Adding a Views scrollbar implementation.

views/controls/scrollbar/base_scroll_bar.h

 // Copyright (c) 2011 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 VIEWS_CONTROLS_SCROLLBAR_BITMAP_SCROLL_BAR_H_
-#define VIEWS_CONTROLS_SCROLLBAR_BITMAP_SCROLL_BAR_H_
+#ifndef VIEWS_CONTROLS_SCROLLBAR_BASE_SCROLL_BAR_H_
+#define VIEWS_CONTROLS_SCROLLBAR_BASE_SCROLL_BAR_H_
 #pragma once
 
 #include "views/context_menu_controller.h"
 #include "views/controls/button/image_button.h"
 #include "views/controls/menu/menu.h"
 #include "views/controls/scrollbar/scroll_bar.h"
 #include "views/repeat_controller.h"
 
 namespace views {
 
-namespace {
-class BitmapScrollBarThumb;
-}
+class BaseScrollBarThumb;
 
 ///////////////////////////////////////////////////////////////////////////////
 //
-// 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.
+// BaseScrollBar
 //
 ///////////////////////////////////////////////////////////////////////////////
-class BitmapScrollBar : public ScrollBar,
-                        public ButtonListener,
-                        public ContextMenuController,
-                        public Menu::Delegate {
+class BaseScrollBar : public ScrollBar,
+                      public ContextMenuController,
+                      public Menu::Delegate {
  public:
-  BitmapScrollBar(bool horizontal, bool show_scroll_buttons);
-  virtual ~BitmapScrollBar() { }
+  BaseScrollBar(bool horizontal, BaseScrollBarThumb* thumb);
+  virtual ~BaseScrollBar() { }
 
   // 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,
-                CustomButton::ButtonState state,
-                SkBitmap* bitmap);
+  virtual gfx::Rect GetTrackBounds() const = 0;
 
   // 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() OVERRIDE;
-  virtual void Layout() OVERRIDE;
+  virtual gfx::Size GetPreferredSize() OVERRIDE = 0;
+  virtual void Layout() OVERRIDE = 0;
   virtual bool OnMousePressed(const MouseEvent& event) OVERRIDE;
   virtual void OnMouseReleased(const MouseEvent& event) OVERRIDE;
   virtual void OnMouseCaptureLost() OVERRIDE;
   virtual bool OnKeyPressed(const KeyEvent& event) OVERRIDE;
   virtual bool OnMouseWheel(const MouseWheelEvent& event) OVERRIDE;
 
-  // BaseButton::ButtonListener overrides:
-  virtual void ButtonPressed(Button* sender,
-                             const views::Event& event) OVERRIDE;
-
   // ScrollBar overrides:
   virtual void Update(int viewport_size,
                       int content_size,
                       int contents_scroll_offset) OVERRIDE;
-  virtual int GetLayoutSize() const OVERRIDE;
+  virtual int GetLayoutSize() const OVERRIDE = 0;
   virtual int GetPosition() const OVERRIDE;
 
   // ContextMenuController overrides.
   virtual void ShowContextMenuForView(View* source,
                                       const gfx::Point& p,
                                       bool is_mouse_gesture) OVERRIDE;
 
   // Menu::Delegate overrides:
   virtual std::wstring GetLabel(int id) const OVERRIDE;
   virtual bool IsCommandEnabled(int id) const OVERRIDE;
   virtual void ExecuteCommand(int id) OVERRIDE;
 
  protected:
   // View overrides:
-  virtual void OnPaint(gfx::Canvas* canvas) OVERRIDE;
+  virtual void OnPaint(gfx::Canvas* canvas) OVERRIDE = 0;
+
+  BaseScrollBarThumb* GetThumb() const;
+
+  virtual void ScrollToPosition(int position);

[Ben Goodger (Google), 2011/08/23 16:05:15]

Are these overrides or introduced here? If the latter, there should be
documentation. If the former, they should be OVERRIDE and have a section marker.

+  virtual int GetScrollIncrement(bool is_page, bool is_positive);
 
  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(CustomButton::ButtonState state);
 
-  // The thumb needs to be able to access the part images.
-  friend BitmapScrollBarThumb;
-  SkBitmap* images_[PART_COUNT][CustomButton::BS_COUNT];
+  BaseScrollBarThumb* thumb_;
 
   // 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.
-  ImageButton* prev_button_;
-  ImageButton* 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).
   CustomButton::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_COPY_AND_ASSIGN(BitmapScrollBar);
+  DISALLOW_COPY_AND_ASSIGN(BaseScrollBar);
 };
 
 }  // namespace views
 
-#endif  // VIEWS_CONTROLS_SCROLLBAR_BITMAP_SCROLL_BAR_H_
+#endif  // VIEWS_CONTROLS_SCROLLBAR_BASE_SCROLL_BAR_H_