如何：从自定义控件中选择墨迹

通过将 IncrementalLassoHitTester 添加到自定义控件，可以启用控件，以便用户可以使用套索工具选择墨迹，这与 InkCanvas 使用套索选择墨迹的方式类似。

此示例假定你熟悉如何创建启用了墨迹的自定义控件。 若要创建接受墨迹输入的自定义控件，请参阅 创建墨迹输入控件。

例

当用户绘制套索时，IncrementalLassoHitTester 预测哪些笔划会在用户完成套索后位于套索路径的范围内。 确定在套索路径边界内的笔划可以视为被选中。 所选笔划也可以变为未选中状态。 例如，如果用户在绘制套索时反转方向，则 IncrementalLassoHitTester 可能会取消选择某些笔划。

IncrementalLassoHitTester 触发 SelectionChanged 事件，使自定义控件能够在用户绘制套索时响应。 例如，可以在用户选择和取消选择笔划时更改笔划的外观。

管理墨迹模式

如果套索的显示方式与控件上的墨迹不同，则对用户有帮助。 为此，自定义控件必须跟踪用户是写入还是选择墨迹。 执行此操作的最简单方法是声明具有两个值的枚举：一个用于指示用户正在写入墨迹，一个用于指示用户正在选择墨迹。

// Enum that keeps track of whether StrokeCollectionDemo is in ink mode
// or select mode.
public enum InkMode
{
    Ink, Select
}

' Enum that keeps track of whether StrokeCollectionDemo is in ink mode 
' or select mode.
Public Enum InkMode
    Ink
    [Select]
End Enum 'InkMode

接下来，将两个 DrawingAttributes 添加到类：一个用于用户写入墨迹时使用，一个用于用户选择墨迹时使用。 在构造函数中，初始化 DrawingAttributes 并将这两个 AttributeChanged 事件附加到同一事件处理程序。 然后将 DynamicRenderer 的 DrawingAttributes 属性设置为墨迹 DrawingAttributes。

DrawingAttributes inkDA;
DrawingAttributes selectDA;

Private inkDA As DrawingAttributes
Private selectDA As DrawingAttributes

// In the constructor.
// Selection drawing attributes use dark gray ink.
selectDA = new DrawingAttributes();
selectDA.Color = Colors.DarkGray;

// ink drawing attributes use default attributes
inkDA = new DrawingAttributes();
inkDA.Width = 5;
inkDA.Height = 5;

inkDA.AttributeChanged += new PropertyDataChangedEventHandler(DrawingAttributesChanged);
selectDA.AttributeChanged += new PropertyDataChangedEventHandler(DrawingAttributesChanged);

' In the constructor.
' Selection drawing attributes use dark gray ink.
selectDA = New DrawingAttributes()
selectDA.Color = Colors.DarkGray

' ink drawing attributes use default attributes
inkDA = New DrawingAttributes()
inkDA.Width = 5
inkDA.Height = 5

AddHandler inkDA.AttributeChanged, _
           AddressOf DrawingAttributesChanged

AddHandler selectDA.AttributeChanged, _
           AddressOf DrawingAttributesChanged

添加公开选择模式的属性。 当用户更改选择模式时，将 DynamicRenderer 的 DrawingAttributes 属性设置为相应的 DrawingAttributes 对象，然后将 RootVisual 属性重新附加到 InkPresenter。

// Property to indicate whether the user is inputting or
// selecting ink.
public InkMode Mode
{
    get
    {
        return mode;
    }

    set
    {
        mode = value;

        // Set the DrawingAttributes of the DynamicRenderer
        if (mode == InkMode.Ink)
        {
            renderer.DrawingAttributes = inkDA;
        }
        else
        {
            renderer.DrawingAttributes = selectDA;
        }

        // Reattach the visual of the DynamicRenderer to the InkPresenter.
        presenter.DetachVisuals(renderer.RootVisual);
        presenter.AttachVisuals(renderer.RootVisual, renderer.DrawingAttributes);
    }
}

' Property to indicate whether the user is inputting or
' selecting ink.  
Public Property Mode() As InkMode
    Get
        Return Mode
    End Get

