wpf - Hittesting vs2008 - Not all visuals found in treeview

[Rolf Welskes]

Hello,
because there are no managed news group for window presentation foundation
and one has told me I can use this, here my problem:

simple example:

<Window x:Class="TreeViewHitTest.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window1" Height="354" Width="644" >
<Grid Background="LightGray">
<TreeView AllowDrop="True" Background="LightBlue"
HorizontalAlignment="Left" Margin="10,10,0,71" Name="treeView" Width="200"
PreviewMouseDown="grid01_PreviewMouseDown">
<TreeViewItem Header="aaa01"/>
<TreeViewItem Header="aaa02"/>
<TreeViewItem Header="aaa03" />
</TreeView>
<ListBox Margin="286,56,138,71" Name="lbxResult" />
</Grid>
</Window>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace TreeViewHitTest
{
/// <summary>
/// Interaction logic for Window1.xaml
/// </summary>
public partial class Window1 : Window
{
public Window1()
{
InitializeComponent();
}

public HitTestResultBehavior HitTestResultFunc(HitTestResult result)
{
DependencyObject dobj = result.VisualHit;
lbxResult.Items.Add(dobj.GetType().Name);
return HitTestResultBehavior.Continue;
}



private void grid01_PreviewMouseDown(object sender,
MouseButtonEventArgs e)
{
lbxResult.Items.Clear();

VisualTreeHelper.HitTest(treeView , null, HitTestResultFunc, new
PointHitTestParameters(e.GetPosition(treeView)));

}
}
}

So if you start the program and left click on a TreeViewItem in the
treeview, you see the hittesting starts
at TextBlock, this seems ok, but then it travers the visual tree and does
not reach each element,
ESPESPIALY I need the TreeViewItem which is clicked, but this is not in the
list of the items found hittesting.

Thank you for any help.
Rolf Welskes

 

[Walter Wang [MSFT]]

Hi Rolf,

This is a quick note to let you know that I am performing research on this
issue and will get back to you as soon as possible. I appreciate your
patience.


Regards,
Walter Wang ([email protected], remove 'online.')
Microsoft Online Community Support

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[Walter Wang [MSFT]]

Hi Rolf,

Not all visuals will be returned in the HitTestResultCallback, instead, we
should use HitTestFilterCallback if we need to know every potential visual
that is hit (in z-order).

If you use following code:

public HitTestResultBehavior HitTestResultFunc(HitTestResult result)
{
DependencyObject dobj = result.VisualHit;
// lbxResult.Items.Add(dobj.GetType().Name);
return HitTestResultBehavior.Continue;
}

public HitTestFilterBehavior HitTestFilterFunc(DependencyObject
potentialHitTestTarget)
{
lbxResult.Items.Add(potentialHitTestTarget.GetType().Name);
return HitTestFilterBehavior.Continue;
}


private void grid01_PreviewMouseDown(object sender,
MouseButtonEventArgs e)
{
lbxResult.Items.Clear();
VisualTreeHelper.HitTest(treeView, HitTestFilterFunc,
HitTestResultFunc, new
PointHitTestParameters(e.GetPosition((UIElement)sender)));


You can see the TreeViewItem is returned correctly.

Another workaround is to use the HitTest to return a DependencyObject, then
walk up the visual tree until you find a TreeViewItem in the TreeView
you're checking.

You can use VisualTreeHelper.GetParent() to return the parent.


Regards,
Walter Wang ([email protected], remove 'online.')
Microsoft Online Community Support

==================================================
When responding to posts, please "Reply to Group" via your newsreader so
that others may learn and benefit from your issue.
==================================================

This posting is provided "AS IS" with no warranties, and confers no rights.

 

[Rolf Welskes]

Hello,
thank you this is a work around.
BUT: I have also tried to override TreeViewItem.HitTestCore().
This method is not called while hittesting.
Furthermore, when I set a filter for hittesting, then what I define as
elemnts for hittesting should be in the Hittestresult,
but is not.

All togehter: Hittesting in wpf is complex (compared to windows forms) and
it is not helpfull, that the hittest-behaver is so,
that no one knows what is hitested in the tree and what is not, so the
programmer is blind because he/she does not know
what realy happens.

Ok, it works.

So, thank you for you help
and best regards
Rolf Welskes