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

   1 /* Copyright (c) 2019 Samsung Electronics Co., Ltd.
   2  *
   3  * Licensed under the Apache License, Version 2.0 (the "License");
   4  * you may not use this file except in compliance with the License.
   5  * You may obtain a copy of the License at
   6  *
   7  * http://www.apache.org/licenses/LICENSE-2.0
   8  *
   9  * Unless required by applicable law or agreed to in writing, software
  10  * distributed under the License is distributed on an "AS IS" BASIS,
  11  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12  * See the License for the specific language governing permissions and
  13  * limitations under the License.
  14  *
  15  */
  16 using System;
  17 using Tizen.NUI.BaseComponents;
  18 using System.ComponentModel;
  19 using System.Diagnostics;
  20
  21 namespace Tizen.NUI.Components
  22 {
  23     /// <summary>
  24     /// [Draft] This class provides a View that can scroll a single View with a layout. This View can be a nest of Views.
  25     /// </summary>
  26     /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API.
  27     [EditorBrowsable(EditorBrowsableState.Never)]
  28     public class ScrollableBase : Control
  29     {
  30             static bool LayoutDebugScrollableBase = false; // Debug flag
  31         private Direction mScrollingDirection = Direction.Vertical;
  32         private bool mScrollEnabled = true;
  33         private int mPageWidth = 0;
  34
  35         private class ScrollableBaseCustomLayout : LayoutGroup
  36         {
  37             protected override void OnMeasure(MeasureSpecification widthMeasureSpec, MeasureSpecification heightMeasureSpec)
  38             {
  39                 Extents padding = Padding;
  40                 float totalHeight = padding.Top + padding.Bottom;
  41                 float totalWidth = padding.Start + padding.End;
  42
  43                 MeasuredSize.StateType childWidthState = MeasuredSize.StateType.MeasuredSizeOK;
  44                 MeasuredSize.StateType childHeightState = MeasuredSize.StateType.MeasuredSizeOK;
  45
  46                 Direction scrollingDirection = Direction.Vertical;
  47                 ScrollableBase scrollableBase = this.Owner as ScrollableBase;
  48                 if (scrollableBase)
  49                 {
  50                    scrollingDirection = scrollableBase.ScrollingDirection;
  51                 }
  52
  53                 // measure child, should be a single scrolling child
  54                 foreach( LayoutItem childLayout in LayoutChildren )
  55                 {
  56                     if (childLayout != null)
  57                     {
  58                         // Get size of child
  59                         // Use an Unspecified MeasureSpecification mode so scrolling child is not restricted to it's parents size in Height (for vertical scrolling)
  60                         // or Width for horizontal scrolling
  61                         MeasureSpecification unrestrictedMeasureSpec = new MeasureSpecification( heightMeasureSpec.Size, MeasureSpecification.ModeType.Unspecified);
  62
  63                         if (scrollingDirection == Direction.Vertical)
  64                         {
  65                             MeasureChild( childLayout, widthMeasureSpec, unrestrictedMeasureSpec );  // Height unrestricted by parent
  66                         }
  67                         else
  68                         {
  69                             MeasureChild( childLayout, unrestrictedMeasureSpec, heightMeasureSpec );  // Width unrestricted by parent
  70                         }
  71
  72                         float childWidth = childLayout.MeasuredWidth.Size.AsDecimal();
  73                         float childHeight = childLayout.MeasuredHeight.Size.AsDecimal();
  74
  75                         // Determine the width and height needed by the children using their given position and size.
  76                         // Children could overlap so find the left most and right most child.
  77                         Position2D childPosition = childLayout.Owner.Position2D;
  78                         float childLeft = childPosition.X;
  79                         float childTop = childPosition.Y;
  80
  81                         // Store current width and height needed to contain all children.