    Set(ByVal value As InkMode)
        modeState = value

        ' Set the DrawingAttributes of the DynamicRenderer
        If modeState = InkMode.Ink Then
            renderer.DrawingAttributes = inkDA
        Else
            renderer.DrawingAttributes = selectDA
        End If

        ' Reattach the visual of the DynamicRenderer to the InkPresenter.
        presenter.DetachVisuals(renderer.RootVisual)
        presenter.AttachVisuals(renderer.RootVisual, renderer.DrawingAttributes)
    End Set
End Property

将 DrawingAttributes 作为属性公开，以便应用程序可以确定墨迹笔划和选择笔划的外观。

// Property to allow the user to change the pen's DrawingAttributes.
public DrawingAttributes InkDrawingAttributes
{
    get
    {
        return inkDA;
    }
}

// Property to allow the user to change the Selector'newStroke DrawingAttributes.
public DrawingAttributes SelectDrawingAttributes
{
    get
    {
        return selectDA;
    }
}

' Property to allow the user to change the pen's DrawingAttributes.
Public ReadOnly Property InkDrawingAttributes() As DrawingAttributes
    Get
        Return inkDA
    End Get
End Property

' Property to allow the user to change the Selector'newStroke DrawingAttributes.
Public ReadOnly Property SelectDrawingAttributes() As DrawingAttributes
    Get
        Return selectDA
    End Get
End Property

当 DrawingAttributes 对象的属性发生更改时，必须将 RootVisual 重新附加到 InkPresenter。 在 AttributeChanged 事件的事件处理程序中，将 RootVisual 重新附加到 InkPresenter。

void DrawingAttributesChanged(object sender, PropertyDataChangedEventArgs e)
{
    // Reattach the visual of the DynamicRenderer to the InkPresenter
    // whenever the DrawingAttributes change.
    presenter.DetachVisuals(renderer.RootVisual);
    presenter.AttachVisuals(renderer.RootVisual, renderer.DrawingAttributes);
}

Private Sub DrawingAttributesChanged(ByVal sender As Object, _
                             ByVal e As PropertyDataChangedEventArgs)

    ' Reattach the visual of the DynamicRenderer to the InkPresenter 
    ' whenever the DrawingAttributes change.
    presenter.DetachVisuals(renderer.RootVisual)
    presenter.AttachVisuals(renderer.RootVisual, _
                            renderer.DrawingAttributes)

End Sub

使用 IncrementalLassoHitTester

创建并初始化包含所选笔划的 StrokeCollection。

// StylusPointCollection that collects the stylus points from the stylus events.
StylusPointCollection stylusPoints;

' StylusPointCollection that collects the stylus points from the stylus events.
Private stylusPoints As StylusPointCollection

当用户开始绘制墨迹或套索笔划时，取消选择所有已选定的笔划。 然后，如果用户正在绘制套索，请通过调用 GetIncrementalLassoHitTester、订阅 SelectionChanged 事件并调用 AddPoints来创建 IncrementalLassoHitTester。 此代码可以是单独的方法，可从 OnStylusDown 和 OnMouseDown 方法调用。

private void InitializeHitTester(StylusPointCollection collectedPoints)
{
    // Deselect any selected strokes.
    foreach (Stroke selectedStroke in selectedStrokes)
    {
        selectedStroke.DrawingAttributes.Color = inkDA.Color;
    }
    selectedStrokes.Clear();

    if (mode == InkMode.Select)
    {
        // Remove the previously drawn lasso, if it exists.
        if (lassoPath != null)
        {
            presenter.Strokes.Remove(lassoPath);
            lassoPath = null;
        }

        selectionTester =
            presenter.Strokes.GetIncrementalLassoHitTester(80);
        selectionTester.SelectionChanged +=
            new LassoSelectionChangedEventHandler(selectionTester_SelectionChanged);
        selectionTester.AddPoints(collectedPoints);
    }
}

Private Sub InitializeHitTester(ByVal collectedPoints As StylusPointCollection)

    ' Deselect any selected strokes.
    Dim selectedStroke As Stroke
    For Each selectedStroke In selectedStrokes
        selectedStroke.DrawingAttributes.Color = inkDA.Color
    Next selectedStroke
    selectedStrokes.Clear()

