src/Tizen.NUI.Components/Controls/Scrollbar.cs

   1 /*
   2  * Copyright(c) 2020 Samsung Electronics Co., Ltd.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  * http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  *
  16  */
  17 using System;
  18 using System.ComponentModel;
  19 using Tizen.NUI.BaseComponents;
  20 using Tizen.NUI.Binding;
  21
  22 namespace Tizen.NUI.Components
  23 {
  24     /// <summary>
  25     /// The Scrollbar is a component that contains track and thumb to indicate the current scrolled position of a scrollable object.
  26     /// </summary>
  27     [EditorBrowsable(EditorBrowsableState.Never)]
  28     public class Scrollbar : ScrollbarBase
  29     {
  30         #region Fields
  31
  32         /// <summary>Bindable property of TrackThickness</summary>
  33         [EditorBrowsable(EditorBrowsableState.Never)]
  34         public static readonly BindableProperty TrackThicknessProperty = BindableProperty.Create(nameof(TrackThickness), typeof(float), typeof(Scrollbar), default(float), propertyChanged: (bindable, oldValue, newValue) =>
  35         {
  36             var instance = ((Scrollbar)bindable);
  37             var thickness = (float?)newValue;
  38
  39             ((ScrollbarStyle)instance.viewStyle).TrackThickness = thickness;
  40             instance.UpdateTrackThickness(thickness ?? 0);
  41         },
  42         defaultValueCreator: (bindable) =>
  43         {
  44             return ((ScrollbarStyle)((Scrollbar)bindable).viewStyle)?.TrackThickness ?? 0;
  45         });
  46
  47         /// <summary>Bindable property of ThumbThickness</summary>
  48         [EditorBrowsable(EditorBrowsableState.Never)]
  49         public static readonly BindableProperty ThumbThicknessProperty = BindableProperty.Create(nameof(ThumbThickness), typeof(float), typeof(Scrollbar), default(float), propertyChanged: (bindable, oldValue, newValue) =>
  50         {
  51             var instance = ((Scrollbar)bindable);
  52             var thickness = (float?)newValue;
  53
  54             ((ScrollbarStyle)instance.viewStyle).ThumbThickness = thickness;
  55             instance.UpdateThumbThickness(thickness ?? 0);
  56         },
  57         defaultValueCreator: (bindable) =>
  58         {
  59             return ((ScrollbarStyle)((Scrollbar)bindable).viewStyle)?.ThumbThickness ?? 0;
  60         });
  61
  62         /// <summary>Bindable property of TrackColor</summary>
  63         [EditorBrowsable(EditorBrowsableState.Never)]
  64         public static readonly BindableProperty TrackColorProperty = BindableProperty.Create(nameof(TrackColor), typeof(Color), typeof(Scrollbar), null, propertyChanged: (bindable, oldValue, newValue) =>
  65         {
  66             var instance = ((Scrollbar)bindable);
  67             var color = (Color)newValue;
  68
  69             ((ScrollbarStyle)instance.viewStyle).TrackColor = color;
  70             instance.UpdateTrackColor(color);
  71         },
  72         defaultValueCreator: (bindable) =>
  73         {
  74             return ((ScrollbarStyle)((Scrollbar)bindable).viewStyle)?.TrackColor;
  75         });
  76
  77         /// <summary>Bindable property of ThumbColor</summary>
  78         [EditorBrowsable(EditorBrowsableState.Never)]
  79         public static readonly BindableProperty ThumbColorProperty = BindableProperty.Create(nameof(ThumbColor), typeof(Color), typeof(Scrollbar), null, propertyChanged: (bindable, oldValue, newValue) =>
  80         {
  81             var instance = ((Scrollbar)bindable);
  82             var color = (Color)newValue;
  83
  84             ((ScrollbarStyle)instance.viewStyle).ThumbColor = color;
  85             instance.UpdateThumbColor(color);
  86         },
  87         defaultValueCreator: (bindable) =>
  88         {
  89             return ((ScrollbarStyle)((Scrollbar)bindable).viewStyle)?.ThumbColor;
  90         });
  91
  92         /// <summary>Bindable property of TrackPadding</summary>
  93         [EditorBrowsable(EditorBrowsableState.Never)]
  94         public static readonly BindableProperty TrackPaddingProperty = BindableProperty.Create(nameof(TrackPadding), typeof(Extents), typeof(Scrollbar), null, propertyChanged: (bindable, oldValue, newValue) =>
  95         {
  96             var instance = ((Scrollbar)bindable);
  97             var trackPadding = (Extents)newValue;
  98
  99             ((ScrollbarStyle)instance.viewStyle).TrackPadding = trackPadding;
 100             instance.UpdateTrackPadding(trackPadding);
 101         },
 102         defaultValueCreator: (bindable) =>
 103         {
 104             return ((ScrollbarStyle)((Scrollbar)bindable).viewStyle)?.TrackPadding;
 105         });
 106
 107         private ColorVisual trackVisual;
 108         private ColorVisual thumbVisual;
 109         private Animation thumbPositionAnimation;
 110         private Animation thumbSizeAnimation;
 111         private Calculator calculator;
 112         private Size containerSize = new Size(0, 0);
 113
 114         #endregion Fields
 115
 116
 117         #region Constructors
 118
 119         /// <summary>
 120         /// Create an empty Scrollbar.