  82                         Extents childMargin = childLayout.Margin;
  83                         totalWidth = childWidth + childMargin.Start + childMargin.End;
  84                         totalHeight = childHeight + childMargin.Top + childMargin.Bottom;
  85
  86                         if (childLayout.MeasuredWidth.State == MeasuredSize.StateType.MeasuredSizeTooSmall)
  87                         {
  88                             childWidthState = MeasuredSize.StateType.MeasuredSizeTooSmall;
  89                         }
  90                         if (childLayout.MeasuredWidth.State == MeasuredSize.StateType.MeasuredSizeTooSmall)
  91                         {
  92                             childHeightState = MeasuredSize.StateType.MeasuredSizeTooSmall;
  93                         }
  94                     }
  95                 }
  96
  97
  98                 MeasuredSize widthSizeAndState = ResolveSizeAndState(new LayoutLength(totalWidth + Padding.Start + Padding.End), widthMeasureSpec, MeasuredSize.StateType.MeasuredSizeOK);
  99                 MeasuredSize heightSizeAndState = ResolveSizeAndState(new LayoutLength(totalHeight + Padding.Top + Padding.Bottom), heightMeasureSpec, MeasuredSize.StateType.MeasuredSizeOK);
 100                 totalWidth = widthSizeAndState.Size.AsDecimal();
 101                 totalHeight = heightSizeAndState.Size.AsDecimal();
 102
 103                 // Ensure layout respects it's given minimum size
 104                 totalWidth = Math.Max( totalWidth, SuggestedMinimumWidth.AsDecimal() );
 105                 totalHeight = Math.Max( totalHeight, SuggestedMinimumHeight.AsDecimal() );
 106
 107                 widthSizeAndState.State = childWidthState;
 108                 heightSizeAndState.State = childHeightState;
 109
 110                 SetMeasuredDimensions( ResolveSizeAndState( new LayoutLength(totalWidth + Padding.Start + Padding.End), widthMeasureSpec, childWidthState ),
 111                                        ResolveSizeAndState( new LayoutLength(totalHeight + Padding.Top + Padding.Bottom), heightMeasureSpec, childHeightState ) );
 112
 113                 // Size of ScrollableBase is changed. Change Page width too.
 114                 scrollableBase.mPageWidth = (int)MeasuredWidth.Size.AsRoundedValue();
 115             }
 116
 117             protected override void OnLayout(bool changed, LayoutLength left, LayoutLength top, LayoutLength right, LayoutLength bottom)
 118             {
 119                 foreach( LayoutItem childLayout in LayoutChildren )
 120                 {
 121                     if( childLayout != null )
 122                     {
 123                         LayoutLength childWidth = childLayout.MeasuredWidth.Size;
 124                         LayoutLength childHeight = childLayout.MeasuredHeight.Size;
 125
 126                         Position2D childPosition = childLayout.Owner.Position2D;
 127                         Extents padding = Padding;
 128                         Extents childMargin = childLayout.Margin;
 129
 130                         LayoutLength childLeft = new LayoutLength(childPosition.X + childMargin.Start + padding.Start);
 131                         LayoutLength childTop = new LayoutLength(childPosition.Y + childMargin.Top + padding.Top);
 132
 133                         childLayout.Layout( childLeft, childTop, childLeft + childWidth, childTop + childHeight );
 134                     }
 135                 }
 136             }
 137         } //  ScrollableBaseCustomLayout
 138
 139         /// <summary>
 140         /// The direction axis to scroll.
 141         /// </summary>
 142         /// <since_tizen> 6 </since_tizen>
 143         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API.
 144         [EditorBrowsable(EditorBrowsableState.Never)]
 145         public enum Direction
 146         {
 147             /// <summary>
 148             /// Horizontal axis.
 149             /// </summary>
 150             /// <since_tizen> 6 </since_tizen>
 151             Horizontal,
 152
 153             /// <summary>
 154             /// Vertical axis.
 155             /// </summary>
 156             /// <since_tizen> 6 </since_tizen>
 157             Vertical
 158         }
 159
 160         /// <summary>
 161         /// [Draft] Configurable speed threshold that register the gestures as a flick.
 162         /// If the flick speed less than the threshold then will not be considered a flick.
 163         /// </summary>
 164         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API.
 165         [EditorBrowsable(EditorBrowsableState.Never)]
 166         public float FlickThreshold { get; set; } = 0.2f;
 167
 168         /// <summary>
 169         /// [Draft] Configurable duration modifer for the flick animation.
 170         /// Determines the speed of the scroll, large value results in a longer flick animation. Range (0.1 - 1.0)
 171         /// </summary>
 172         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 173         [EditorBrowsable(EditorBrowsableState.Never)]
 174         public float FlickAnimationSpeed { get; set; } = 0.4f;
 175
 176         /// <summary>
 177         /// [Draft] Configurable modifer for the distance to be scrolled when flicked detected.
 178         /// It a ratio of the ScrollableBase's length. (not child's length).
 179         /// First value is the ratio of the distance to scroll with the weakest flick.
 180         /// Second value is the ratio of the distance to scroll with the strongest flick.
