus, the password editor may have
     * special rules on some platforms.
     */
    PASSWORD,
    /**
     * This state is used when a plugin is focused.
     * When a plug-in is focused content, we should send native events
     * directly. Because we don't process some native events, but they may
     * be needed by the plug-in.
     */
    PLUGIN,
    /**
     * 'Unknown' is useful when you cache this enum.  So, this shouldn't be
     * used with nsIWidget::SetInputContext().
     */
    UNKNOWN
  };
  Enabled mEnabled;

  /**
   * IME open states the mOpen value of SetInputContext() should be one value of
   * OPEN, CLOSE or DONT_CHANGE_OPEN_STATE.  GetInputContext() should return
   * OPEN, CLOSE or OPEN_STATE_NOT_SUPPORTED.
   */
  enum Open
  {
    /**
     * 'Unsupported' means the platform cannot return actual IME open state.
     * This value is used only by GetInputContext().
     */
    OPEN_STATE_NOT_SUPPORTED,
    /**
     * 'Don't change' means the widget shouldn't change IME open state when
     * SetInputContext() is called.
     */
    DONT_CHANGE_OPEN_STATE = OPEN_STATE_NOT_SUPPORTED,
    /**
     * 'Open' means that IME should compose in its primary language (or latest
     * input mode except direct ASCII character input mode).  Even if IME is
     * opened by this value, users should be able to close IME by theirselves.
     * Web contents can specify this value by |ime-mode: active;|.
     */
    OPEN,
    /**
     * 'Closed' means that IME shouldn't handle key events (or should handle
     * as ASCII character inputs on mobile device).  Even if IME is closed by
     * this value, users should be able to open IME by theirselves.
     * Web contents can specify this value by |ime-mode: inactive;|.
     */
    CLOSED
  };
  Open mOpen;

  IMEState()
    : mEnabled(ENABLED)
    , mOpen(DONT_CHANGE_OPEN_STATE)
  {
  }

  explicit IMEState(Enabled aEnabled, Open aOpen = DONT_CHANGE_OPEN_STATE)
    : mEnabled(aEnabled)
    , mOpen(aOpen)
  {
  }

  // Returns true if the user can input characters.
  // This means that a plain text editor, an HTML editor, a password editor or
  // a plain text editor whose ime-mode is "disabled".
  bool IsEditable() const
  {
    return mEnabled == ENABLED || mEnabled == PASSWORD;
  }
  // Returns true if the user might be able to input characters.
  // This means that a plain text editor, an HTML editor, a password editor,
  // a plain text editor whose ime-mode is "disabled" or a windowless plugin
  // has focus.
  bool MaybeEditable() const
  {
    return IsEditable() || mEnabled == PLUGIN;
  }
};

// NS_ONLY_ONE_NATIVE_IME_CONTEXT is a special value of native IME context.
// If there can be only one IME composition in a process, this can be used.
#define NS_ONLY_ONE_NATIVE_IME_CONTEXT \
  (reinterpret_cast<void*>(static_cast<intptr_t>(-1)))

struct NativeIMEContext final
{
  // Pointer to native IME context.  Typically this is the result of
  // nsIWidget::GetNativeData(NS_RAW_NATIVE_IME_CONTEXT) in the parent process.
  // See also NS_ONLY_ONE_NATIVE_IME_CONTEXT.
  uintptr_t mRawNativeIMEContext;
  // Process ID of the origin of mNativeIMEContext.
  uint64_t mOriginProcessID;

  NativeIMEContext()
  {
    Init(nullptr);
  }

  explicit NativeIMEContext(nsIWidget* aWidget)
  {
    Init(aWidget);
  }

  bool IsValid() const
  {
    return mRawNativeIMEContext &&
           mOriginProcessID != static_cast<uintptr_t>(-1);
  }

  void Init(nsIWidget* aWidget);
  void InitWithRawNativeIMEContext(const void* aRawNativeIMEContext)
  {
    InitWithRawNativeIMEContext(const_cast<void*>(aRawNativeIMEContext));
  }
  void InitWithRawNativeIMEContext(void* aRawNativeIMEContext);

  bool operator==(const NativeIMEContext& aOther) const
  {
    return mRawNativeIMEContext == aOther.mRawNativeIMEContext &&
           mOriginProcessID == aOther.mOriginProcessID;
  }
  bool operator!=(const NativeIMEContext& aOther) const
  {
    return !(*this == aOther);
  }
};

struct InputContext final
{
  InputContext()
    : mOrigin(XRE_IsParentProcess() ? ORIGIN_MAIN : ORIGIN_CONTENT)
    , mMayBeIMEUnaware(false)
    , mInPrivateBrowsing(false)
  {
  }