    If modeState = InkMode.Select Then
        ' Remove the previously drawn lasso, if it exists.
        If Not (lassoPath Is Nothing) Then
            presenter.Strokes.Remove(lassoPath)
            lassoPath = Nothing
        End If

        selectionTester = presenter.Strokes.GetIncrementalLassoHitTester(80)
        AddHandler selectionTester.SelectionChanged, AddressOf selectionTester_SelectionChanged
        selectionTester.AddPoints(collectedPoints)
    End If

End Sub

当用户绘制套索时，添加触笔点到 IncrementalLassoHitTester。 从 OnStylusMove、OnStylusUp、OnMouseMove和 OnMouseLeftButtonUp 方法中调用以下方法。

private void AddPointsToHitTester(StylusPointCollection collectedPoints)
{

    if (mode == InkMode.Select &&
        selectionTester != null &&
        selectionTester.IsValid)
    {
        // When the control is selecting strokes, add the
        // stylus packetList to selectionTester.
        selectionTester.AddPoints(collectedPoints);
    }
}

Private Sub AddPointsToHitTester(ByVal collectedPoints As StylusPointCollection)

    If modeState = InkMode.Select AndAlso _
       Not selectionTester Is Nothing AndAlso _
       selectionTester.IsValid Then

        ' When the control is selecting strokes, add the
        ' stylus packetList to selectionTester.
        selectionTester.AddPoints(collectedPoints)
    End If

End Sub

处理 IncrementalLassoHitTester.SelectionChanged 事件以响应用户选择或取消选择笔画的操作。 LassoSelectionChangedEventArgs 类具有 SelectedStrokes 和 DeselectedStrokes 属性，分别用于获取已选笔划和未选笔划。

void selectionTester_SelectionChanged(object sender,
    LassoSelectionChangedEventArgs args)
{
    // Change the color of all selected strokes to red.
    foreach (Stroke selectedStroke in args.SelectedStrokes)
    {
        selectedStroke.DrawingAttributes.Color = Colors.Red;
        selectedStrokes.Add(selectedStroke);
    }

    // Change the color of all unselected strokes to
    // their original color.
    foreach (Stroke unselectedStroke in args.DeselectedStrokes)
    {
        unselectedStroke.DrawingAttributes.Color = inkDA.Color;
        selectedStrokes.Remove(unselectedStroke);
    }
}

Private Sub selectionTester_SelectionChanged(ByVal sender As Object, _
                                     ByVal args As LassoSelectionChangedEventArgs)

    ' Change the color of all selected strokes to red.
    Dim selectedStroke As Stroke
    For Each selectedStroke In args.SelectedStrokes
        selectedStroke.DrawingAttributes.Color = Colors.Red
        selectedStrokes.Add(selectedStroke)
    Next selectedStroke

    ' Change the color of all unselected strokes to 
    ' their original color.
    Dim unselectedStroke As Stroke
    For Each unselectedStroke In args.DeselectedStrokes
        unselectedStroke.DrawingAttributes.Color = inkDA.Color
        selectedStrokes.Remove(unselectedStroke)
    Next unselectedStroke

End Sub

当用户完成绘制套索时，请取消订阅 SelectionChanged 事件并调用 EndHitTesting。

if (mode == InkMode.Select && lassoPath == null)
{
    // Add the lasso to the InkPresenter and add the packetList
    // to selectionTester.
    lassoPath = newStroke;
    lassoPath.DrawingAttributes = selectDA.Clone();
    presenter.Strokes.Add(lassoPath);
    selectionTester.SelectionChanged -= new LassoSelectionChangedEventHandler
                    (selectionTester_SelectionChanged);
    selectionTester.EndHitTesting();
}

If modeState = InkMode.Select AndAlso lassoPath Is Nothing Then
    ' Add the lasso to the InkPresenter and add the packetList
    ' to selectionTester.
    lassoPath = newStroke
    lassoPath.DrawingAttributes = selectDA.Clone()
    presenter.Strokes.Add(lassoPath)
    RemoveHandler selectionTester.SelectionChanged, _
                  AddressOf selectionTester_SelectionChanged
    selectionTester.EndHitTesting()
End If