 181         /// Second > First.
 182         /// </summary>
 183         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 184         [EditorBrowsable(EditorBrowsableState.Never)]
 185         public Vector2 FlickDistanceMultiplierRange { get; set; } = new Vector2(0.6f, 1.8f);
 186
 187         /// <summary>
 188         /// [Draft] Scrolling direction mode.
 189         /// Default is Vertical scrolling.
 190         /// </summary>
 191         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 192         [EditorBrowsable(EditorBrowsableState.Never)]
 193         public Direction ScrollingDirection
 194         {
 195             get
 196             {
 197                 return mScrollingDirection;
 198             }
 199             set
 200             {
 201                 if(value != mScrollingDirection)
 202                 {
 203                     mScrollingDirection = value;
 204                     mPanGestureDetector.RemoveDirection(value == Direction.Horizontal ? PanGestureDetector.DirectionVertical : PanGestureDetector.DirectionHorizontal);
 205                     mPanGestureDetector.AddDirection(value == Direction.Horizontal ? PanGestureDetector.DirectionHorizontal : PanGestureDetector.DirectionVertical);
 206                 }
 207             }
 208         }
 209
 210         /// <summary>
 211         /// [Draft] Enable or disable scrolling.
 212         /// </summary>
 213         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 214         [EditorBrowsable(EditorBrowsableState.Never)]
 215         public bool ScrollEnabled
 216         {
 217             get
 218             {
 219                 return mScrollEnabled;
 220             }
 221             set
 222             {
 223                 if (value != mScrollEnabled)
 224                 {
 225                     mScrollEnabled = value;
 226                     if(mScrollEnabled)
 227                     {
 228                         mPanGestureDetector.Detected += OnPanGestureDetected;
 229                         mTapGestureDetector.Detected += OnTapGestureDetected;
 230                     }
 231                     else
 232                     {
 233                         mPanGestureDetector.Detected -= OnPanGestureDetected;
 234                         mTapGestureDetector.Detected -= OnTapGestureDetected;
 235                     }
 236                 }
 237             }
 238         }
 239
 240         /// <summary>
 241         /// [Draft] Pages mode, enables moving to the next or return to current page depending on pan displacement.
 242         /// Default is false.
 243         /// </summary>
 244         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 245         [EditorBrowsable(EditorBrowsableState.Never)]
 246         public bool SnapToPage { set; get; } = false;
 247
 248         /// <summary>
 249         /// [Draft] Get current page.
 250         /// Working propery with SnapToPage property.
 251         /// </summary>
 252         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 253         [EditorBrowsable(EditorBrowsableState.Never)]
 254         public int CurrentPage { get; private set; } = 0;
 255
 256         /// <summary>
 257         /// [Draft] Duration of scroll animation.
 258         /// </summary>
 259         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 260         [EditorBrowsable(EditorBrowsableState.Never)]
 261
 262         public int ScrollDuration { set; get; } = 125;
 263         /// <summary>
 264         /// [Draft] Scroll Available area.
 265         /// </summary>
 266         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 267         [EditorBrowsable(EditorBrowsableState.Never)]
 268         public Rectangle ScrollAvailableArea { set; get; }
 269
 270         /// <summary>
 271         /// ScrollEventArgs is a class to record scroll event arguments which will sent to user.
 272         /// </summary>
 273         /// <since_tizen> 6 </since_tizen>
 274         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 275         [EditorBrowsable(EditorBrowsableState.Never)]
 276         public class ScrollEventArgs : EventArgs
 277         {
 278             Position position;
 279
 280             /// <summary>
 281             /// Default constructor.
 282             /// </summary>
 283             /// <param name="position">Current scroll position</param>
 284             /// <since_tizen> 6 </since_tizen>
 285             /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 286             public ScrollEventArgs(Position position)
 287             {
 288                 this.position = position;
 289             }
 290
 291             /// <summary>
 292             /// [Draft] Current scroll position.