 121         /// </summary>
 122         public Scrollbar() : base(new ScrollbarStyle())
 123         {
 124         }
 125
 126         /// <summary>
 127         /// Create a Scrollbar and initialize with properties.
 128         /// </summary>
 129         /// <param name="contentLength">The length of the scrollable content area.</param>
 130         /// <param name="viewportLength">The length of the viewport representing the amount of visible content.</param>
 131         /// <param name="currentPosition">The current position of the viewport in scrollable content area. This is the viewport's top position if the scroller is vertical, otherwise, left.</param>
 132         /// <param name="isHorizontal">Whether the direction of scrolling is horizontal or not. It is vertical by default.</param>
 133         [EditorBrowsable(EditorBrowsableState.Never)]
 134         public Scrollbar(float contentLength, float viewportLength, float currentPosition, bool isHorizontal = false) : base(new ScrollbarStyle())
 135         {
 136             Initialize(contentLength, viewportLength, currentPosition, isHorizontal);
 137         }
 138
 139         /// <summary>
 140         /// Create an empty Scrollbar with a ScrollbarStyle instance to set style properties.
 141         /// </summary>
 142         [EditorBrowsable(EditorBrowsableState.Never)]
 143         public Scrollbar(ScrollbarStyle style) : base(style)
 144         {
 145         }
 146
 147         /// <summary>
 148         /// Static constructor to initialize bindable properties when loading.
 149         /// </summary>
 150         static Scrollbar()
 151         {
 152         }
 153
 154         #endregion Constructors
 155
 156
 157         #region Properties
 158
 159         /// <summary>
 160         /// The thickness of the track.
 161         /// </summary>
 162         [EditorBrowsable(EditorBrowsableState.Never)]
 163         public float TrackThickness
 164         {
 165             get => (float)GetValue(TrackThicknessProperty);
 166             set => SetValue(TrackThicknessProperty, value);
 167         }
 168
 169         /// <summary>
 170         /// The thickness of the thumb.
 171         /// </summary>
 172         [EditorBrowsable(EditorBrowsableState.Never)]
 173         public float ThumbThickness
 174         {
 175             get => (float)GetValue(ThumbThicknessProperty);
 176             set => SetValue(ThumbThicknessProperty, value);
 177         }
 178
 179         /// <summary>
 180         /// The color of the track part.
 181         /// </summary>
 182         [EditorBrowsable(EditorBrowsableState.Never)]
 183         public Color TrackColor
 184         {
 185             get => (Color)GetValue(TrackColorProperty);
 186             set => SetValue(TrackColorProperty, value);
 187         }
 188
 189         /// <summary>
 190         /// The color of the thumb part.
 191         /// </summary>
 192         [EditorBrowsable(EditorBrowsableState.Never)]
 193         public Color ThumbColor
 194         {
 195             get => (Color)GetValue(ThumbColorProperty);
 196             set => SetValue(ThumbColorProperty, value);
 197         }
 198
 199         /// <summary>
 200         /// The padding value of the track.