把它全部放在一起。

下面的示例是一个自定义控件，使用户能够使用套索选择墨迹。

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Input;
using System.Windows.Input.StylusPlugIns;
using System.Windows.Ink;

// Enum that keeps track of whether StrokeCollectionDemo is in ink mode
// or select mode.
public enum InkMode
{
    Ink, Select
}

// This control allows the user to input and select ink.  When the
// user selects ink, the lasso remains visible until they erase, or clip
// the selected strokes, or clear the selection.  When the control is
// in selection mode, strokes that are selected turn red.
public class InkSelector : Label
{
    InkMode mode;

    DrawingAttributes inkDA;
    DrawingAttributes selectDA;

    InkPresenter presenter;
    IncrementalLassoHitTester selectionTester;
    StrokeCollection selectedStrokes = new StrokeCollection();

    // StylusPointCollection that collects the stylus points from the stylus events.
    StylusPointCollection stylusPoints;
    // Stroke that represents the lasso.
    Stroke lassoPath;

    DynamicRenderer renderer;

    public InkSelector()
    {
        mode = InkMode.Ink;

        // Use an InkPresenter to display the strokes on the custom control.
        presenter = new InkPresenter();
        this.Content = presenter;

        // In the constructor.
        // Selection drawing attributes use dark gray ink.
        selectDA = new DrawingAttributes();
        selectDA.Color = Colors.DarkGray;

        // ink drawing attributes use default attributes
        inkDA = new DrawingAttributes();
        inkDA.Width = 5;
        inkDA.Height = 5;

        inkDA.AttributeChanged += new PropertyDataChangedEventHandler(DrawingAttributesChanged);
        selectDA.AttributeChanged += new PropertyDataChangedEventHandler(DrawingAttributesChanged);

        // Add a DynmaicRenderer to the control so ink appears
        // to "flow" from the tablet pen.
        renderer = new DynamicRenderer();
        renderer.DrawingAttributes = inkDA;
        this.StylusPlugIns.Add(renderer);
        presenter.AttachVisuals(renderer.RootVisual,
            renderer.DrawingAttributes);
    }

    static InkSelector()
    {
        // Allow ink to be drawn only within the bounds of the control.
        Type owner = typeof(InkSelector);
        ClipToBoundsProperty.OverrideMetadata(owner,
            new FrameworkPropertyMetadata(true));
    }

    // Prepare to collect stylus packets. If Mode is set to Select,
    // get the IncrementalHitTester from the InkPresenter'newStroke
    // StrokeCollection and subscribe to its StrokeHitChanged event.
    protected override void OnStylusDown(StylusDownEventArgs e)
    {
        base.OnStylusDown(e);

        Stylus.Capture(this);

        // Create a new StylusPointCollection using the StylusPointDescription
        // from the stylus points in the StylusDownEventArgs.
        stylusPoints = new StylusPointCollection();
        StylusPointCollection eventPoints = e.GetStylusPoints(this, stylusPoints.Description);

        stylusPoints.Add(eventPoints);

        InitializeHitTester(eventPoints);
    }

    protected override void OnMouseLeftButtonDown(MouseButtonEventArgs e)
    {
        base.OnMouseLeftButtonDown(e);

        Mouse.Capture(this);

        if (e.StylusDevice != null)
        {
            return;
        }

        Point pt = e.GetPosition(this);

        StylusPointCollection collectedPoints = new StylusPointCollection(new Point[] { pt });

        stylusPoints = new StylusPointCollection();

        stylusPoints.Add(collectedPoints);

        InitializeHitTester(collectedPoints);
    }
    private void InitializeHitTester(StylusPointCollection collectedPoints)
    {
        // Deselect any selected strokes.
        foreach (Stroke selectedStroke in selectedStrokes)
        {
            selectedStroke.DrawingAttributes.Color = inkDA.Color;
        }
        selectedStrokes.Clear();

        if (mode == InkMode.Select)
        {
            // Remove the previously drawn lasso, if it exists.
            if (lassoPath != null)
            {
                presenter.Strokes.Remove(lassoPath);
                lassoPath = null;
            }

            selectionTester =
                presenter.Strokes.GetIncrementalLassoHitTester(80);
            selectionTester.SelectionChanged +=
                new LassoSelectionChangedEventHandler(selectionTester_SelectionChanged);
            selectionTester.AddPoints(collectedPoints);
        }
    }

