/* -*- 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/. */

#ifndef AccessibleCaret_h__

#define AccessibleCaret_h__

#include "mozilla/Attributes.h"

#include "mozilla/dom/AnonymousContent.h"

#include "mozilla/dom/Element.h"

#include "nsCOMPtr.h"

#include "nsIDOMEventListener.h"

#include "nsISupportsBase.h"

#include "nsISupportsImpl.h"

#include "nsLiteralString.h"

#include "nsRect.h"

#include "mozilla/RefPtr.h"

#include "nsString.h"

class nsIDocument;

class nsIFrame;

class nsIPresShell;

struct nsPoint;

namespace mozilla {

namespace dom {

class Event;

} // namespace dom

// -----------------------------------------------------------------------------

// Upon the creation of AccessibleCaret, it will insert DOM Element as an

// anonymous content containing the caret image. The caret appearance and

// position can be controlled by SetAppearance() and SetPosition().

//

// All the rect or point are relative to root frame except being specified

// explicitly.

//

// None of the methods in AccessibleCaret will flush layout or style. To ensure

// that SetPosition() works correctly, the caller must make sure the layout is

// up to date.

//

// Please see the wiki page for more information.

// https://wiki.mozilla.org/AccessibleCaret

//

class AccessibleCaret

{

public:

  explicit AccessibleCaret(nsIPresShell* aPresShell);

  virtual ~AccessibleCaret();

  // This enumeration representing the visibility and visual style of an

  // AccessibleCaret.

  //

  // Use SetAppearance() to change the appearance, and use GetAppearance() to

  // get the current appearance.

  enum class Appearance : uint8_t {

    // Do not display the caret at all.

    None,

    // Display the caret in default style.

    Normal,

    // The caret should be displayed logically but it is kept invisible to the

    // user. This enum is the only difference between "logically visible" and

    // "visually visible". It can be used for reasons such as:

    // 1. Out of scroll port.

    // 2. For UX requirement such as hide a caret in an empty text area.

    NormalNotShown,

    // Display the caret which is tilted to the left.

    Left,

    // Display the caret which is tilted to the right.

    Right

  };

  friend std::ostream& operator<<(std::ostream& aStream,

                                  const Appearance& aAppearance);

  Appearance GetAppearance() const

  {

    return mAppearance;

  }

  virtual void SetAppearance(Appearance aAppearance);

  // Return true if current appearance is either Normal, NormalNotShown, Left,

  // or Right.

  bool IsLogicallyVisible() const

  {

      return mAppearance != Appearance::None;

  }

  // Return true if current appearance is either Normal, Left, or Right.

  bool IsVisuallyVisible() const

  {

    return (mAppearance != Appearance::None) &&

           (mAppearance != Appearance::NormalNotShown);

  }

  // This enumeration representing the result returned by SetPosition().

  enum class PositionChangedResult : uint8_t {

    // Position is not changed.

    NotChanged,

    // Position or zoom level is changed.

    Changed,

    // Position is out of scroll port.

    Invisible

  };

  friend std::ostream& operator<<(std::ostream& aStream,

                                  const PositionChangedResult& aResult);

  virtual PositionChangedResult SetPosition(nsIFrame* aFrame, int32_t aOffset);

  // Does two AccessibleCarets overlap?

  bool Intersects(const AccessibleCaret& aCaret) const;

  // Is the point within the caret's rect? The point should be relative to root

  // frame.

  enum class TouchArea {

    Full, // Contains both text overlay and caret image.

    CaretImage

  };

  bool Contains(const nsPoint& aPoint, TouchArea aTouchArea) const;

  // The geometry center of the imaginary caret (nsCaret) to which this

  // AccessibleCaret is attached. It is needed when dragging the caret.

  nsPoint LogicalPosition() const

  {

    return mImaginaryCaretRect.Center();

  }

  // Element for 'Intersects' test. This is the container of the caret image

  // and text-overlay elements. See CreateCaretElement() for the content

  // structure.

  dom::Element& CaretElement() const

  {

    return mCaretElementHolder->ContentNode();

  }

  // Ensures that the caret element is made "APZ aware" so that the APZ code

  // doesn't scroll the page when the user is trying to drag the caret.

  void EnsureApzAware();

protected:

  // Argument aRect should be relative to CustomContentContainerFrame().

  void SetCaretElementStyle(const nsRect& aRect, float aZoomLevel);

  void SetTextOverlayElementStyle(const nsRect& aRect, float aZoomLevel);

  void SetCaretImageElementStyle(const nsRect& aRect, float aZoomLevel);

  // Get current zoom level.

  float GetZoomLevel();

  // Element which contains the text overly for the 'Contains' test.

  dom::Element* TextOverlayElement() const

  {

    return mCaretElementHolder->GetElementById(sTextOverlayElementId);

  }

  // Element which contains the caret image for 'Contains' test.

  dom::Element* CaretImageElement() const

  {

    return mCaretElementHolder->GetElementById(sCaretImageElementId);

  }

  nsIFrame* RootFrame() const

  {

    return mPresShell->GetRootFrame();

  }

  nsIFrame* CustomContentContainerFrame() const;

  // Transform Appearance to CSS id used in ua.css.

  static nsAutoString AppearanceString(Appearance aAppearance);

  already_AddRefed<dom::Element> CreateCaretElement(nsIDocument* aDocument) const;

  // Inject caret element into custom content container.

  void InjectCaretElement(nsIDocument* aDocument);

  // Remove caret element from custom content container.

  void RemoveCaretElement(nsIDocument* aDocument);

  // The top-center of the imaginary caret to which this AccessibleCaret is

  // attached.

  static nsPoint CaretElementPosition(const nsRect& aRect)

  {

    return aRect.TopLeft() + nsPoint(aRect.width / 2, 0);

  }

  class DummyTouchListener final : public nsIDOMEventListener

  {

  public:

    NS_DECL_ISUPPORTS

    NS_IMETHOD HandleEvent(mozilla::dom::Event* aEvent) override

    {

      return NS_OK;

    }

  private:

    virtual ~DummyTouchListener() {};

  };

  // Member variables

  Appearance mAppearance = Appearance::None;

  // AccessibleCaretManager owns us by a UniquePtr. When it's terminated by

  // AccessibleCaretEventHub::Terminate() which is called in

  // PresShell::Destroy(), it frees us automatically. No need to worry if we

  // outlive mPresShell.

  nsIPresShell* MOZ_NON_OWNING_REF const mPresShell = nullptr;

  RefPtr<dom::AnonymousContent> mCaretElementHolder;

  // mImaginaryCaretRect is relative to root frame.

  nsRect mImaginaryCaretRect;

  // Cache current zoom level to determine whether position is changed.

  float mZoomLevel = 0.0f;

  // A no-op touch-start listener which prevents APZ from panning when dragging

  // the caret.

  RefPtr<DummyTouchListener> mDummyTouchListener{new DummyTouchListener()};

  // Static class variables

  static const nsLiteralString sTextOverlayElementId;

  static const nsLiteralString sCaretImageElementId;

}; // class AccessibleCaret

std::ostream& operator<<(std::ostream& aStream,

                         const AccessibleCaret::Appearance& aAppearance);

std::ostream& operator<<(std::ostream& aStream,

                         const AccessibleCaret::PositionChangedResult& aResult);

} // namespace mozilla

#endif // AccessibleCaret_h__