 293             /// </summary>
 294             /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 295             [EditorBrowsable(EditorBrowsableState.Never)]
 296             public Position Position
 297             {
 298                 get
 299                 {
 300                     return position;
 301                 }
 302             }
 303         }
 304
 305         /// <summary>
 306         /// An event emitted when user starts dragging ScrollableBase, user can subscribe or unsubscribe to this event handler.<br />
 307         /// </summary>
 308         /// <since_tizen> 6 </since_tizen>
 309         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 310         [EditorBrowsable(EditorBrowsableState.Never)]
 311         public event EventHandler<ScrollEventArgs> ScrollDragStartEvent;
 312
 313         /// <summary>
 314         /// An event emitted when user stops dragging ScrollableBase, user can subscribe or unsubscribe to this event handler.<br />
 315         /// </summary>
 316         /// <since_tizen> 6 </since_tizen>
 317         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 318         [EditorBrowsable(EditorBrowsableState.Never)]
 319         public event EventHandler<ScrollEventArgs> ScrollDragEndEvent;
 320
 321
 322         /// <summary>
 323         /// An event emitted when the scrolling slide animation starts, user can subscribe or unsubscribe to this event handler.<br />
 324         /// </summary>
 325         /// <since_tizen> 6 </since_tizen>
 326         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 327         [EditorBrowsable(EditorBrowsableState.Never)]
 328         public event EventHandler<ScrollEventArgs> ScrollAnimationStartEvent;
 329
 330         /// <summary>
 331         /// An event emitted when the scrolling slide animation ends, user can subscribe or unsubscribe to this event handler.<br />
 332         /// </summary>
 333         /// <since_tizen> 6 </since_tizen>
 334         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 335         [EditorBrowsable(EditorBrowsableState.Never)]
 336         public event EventHandler<ScrollEventArgs> ScrollAnimationEndEvent;
 337
 338
 339         /// <summary>
 340         /// An event emitted when scrolling, user can subscribe or unsubscribe to this event handler.<br />
 341         /// </summary>
 342         /// <since_tizen> 6 </since_tizen>
 343         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 344         [EditorBrowsable(EditorBrowsableState.Never)]
 345         public event EventHandler<ScrollEventArgs> ScrollEvent;
 346
 347         private Animation scrollAnimation;
 348         private float maxScrollDistance;
 349         private float childTargetPosition = 0.0f;
 350         private PanGestureDetector mPanGestureDetector;
 351         private TapGestureDetector mTapGestureDetector;
 352         private View mScrollingChild;
 353         private float multiplier =1.0f;
 354         private bool scrolling = false;
 355         private float ratioOfScreenWidthToCompleteScroll = 0.5f;
 356         private float totalDisplacementForPan = 0.0f;
 357
 358         // If false then can only flick pages when the current animation/scroll as ended.
 359         private bool flickWhenAnimating = false;
 360         private PropertyNotification propertyNotification;
 361
 362         /// <summary>
 363         /// [Draft] Constructor
 364         /// </summary>
 365         /// <since_tizen> 6 </since_tizen>
 366         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 367         [EditorBrowsable(EditorBrowsableState.Never)]
 368         public ScrollableBase() : base()
 369         {
 370             mPanGestureDetector = new PanGestureDetector();
 371             mPanGestureDetector.Attach(this);
 372             mPanGestureDetector.AddDirection(PanGestureDetector.DirectionVertical);
 373             mPanGestureDetector.Detected += OnPanGestureDetected;
 374
 375             mTapGestureDetector = new TapGestureDetector();
 376             mTapGestureDetector.Attach(this);
 377             mTapGestureDetector.Detected += OnTapGestureDetected;
 378
 379
 380             ClippingMode = ClippingModeType.ClipToBoundingBox;
 381
 382             mScrollingChild = new View();
 383             mScrollingChild.Name = "DefaultScrollingChild";
 384
 385             Layout = new ScrollableBaseCustomLayout();
 386         }
 387
 388         private void OnPropertyChanged(object source, PropertyNotification.NotifyEventArgs args)
 389         {
 390             OnScroll();
 391         }
 392
 393         /// <summary>
 394         /// Called after a child has been added to the owning view.
 395         /// </summary>
 396         /// <param name="view">The child which has been added.</param>
 397         /// <since_tizen> 6 </since_tizen>
 398         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 399         [EditorBrowsable(EditorBrowsableState.Never)]
 400         public override void OnChildAdd(View view)
 401         {
 402             if(mScrollingChild.Name != "DefaultScrollingChild")
 403             {
 404                 propertyNotification.Notified -= OnPropertyChanged;
 405                 mScrollingChild.RemovePropertyNotification(propertyNotification);
 406             }
 407
 408             mScrollingChild = view;
 409             propertyNotification = mScrollingChild?.AddPropertyNotification("position", PropertyCondition.Step(1.0f));
 410             propertyNotification.Notified += OnPropertyChanged;
 411
 412             {
 413                 if (Children.Count > 1)
 414                     Log.Error("ScrollableBase", $"Only 1 child should be added to ScrollableBase.");
 415             }
 416         }
 417
 418         /// <summary>
 419         /// Called after a child has been removed from the owning view.