    // Collect the stylus packets as the stylus moves.
    protected override void OnStylusMove(StylusEventArgs e)
    {
        if (stylusPoints == null)
        {
            return;
        }

        StylusPointCollection collectedPoints = e.GetStylusPoints(this, stylusPoints.Description);
        stylusPoints.Add(collectedPoints);
        AddPointsToHitTester(collectedPoints);
    }

    protected override void OnMouseMove(MouseEventArgs e)
    {

        base.OnMouseMove(e);

        if (e.StylusDevice != null)
        {
            return;
        }

        if (e.LeftButton == MouseButtonState.Released)
        {
            return;
        }

        stylusPoints ??= new StylusPointCollection();

        Point pt = e.GetPosition(this);

        StylusPointCollection collectedPoints = new StylusPointCollection(new Point[] { pt });

        stylusPoints.Add(collectedPoints);

        AddPointsToHitTester(collectedPoints);
    }

    private void AddPointsToHitTester(StylusPointCollection collectedPoints)
    {

        if (mode == InkMode.Select &&
            selectionTester != null &&
            selectionTester.IsValid)
        {
            // When the control is selecting strokes, add the
            // stylus packetList to selectionTester.
            selectionTester.AddPoints(collectedPoints);
        }
    }

    // When the user lifts the stylus, create a Stroke from the
    // collected stylus points and add it to the InkPresenter.
    // When the control is selecting strokes, add the
    // point data to the IncrementalHitTester.
    protected override void OnStylusUp(StylusEventArgs e)
    {
        stylusPoints ??= new StylusPointCollection();
        StylusPointCollection collectedPoints =
            e.GetStylusPoints(this, stylusPoints.Description);

        stylusPoints.Add(collectedPoints);
        AddPointsToHitTester(collectedPoints);
        AddStrokeToPresenter();
        stylusPoints = null;

        Stylus.Capture(null);
    }

    protected override void OnMouseLeftButtonUp(MouseButtonEventArgs e)
    {

        base.OnMouseLeftButtonUp(e);

        if (e.StylusDevice != null) return;

        if (stylusPoints == null) stylusPoints = new StylusPointCollection();

        Point pt = e.GetPosition(this);

        StylusPointCollection collectedPoints = new StylusPointCollection(new Point[] { pt });

        stylusPoints.Add(collectedPoints);
        AddPointsToHitTester(collectedPoints);
        AddStrokeToPresenter();

        stylusPoints = null;

        Mouse.Capture(null);
    }

    private void AddStrokeToPresenter()
    {
        Stroke newStroke = new Stroke(stylusPoints);

        if (mode == InkMode.Ink)
        {
            // Add the stroke to the InkPresenter.
            newStroke.DrawingAttributes = inkDA.Clone();
            presenter.Strokes.Add(newStroke);
        }

        if (mode == InkMode.Select && lassoPath == null)
        {
            // Add the lasso to the InkPresenter and add the packetList
            // to selectionTester.
            lassoPath = newStroke;
            lassoPath.DrawingAttributes = selectDA.Clone();
            presenter.Strokes.Add(lassoPath);
            selectionTester.SelectionChanged -= new LassoSelectionChangedEventHandler
                            (selectionTester_SelectionChanged);
            selectionTester.EndHitTesting();
        }
    }

    void selectionTester_SelectionChanged(object sender,
        LassoSelectionChangedEventArgs args)
    {
        // Change the color of all selected strokes to red.
        foreach (Stroke selectedStroke in args.SelectedStrokes)
        {
            selectedStroke.DrawingAttributes.Color = Colors.Red;
            selectedStrokes.Add(selectedStroke);
        }