  // If InputContext instance is a static variable, any heap allocated stuff
  // of its members need to be deleted at XPCOM shutdown.  Otherwise, it's
  // detected as memory leak.
  void ShutDown()
  {
    // The buffer for nsString will be released with a call of SetCapacity(0).
    // Truncate() isn't enough because it just sets length to 0.
    mHTMLInputType.SetCapacity(0);
    mHTMLInputInputmode.SetCapacity(0);
    mActionHint.SetCapacity(0);
  }

  bool IsPasswordEditor() const
  {
    return mHTMLInputType.LowerCaseEqualsLiteral("password");
  }

  IMEState mIMEState;

  /* The type of the input if the input is a html input field */
  nsString mHTMLInputType;

  /* The type of the inputmode */
  nsString mHTMLInputInputmode;

  /* A hint for the action that is performed when the input is submitted */
  nsString mActionHint;

  /**
   * mOrigin indicates whether this focus event refers to main or remote
   * content.
   */
  enum Origin
  {
    // Adjusting focus of content on the main process
    ORIGIN_MAIN,
    // Adjusting focus of content in a remote process
    ORIGIN_CONTENT
  };
  Origin mOrigin;

  /* True if the webapp may be unaware of IME events such as input event or
   * composiion events. This enables a key-events-only mode on Android for
   * compatibility with webapps relying on key listeners. */
  bool mMayBeIMEUnaware;

  /**
   * True if the document has ever received user input
   */
  bool mHasHandledUserInput;

  /* Whether the owning document of the input element has been loaded
   * in private browsing mode. */
  bool mInPrivateBrowsing;

  bool IsOriginMainProcess() const
  {
    return mOrigin == ORIGIN_MAIN;
  }

  bool IsOriginContentProcess() const
  {
    return mOrigin == ORIGIN_CONTENT;
  }

  bool IsOriginCurrentProcess() const
  {
    if (XRE_IsParentProcess()) {
      return IsOriginMainProcess();
    }
    return IsOriginContentProcess();
  }
};

// FYI: Implemented in nsBaseWidget.cpp
const char* ToChar(InputContext::Origin aOrigin);

struct InputContextAction final
{
  /**
   * mCause indicates what action causes calling nsIWidget::SetInputContext().
   * It must be one of following values.
   */
  enum Cause
  {
    // The cause is unknown but originated from content. Focus might have been
    // changed by content script.
    CAUSE_UNKNOWN,
    // The cause is unknown but originated from chrome. Focus might have been
    // changed by chrome script.
    CAUSE_UNKNOWN_CHROME,
    // The cause is user's keyboard operation.
    CAUSE_KEY,
    // The cause is user's mouse operation.
    CAUSE_MOUSE,
    // The cause is user's touch operation (implies mouse)
    CAUSE_TOUCH,
    // The cause is unknown but it occurs during user input except keyboard
    // input.  E.g., an event handler of a user input event moves focus.
    CAUSE_UNKNOWN_DURING_NON_KEYBOARD_INPUT,
    // The cause is unknown but it occurs during keyboard input.
    CAUSE_UNKNOWN_DURING_KEYBOARD_INPUT,
  };
  Cause mCause;

  /**
   * mFocusChange indicates what happened for focus.
   */
  enum FocusChange
  {
    FOCUS_NOT_CHANGED,
    // A content got focus.
    GOT_FOCUS,
    // Focused content lost focus.
    LOST_FOCUS,
    // Menu got pseudo focus that means focused content isn't changed but
    // keyboard events will be handled by menu.
    MENU_GOT_PSEUDO_FOCUS,
    // Menu lost pseudo focus that means focused content will handle keyboard
    // events.
    MENU_LOST_PSEUDO_FOCUS,
    // The widget is created.  When a widget is crated, it may need to notify
    // IME module to initialize its native IME context.  In such case, this is
    // used.  I.e., this isn't used by IMEStateManager.
    WIDGET_CREATED
  };
  FocusChange mFocusChange;

  bool ContentGotFocusByTrustedCause() const
  {
    return (mFocusChange == GOT_FOCUS &&
            mCause != CAUSE_UNKNOWN);
  }

