如何：從自訂控制項選取筆墨

藉由將 IncrementalLassoHitTester 新增至自訂控制項，您可以啟用控制項，讓使用者可以使用套索工具選取筆跡，類似於 InkCanvas 使用套索選取筆跡的方式。

此範例假設您已熟悉如何建立已啟用筆跡的自訂控制項。 若要建立接受筆跡輸入的自訂控制項，請參閱建立筆跡輸入控制項。

範例

當使用者繪製套索時，IncrementalLassoHitTester 會預測使用者完成套索之後，套索路徑界限內的筆劃。 判定為在套索路徑界限內的筆劃可以視為已選取。 選取的筆劃也可以變成未選取。 例如，如果使用者在繪製套索時反轉方向，則 IncrementalLassoHitTester 可能會取消選取一些筆劃。

IncrementalLassoHitTester 會引發 SelectionChanged 事件，這可讓您的自訂控制項在使用者繪製套索時回應。 例如，您可以在使用者選取和取消選取筆劃時變更筆劃的外觀。

管理筆跡模式

如果套索與控制項上的筆跡不同，則對使用者很有幫助。 若要達成此目的，您的自訂控制項必須追蹤使用者正在寫入或選取筆跡。 若要這樣做，最簡單的方式是宣告具有兩個值的列舉：一個表示使用者正在寫入筆跡，另一個表示使用者正在選取筆跡。

// 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

接下來，將兩個 DrawingAttributes 新增至類別：一個用於使用者寫入筆跡時使用，一個用於使用者選取筆跡時使用。 在建構函式中，初始化 DrawingAttributes，並將這兩個 AttributeChanged 事件附加至相同的事件處理常式。 將 DynamicRenderer 的 DrawingAttributes 屬性設定為 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

新增公開選取模式的屬性。 當使用者變更選取模式時，將 DynamicRenderer 的 DrawingAttributes 屬性設定為適當的 DrawingAttributes 物件，然後將 RootVisual 屬性重新附加至 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

將 DrawingAttributes 公開為屬性，讓應用程式可以判斷筆跡筆劃和選取筆劃的外觀。

// 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

當 DrawingAttributes 物件的屬性變更時，必須將 RootVisual 重新附加至 InkPresenter。 在 AttributeChanged 事件的事件處理常式中，將 RootVisual 重新附加至 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

建立並初始化包含所選取筆劃的 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

當使用者開始繪製筆劃時，不論筆跡或套索會取消選取任何選取的筆劃。 然後，如果使用者繪製套索，呼叫 GetIncrementalLassoHitTester、訂閱 SelectionChanged 事件，以及呼叫 AddPoints 來建立 IncrementalLassoHitTester。 此程式碼可以是個別的方法，並從 OnStylusDown 和 OnMouseDown 方法呼叫。

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

在使用者繪製套索時，將手寫筆指向 IncrementalLassoHitTester。 從 OnStylusMove、OnStylusUp、OnMouseMove 和 OnMouseLeftButtonUp 方法呼叫下列方法。

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

處理當使用者選取和取消選取筆劃時要回應的 IncrementalLassoHitTester.SelectionChanged 事件。 LassoSelectionChangedEventArgs 類別具有 SelectedStrokes 和 DeselectedStrokes 屬性，分別取得已選取和取消選取的筆劃。

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

當使用者完成繪製套索時，請取消訂閱 SelectionChanged 事件，並呼叫 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

整體回顧。

下列範例是自訂控制項，可讓使用者使用套索選取筆跡。

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

另請參閱

• IncrementalLassoHitTester
• StrokeCollection
• StylusPointCollection
• 建立筆墨輸入控制項