mcs/class/referencesource/System.Activities.Presentation/System.Activities.Presentation/System/Activities/Presentation/View/ScrollViewerPanner.cs

   1 //----------------------------------------------------------------
   2 // <copyright company="Microsoft Corporation">
   3 //     Copyright (c) Microsoft Corporation.  All rights reserved.
   4 // </copyright>
   5 //----------------------------------------------------------------
   6
   7 namespace System.Activities.Presentation.View
   8 {
   9     using System.Runtime;
  10     using System.Windows;
  11     using System.Windows.Controls;
  12     using System.Windows.Input;
  13
  14     internal class ScrollViewerPanner
  15     {
  16         private ScrollViewer scrollViewer;
  17         private Point panningStartPosition;
  18         private PanState currentPanState;
  19         private bool inPanMode;
  20         private MouseButton draggingMouseButton;
  21
  22         public ScrollViewerPanner(ScrollViewer scrollViewer)
  23         {
  24             Fx.Assert(scrollViewer != null, "ScrollViewer should never be null");
  25             this.ScrollViewer = scrollViewer;
  26         }
  27
  28         internal enum PanState
  29         {
  30             Normal,     // Normal editing mode
  31             ReadyToPan,
  32             Panning,
  33         }
  34
  35         public ScrollViewer ScrollViewer
  36         {
  37             get
  38             {
  39                 return this.scrollViewer;
  40             }
  41
  42             set
  43             {
  44                 if (value != this.scrollViewer)
  45                 {
  46                     if (this.scrollViewer != null)
  47                     {
  48                         this.UnregisterEvents();
  49                     }
  50
  51                     this.scrollViewer = value;
  52                     if (this.scrollViewer != null)
  53                     {
  54                         this.RegisterEvents();
  55                     }
  56                 }
  57             }
  58         }
  59
  60         public bool InPanMode
  61         {
  62             get
  63             {
  64                 return this.inPanMode;
  65             }
  66
  67             set
  68             {
  69                 if (this.inPanMode != value)
  70                 {
  71                     this.inPanMode = value;
  72                     if (this.inPanMode)
  73                     {
  74                         this.CurrentPanState = PanState.ReadyToPan;
  75                     }
  76                     else
  77                     {
  78                         this.CurrentPanState = PanState.Normal;
  79                     }
  80                 }
  81             }
  82         }
  83
  84         public Cursor Hand { get; set; }
  85
  86         public Cursor DraggingHand { get; set; }
  87
  88         internal PanState CurrentPanState
  89         {
  90             get
  91             {
  92                 return this.currentPanState;
  93             }
  94
  95             set
  96             {
  97                 if (this.currentPanState != value)
  98                 {
  99                     this.currentPanState = value;
 100                     switch (this.currentPanState)
 101                     {
 102                         case PanState.ReadyToPan:
 103                             this.scrollViewer.Cursor = this.Hand;
 104                             break;
 105                         case PanState.Panning:
 106                             this.scrollViewer.Cursor = this.DraggingHand;
 107                             break;
 108                         default:
 109                             this.scrollViewer.Cursor = null;
 110                             break;
 111                     }
 112
 113                     this.UpdateForceCursorProperty();
 114                 }
 115             }
 116         }
 117
 118         internal bool IsInScrollableArea(Point mousePosition)
 119         {
 120             return mousePosition.X < this.scrollViewer.ViewportWidth && mousePosition.Y < this.scrollViewer.ViewportHeight;
 121         }
 122
 123         internal void OnScrollViewerMouseDown(object sender, MouseButtonEventArgs e)
 124         {
 125             switch (this.CurrentPanState)
 126             {
 127                 case PanState.Normal:
 128                     if (e.ChangedButton == MouseButton.Middle)
 129                     {
 130                         this.StartPanningIfNecessary(e);
 131                     }
 132
 133                     break;
 134                 case PanState.ReadyToPan:
 135                     switch (e.ChangedButton)
 136                     {
 137                         case MouseButton.Left:
 138                             this.StartPanningIfNecessary(e);
 139                             break;
 140                         case MouseButton.Middle:
 141                             this.StartPanningIfNecessary(e);
 142                             break;
 143                         case MouseButton.Right:
 144                             e.Handled = true;
 145                             break;
 146                     }
 147
 148                     break;
 149                 case PanState.Panning:
 150                     e.Handled = true;
 151                     break;
 152                 default:
 153                     break;
 154             }
 155         }
 156
 157         internal void OnLostMouseCapture(object sender, MouseEventArgs e)
 158         {
 159             this.StopPanning();
 160         }
 161
 162         internal void OnScrollViewerMouseMove(object sender, MouseEventArgs e)
 163         {
 164             switch (this.CurrentPanState)
 165             {
 166                 case PanState.Panning:
 167                     Point currentPosition = Mouse.GetPosition(this.scrollViewer);
 168                     Vector offset = Point.Subtract(currentPosition, this.panningStartPosition);
 169                     this.panningStartPosition = currentPosition;
 170                     this.scrollViewer.ScrollToHorizontalOffset(this.scrollViewer.HorizontalOffset - offset.X);
 171                     this.scrollViewer.ScrollToVerticalOffset(this.scrollViewer.VerticalOffset - offset.Y);
 172                     e.Handled = true;
 173                     break;
 174                 case PanState.ReadyToPan:
 175                     this.UpdateForceCursorProperty();
 176                     break;
 177                 default:
 178                     break;
 179             }
 180         }
 181
 182         internal void OnScrollViewerMouseUp(object sender, MouseButtonEventArgs e)
 183         {
 184             switch (this.CurrentPanState)
 185             {
 186                 case PanState.ReadyToPan:
 187                     this.StopPanningIfNecessary(e);
 188
 189                     // When the mouse is captured by other windows/views, that
 190                     // window/view needs this mouse-up message to release
 191                     // the capture.