 420         /// </summary>
 421         /// <param name="view">The child which has been removed.</param>
 422         /// <since_tizen> 6 </since_tizen>
 423         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 424         [EditorBrowsable(EditorBrowsableState.Never)]
 425         public override void OnChildRemove(View view)
 426         {
 427             propertyNotification.Notified -= OnPropertyChanged;
 428             mScrollingChild.RemovePropertyNotification(propertyNotification);
 429
 430             mScrollingChild = new View();
 431         }
 432
 433
 434         /// <summary>
 435         /// Scrolls to the item at the specified index.
 436         /// </summary>
 437         /// <param name="index">Index of item.</param>
 438         /// <since_tizen> 6 </since_tizen>
 439         /// This may be public opened in tizen_6.0 after ACR done. Before ACR, need to be hidden as inhouse API
 440         [EditorBrowsable(EditorBrowsableState.Never)]
 441         public void ScrollToIndex(int index)
 442         {
 443             if(mScrollingChild.ChildCount-1 < index || index < 0)
 444             {
 445                 return;
 446             }
 447
 448             if(SnapToPage)
 449             {
 450                 CurrentPage = index;
 451             }
 452
 453             maxScrollDistance = CalculateMaximumScrollDistance();
 454
 455             float targetPosition = Math.Min(ScrollingDirection == Direction.Vertical ? mScrollingChild.Children[index].Position.Y : mScrollingChild.Children[index].Position.X, maxScrollDistance);
 456             AnimateChildTo(ScrollDuration, -targetPosition);
 457         }
 458
 459         private void OnScrollDragStart()
 460         {
 461             ScrollEventArgs eventArgs = new ScrollEventArgs(mScrollingChild.CurrentPosition);
 462             ScrollDragStartEvent?.Invoke(this, eventArgs);
 463         }
 464
 465         private void OnScrollDragEnd()
 466         {
 467             ScrollEventArgs eventArgs = new ScrollEventArgs(mScrollingChild.CurrentPosition);
 468             ScrollDragEndEvent?.Invoke(this, eventArgs);
 469         }
 470
 471         private void OnScrollAnimationStart()
 472         {
 473             ScrollEventArgs eventArgs = new ScrollEventArgs(mScrollingChild.CurrentPosition);
 474             ScrollAnimationStartEvent?.Invoke(this, eventArgs);
 475         }
 476
 477         private void OnScrollAnimationEnd()
 478         {
 479             ScrollEventArgs eventArgs = new ScrollEventArgs(mScrollingChild.CurrentPosition);
 480             ScrollAnimationEndEvent?.Invoke(this, eventArgs);
 481         }
 482
 483         private void OnScroll()
 484         {
 485             ScrollEventArgs eventArgs = new ScrollEventArgs(mScrollingChild.CurrentPosition);
 486             ScrollEvent?.Invoke(this, eventArgs);
 487         }
 488
 489         private void StopScroll()
 490         {
 491             if (scrollAnimation != null)
 492             {
 493                 if (scrollAnimation.State == Animation.States.Playing)
 494                 {
 495                     Debug.WriteLineIf(LayoutDebugScrollableBase, "StopScroll Animation Playing");
 496                     scrollAnimation.Stop(Animation.EndActions.Cancel);
 497                     OnScrollAnimationEnd();
 498                 }
 499                 scrollAnimation.Clear();
 500             }
 501         }
 502
 503         // static constructor registers the control type
 504         static ScrollableBase()
 505         {
 506             // ViewRegistry registers control type with DALi type registry
 507             // also uses introspection to find any properties that need to be registered with type registry
 508             CustomViewRegistry.Instance.Register(CreateInstance, typeof(ScrollableBase));
 509         }
 510
 511         internal static CustomView CreateInstance()
 512         {
 513             return new ScrollableBase();
 514         }
 515
 516         private void AnimateChildTo(int duration, float axisPosition)
 517         {
 518             Debug.WriteLineIf(LayoutDebugScrollableBase, "AnimationTo Animation Duration:" + duration + " Destination:" + axisPosition);
