An animated Ellipse traces the outline of rendered text by using the path geometry of the text.
<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
x:Class="WpfApplication1.Window1"
Title="Using a Path Geometry to Highlight Text"
Background="PowderBlue">
<StackPanel>
<Button Margin="10" Grid.Column="2" Grid.Row="0" FontSize="16" Click="OnDisplayTextClick">Display Text</Button>
<Canvas Margin="20" Height="150">
<Path Canvas.Top="15" Canvas.Left="15" Stroke="SteelBlue" StrokeThickness="3" Fill="LightSteelBlue" Name="path" />
<Ellipse Canvas.Top="0" Canvas.Left="0" Width="30" Height="30">
<Ellipse.Fill>
<RadialGradientBrush GradientOrigin="0.5,0.5" Center="0.5,0.5" RadiusX="0.5" RadiusY="0.5">
<RadialGradientBrush.GradientStops>
<GradientStop Color="Yellow" Offset="0.25" />
<GradientStop Color="Transparent" Offset="1" />
</RadialGradientBrush.GradientStops>
</RadialGradientBrush>
</Ellipse.Fill>
<Ellipse.RenderTransform>
<MatrixTransform />
</Ellipse.RenderTransform>
<Ellipse.Triggers>
<EventTrigger RoutedEvent="FrameworkElement.Loaded">
<EventTrigger.Actions>
<BeginStoryboard>
<Storyboard x:Name="storyboard">
<MatrixAnimationUsingPath
x:Name="matrixAnimation"
Duration="0:00:40"
RepeatBehavior="Forever"
Storyboard.TargetProperty="RenderTransform.Matrix" />
</Storyboard>
</BeginStoryboard>
</EventTrigger.Actions>
</EventTrigger>
</Ellipse.Triggers>
</Ellipse>
</Canvas>
</StackPanel>
</Window>
//File:Window.xaml.vb
Imports System
Imports System.Globalization
Imports System.Windows
Imports System.Windows.Media
Namespace WpfApplication1
Public Partial Class Window1
Inherits Window
Public Sub New()
InitializeComponent()
End Sub
Public Sub OnDisplayTextClick(sender As Object, e As EventArgs)
Dim formattedText As New FormattedText("asdf", CultureInfo.GetCultureInfo("en-us"), FlowDirection.LeftToRight, New Typeface("Verdana"), 96, Brushes.Black)
formattedText.SetFontWeight(FontWeights.Bold)
Dim geometry As Geometry = formattedText.BuildGeometry(New Point(0, 0))
Dim pathGeometry As PathGeometry = geometry.GetFlattenedPathGeometry()
path.Data = pathGeometry
matrixAnimation.PathGeometry = pathGeometry
End Sub
End Class
End Namespace
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