        // Change the color of all unselected strokes to
        // their original color.
        foreach (Stroke unselectedStroke in args.DeselectedStrokes)
        {
            unselectedStroke.DrawingAttributes.Color = inkDA.Color;
            selectedStrokes.Remove(unselectedStroke);
        }
    }

    // Property to indicate whether the user is inputting or
    // selecting ink.
    public InkMode Mode
    {
        get
        {
            return mode;
        }

        set
        {
            mode = value;

            // Set the DrawingAttributes of the DynamicRenderer
            if (mode == InkMode.Ink)
            {
                renderer.DrawingAttributes = inkDA;
            }
            else
            {
                renderer.DrawingAttributes = selectDA;
            }

            // Reattach the visual of the DynamicRenderer to the InkPresenter.
            presenter.DetachVisuals(renderer.RootVisual);
            presenter.AttachVisuals(renderer.RootVisual, renderer.DrawingAttributes);
        }
    }
    void DrawingAttributesChanged(object sender, PropertyDataChangedEventArgs e)
    {
        // Reattach the visual of the DynamicRenderer to the InkPresenter
        // whenever the DrawingAttributes change.
        presenter.DetachVisuals(renderer.RootVisual);
        presenter.AttachVisuals(renderer.RootVisual, renderer.DrawingAttributes);
    }

    // Property to allow the user to change the pen's DrawingAttributes.
    public DrawingAttributes InkDrawingAttributes
    {
        get
        {
            return inkDA;
        }
    }

    // Property to allow the user to change the Selector'newStroke DrawingAttributes.
    public DrawingAttributes SelectDrawingAttributes
    {
        get
        {
            return selectDA;
        }
    }
}

Imports System.Windows
Imports System.Windows.Controls
Imports System.Windows.Media
Imports System.Windows.Input
Imports System.Windows.Input.StylusPlugIns
Imports System.Windows.Ink


' Enum that keeps track of whether StrokeCollectionDemo is in ink mode 
' or select mode.
Public Enum InkMode
    Ink
    [Select]
End Enum 'InkMode

' This control allows the user to input and select ink.  When the
' user selects ink, the lasso remains visible until they erase, or clip
' the selected strokes, or clear the selection.  When the control is
' in selection mode, strokes that are selected turn red.
Public Class InkSelector
    Inherits Label

    Private modeState As InkMode

    Private inkDA As DrawingAttributes
    Private selectDA As DrawingAttributes

    Private presenter As InkPresenter
    Private selectionTester As IncrementalLassoHitTester
    Private selectedStrokes As New StrokeCollection()

    ' StylusPointCollection that collects the stylus points from the stylus events.
    Private stylusPoints As StylusPointCollection

    ' Stroke that represents the lasso.
    Private lassoPath As Stroke

    Private renderer As DynamicRenderer


    Public Sub New()
        modeState = InkMode.Ink

        ' Use an InkPresenter to display the strokes on the custom control.
        presenter = New InkPresenter()
        Me.Content = presenter

        ' In the constructor.
        ' Selection drawing attributes use dark gray ink.
        selectDA = New DrawingAttributes()
        selectDA.Color = Colors.DarkGray

        ' ink drawing attributes use default attributes
        inkDA = New DrawingAttributes()
        inkDA.Width = 5
        inkDA.Height = 5

        AddHandler inkDA.AttributeChanged, _
                   AddressOf DrawingAttributesChanged

        AddHandler selectDA.AttributeChanged, _
                   AddressOf DrawingAttributesChanged

        ' Add a DynmaicRenderer to the control so ink appears
        ' to "flow" from the tablet pen.
        renderer = New DynamicRenderer()
        renderer.DrawingAttributes = inkDA
        Me.StylusPlugIns.Add(renderer)
        presenter.AttachVisuals(renderer.RootVisual, _
            renderer.DrawingAttributes)

    End Sub


    Shared Sub New()
        ' Allow ink to be drawn only within the bounds of the control.
        Dim owner As Type = GetType(InkSelector)
        ClipToBoundsProperty.OverrideMetadata(owner, _
            New FrameworkPropertyMetadata(True))