 201         /// </summary>
 202         [EditorBrowsable(EditorBrowsableState.Never)]
 203         public Extents TrackPadding
 204         {
 205             get => (Extents)GetValue(TrackPaddingProperty);
 206             set => SetValue(TrackPaddingProperty, value);
 207         }
 208
 209         #endregion Properties
 210
 211
 212         #region Methods
 213
 214         /// <inheritdoc/>
 215         [EditorBrowsable(EditorBrowsableState.Never)]
 216         public override void Initialize(float contentLength, float viewportLength, float currentPosition, bool isHorizontal = false)
 217         {
 218             if (isHorizontal)
 219             {
 220                 calculator = new HorizontalCalculator(contentLength > 0.0f ? contentLength : 0.0f, viewportLength, currentPosition);
 221             }
 222             else
 223             {
 224                 calculator = new VerticalCalculator(contentLength > 0.0f ? contentLength : 0.0f, viewportLength, currentPosition);
 225             }
 226
 227             thumbPositionAnimation?.Stop();
 228             thumbPositionAnimation = null;
 229
 230             thumbSizeAnimation?.Stop();
 231             thumbSizeAnimation = null;
 232
 233             Size trackSize = calculator.CalculateTrackSize(TrackThickness, containerSize, TrackPadding);
 234             Vector2 trackPosition = calculator.CalculateTrackPosition(TrackPadding);
 235             Size thumbSize = calculator.CalculateThumbSize(ThumbThickness, trackSize);
 236             Vector2 thumbPosition = calculator.CalculateThumbPosition(trackSize, thumbSize, TrackPadding);
 237
 238             if (trackVisual == null)
 239             {
 240                 trackVisual = new ColorVisual
 241                 {
 242                     SuppressUpdateVisual = true,
 243                     Color = TrackColor,
 244                     SizePolicy = VisualTransformPolicyType.Absolute,
 245                     Origin = calculator.CalculatorTrackAlign(),
 246                     AnchorPoint = calculator.CalculatorTrackAlign(),
 247                     Size = trackSize,
 248                     Position = trackPosition,
 249                 };
 250
 251                 AddVisual("Track", trackVisual);
 252             }
 253             else
 254             {
 255                 trackVisual.Size = trackSize;
 256                 trackVisual.Position = trackPosition;
 257                 trackVisual.UpdateVisual(true);
 258             }
 259
 260             if (thumbVisual == null)
 261             {
 262                 thumbVisual = new ColorVisual
 263                 {
 264                     SuppressUpdateVisual = true,
 265                     MixColor = ThumbColor,
 266                     SizePolicy = VisualTransformPolicyType.Absolute,
 267                     Origin = calculator.CalculatorThumbAlign(),
 268                     AnchorPoint = calculator.CalculatorThumbAlign(),
 269                     Opacity = calculator.CalculateThumbVisibility() ? 1.0f : 0.0f,
 270                     Size = thumbSize,
 271                     Position = thumbPosition,
 272                 };
 273
 274                 AddVisual("Thumb", thumbVisual);
 275             }
 276             else
 277             {
 278                 thumbVisual.Size = thumbSize;
 279                 thumbVisual.Position = thumbPosition;
 280                 thumbVisual.UpdateVisual(true);
 281             }
 282         }
 283
 284         /// <inheritdoc/>
 285         /// <remarks>Please note that, for now, only alpha functions created with BuiltinFunctions are valid when animating. Otherwise, it will be treated as a linear alpha function. </remarks>
 286         [EditorBrowsable(EditorBrowsableState.Never)]
 287         public override void Update(float contentLength, float position, uint durationMs = 0, AlphaFunction alphaFunction = null)
 288         {
 289             if (calculator == null)
 290             {
 291                 return;
 292             }
 293
 294             calculator.contentLength = contentLength > 0.0f ? contentLength : 0.0f;
 295             calculator.currentPosition = position;
 296
 297             thumbVisual.Size = calculator.CalculateThumbSize(ThumbThickness, trackVisual.Size);
 298             thumbVisual.Position = calculator.CalculateThumbScrollPosition(trackVisual.Size, thumbVisual.Position, TrackPadding);
 299             thumbVisual.Opacity = calculator.CalculateThumbVisibility() ? 1.0f : 0.0f;
 300
 301             if (durationMs == 0)
 302             {
 303                 thumbVisual.UpdateVisual(true);
 304
 305                 return;
 306             }
 307
 308             // TODO Support non built-in alpha function for visual trainsition in DALi.