 519
 520             StopScroll(); // Will replace previous animation so will stop existing one.
 521
 522             if (scrollAnimation == null)
 523             {
 524                 scrollAnimation = new Animation();
 525                 scrollAnimation.Finished += ScrollAnimationFinished;
 526             }
 527
 528             scrollAnimation.Duration = duration;
 529             scrollAnimation.DefaultAlphaFunction = new AlphaFunction(AlphaFunction.BuiltinFunctions.EaseOutSine);
 530             scrollAnimation.AnimateTo(mScrollingChild, (ScrollingDirection == Direction.Horizontal) ? "PositionX" : "PositionY", axisPosition);
 531             scrolling = true;
 532             OnScrollAnimationStart();
 533             scrollAnimation.Play();
 534         }
 535
 536         private void ScrollBy(float displacement, bool animate)
 537         {
 538             if (GetChildCount() == 0 || displacement == 0 || maxScrollDistance < 0)
 539             {
 540                 return;
 541             }
 542
 543             float childCurrentPosition = (ScrollingDirection == Direction.Horizontal) ? mScrollingChild.PositionX: mScrollingChild.PositionY;
 544
 545             Debug.WriteLineIf(LayoutDebugScrollableBase, "ScrollBy childCurrentPosition:" + childCurrentPosition +
 546                                                    " displacement:" + displacement,
 547                                                    " maxScrollDistance:" + maxScrollDistance );
 548
 549             childTargetPosition = childCurrentPosition + displacement; // child current position + gesture displacement
 550
 551             if(ScrollAvailableArea != null)
 552             {
 553                 float minScrollPosition = ScrollingDirection == Direction.Horizontal? ScrollAvailableArea.X:ScrollAvailableArea.Y;
 554                 float maxScrollPosition = ScrollingDirection == Direction.Horizontal?
 555                                         ScrollAvailableArea.X + ScrollAvailableArea.Width:
 556                                         ScrollAvailableArea.Y + ScrollAvailableArea.Height;
 557
 558                 childTargetPosition = Math.Min( -minScrollPosition, childTargetPosition );
 559                 childTargetPosition = Math.Max( -maxScrollPosition, childTargetPosition );
 560             }
 561             else
 562             {
 563                 childTargetPosition = Math.Min(0, childTargetPosition);
 564                 childTargetPosition = Math.Max(-maxScrollDistance, childTargetPosition);
 565             }
 566
 567             Debug.WriteLineIf( LayoutDebugScrollableBase, "ScrollBy currentAxisPosition:" + childCurrentPosition + "childTargetPosition:" + childTargetPosition);
 568
 569             if (animate)
 570             {
 571                 // Calculate scroll animaton duration
 572                 float scrollDistance = Math.Abs(displacement);
 573                 int duration = (int)((320*FlickAnimationSpeed) + (scrollDistance * FlickAnimationSpeed));
 574                 Debug.WriteLineIf(LayoutDebugScrollableBase, "Scroll Animation Duration:" + duration + " Distance:" + scrollDistance);
 575
 576                 AnimateChildTo(duration, childTargetPosition);
 577             }
 578             else
 579             {
 580                 // Set position of scrolling child without an animation
 581                 if (ScrollingDirection == Direction.Horizontal)
 582                 {
 583                     mScrollingChild.PositionX = childTargetPosition;
 584                 }
 585                 else
 586                 {
 587                     mScrollingChild.PositionY = childTargetPosition;
 588                 }
 589             }
 590         }
 591
 592         /// <summary>
 593         /// you can override it to clean-up your own resources.
 594         /// </summary>
 595         /// <param name="type">DisposeTypes</param>
 596         /// <since_tizen> 6 </since_tizen>
 597         /// This will be public opened in tizen_5.5 after ACR done. Before ACR, need to be hidden as inhouse API.
