2019-11-29-WPF-高速书写-StylusPlugIn-原理

		private void ProcessInputReport(RawStylusInputReport inputReport)
		{
			WispStylusDevice wispStylusDevice = this.FindStylusDeviceWithLock(inputReport.StylusDeviceId);
			inputReport.StylusDevice = ((wispStylusDevice != null) ? wispStylusDevice.StylusDevice : null);
			if (!this._inDragDrop || !inputReport.PenContext.Contexts.IsWindowDisabled)
			{
				this.InvokeStylusPluginCollection(inputReport);
			}
			this.CoalesceAndQueueStylusEvent(inputReport);
		}

		internal StylusPlugInCollection TargetPlugInCollection(RawStylusInputReport inputReport)
		{
			var wispStylusDevice = inputReport.StylusDevice.As<WispStylusDevice>();
			
			// We‘re on the pen thread so can‘t touch visual tree.  Use capturedPlugIn (if capture on) or cached rects.
			// 现在是 Pen 的线程不在主线程，无法直接访问到视觉树
			StylusPlugInCollection stylusPlugInCollection = wispStylusDevice.GetCapturedPlugInCollection(our bool elementHasCapture);

			// 没有拿到值的时候就使用 HittestPlugInCollection 函数
			if (!elementHasCapture)
			{
				int[] data = inputReport.Data;
				// 下面这句话是被简化，会在本文下面仔细说明
				Point point = new Point((double)data[xx], (double)data[xx]);

				stylusPlugInCollection = this.HittestPlugInCollection(point);
			}
			
			return stylusPlugInCollection;
		}

    internal override StylusPlugInCollection GetCapturedPlugInCollection(ref bool elementHasCapture)
    {
        elementHasCapture = _stylusCapture != null;
        return _stylusCapturePlugInCollection;
    }

int inputArrayLengthPerPoint = inputReport.PenContext.StylusPointDescription.GetInputArrayLengthPerPoint();
int[] data = inputReport.Data;
Point point = new Point((double)data[data.Length - inputArrayLengthPerPoint], (double)data[data.Length - inputArrayLengthPerPoint + 1]);

        /// <summary>
        /// Internal helper for determining how many ints in a raw int array 
        /// correspond to one point we get from the input system
        /// </summary>
        internal int GetInputArrayLengthPerPoint()
        { 
            int buttonLength = _buttonCount > 0 ? 1 : 0;
            int propertyLength = (_stylusPointPropertyInfos.Length - _buttonCount) + buttonLength; 
            if (!this.ContainsTruePressure) 
            {
                propertyLength--; 
            }
            return propertyLength;
        }

        StylusPlugInCollection HittestPlugInCollection(Point pt)
        {
            foreach (StylusPlugInCollection plugInCollection in _plugInCollectionList)
            { 
                if (plugInCollection.IsHit(pt)) 
                {
                    return plugInCollection; 
                }
            }
 
            return null; 
        }

        internal void AddStylusPlugInCollection(StylusPlugInCollection pic)
        {
            this._plugInCollectionList.Insert(this.FindZOrderIndex(pic), pic);
        }

        /// <summary> 
        /// Check whether a point hits the element
        /// This method is called from the real-time context. 
        /// </summary> 
        /// <param name="pt">a point to check
        /// <returns>true if the point is within the bound of the element; false otherwise</returns> 
        internal bool IsHit(Point pt)
        {
            Point ptElement = pt;
            _viewToElement.TryTransform(ptElement, out ptElement); 
            return _rc.Contains(ptElement);
        } 

            if (_element.IsArrangeValid && _element.IsEnabled && _element.IsVisible && _element.IsHitTestVisible) 
            {
                _rc = new Rect(new Point(), _element.RenderSize);// _element.GetContentBoundingBox(); 
            }
            else
            {
            	_rc = new Rect(); // empty rect so we don‘t hittest it.
            }

internal void InvokeStylusPluginCollection(RawStylusInputReport inputReport) 
{
	StylusPlugInCollection pic = TargetPlugInCollection(inputReport); 
	if (pic != null)
	{
		RawStylusInput rawStylusInput = new RawStylusInput(inputReport, pic);
		// We are on the pen thread, just call directly
		pic.FireRawStylusInput(rawStylusInput);
	}
}