 309             AlphaFunction.BuiltinFunctions builtinAlphaFunction = alphaFunction?.GetBuiltinFunction() ?? AlphaFunction.BuiltinFunctions.Default;
 310
 311             thumbPositionAnimation?.Stop();
 312             thumbPositionAnimation = AnimateVisual(thumbVisual, "position", thumbVisual.Position, 0, (int)durationMs, builtinAlphaFunction);
 313             thumbPositionAnimation.Play();
 314
 315             thumbSizeAnimation?.Stop();
 316             thumbSizeAnimation = AnimateVisual(thumbVisual, "size", thumbVisual.Size, 0, (int)durationMs, builtinAlphaFunction);
 317             thumbSizeAnimation.Play();
 318         }
 319
 320         /// <inheritdoc/>
 321         /// <remarks>Please note that, for now, only alpha functions created with BuiltinFunctions are valid when animating. Otherwise, it will be treated as a linear alpha function. </remarks>
 322         [EditorBrowsable(EditorBrowsableState.Never)]
 323         public override void ScrollTo(float position, uint durationMs = 0, AlphaFunction alphaFunction = null)
 324         {
 325             if (calculator == null)
 326             {
 327                 return;
 328             }
 329
 330             calculator.currentPosition = position;
 331             thumbVisual.Position = calculator.CalculateThumbScrollPosition(trackVisual.Size, thumbVisual.Position, TrackPadding);
 332
 333             if (durationMs == 0)
 334             {
 335                 thumbVisual.UpdateVisual(true);
 336
 337                 return;
 338             }
 339
 340             // TODO Support non built-in alpha function for visual trainsition in DALi.
 341             AlphaFunction.BuiltinFunctions builtinAlphaFunction = alphaFunction?.GetBuiltinFunction() ?? AlphaFunction.BuiltinFunctions.Default;
 342
 343             thumbPositionAnimation?.Stop();
 344             thumbPositionAnimation = AnimateVisual(thumbVisual, "position", thumbVisual.Position, 0, (int)durationMs, builtinAlphaFunction);
 345             thumbPositionAnimation.Play();
 346         }
 347
 348         /// <inheritdoc/>
 349         [EditorBrowsable(EditorBrowsableState.Never)]
 350         public override void OnRelayout(Vector2 size, RelayoutContainer container)
 351         {
 352             base.OnRelayout(size, container);
 353
 354             if (size.Width == containerSize.Width && size.Height == containerSize.Height)
 355             {
 356                 return;
 357             }
 358
 359             containerSize = new Size(size.Width, size.Height);
 360
 361             if (calculator == null)
 362             {
 363                 return;
 364             }
 365
 366             trackVisual.Size = calculator.CalculateTrackSize(TrackThickness, containerSize, TrackPadding);
 367             trackVisual.Position = calculator.CalculateTrackPosition(TrackPadding);
 368             thumbVisual.Size = calculator.CalculateThumbSize(ThumbThickness, trackVisual.Size);
 369             thumbVisual.Position = calculator.CalculateThumbPosition(trackVisual.Size, thumbVisual.Size, TrackPadding);
 370
 371             trackVisual.UpdateVisual(true);
 372             thumbVisual.UpdateVisual(true);
 373         }
 374
 375         /// <inheritdoc/>
 376         [EditorBrowsable(EditorBrowsableState.Never)]
 377         protected override ViewStyle GetViewStyle()
 378         {
 379             return new ScrollbarStyle();
 380         }
 381
 382         /// <summary>
 383         /// Update TrackThickness property of the scrollbar.
 384         /// </summary>
 385         /// <param name="thickness">The width of the track.</param>
 386         [EditorBrowsable(EditorBrowsableState.Never)]
 387         protected virtual void UpdateTrackThickness(float thickness)
 388         {
 389             if (trackVisual == null)
 390             {
 391                 return;
 392             }
 393
 394             trackVisual.Size = calculator.CalculateTrackSize(thickness, containerSize, TrackPadding);
 395             trackVisual.UpdateVisual(true);
 396         }
 397
 398         /// <summary>
 399         /// Update ThumbThickness property of the scrollbar.