  bool UserMightRequestOpenVKB() const
  {
    // If focus is changed, user must not request to open VKB.
    if (mFocusChange != FOCUS_NOT_CHANGED) {
      return false;
    }
    switch (mCause) {
      // If user clicks or touches focused editor, user must request to open
      // VKB.
      case CAUSE_MOUSE:
      case CAUSE_TOUCH:
      // If script does something during a user input and that causes changing
      // input context, user might request to open VKB.  E.g., user clicks
      // dummy editor and JS moves focus to an actual editable node.  However,
      // this should return false if the user input is a keyboard event since
      // physical keyboard operation shouldn't cause opening VKB.
      case CAUSE_UNKNOWN_DURING_NON_KEYBOARD_INPUT:
        return true;
      default:
        return false;
    }
  }

  /**
   * IsHandlingUserInput() returns true if it's caused by a user action directly
   * or it's caused by script or something but it occurred while we're handling
   * a user action.  E.g., when it's caused by Element.focus() in an event
   * handler of a user input, this returns true.
   */
  static bool IsHandlingUserInput(Cause aCause)
  {
    switch (aCause) {
      case CAUSE_KEY:
      case CAUSE_MOUSE:
      case CAUSE_TOUCH:
      case CAUSE_UNKNOWN_DURING_NON_KEYBOARD_INPUT:
      case CAUSE_UNKNOWN_DURING_KEYBOARD_INPUT:
        return true;
      default:
        return false;
    }
  }

  bool IsHandlingUserInput() const {
    return IsHandlingUserInput(mCause);
  }

  InputContextAction()
    : mCause(CAUSE_UNKNOWN)
    , mFocusChange(FOCUS_NOT_CHANGED)
  {
  }

  explicit InputContextAction(Cause aCause,
                              FocusChange aFocusChange = FOCUS_NOT_CHANGED)
    : mCause(aCause)
    , mFocusChange(aFocusChange)
  {
  }
};

// IMEMessage is shared by IMEStateManager and TextComposition.
// Update values in GeckoEditable.java if you make changes here.
// XXX Negative values are used in Android...
typedef int8_t IMEMessageType;
enum IMEMessage : IMEMessageType
{
  // This is used by IMENotification internally.  This means that the instance
  // hasn't been initialized yet.
  NOTIFY_IME_OF_NOTHING,
  // An editable content is getting focus
  NOTIFY_IME_OF_FOCUS,
  // An editable content is losing focus
  NOTIFY_IME_OF_BLUR,
  // Selection in the focused editable content is changed
  NOTIFY_IME_OF_SELECTION_CHANGE,
  // Text in the focused editable content is changed
  NOTIFY_IME_OF_TEXT_CHANGE,
  // Notified when a dispatched composition event is handled by the
  // contents.  This must be notified after the other notifications.
  // Note that if a remote process has focus, this is notified only once when
  // all dispatched events are handled completely.  So, the receiver shouldn't
  // count number of received this notification for comparing with the number
  // of dispatched events.
  // NOTE: If a composition event causes moving focus from the focused editor,
  //       this notification may not be notified as usual.  Even in such case,
  //       NOTIFY_IME_OF_BLUR is always sent.  So, notification listeners
  //       should tread the blur notification as including this if there is
  //       pending composition events.
  NOTIFY_IME_OF_COMPOSITION_EVENT_HANDLED,
  // Position or size of focused element may be changed.
  NOTIFY_IME_OF_POSITION_CHANGE,
  // Mouse button event is fired on a character in focused editor
  NOTIFY_IME_OF_MOUSE_BUTTON_EVENT,
  // Request to commit current composition to IME
  // (some platforms may not support)
  REQUEST_TO_COMMIT_COMPOSITION,
  // Request to cancel current composition to IME
  // (some platforms may not support)
  REQUEST_TO_CANCEL_COMPOSITION
};

// FYI: Implemented in nsBaseWidget.cpp
const char* ToChar(IMEMessage aIMEMessage);

struct IMENotification final
{
  IMENotification()
    : mMessage(NOTIFY_IME_OF_NOTHING)
  {
  }

  IMENotification(const IMENotification& aOther)
    : mMessage(NOTIFY_IME_OF_NOTHING)
  {
    Assign(aOther);
  }