    End Sub

    ' Prepare to collect stylus packets. If Mode is set to Select,  
    ' get the IncrementalHitTester from the InkPresenter'newStroke 
    ' StrokeCollection and subscribe to its StrokeHitChanged event.
    Protected Overrides Sub OnStylusDown(ByVal e As StylusDownEventArgs)
        MyBase.OnStylusDown(e)

        Stylus.Capture(Me)

        ' Create a new StylusPointCollection using the StylusPointDescription
        ' from the stylus points in the StylusDownEventArgs.
        stylusPoints = New StylusPointCollection()
        Dim eventPoints As StylusPointCollection = e.GetStylusPoints(Me, stylusPoints.Description)

        stylusPoints.Add(eventPoints)

        InitializeHitTester(eventPoints)

    End Sub


    Protected Overrides Sub OnMouseLeftButtonDown(ByVal e As MouseButtonEventArgs)
        MyBase.OnMouseLeftButtonDown(e)

        Mouse.Capture(Me)

        If Not (e.StylusDevice Is Nothing) Then
            Return
        End If

        Dim pt As Point = e.GetPosition(Me)

        Dim collectedPoints As New StylusPointCollection(New Point() {pt})

        stylusPoints = New StylusPointCollection()

        stylusPoints.Add(collectedPoints)

        InitializeHitTester(collectedPoints)

    End Sub


    Private Sub InitializeHitTester(ByVal collectedPoints As StylusPointCollection)

        ' Deselect any selected strokes.
        Dim selectedStroke As Stroke
        For Each selectedStroke In selectedStrokes
            selectedStroke.DrawingAttributes.Color = inkDA.Color
        Next selectedStroke
        selectedStrokes.Clear()

        If modeState = InkMode.Select Then
            ' Remove the previously drawn lasso, if it exists.
            If Not (lassoPath Is Nothing) Then
                presenter.Strokes.Remove(lassoPath)
                lassoPath = Nothing
            End If

            selectionTester = presenter.Strokes.GetIncrementalLassoHitTester(80)
            AddHandler selectionTester.SelectionChanged, AddressOf selectionTester_SelectionChanged
            selectionTester.AddPoints(collectedPoints)
        End If

    End Sub

    ' Collect the stylus packets as the stylus moves.
    Protected Overrides Sub OnStylusMove(ByVal e As StylusEventArgs)

        If stylusPoints Is Nothing Then
            Return
        End If

        Dim collectedPoints As StylusPointCollection = e.GetStylusPoints(Me, stylusPoints.Description)
        stylusPoints.Add(collectedPoints)
        AddPointsToHitTester(collectedPoints)

    End Sub


    Protected Overrides Sub OnMouseMove(ByVal e As MouseEventArgs)

        MyBase.OnMouseMove(e)

        If Not (e.StylusDevice Is Nothing) Then
            Return
        End If

        If e.LeftButton = MouseButtonState.Released Then
            Return
        End If

        If stylusPoints Is Nothing Then
            stylusPoints = New StylusPointCollection()
        End If

        Dim pt As Point = e.GetPosition(Me)

        Dim collectedPoints As New StylusPointCollection(New Point() {pt})

        stylusPoints.Add(collectedPoints)

        AddPointsToHitTester(collectedPoints)

    End Sub


    Private Sub AddPointsToHitTester(ByVal collectedPoints As StylusPointCollection)

        If modeState = InkMode.Select AndAlso _
           Not selectionTester Is Nothing AndAlso _
           selectionTester.IsValid Then

            ' When the control is selecting strokes, add the
            ' stylus packetList to selectionTester.
            selectionTester.AddPoints(collectedPoints)
        End If

    End Sub

    ' When the user lifts the stylus, create a Stroke from the
    ' collected stylus points and add it to the InkPresenter.
    ' When the control is selecting strokes, add the
    ' point data to the IncrementalHitTester.
    Protected Overrides Sub OnStylusUp(ByVal e As StylusEventArgs)

        If stylusPoints Is Nothing Then
            stylusPoints = New StylusPointCollection()
        End If

        Dim collectedPoints As StylusPointCollection = _
            e.GetStylusPoints(Me, stylusPoints.Description)

        stylusPoints.Add(collectedPoints)
        AddPointsToHitTester(collectedPoints)
        AddStrokeToPresenter()

        stylusPoints = Nothing

        Stylus.Capture(Nothing)