 400         /// </summary>
 401         /// <param name="thickness">The width of the track.</param>
 402         [EditorBrowsable(EditorBrowsableState.Never)]
 403         protected virtual void UpdateThumbThickness(float thickness)
 404         {
 405             if (thumbVisual == null)
 406             {
 407                 return;
 408             }
 409
 410             thumbVisual.Size = calculator.CalculateThumbSize(thickness, trackVisual.Size);
 411             thumbVisual.UpdateVisual(true);
 412         }
 413
 414         /// <summary>
 415         /// Update TrackColor property of the scrollbar.
 416         /// </summary>
 417         /// <param name="color">The color of the track.</param>
 418         [EditorBrowsable(EditorBrowsableState.Never)]
 419         protected virtual void UpdateTrackColor(Color color)
 420         {
 421             if (trackVisual == null)
 422             {
 423                 return;
 424             }
 425
 426             trackVisual.MixColor = color;
 427             trackVisual.UpdateVisual(true);
 428         }
 429
 430         /// <summary>
 431         /// Update ThumbColor property of the scrollbar.
 432         /// </summary>
 433         /// <param name="color">The color of the thumb.</param>
 434         [EditorBrowsable(EditorBrowsableState.Never)]
 435         protected virtual void UpdateThumbColor(Color color)
 436         {
 437             if (thumbVisual == null)
 438             {
 439                 return;
 440             }
 441
 442             thumbVisual.MixColor = color;
 443             thumbVisual.UpdateVisual(true);
 444         }
 445
 446         /// <summary>
 447         /// Update TrackPadding property of the scrollbar.
 448         /// </summary>
 449         /// <param name="trackPadding">The padding of the track.</param>
 450         protected virtual void UpdateTrackPadding(Extents trackPadding)
 451         {
 452             if (calculator == null)
 453             {
 454                 return;
 455             }
 456
 457             trackVisual.Size = calculator.CalculateTrackSize(TrackThickness, containerSize, trackPadding);
 458             trackVisual.Position = calculator.CalculateTrackPosition(trackPadding);
 459             thumbVisual.Size = calculator.CalculateThumbSize(ThumbThickness, trackVisual.Size);
 460             thumbVisual.Position = calculator.CalculateThumbPaddingPosition(trackVisual.Size, thumbVisual.Size, thumbVisual.Position, trackPadding);
 461
 462             trackVisual.UpdateVisual(true);
 463             thumbVisual.UpdateVisual(true);
 464         }
 465
 466         #endregion Methods
 467
 468
 469         #region Classes
 470
 471         private abstract class Calculator
 472         {
 473             public float contentLength;
 474             public float visibleLength;
 475             public float currentPosition;
 476
 477             public Calculator(float contentLength, float visibleLength, float currentPosition)
 478             {
 479                 this.contentLength = contentLength;
 480                 this.visibleLength = visibleLength;
 481                 this.currentPosition = currentPosition;
 482             }
 483
 484             public bool CalculateThumbVisibility()
 485             {
 486                 return contentLength > visibleLength;
 487             }
 488
 489             public abstract Visual.AlignType CalculatorTrackAlign();
 490             public abstract Visual.AlignType CalculatorThumbAlign();
 491             public abstract Size CalculateTrackSize(float thickness, Size containerSize, Extents trackPadding);
 492             public abstract Vector2 CalculateTrackPosition(Extents trackPadding);
 493             public abstract Size CalculateThumbSize(float thickness, Size trackSize);
 494             public abstract Vector2 CalculateThumbPosition(Size trackSize, Size thumbSize, Extents trackPadding);
 495             public abstract Vector2 CalculateThumbPaddingPosition(Size trackSize, Size thumbSize, Vector2 thumbCurrentPosition, Extents trackPadding);
 496             public abstract Vector2 CalculateThumbScrollPosition(Size trackSize, Vector2 thumbCurrentPosition, Extents trackPadding);
 497         }
 498
 499         private class HorizontalCalculator : Calculator
 500         {
 501             public HorizontalCalculator(float contentLength, float visibleLength, float currentPosition) : base(contentLength, visibleLength, currentPosition)
 502             {
 503             }
 504
 505             public override Visual.AlignType CalculatorTrackAlign()
 506             {
 507                 return Visual.AlignType.BottomCenter;
 508             }
 509
 510             public override Visual.AlignType CalculatorThumbAlign()