 598         [EditorBrowsable(EditorBrowsableState.Never)]
 599         protected override void Dispose(DisposeTypes type)
 600         {
 601             if (disposed)
 602             {
 603                 return;
 604             }
 605
 606             if (type == DisposeTypes.Explicit)
 607             {
 608                 StopScroll();
 609
 610                 if (mPanGestureDetector != null)
 611                 {
 612                     mPanGestureDetector.Detected -= OnPanGestureDetected;
 613                     mPanGestureDetector.Dispose();
 614                     mPanGestureDetector = null;
 615                 }
 616
 617                 if (mTapGestureDetector != null)
 618                 {
 619                     mTapGestureDetector.Detected -= OnTapGestureDetected;
 620                     mTapGestureDetector.Dispose();
 621                     mTapGestureDetector = null;
 622                 }
 623             }
 624             base.Dispose(type);
 625         }
 626
 627         private float CalculateDisplacementFromVelocity(float axisVelocity)
 628         {
 629             // Map: flick speed of range (2.0 - 6.0) to flick multiplier of range (0.7 - 1.6)
 630             float speedMinimum = FlickThreshold;
 631             float speedMaximum = FlickThreshold + 6.0f;
 632             float multiplierMinimum = FlickDistanceMultiplierRange.X;
 633             float multiplierMaximum = FlickDistanceMultiplierRange.Y;
 634
 635             float flickDisplacement = 0.0f;
 636
 637             float speed = Math.Min(4.0f,Math.Abs(axisVelocity));
 638
 639             Debug.WriteLineIf(LayoutDebugScrollableBase, "ScrollableBase Candidate Flick speed:" + speed);
 640
 641             if (speed > FlickThreshold)
 642             {
 643                 // Flick length is the length of the ScrollableBase.
 644                 float flickLength = (ScrollingDirection == Direction.Horizontal) ?CurrentSize.Width:CurrentSize.Height;
 645
 646                 // Calculate multiplier by mapping speed between the multiplier minimum and maximum.
 647                 multiplier =( (speed - speedMinimum) / ( (speedMaximum - speedMinimum) * (multiplierMaximum - multiplierMinimum) ) )+ multiplierMinimum;
 648
 649                 // flick displacement is the product of the flick length and multiplier
 650                 flickDisplacement = ((flickLength * multiplier) * speed) / axisVelocity;  // *speed and /velocity to perserve sign.
 651
 652                 Debug.WriteLineIf(LayoutDebugScrollableBase, "Calculated FlickDisplacement[" + flickDisplacement +"] from speed[" + speed + "] multiplier:"
 653                                                         + multiplier);
 654             }
 655             return flickDisplacement;
 656         }
 657
 658         private float CalculateMaximumScrollDistance()
 659         {
 660             int scrollingChildLength = 0;
 661             int scrollerLength = 0;
 662             if (ScrollingDirection == Direction.Horizontal)
 663             {
 664                 Debug.WriteLineIf(LayoutDebugScrollableBase, "Horizontal");
 665
 666                 scrollingChildLength = (int)mScrollingChild.Layout.MeasuredWidth.Size.AsRoundedValue();
 667                 scrollerLength = CurrentSize.Width;
 668             }
 669             else
 670             {
 671                 Debug.WriteLineIf(LayoutDebugScrollableBase, "Vertical");
 672                 scrollingChildLength = (int)mScrollingChild.Layout.MeasuredHeight.Size.AsRoundedValue();
 673                 scrollerLength = CurrentSize.Height;
 674             }
 675
 676             Debug.WriteLineIf(LayoutDebugScrollableBase, "ScrollBy maxScrollDistance:" + (scrollingChildLength - scrollerLength) +
 677                                                    " parent length:" + scrollerLength +
 678                                                    " scrolling child length:" + scrollingChildLength);
 679
 680             return Math.Max(scrollingChildLength - scrollerLength,0);
 681         }
 682
 683         private void PageSnap()
 684         {
 685             Debug.WriteLineIf(LayoutDebugScrollableBase, "PageSnap with pan candidate totalDisplacement:" + totalDisplacementForPan +
 686                                                                 " currentPage[" + CurrentPage + "]" );
 687
 688             //Increment current page if total displacement enough to warrant a page change.