                        for (int i = 0; i < this.Count; i++) 
                        {
                            StylusPlugIn plugIn = base[i];
                            // set current plugin so any callback data gets an owner.
                            args.CurrentNotifyPlugIn = plugIn; 
                            plugIn.RawStylusInput(args);
                        } 

		internal void OnPenDown(PenContext penContext, int tabletDeviceId, int stylusPointerId, int[] data, int timestamp)
		{
			this.ProcessInput(RawStylusActions.Down, penContext, tabletDeviceId, stylusPointerId, data, timestamp);
		}

		internal void OnPenUp(PenContext penContext, int tabletDeviceId, int stylusPointerId, int[] data, int timestamp)
		{
			this.ProcessInput(RawStylusActions.Up, penContext, tabletDeviceId, stylusPointerId, data, timestamp);
		}

		internal void OnPackets(PenContext penContext, int tabletDeviceId, int stylusPointerId, int[] data, int timestamp)
		{
			this.ProcessInput(RawStylusActions.Move, penContext, tabletDeviceId, stylusPointerId, data, timestamp);
		}

// StylusPlugIn
       internal void RawStylusInput(RawStylusInput rawStylusInput) 
        {
            // Only fire if plugin is enabled and hooked up to plugincollection. 
            
            switch( rawStylusInput.Report.Actions ) 
            {
                case RawStylusActions.Down:
                    OnStylusDown(rawStylusInput);
                    break; 
                case RawStylusActions.Move:
                    OnStylusMove(rawStylusInput); 
                    break; 
                case RawStylusActions.Up:
                    OnStylusUp(rawStylusInput); 
                    break;
            }
            
        } 

        protected virtual void OnStylusDown(RawStylusInput rawStylusInput)
        { 
        }
        
        protected virtual void OnStylusMove(RawStylusInput rawStylusInput) 
        {
        } 
        
        protected virtual void OnStylusUp(RawStylusInput rawStylusInput) 
        { 
        }

public class StylusPlugInCollection : Collection<StylusPlugIn>
{
        protected override void InsertItem(int index, StylusPlugIn plugIn)
		{
			this._element.VerifyAccess();
            // 你以为下面就没代码了？
		}
}

                _element.IsEnabledChanged += _isEnabledChangedEventHandler; 
                _element.IsVisibleChanged += _isVisibleChangedEventHandler;
                _element.IsHitTestVisibleChanged += _isHitTestVisibleChangedEventHandler; 
                PresentationSource.AddSourceChangedHandler(_element, _sourceChangedEventHandler);  // has a security linkdemand
                _element.LayoutUpdated += _layoutChangedEventHandler;

        private void OnIsEnabledChanged(object sender, DependencyPropertyChangedEventArgs e) 
        {
            UpdatePenContextsState();
        } 
 
        private void OnIsVisibleChanged(object sender, DependencyPropertyChangedEventArgs e) 
        { 
            UpdatePenContextsState(); 
        }
 
        private void OnIsHitTestVisibleChanged(object sender, DependencyPropertyChangedEventArgs e)
        { 
            UpdatePenContextsState(); 
        } 
 
        private void OnRenderTransformChanged(object sender, EventArgs e) 
        {
            OnLayoutUpdated(sender, e);
        }
  
        private void OnSourceChanged(object sender, SourceChangedEventArgs e)
        { 
            // This means that the element has been added or remvoed from its source. 
            UpdatePenContextsState();
        } 

        protected override void InsertItem(int index, StylusPlugIn plugIn)
        {
        	EnsureEventsHooked();
        	base.InsertItem(index, plugIn); 
        	plugIn.Added(this);
            UpdatePenContextsState(); // Add to PenContexts if element is in proper state (can fire isactiveforinput). 
        }

private void UpdatePenContextsState()
{
	PresentationSource presentationSource = PresentationSource.CriticalFromVisual(_element as Visual);
	InputManager inputManager = (InputManager)_element.Dispatcher.InputManager;
    PenContexts penContexts = inputManager.StylusLogic.GetPenContextsFromHwnd(presentationSource); 
    // 下面还有一半
}

 penContexts.AddStylusPlugInCollection(this);

		internal StylusPlugInCollection(UIElement element)
		{
			this._stylusPlugInCollectionImpl = StylusPlugInCollectionBase.Create(this);
			
		}

		internal static StylusPlugInCollectionBase Create(StylusPlugInCollection wrapper)
		{
			StylusPlugInCollectionBase stylusPlugInCollectionBase;
			if (StylusLogic.IsPointerStackEnabled)
			{
				stylusPlugInCollectionBase = new PointerStylusPlugInCollection();
			}
			else
			{
				stylusPlugInCollectionBase = new WispStylusPlugInCollection();
			}
			stylusPlugInCollectionBase.Wrapper = wrapper;
			return stylusPlugInCollectionBase;
		}