    End Sub


    Protected Overrides Sub OnMouseLeftButtonUp(ByVal e As MouseButtonEventArgs)

        MyBase.OnMouseLeftButtonUp(e)

        If Not (e.StylusDevice Is Nothing) Then
            Return
        End If
        If stylusPoints Is Nothing Then
            stylusPoints = New StylusPointCollection()
        End If
        Dim pt As Point = e.GetPosition(Me)

        Dim collectedPoints As New StylusPointCollection(New Point() {pt})

        stylusPoints.Add(collectedPoints)
        AddPointsToHitTester(collectedPoints)
        AddStrokeToPresenter()

        stylusPoints = Nothing

        Mouse.Capture(Nothing)

    End Sub


    Private Sub AddStrokeToPresenter()
        Dim newStroke As New Stroke(stylusPoints)

        If modeState = InkMode.Ink Then
            ' Add the stroke to the InkPresenter.
            newStroke.DrawingAttributes = inkDA.Clone()
            presenter.Strokes.Add(newStroke)
        End If

        If modeState = InkMode.Select AndAlso lassoPath Is Nothing Then
            ' Add the lasso to the InkPresenter and add the packetList
            ' to selectionTester.
            lassoPath = newStroke
            lassoPath.DrawingAttributes = selectDA.Clone()
            presenter.Strokes.Add(lassoPath)
            RemoveHandler selectionTester.SelectionChanged, _
                          AddressOf selectionTester_SelectionChanged
            selectionTester.EndHitTesting()
        End If

    End Sub

    Private Sub selectionTester_SelectionChanged(ByVal sender As Object, _
                                         ByVal args As LassoSelectionChangedEventArgs)

        ' Change the color of all selected strokes to red.
        Dim selectedStroke As Stroke
        For Each selectedStroke In args.SelectedStrokes
            selectedStroke.DrawingAttributes.Color = Colors.Red
            selectedStrokes.Add(selectedStroke)
        Next selectedStroke

        ' Change the color of all unselected strokes to 
        ' their original color.
        Dim unselectedStroke As Stroke
        For Each unselectedStroke In args.DeselectedStrokes
            unselectedStroke.DrawingAttributes.Color = inkDA.Color
            selectedStrokes.Remove(unselectedStroke)
        Next unselectedStroke

    End Sub

    ' Property to indicate whether the user is inputting or
    ' selecting ink.  
    Public Property Mode() As InkMode
        Get
            Return Mode
        End Get

        Set(ByVal value As InkMode)
            modeState = value

            ' Set the DrawingAttributes of the DynamicRenderer
            If modeState = InkMode.Ink Then
                renderer.DrawingAttributes = inkDA
            Else
                renderer.DrawingAttributes = selectDA
            End If

            ' Reattach the visual of the DynamicRenderer to the InkPresenter.
            presenter.DetachVisuals(renderer.RootVisual)
            presenter.AttachVisuals(renderer.RootVisual, renderer.DrawingAttributes)
        End Set
    End Property
    Private Sub DrawingAttributesChanged(ByVal sender As Object, _
                                 ByVal e As PropertyDataChangedEventArgs)

        ' Reattach the visual of the DynamicRenderer to the InkPresenter 
        ' whenever the DrawingAttributes change.
        presenter.DetachVisuals(renderer.RootVisual)
        presenter.AttachVisuals(renderer.RootVisual, _
                                renderer.DrawingAttributes)

    End Sub

    ' Property to allow the user to change the pen's DrawingAttributes.
    Public ReadOnly Property InkDrawingAttributes() As DrawingAttributes
        Get
            Return inkDA
        End Get
    End Property

    ' Property to allow the user to change the Selector'newStroke DrawingAttributes.
    Public ReadOnly Property SelectDrawingAttributes() As DrawingAttributes
        Get
            Return selectDA
        End Get
    End Property

End Class

另请参阅

• IncrementalLassoHitTester
• StrokeCollection
• StylusPointCollection
• 创建墨迹输入控件