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POWPF UserControl HitTest
 

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  1. POWPF UserControl HitTest
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    <p>I have the following user control: a dot and its name: </p> <pre><code>&lt;UserControl x:Class="ShapeTester.StopPoint" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" mc:Ignorable="d" d:DesignHeight="25" d:DesignWidth="100"&gt; &lt;StackPanel&gt; &lt;Ellipse Stroke="DarkBlue" Fill="LightBlue" Height="10" Width="10"/&gt; &lt;TextBlock Text="Eiffel Tower"/&gt; &lt;/StackPanel&gt; &lt;/UserControl&gt; </code></pre> <p>This is cool. </p> <p>Now, I have a panel, in witch I need to recuperate my StopPoints that I hit with the Mouse: </p> <pre><code>public partial class StopsPanel : UserControl { private List&lt;StopPoint&gt; hitList = new List&lt;StopPoint&gt;(); private EllipseGeometry hitArea = new EllipseGeometry(); public StopsPanel() { InitializeComponent(); Initialize(); } private void Initialize() { foreach (StopPoint point in StopsCanvas.Children) { point.Background = Brushes.LightBlue; } } private void OnMouseLeftButtonDown(object sender, MouseButtonEventArgs e) { // Initialization: Initialize(); // Get mouse click point: Point pt = e.GetPosition(StopsCanvas); // Define hit-testing area: hitArea = new EllipseGeometry(pt, 1.0, 1.0); hitList.Clear(); // Call HitTest method: VisualTreeHelper.HitTest(StopsCanvas, null, new HitTestResultCallback(HitTestCallback), new GeometryHitTestParameters(hitArea)); if (hitList.Count &gt; 0) { foreach (StopPoint point in hitList) { // Change rectangle fill color if it is hit: point.Background = Brushes.LightCoral; } MessageBox.Show(string.Format( "You hit {0} StopPoint(s)", hitList.Count)); } } public HitTestResultBehavior HitTestCallback(HitTestResult result) { if (result.VisualHit is StopPoint) { // //-------- NEVER ENTER HERE!!! :( // // Retrieve the results of the hit test. IntersectionDetail intersectionDetail = ((GeometryHitTestResult)result).IntersectionDetail; switch (intersectionDetail) { case IntersectionDetail.FullyContains: // Add the hit test result to the list: hitList.Add((StopPoint)result.VisualHit); return HitTestResultBehavior.Continue; case IntersectionDetail.Intersects: // Set the behavior to return visuals at all z-order levels: return HitTestResultBehavior.Continue; case IntersectionDetail.FullyInside: // Set the behavior to return visuals at all z-order levels: return HitTestResultBehavior.Continue; default: return HitTestResultBehavior.Stop; } } else { return HitTestResultBehavior.Continue; } } } </code></pre> <p>So, as you can see, the problem that <strong>the HitTest never identifies an UserControl(StopPoint) as it is, but rather its components</strong>(<em>TextBlock</em>, <em>Ellipse</em> or even <em>Border</em>).<br> As I associate the business object to the StopPoint element, I need to obtain it when MouseHitting, and not its composing elements.</p> <p>Is there a way to do it?</p> <p>EDIT: </p> <p>Using filter (now, it does not enter at all in the HitTestCallback): </p> <pre><code>using System.Collections.Generic; using System.Windows; using System.Windows.Controls; using System.Windows.Input; using System.Windows.Media; namespace ShapeTester { /// &lt;summary&gt; /// Interaction logic for StopsPanel.xaml /// &lt;/summary&gt; public partial class StopsPanel : UserControl { private List&lt;StopPoint&gt; hitList = new List&lt;StopPoint&gt;(); private EllipseGeometry hitArea = new EllipseGeometry(); public StopsPanel() { InitializeComponent(); Initialize(); } private void Initialize() { foreach (StopPoint point in StopsCanvas.Children) { point.Background = Brushes.LightBlue; } } private void OnMouseLeftButtonDown(object sender, MouseButtonEventArgs e) { // Initialization: Initialize(); // Get mouse click point: Point pt = e.GetPosition(StopsCanvas); // Define hit-testing area: hitArea = new EllipseGeometry(pt, 1.0, 1.0); hitList.Clear(); // Call HitTest method: VisualTreeHelper.HitTest(StopsCanvas, new HitTestFilterCallback(MyHitTestFilter), new HitTestResultCallback(HitTestCallback), new GeometryHitTestParameters(hitArea)); if (hitList.Count &gt; 0) { foreach (StopPoint point in hitList) { // Change rectangle fill color if it is hit: point.Background = Brushes.LightCoral; } MessageBox.Show(string.Format( "You hit {0} StopPoint(s)", hitList.Count)); } } public HitTestResultBehavior HitTestCallback(HitTestResult result) { if (result.VisualHit is StopPoint) { // //-------- NEVER ENTER HERE!!! :( // // Retrieve the results of the hit test. IntersectionDetail intersectionDetail = ((GeometryHitTestResult)result).IntersectionDetail; switch (intersectionDetail) { case IntersectionDetail.FullyContains: // Add the hit test result to the list: hitList.Add((StopPoint)result.VisualHit); return HitTestResultBehavior.Continue; case IntersectionDetail.Intersects: // Set the behavior to return visuals at all z-order levels: return HitTestResultBehavior.Continue; case IntersectionDetail.FullyInside: // Set the behavior to return visuals at all z-order levels: return HitTestResultBehavior.Continue; default: return HitTestResultBehavior.Stop; } } else { return HitTestResultBehavior.Continue; } } // Filter the hit test values for each object in the enumeration. public HitTestFilterBehavior MyHitTestFilter(DependencyObject o) { // Test for the object value you want to filter. if (o.GetType() == typeof(StopPoint)) { // Visual object's descendants are // NOT part of hit test results enumeration. return HitTestFilterBehavior.ContinueSkipChildren; } else { // Visual object is part of hit test results enumeration. return HitTestFilterBehavior.Continue; } } } } </code></pre>
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    1. CODid you try adding a HitTestFilterCallback and returning ContinueSkipChildren if it's on a StopPoint? I see you currently pass null as the filter callback.
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    2. CO@Bubblewrap: hmm... e... what do you mean ?..
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    3. COThe 2nd parameter of VisualTreeHelper.HitTest, you can specify a HitTestFilterCallback. See here: http://msdn.microsoft.com/en-us/library/ms752097.aspx#using_a_hit_test_filter_callback
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