       /// <securitynote>
        /// Critical - InputReport.InputSource has a LinkDemand so we need to be SecurityCritical. 
        ///             Called by InvokeStylusPluginCollection.
        ///             TreatAsSafe boundary is mainly PenThread.ThreadProc and HwndWrapperHook class (via HwndSource.InputFilterMessage).
        ///                 It can also be called via anyone with priviledge to call InputManager.ProcessInput().
        /// </securitynote> 
        [SecurityCritical]
        internal StylusPlugInCollection TargetPlugInCollection(RawStylusInputReport inputReport) 
        { 
            // Caller must make call to this routine inside of lock(__rtiLock)!
            StylusPlugInCollection pic = null; 
 
            // We should only be called when not on the application thread!
            System.Diagnostics.Debug.Assert(!inputReport.StylusDevice.CheckAccess());
  
            // We‘re on the pen thread so can‘t touch visual tree.  Use capturedPlugIn (if capture on) or cached rects.
            bool elementHasCapture = false; 
            pic = inputReport.StylusDevice.GetCapturedPlugInCollection(ref elementHasCapture); 
            int pointLength = inputReport.PenContext.StylusPointDescription.GetInputArrayLengthPerPoint();
            // Make sure that the captured Plugin Collection is still in the list.  CaptureChanges are 
            // deferred so there is a window where the stylus device is not updated yet.  This protects us
            // from using a bogus plugin collecton for an element that is in an invalid state.
            if (elementHasCapture && !_plugInCollectionList.Contains(pic))
            { 
                elementHasCapture = false;  // force true hittesting to be done!
            } 
  
            if (!elementHasCapture && inputReport.Data != null && inputReport.Data.Length >= pointLength)
            { 
                int[] data = inputReport.Data;
                System.Diagnostics.Debug.Assert(data.Length % pointLength == 0);
                Point ptTablet = new Point(data[data.Length - pointLength], data[data.Length - pointLength + 1]);
                // Note: the StylusLogic data inside DeviceUnitsFromMeasurUnits is protected by __rtiLock. 
                ptTablet = ptTablet * inputReport.StylusDevice.TabletDevice.TabletToScreen;
                ptTablet.X = (int)Math.Round(ptTablet.X); // Make sure we snap to whole window pixels. 
                ptTablet.Y = (int)Math.Round(ptTablet.Y); 
                // 经常这里不会对点修改，这里使用的是 measurePoint * _transformToDevice.Invert();
                ptTablet = _stylusLogic.MeasureUnitsFromDeviceUnits(ptTablet); // change to measured units now.
  
                pic = HittestPlugInCollection(ptTablet); // Use cached rectangles for UIElements.
            }
            return pic;
        } 
 

       private void UpdatePenContextsState()
        { 
            bool unhookPenContexts = true;
  
            // Disable processing of the queue during blocking operations to prevent unrelated reentrancy 
            // which a call to Lock() can cause.
            using (_element.Dispatcher.DisableProcessing()) 
            {
                // See if we should be enabled
                if (_element.IsVisible && _element.IsEnabled && _element.IsHitTestVisible)
                { 
                    PresentationSource presentationSource = PresentationSource.CriticalFromVisual(_element as Visual);
  
                    if (presentationSource != null) 
                    {
                        unhookPenContexts = false; 
 
                        // Are we currently hooked up?  If not then hook up.
                        if (_penContexts == null)
                        { 
                            InputManager inputManager = (InputManager)_element.Dispatcher.InputManager;
                            PenContexts penContexts = inputManager.StylusLogic.GetPenContextsFromHwnd(presentationSource); 
  
                            // _penContexts must be non null or don‘t do anything.
                            if (penContexts != null) 
                            {
                                _penContexts = penContexts;
 
                                lock(penContexts.SyncRoot) 
                                {
                                    penContexts.AddStylusPlugInCollection(this); 
  
                                    foreach (StylusPlugIn spi in this)
                                    { 
                                        spi.InvalidateIsActiveForInput(); // Uses _penContexts being set to determine active state.
 