 511             {
 512                 return Visual.AlignType.BottomBegin;
 513             }
 514
 515             public override Size CalculateTrackSize(float thickness, Size containerSize, Extents trackPadding)
 516             {
 517                 return new Size(containerSize.Width - trackPadding.Start - trackPadding.End, thickness);
 518             }
 519
 520             public override Vector2 CalculateTrackPosition(Extents trackPadding)
 521             {
 522                 return new Vector2(0, -trackPadding.Bottom);
 523             }
 524
 525             public override Size CalculateThumbSize(float thickness, Size trackSize)
 526             {
 527                 return new Size(trackSize.Width * visibleLength / contentLength, thickness);
 528             }
 529
 530             public override Vector2 CalculateThumbPosition(Size trackSize, Size thumbSize, Extents trackPadding)
 531             {
 532                 float padding = ((trackSize.Height - thumbSize.Height) / 2.0f) + trackPadding.Bottom;
 533                 float pos = Math.Min(Math.Max(currentPosition, 0.0f), contentLength - visibleLength);
 534                 return new Vector2(trackPadding.Start + trackSize.Width * pos / contentLength, -padding);
 535             }
 536
 537             public override Vector2 CalculateThumbPaddingPosition(Size trackSize, Size thumbSize, Vector2 thumbCurrentPosition, Extents trackPadding)
 538             {
 539                 float padding = ((trackSize.Height - thumbSize.Height) / 2.0f) + trackPadding.Bottom;
 540                 return new Vector2(thumbCurrentPosition.X, -padding);
 541             }
 542
 543             public override Vector2 CalculateThumbScrollPosition(Size trackSize, Vector2 thumbCurrentPosition, Extents trackPadding)
 544             {
 545                 float pos = Math.Min(Math.Max(currentPosition, 0.0f), contentLength - visibleLength);
 546                 return new Vector2(trackPadding.Start + trackSize.Width * pos / contentLength, thumbCurrentPosition.Y);
 547             }
 548         }
 549
 550         private class VerticalCalculator : Calculator
 551         {
 552             public VerticalCalculator(float contentLength, float visibleLength, float currentPosition) : base(contentLength, visibleLength, currentPosition)
 553             {
 554             }
 555
 556             public override Visual.AlignType CalculatorTrackAlign()
 557             {
 558                 return Visual.AlignType.CenterEnd;
 559             }
 560
 561             public override Visual.AlignType CalculatorThumbAlign()
 562             {
 563                 return Visual.AlignType.TopEnd;
 564             }
 565
 566             public override Size CalculateTrackSize(float thickness, Size containerSize, Extents trackPadding)
 567             {
 568                 return new Size(thickness, containerSize.Height - trackPadding.Top - trackPadding.Bottom);
 569             }
 570
 571             public override Vector2 CalculateTrackPosition(Extents trackPadding)
 572             {
 573                 return new Vector2(-trackPadding.End, 0);
 574             }
 575
 576             public override Size CalculateThumbSize(float thickness, Size trackSize)
 577             {
 578                 return new Size(thickness, trackSize.Height * visibleLength / contentLength);
 579             }
 580
 581             public override Vector2 CalculateThumbPosition(Size trackSize, Size thumbSize, Extents trackPadding)
 582             {
 583                 float padding = ((trackSize.Width - thumbSize.Width) / 2.0f) + trackPadding.End;
 584                 float pos = Math.Min(Math.Max(currentPosition, 0.0f), contentLength - visibleLength);
 585                 return new Vector2(-padding, trackPadding.Top + trackSize.Height * pos / contentLength);
 586             }
 587
 588             public override Vector2 CalculateThumbPaddingPosition(Size trackSize, Size thumbSize, Vector2 thumbCurrentPosition, Extents trackPadding)
 589             {
 590                 float padding = ((trackSize.Width - thumbSize.Width) / 2.0f) + trackPadding.End;
 591                 return new Vector2(-padding, thumbCurrentPosition.Y);
 592             }
 593
 594             public override Vector2 CalculateThumbScrollPosition(Size trackSize, Vector2 thumbPosition, Extents trackPadding)
 595             {
 596                 float pos = Math.Min(Math.Max(currentPosition, 0.0f), contentLength - visibleLength);
 597                 return new Vector2(thumbPosition.X, trackPadding.Top + trackSize.Height * pos / contentLength);
 598             }
 599         }
 600
 601         #endregion Classes
 602     }
 603 }