ui/views/controls/scrollbar/scroll_bar.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef UI_VIEWS_CONTROLS_SCROLLBAR_SCROLL_BAR_H_
   6 #define UI_VIEWS_CONTROLS_SCROLLBAR_SCROLL_BAR_H_
   7
   8 #include "base/basictypes.h"
   9 #include "base/compiler_specific.h"
  10 #include "ui/views/view.h"
  11 #include "ui/views/views_export.h"
  12
  13 namespace views {
  14
  15 class ScrollBar;
  16
  17 /////////////////////////////////////////////////////////////////////////////
  18 //
  19 // ScrollBarController
  20 //
  21 // ScrollBarController defines the method that should be implemented to
  22 // receive notification from a scrollbar
  23 //
  24 /////////////////////////////////////////////////////////////////////////////
  25 class VIEWS_EXPORT ScrollBarController {
  26  public:
  27   // Invoked by the scrollbar when the scrolling position changes
  28   // This method typically implements the actual scrolling.
  29   //
  30   // The provided position is expressed in pixels. It is the new X or Y
  31   // position which is in the GetMinPosition() / GetMaxPosition range.
  32   virtual void ScrollToPosition(ScrollBar* source, int position) = 0;
  33
  34   // Returns the amount to scroll. The amount to scroll may be requested in
  35   // two different amounts. If is_page is true the 'page scroll' amount is
  36   // requested. The page scroll amount typically corresponds to the
  37   // visual size of the view. If is_page is false, the 'line scroll' amount
  38   // is being requested. The line scroll amount typically corresponds to the
  39   // size of one row/column.
  40   //
  41   // The return value should always be positive. A value <= 0 results in
  42   // scrolling by a fixed amount.
  43   virtual int GetScrollIncrement(ScrollBar* source,
  44                                  bool is_page,
  45                                  bool is_positive) = 0;
  46 };
  47
  48 /////////////////////////////////////////////////////////////////////////////
  49 //
  50 // ScrollBar
  51 //
  52 // A View subclass to wrap to implement a ScrollBar. Our current windows
  53 // version simply wraps a native windows scrollbar.
  54 //
  55 // A scrollbar is either horizontal or vertical
  56 //
  57 /////////////////////////////////////////////////////////////////////////////
  58 class VIEWS_EXPORT ScrollBar : public View {
  59  public:
  60   ~ScrollBar() override;
  61
  62   // Overridden from View:
  63   void GetAccessibleState(ui::AXViewState* state) override;
  64
  65   // Returns whether this scrollbar is horizontal.
  66   bool IsHorizontal() const;
  67
  68   void set_controller(ScrollBarController* controller) {
  69      controller_ = controller;
  70   }
  71   ScrollBarController* controller() const { return controller_; }
  72
  73   // Update the scrollbar appearance given a viewport size, content size and
  74   // current position
  75   virtual void Update(int viewport_size, int content_size, int current_pos);
  76
  77   // Returns the max and min positions.
  78   int GetMaxPosition() const;
  79   int GetMinPosition() const;
  80
  81   // Returns the position of the scrollbar.
  82   virtual int GetPosition() const = 0;
  83
  84   // Get the width or height of this scrollbar, for use in layout calculations.
  85   // For a vertical scrollbar, this is the width of the scrollbar, likewise it
  86   // is the height for a horizontal scrollbar.
  87   virtual int GetLayoutSize() const = 0;
  88
  89   // Get the width or height for this scrollbar which overlaps with the content.
  90   // Default is 0.
  91   virtual int GetContentOverlapSize() const;
  92
  93   virtual void OnMouseEnteredScrollView(const ui::MouseEvent& event);
  94   virtual void OnMouseExitedScrollView(const ui::MouseEvent& event);
  95
  96  protected:
  97   // Create new scrollbar, either horizontal or vertical. These are protected
  98   // since you need to be creating either a NativeScrollBar or a
  99   // ImageScrollBar.
 100   explicit ScrollBar(bool is_horiz);
 101
 102  private:
 103   const bool is_horiz_;
 104
 105   ScrollBarController* controller_;
 106
 107   int max_pos_;
 108
 109   DISALLOW_COPY_AND_ASSIGN(ScrollBar);
 110 };
 111
 112 }  // namespace views
 113
 114 #endif  // UI_VIEWS_CONTROLS_SCROLLBAR_SCROLL_BAR_H_