 689             if (Math.Abs(totalDisplacementForPan) > (mPageWidth * ratioOfScreenWidthToCompleteScroll))
 690             {
 691                 if (totalDisplacementForPan < 0)
 692                 {
 693                     CurrentPage = Math.Min(Math.Max(mScrollingChild.Children.Count - 1,0), ++CurrentPage);
 694                 }
 695                 else
 696                 {
 697                     CurrentPage = Math.Max(0, --CurrentPage);
 698                 }
 699             }
 700
 701             // Animate to new page or reposition to current page
 702             float destinationX = -(mScrollingChild.Children[CurrentPage].Position.X + mScrollingChild.Children[CurrentPage].CurrentSize.Width/2 - CurrentSize.Width/2); // set to middle of current page
 703             Debug.WriteLineIf(LayoutDebugScrollableBase, "Snapping to page[" + CurrentPage + "] to:" + destinationX + " from:" + mScrollingChild.PositionX);
 704             AnimateChildTo(ScrollDuration, destinationX);
 705         }
 706
 707         private void Flick(float flickDisplacement)
 708         {
 709           if (SnapToPage)
 710           {
 711               if ( ( flickWhenAnimating && scrolling == true) || ( scrolling == false) )
 712               {
 713                   if(flickDisplacement < 0)
 714                   {
 715                       CurrentPage = Math.Min(Math.Max(mScrollingChild.Children.Count - 1,0), CurrentPage + 1);
 716                       Debug.WriteLineIf(LayoutDebugScrollableBase, "Snap - to page:" + CurrentPage);
 717                   }
 718                   else
 719                   {
 720                       CurrentPage = Math.Max(0, CurrentPage - 1);
 721                       Debug.WriteLineIf(LayoutDebugScrollableBase, "Snap + to page:" + CurrentPage);
 722                   }
 723
 724                   float destinationX = -(mScrollingChild.Children[CurrentPage].Position.X + mScrollingChild.Children[CurrentPage].CurrentSize.Width/2.0f - CurrentSize.Width/2.0f); // set to middle of current page
 725                   Debug.WriteLineIf(LayoutDebugScrollableBase, "Snapping to :" + destinationX);
 726                   AnimateChildTo(ScrollDuration, destinationX);
 727               }
 728           }
 729           else
 730           {
 731               ScrollBy(flickDisplacement, true); // Animate flickDisplacement.
 732           }
 733         }
 734
 735         private void OnPanGestureDetected(object source, PanGestureDetector.DetectedEventArgs e)
 736         {
 737             if (e.PanGesture.State == Gesture.StateType.Started)
 738             {
 739                 Debug.WriteLineIf(LayoutDebugScrollableBase, "Gesture Start");
 740                 if (scrolling && !SnapToPage)
 741                 {
 742                     StopScroll();
 743                 }
 744                 maxScrollDistance = CalculateMaximumScrollDistance();
 745                 totalDisplacementForPan = 0.0f;
 746                 OnScrollDragStart();
 747             }
 748             else if (e.PanGesture.State == Gesture.StateType.Continuing)
 749             {
 750                 if (ScrollingDirection == Direction.Horizontal)
 751                 {
 752                     ScrollBy(e.PanGesture.Displacement.X, false);
 753                     totalDisplacementForPan += e.PanGesture.Displacement.X;
 754                 }
 755                 else
 756                 {
 757                     ScrollBy(e.PanGesture.Displacement.Y, false);
 758                     totalDisplacementForPan += e.PanGesture.Displacement.Y;
 759                 }
 760                 Debug.WriteLineIf(LayoutDebugScrollableBase, "OnPanGestureDetected Continue totalDisplacementForPan:" + totalDisplacementForPan);
 761             }
 762             else if (e.PanGesture.State == Gesture.StateType.Finished)
 763             {
 764                 float axisVelocity = (ScrollingDirection == Direction.Horizontal) ? e.PanGesture.Velocity.X : e.PanGesture.Velocity.Y;
 765                 float flickDisplacement = CalculateDisplacementFromVelocity(axisVelocity);
 766
 767                 Debug.WriteLineIf(LayoutDebugScrollableBase, "FlickDisplacement:" + flickDisplacement + "TotalDisplacementForPan:" + totalDisplacementForPan);
 768                 OnScrollDragEnd();
 769
 770                 if (flickDisplacement > 0 | flickDisplacement < 0)// Flick detected
 771                 {
 772                     Flick(flickDisplacement);
 773                 }
 774                 else
 775                 {
 776                     // End of panning gesture but was not a flick
 777                     if (SnapToPage)
 778                     {
 779                         PageSnap();
 780                     }
 781                 }
 782                 totalDisplacementForPan = 0;
 783             }
 784         }
 785
 786         private new void OnTapGestureDetected(object source, TapGestureDetector.DetectedEventArgs e)
 787         {
 788             if (e.TapGesture.Type == Gesture.GestureType.Tap)
 789             {
 790                 // Stop scrolling if tap detected (press then relase).
 791                 // Unless in Pages mode, do not want a page change to stop part way.
 792                 if(scrolling && !SnapToPage)
 793                 {
 794                     StopScroll();
 795                 }
 796             }
 797         }
 798
 799         private void ScrollAnimationFinished(object sender, EventArgs e)
 800         {
 801             scrolling = false;
 802             OnScrollAnimationEnd();
 803         }
 804     }
 805
 806 } // namespace