 192                     if (!this.IsMouseCapturedByOthers())
 193                     {
 194                         e.Handled = true;
 195                     }
 196
 197                     break;
 198                 case PanState.Panning:
 199                     this.StopPanningIfNecessary(e);
 200                     e.Handled = true;
 201                     break;
 202                 default:
 203                     break;
 204             }
 205         }
 206
 207         internal void OnScrollViewerKeyDown(object sender, KeyEventArgs e)
 208         {
 209             switch (this.CurrentPanState)
 210             {
 211                 // Don't change to ReadyToPan mode if the space is a
 212                 // repeated input, because repeated-key input may come
 213                 // from activity element on the scroll view.
 214                 case PanState.Normal:
 215                     if (e.Key == Key.Space
 216                         && !e.IsRepeat
 217                         && this.AllowSwitchToPanning())
 218                     {
 219                         this.CurrentPanState = PanState.ReadyToPan;
 220                     }
 221
 222                     break;
 223                 default:
 224                     break;
 225             }
 226         }
 227
 228         internal void OnScrollViewerKeyUp(object sender, KeyEventArgs e)
 229         {
 230             switch (this.CurrentPanState)
 231             {
 232                 case PanState.ReadyToPan:
 233                     if (e.Key == Key.Space && !this.InPanMode)
 234                     {
 235                         this.CurrentPanState = PanState.Normal;
 236                     }
 237
 238                     break;
 239                 default:
 240                     break;
 241             }
 242         }
 243
 244         private void StartPanningIfNecessary(MouseButtonEventArgs e)
 245         {
 246             if (DesignerView.IsMouseInViewport(e, this.scrollViewer))
 247             {
 248                 this.draggingMouseButton = e.ChangedButton;
 249                 this.CurrentPanState = PanState.Panning;
 250                 this.scrollViewer.Focus();
 251                 this.panningStartPosition = Mouse.GetPosition(this.scrollViewer);
 252                 Mouse.Capture(this.scrollViewer);
 253                 e.Handled = true;
 254             }
 255         }
 256
 257         private void StopPanningIfNecessary(MouseButtonEventArgs e)
 258         {
 259             if (e.ChangedButton == this.draggingMouseButton && object.Equals(this.scrollViewer, Mouse.Captured))
 260             {
 261                 // Trigers OnLostMouseCapture
 262                 this.scrollViewer.ReleaseMouseCapture();
 263             }
 264         }
 265
 266         private void StopPanning()
 267         {
 268             // stop panning
 269             if (this.InPanMode
 270                 || (Keyboard.IsKeyDown(Key.Space) && this.CurrentPanState == PanState.Panning))
 271             {
 272                 this.CurrentPanState = PanState.ReadyToPan;
 273             }
 274             else
 275             {
 276                 this.CurrentPanState = PanState.Normal;
 277             }
 278         }
 279
 280         private void UpdateForceCursorProperty()
 281         {
 282             Point pt = Mouse.GetPosition(this.ScrollViewer);
 283             if (this.IsInScrollableArea(pt))
 284             {
 285                 this.scrollViewer.ForceCursor = true;
 286             }
 287             else
 288             {
 289                 this.scrollViewer.ForceCursor = false;
 290             }
 291         }
 292
 293         // Mouse is sometimes captured by ScrollViewer's children, like
 294         // RepeatButton in Scroll Bar.
 295         private bool IsMouseCapturedByOthers()
 296         {
 297             return (Mouse.Captured != null)
 298                 && !object.Equals(Mouse.Captured, this.ScrollViewer);
 299         }
 300
 301         private bool AllowSwitchToPanning()
 302         {
 303             return Mouse.LeftButton == MouseButtonState.Released
 304                 && Mouse.RightButton == MouseButtonState.Released;
 305         }
 306
 307         private void RegisterEvents()
 308         {
 309             this.scrollViewer.PreviewMouseDown  += new MouseButtonEventHandler(this.OnScrollViewerMouseDown);
 310             this.scrollViewer.PreviewMouseMove  += new MouseEventHandler(this.OnScrollViewerMouseMove);
 311             this.scrollViewer.PreviewMouseUp    += new MouseButtonEventHandler(this.OnScrollViewerMouseUp);
 312             this.scrollViewer.LostMouseCapture  += new MouseEventHandler(this.OnLostMouseCapture);
 313             this.scrollViewer.KeyDown           += new KeyEventHandler(this.OnScrollViewerKeyDown);
 314             this.scrollViewer.KeyUp             += new KeyEventHandler(this.OnScrollViewerKeyUp);
 315         }
 316
 317         private void UnregisterEvents()
 318         {
 319             this.scrollViewer.PreviewMouseDown  -= new MouseButtonEventHandler(this.OnScrollViewerMouseDown);
 320             this.scrollViewer.PreviewMouseMove  -= new MouseEventHandler(this.OnScrollViewerMouseMove);
 321             this.scrollViewer.PreviewMouseUp    -= new MouseButtonEventHandler(this.OnScrollViewerMouseUp);
 322             this.scrollViewer.LostMouseCapture  -= new MouseEventHandler(this.OnLostMouseCapture);
 323             this.scrollViewer.KeyDown           -= new KeyEventHandler(this.OnScrollViewerKeyDown);
 324             this.scrollViewer.KeyUp             -= new KeyEventHandler(this.OnScrollViewerKeyUp);
 325         }
 326     }
 327 }