  ~IMENotification()
  {
    Clear();
  }

  MOZ_IMPLICIT IMENotification(IMEMessage aMessage)
    : mMessage(aMessage)
  {
    switch (aMessage) {
      case NOTIFY_IME_OF_SELECTION_CHANGE:
        mSelectionChangeData.mString = new nsString();
        mSelectionChangeData.Clear();
        break;
      case NOTIFY_IME_OF_TEXT_CHANGE:
        mTextChangeData.Clear();
        break;
      case NOTIFY_IME_OF_MOUSE_BUTTON_EVENT:
        mMouseButtonEventData.mEventMessage = eVoidEvent;
        mMouseButtonEventData.mOffset = UINT32_MAX;
        mMouseButtonEventData.mCursorPos.Set(nsIntPoint(0, 0));
        mMouseButtonEventData.mCharRect.Set(nsIntRect(0, 0, 0, 0));
        mMouseButtonEventData.mButton = -1;
        mMouseButtonEventData.mButtons = 0;
        mMouseButtonEventData.mModifiers = 0;
        break;
      default:
        break;
    }
  }

  void Assign(const IMENotification& aOther)
  {
    bool changingMessage = mMessage != aOther.mMessage;
    if (changingMessage) {
      Clear();
      mMessage = aOther.mMessage;
    }
    switch (mMessage) {
      case NOTIFY_IME_OF_SELECTION_CHANGE:
        if (changingMessage) {
          mSelectionChangeData.mString = new nsString();
        }
        mSelectionChangeData.Assign(aOther.mSelectionChangeData);
        break;
      case NOTIFY_IME_OF_TEXT_CHANGE:
        mTextChangeData = aOther.mTextChangeData;
        break;
      case NOTIFY_IME_OF_MOUSE_BUTTON_EVENT:
        mMouseButtonEventData = aOther.mMouseButtonEventData;
        break;
      default:
        break;
    }
  }

  IMENotification& operator=(const IMENotification& aOther)
  {
    Assign(aOther);
    return *this;
  }

  void Clear()
  {
    if (mMessage == NOTIFY_IME_OF_SELECTION_CHANGE) {
      MOZ_ASSERT(mSelectionChangeData.mString);
      delete mSelectionChangeData.mString;
      mSelectionChangeData.mString = nullptr;
    }
    mMessage = NOTIFY_IME_OF_NOTHING;
  }

  bool HasNotification() const
  {
    return mMessage != NOTIFY_IME_OF_NOTHING;
  }

  void MergeWith(const IMENotification& aNotification)
  {
    switch (mMessage) {
      case NOTIFY_IME_OF_NOTHING:
        MOZ_ASSERT(aNotification.mMessage != NOTIFY_IME_OF_NOTHING);
        Assign(aNotification);
        break;
      case NOTIFY_IME_OF_SELECTION_CHANGE:
        MOZ_ASSERT(aNotification.mMessage == NOTIFY_IME_OF_SELECTION_CHANGE);
        mSelectionChangeData.Assign(aNotification.mSelectionChangeData);
        break;
      case NOTIFY_IME_OF_TEXT_CHANGE:
        MOZ_ASSERT(aNotification.mMessage == NOTIFY_IME_OF_TEXT_CHANGE);
        mTextChangeData += aNotification.mTextChangeData;
        break;
      case NOTIFY_IME_OF_POSITION_CHANGE:
      case NOTIFY_IME_OF_COMPOSITION_EVENT_HANDLED:
        MOZ_ASSERT(aNotification.mMessage == mMessage);
        break;
      default:
        MOZ_CRASH("Merging notification isn't supported");
        break;
    }
  }

  IMEMessage mMessage;

  struct Point
  {
    int32_t mX;
    int32_t mY;

    void Set(const nsIntPoint& aPoint)
    {
      mX = aPoint.x;
      mY = aPoint.y;
    }
    nsIntPoint AsIntPoint() const
    {
      return nsIntPoint(mX, mY);
    }
  };

  struct Rect
  {
    int32_t mX;
    int32_t mY;
    int32_t mWidth;
    int32_t mHeight;

    void Set(const nsIntRect& aRect)
    {
      mX = aRect.x;
      mY = aRect.y;
      mWidth = aRect.Width();
      mHeight = aRect.Height();
    }
    nsIntRect AsIntRect() const
    {
      return nsIntRect(mX, mY, mWidth, mHeight);
    }
  };

  // NOTIFY_IME_OF_SELECTION_CHANGE specific data
  struct SelectionChangeDataBase
  {
    // Selection range.
    uint32_t mOffset;

    // Selected string
    nsString* mString;

