// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CHROME_VIEWS_BITMAP_SCROLL_BAR_H__
#define CHROME_VIEWS_BITMAP_SCROLL_BAR_H__

#include "chrome/views/button.h"
#include "chrome/views/menu.h"
#include "chrome/views/repeat_controller.h"
#include "chrome/views/scroll_bar.h"

namespace views {

namespace {
class BitmapScrollBarThumb;
}

///////////////////////////////////////////////////////////////////////////////
//
// BitmapScrollBar
//
//  A ScrollBar subclass that implements a scroll bar rendered using bitmaps
//  that the user provides. There are bitmaps for the up and down buttons, as
//  well as for the thumb and track. This is intended for creating UIs that
//  have customized, non-native appearances, like floating HUDs etc.
//
//  Maybe TODO(beng): (Cleanup) If we need to, we may want to factor rendering
//                    out of this altogether and have the user supply
//                    Background impls for each component, and just use those
//                    to render, so that for example we get native theme
//                    rendering.
//
///////////////////////////////////////////////////////////////////////////////
class BitmapScrollBar : public ScrollBar,
                        public BaseButton::ButtonListener,
                        public ContextMenuController,
                        public Menu::Delegate {
 public:
  BitmapScrollBar(bool horizontal, bool show_scroll_buttons);
  virtual ~BitmapScrollBar() { }

  // Get the bounds of the "track" area that the thumb is free to slide within.
  gfx::Rect GetTrackBounds() const;

  // A list of parts that the user may supply bitmaps for.
  enum ScrollBarPart {
    // The button used to represent scrolling up/left by 1 line.
    PREV_BUTTON = 0,
    // The button used to represent scrolling down/right by 1 line.
    // IMPORTANT: The code assumes the prev and next
    // buttons have equal width and equal height.
    NEXT_BUTTON,
    // The top/left segment of the thumb on the scrollbar.
    THUMB_START_CAP,
    // The tiled background image of the thumb.
    THUMB_MIDDLE,
    // The bottom/right segment of the thumb on the scrollbar.
    THUMB_END_CAP,
    // The grippy that is rendered in the center of the thumb.
    THUMB_GRIPPY,
    // The tiled background image of the thumb track.
    THUMB_TRACK,
    PART_COUNT
  };

  // Sets the bitmap to be rendered for the specified part and state.
  void SetImage(ScrollBarPart part,
                BaseButton::ButtonState state,
                SkBitmap* bitmap);

  // An enumeration of different amounts of incremental scroll, representing
  // events sent from different parts of the UI/keyboard.
  enum ScrollAmount {
    SCROLL_NONE = 0,
    SCROLL_START,
    SCROLL_END,
    SCROLL_PREV_LINE,
    SCROLL_NEXT_LINE,
    SCROLL_PREV_PAGE,
    SCROLL_NEXT_PAGE,
  };

  // Scroll the contents by the specified type (see ScrollAmount above).
  void ScrollByAmount(ScrollAmount amount);

  // Scroll the contents to the appropriate position given the supplied
  // position of the thumb (thumb track coordinates). If |scroll_to_middle| is
  // true, then the conversion assumes |thumb_position| is in the middle of the
  // thumb rather than the top.
  void ScrollToThumbPosition(int thumb_position, bool scroll_to_middle);

  // Scroll the contents by the specified offset (contents coordinates).
  void ScrollByContentsOffset(int contents_offset);

  // View overrides:
  virtual gfx::Size GetPreferredSize();
  virtual void Paint(ChromeCanvas* canvas);
  virtual void Layout();
  virtual bool OnMousePressed(const MouseEvent& event);
  virtual void OnMouseReleased(const MouseEvent& event, bool canceled);
  virtual bool OnMouseWheel(const MouseWheelEvent& event);
  virtual bool OnKeyPressed(const KeyEvent& event);

  // BaseButton::ButtonListener overrides:
  virtual void ButtonPressed(BaseButton* sender);

  // ScrollBar overrides:
  virtual void Update(int viewport_size,
                      int content_size,
                      int contents_scroll_offset);
  virtual int GetLayoutSize() const;
  virtual int GetPosition() const;

  // ContextMenuController overrides.
  virtual void ShowContextMenu(View* source,
                               int x,
                               int y,
                               bool is_mouse_gesture);

  // Menu::Delegate overrides:
  virtual std::wstring GetLabel(int id) const;
  virtual bool IsCommandEnabled(int id) const;
  virtual void ExecuteCommand(int id);

 private:
  // Called when the mouse is pressed down in the track area.
  void TrackClicked();

  // Responsible for scrolling the contents and also updating the UI to the
  // current value of the Scroll Offset.
  void ScrollContentsToOffset();

  // Returns the size (width or height) of the track area of the ScrollBar.
  int GetTrackSize() const;

  // Calculate the position of the thumb within the track based on the
  // specified scroll offset of the contents.
  int CalculateThumbPosition(int contents_scroll_offset) const;

  // Calculates the current value of the contents offset (contents coordinates)
  // based on the current thumb position (thumb track coordinates). See
  // |ScrollToThumbPosition| for an explanation of |scroll_to_middle|.
  int CalculateContentsOffset(int thumb_position,
                              bool scroll_to_middle) const;

  // Called when the state of the thumb track changes (e.g. by the user
  // pressing the mouse button down in it).
  void SetThumbTrackState(BaseButton::ButtonState state);

  // The thumb needs to be able to access the part images.
  friend BitmapScrollBarThumb;
  SkBitmap* images_[PART_COUNT][BaseButton::kButtonStateCount];

  // The size of the scrolled contents, in pixels.
  int contents_size_;

  // The current amount the contents is offset by in the viewport.
  int contents_scroll_offset_;

  // Up/Down/Left/Right buttons and the Thumb.
  Button* prev_button_;
  Button* next_button_;
  BitmapScrollBarThumb* thumb_;

  // The state of the scrollbar track. Typically, the track will highlight when
  // the user presses the mouse on them (during page scrolling).
  BaseButton::ButtonState thumb_track_state_;

  // The last amount of incremental scroll that this scrollbar performed. This
  // is accessed by the callbacks for the auto-repeat up/down buttons to know
  // what direction to repeatedly scroll in.
  ScrollAmount last_scroll_amount_;

  // An instance of a RepeatController which scrolls the scrollbar continuously
  // as the user presses the mouse button down on the up/down buttons or the
  // track.
  RepeatController repeater_;

  // The position of the mouse within the scroll bar when the context menu
  // was invoked.
  int context_menu_mouse_position_;

  // True if the scroll buttons at each end of the scroll bar should be shown.
  bool show_scroll_buttons_;

  DISALLOW_EVIL_CONSTRUCTORS(BitmapScrollBar);
};

}  // namespace views

#endif  // #ifndef CHROME_VIEWS_BITMAP_SCROLL_BAR_H__