                                    }
                                    // NTRAID:WINDOWSOS#1677277-2006/06/05-WAYNEZEN, 
                                    // Normally the Rect will be updated when we receive the LayoutUpdate.
                                    // However there could be a race condition which the LayoutUpdate gets received 
                                    // before the properties like IsVisible being set. 
                                    // So we should always force to call OnLayoutUpdated whenever the input is active.
                                    OnLayoutUpdated(this, EventArgs.Empty); 
                                }
 
                            }
                        } 
                    }
                } 
  
                if (unhookPenContexts)
                { 
                    UnhookPenContexts();
                }
            }
        } 

    public sealed class StylusPlugInCollection : Collection<stylusplugin>
    { 
        #region Protected APIs 
        /// <summary>
        /// Insert a StylusPlugIn in the collection at a specific index. 
        /// This method should be called from the application context only
        /// </summary>
        /// <param name="index">index at which to insert the StylusPlugIn object
        /// <param name="plugIn">StylusPlugIn object to insert, downcast to an object 
        protected override void InsertItem(int index, StylusPlugIn plugIn)
        { 
            // Verify it‘s called from the app dispatcher 
            _element.VerifyAccess();
  
            // Validate the input parameter
            if (null == plugIn)
            {
                throw new ArgumentNullException("plugIn", SR.Get(SRID.Stylus_PlugInIsNull)); 
            }
  
            if (IndexOf(plugIn) != -1) 
            {
                throw new ArgumentException(SR.Get(SRID.Stylus_PlugInIsDuplicated), "plugIn"); 
            }
 
            // Disable processing of the queue during blocking operations to prevent unrelated reentrancy
            // which a call to Lock() can cause. 
            using (_element.Dispatcher.DisableProcessing())
            { 
                if (IsActiveForInput) 
                {
                    // If we are currently active for input then we have a _penContexts that we must lock! 
                    lock(PenContextsSyncRoot)
                    {
                        System.Diagnostics.Debug.Assert(this.Count > 0); // If active must have more than one plugin already
                        base.InsertItem(index, plugIn); 
                        plugIn.Added(this);
                    } 
                } 
                else
                { 
                    EnsureEventsHooked(); // Hook up events to track changes to the plugin‘s element
                    base.InsertItem(index, plugIn);
                    try
                    { 
                        plugIn.Added(this); // Notify plugin that it has been added to collection
                    } 
                    finally
                    {
                        UpdatePenContextsState(); // Add to PenContexts if element is in proper state (can fire isactiveforinput). 
                    }
                }
            }
        } 
    }

		internal override void UpdateState(UIElement element)
		{
			bool flag = true;
			using (element.Dispatcher.DisableProcessing())
			{
				if (element.IsVisible && element.IsEnabled && element.IsHitTestVisible)
				{
					PresentationSource presentationSource = PresentationSource.CriticalFromVisual(element);
					if (presentationSource != null)
					{
						flag = false;
						if (this._penContexts == null)
						{
							InputManager inputManager = (InputManager)element.Dispatcher.InputManager;
							PenContexts penContextsFromHwnd = StylusLogic.GetCurrentStylusLogicAs<WispLogic>().GetPenContextsFromHwnd(presentationSource);
							if (penContextsFromHwnd != null)
							{
								this._penContexts = penContextsFromHwnd;
								object syncRoot = penContextsFromHwnd.SyncRoot;
								lock (syncRoot)
								{
									penContextsFromHwnd.AddStylusPlugInCollection(base.Wrapper);
									foreach (StylusPlugIn stylusPlugIn in base.Wrapper)
									{
										stylusPlugIn.InvalidateIsActiveForInput();
									}
									base.Wrapper.OnLayoutUpdated(base.Wrapper, EventArgs.Empty);
								}
							}
						}
					}
				}
				if (flag)
				{
					this.Unhook();
				}
			}
		}

		internal override void UpdateState(UIElement element)
		{
			bool flag = true;
			if (element.IsVisible && element.IsEnabled && element.IsHitTestVisible)
			{
				PresentationSource presentationSource = PresentationSource.CriticalFromVisual(element);
				if (presentationSource != null)
				{
					flag = false;
					if (this._manager == null)
					{
						this._manager = StylusLogic.GetCurrentStylusLogicAs<PointerLogic>().PlugInManagers[presentationSource];
						if (this._manager != null)
						{
							this._manager.AddStylusPlugInCollection(base.Wrapper);
							foreach (StylusPlugIn stylusPlugIn in base.Wrapper)
							{
								stylusPlugIn.InvalidateIsActiveForInput();
							}
							base.Wrapper.OnLayoutUpdated(base.Wrapper, EventArgs.Empty);
						}
					}
				}
				if (flag)
				{
					this.Unhook();
				}
			}
		}