    // Writing mode at the selection.
    uint8_t mWritingMode;

    bool mReversed;
    bool mCausedByComposition;
    bool mCausedBySelectionEvent;
    bool mOccurredDuringComposition;

    void SetWritingMode(const WritingMode& aWritingMode);
    WritingMode GetWritingMode() const;

    uint32_t StartOffset() const
    {
      return mOffset + (mReversed ? Length() : 0);
    }
    uint32_t EndOffset() const
    {
      return mOffset + (mReversed ? 0 : Length());
    }
    const nsString& String() const
    {
      return *mString;
    }
    uint32_t Length() const
    {
      return mString->Length();
    }
    bool IsInInt32Range() const
    {
      return mOffset + Length() <= INT32_MAX;
    }
    bool IsCollapsed() const
    {
      return mString->IsEmpty();
    }
    void ClearSelectionData()
    {
      mOffset = UINT32_MAX;
      mString->Truncate();
      mWritingMode = 0;
      mReversed = false;
    }
    void Clear()
    {
      ClearSelectionData();
      mCausedByComposition = false;
      mCausedBySelectionEvent = false;
      mOccurredDuringComposition = false;
    }
    bool IsValid() const
    {
      return mOffset != UINT32_MAX;
    }
    void Assign(const SelectionChangeDataBase& aOther)
    {
      mOffset = aOther.mOffset;
      *mString = aOther.String();
      mWritingMode = aOther.mWritingMode;
      mReversed = aOther.mReversed;
      AssignReason(aOther.mCausedByComposition,
                   aOther.mCausedBySelectionEvent,
                   aOther.mOccurredDuringComposition);
    }
    void AssignReason(bool aCausedByComposition,
                      bool aCausedBySelectionEvent,
                      bool aOccurredDuringComposition)
    {
      mCausedByComposition = aCausedByComposition;
      mCausedBySelectionEvent = aCausedBySelectionEvent;
      mOccurredDuringComposition = aOccurredDuringComposition;
    }
  };

  // SelectionChangeDataBase cannot have constructors because it's used in
  // the union.  Therefore, SelectionChangeData should only implement
  // constructors.  In other words, add other members to
  // SelectionChangeDataBase.
  struct SelectionChangeData final : public SelectionChangeDataBase
  {
    SelectionChangeData()
    {
      mString = &mStringInstance;
      Clear();
    }
    explicit SelectionChangeData(const SelectionChangeDataBase& aOther)
    {
      mString = &mStringInstance;
      Assign(aOther);
    }
    SelectionChangeData(const SelectionChangeData& aOther)
    {
      mString = &mStringInstance;
      Assign(aOther);
    }
    SelectionChangeData& operator=(const SelectionChangeDataBase& aOther)
    {
      mString = &mStringInstance;
      Assign(aOther);
      return *this;
    }
    SelectionChangeData& operator=(const SelectionChangeData& aOther)
    {
      mString = &mStringInstance;
      Assign(aOther);
      return *this;
    }

  private:
    // When SelectionChangeData is used outside of union, it shouldn't create
    // nsString instance in the heap as far as possible.
    nsString mStringInstance;
  };

  struct TextChangeDataBase
  {
    // mStartOffset is the start offset of modified or removed text in
    // original content and inserted text in new content.
    uint32_t mStartOffset;
    // mRemovalEndOffset is the end offset of modified or removed text in
    // original content.  If the value is same as mStartOffset, no text hasn't
    // been removed yet.
    uint32_t mRemovedEndOffset;
    // mAddedEndOffset is the end offset of inserted text or same as
    // mStartOffset if just removed.  The vlaue is offset in the new content.
    uint32_t mAddedEndOffset;

    // Note that TextChangeDataBase may be the result of merging two or more
    // changes especially in e10s mode.

    // mCausedOnlyByComposition is true only when *all* merged changes are
    // caused by composition.
    bool mCausedOnlyByComposition;
    // mIncludingChangesDuringComposition is true if at least one change which
    // is not caused by composition occurred during the last composition.
    // Note that if after the last composition is finished and there are some
    // changes not caused by composition, this is set to false.
    bool mIncludingChangesDuringComposition;
    // mIncludingChangesWithoutComposition is true if there is at least one
    // change which did occur when there wasn't a composition ongoing.
    bool mIncludingChangesWithoutComposition;

    uint32_t OldLength() const
    {
      MOZ_ASSERT(IsValid());
      return mRemovedEndOffset - mStartOffset;
    }
    uint32_t NewLength() const
    {
      MOZ_ASSERT(IsValid());
      return mAddedEndOffset - mStartOffset;
    }

    // Positive if text is added. Negative if text is removed.
    int64_t Difference() const
    {
      return mAddedEndOffset - mRemovedEndOffset;
    }

    bool IsInInt32Range() const
    {
      MOZ_ASSERT(IsValid());
      return mStartOffset <= INT32_MAX &&
             mRemovedEndOffset <= INT32_MAX &&
             mAddedEndOffset <= INT32_MAX;
    }

    bool IsValid() const
    {
      return !(mStartOffset == UINT32_MAX &&
               !mRemovedEndOffset && !mAddedEndOffset);
    }

    void Clear()
    {
      mStartOffset = UINT32_MAX;
      mRemovedEndOffset = mAddedEndOffset = 0;
    }

    void MergeWith(const TextChangeDataBase& aOther);
    TextChangeDataBase& operator+=(const TextChangeDataBase& aOther)
    {
      MergeWith(aOther);
      return *this;
    }

#ifdef DEBUG
    void Test();
#endif // #ifdef DEBUG
  };

  // TextChangeDataBase cannot have constructors because they are used in union.
  // Therefore, TextChangeData should only implement constructor.  In other
  // words, add other members to TextChangeDataBase.
  struct TextChangeData : public TextChangeDataBase
  {
    TextChangeData() { Clear(); }

    TextChangeData(uint32_t aStartOffset,
                   uint32_t aRemovedEndOffset,
                   uint32_t aAddedEndOffset,
                   bool aCausedByComposition,
                   bool aOccurredDuringComposition)
    {
      MOZ_ASSERT(aRemovedEndOffset >= aStartOffset,
                 "removed end offset must not be smaller than start offset");
      MOZ_ASSERT(aAddedEndOffset >= aStartOffset,
                 "added end offset must not be smaller than start offset");
      mStartOffset = aStartOffset;
      mRemovedEndOffset = aRemovedEndOffset;
      mAddedEndOffset = aAddedEndOffset;
      mCausedOnlyByComposition = aCausedByComposition;
      mIncludingChangesDuringComposition =
        !aCausedByComposition && aOccurredDuringComposition;
      mIncludingChangesWithoutComposition =
        !aCausedByComposition && !aOccurredDuringComposition;
    }
  };

  struct MouseButtonEventData
  {
    // The value of WidgetEvent::mMessage
    EventMessage mEventMessage;
    // Character offset from the start of the focused editor under the cursor
    uint32_t mOffset;
    // Cursor position in pixels relative to the widget
    Point mCursorPos;
    // Character rect in pixels under the cursor relative to the widget
    Rect mCharRect;
    // The value of WidgetMouseEventBase::button and buttons
    int16_t mButton;
    int16_t mButtons;
    // The value of WidgetInputEvent::modifiers
    Modifiers mModifiers;
  };

  union
  {
    // NOTIFY_IME_OF_SELECTION_CHANGE specific data
    SelectionChangeDataBase mSelectionChangeData;

    // NOTIFY_IME_OF_TEXT_CHANGE specific data
    TextChangeDataBase mTextChangeData;

    // NOTIFY_IME_OF_MOUSE_BUTTON_EVENT specific data
    MouseButtonEventData mMouseButtonEventData;
  };

  void SetData(const SelectionChangeDataBase& aSelectionChangeData)
  {
    MOZ_RELEASE_ASSERT(mMessage == NOTIFY_IME_OF_SELECTION_CHANGE);
    mSelectionChangeData.Assign(aSelectionChangeData);
  }

  void SetData(const TextChangeDataBase& aTextChangeData)
  {
    MOZ_RELEASE_ASSERT(mMessage == NOTIFY_IME_OF_TEXT_CHANGE);
    mTextChangeData = aTextChangeData;
  }
};

struct CandidateWindowPosition
{
  // Upper left corner of the candidate window if mExcludeRect is false.
  // Otherwise, the position currently interested.  E.g., caret position.
  LayoutDeviceIntPoint mPoint;
  // Rect which shouldn't be overlapped with the candidate window.
  // This is valid only when mExcludeRect is true.
  LayoutDeviceIntRect mRect;
  // See explanation of mPoint and mRect.
  bool mExcludeRect;
};

} // namespace widget
} // namespace mozilla

#endif // #ifndef mozilla_widget_IMEData_h_