View Issue Details

IDProjectCategoryView StatusLast Update
0001222NoesisGUIUnity3Dpublic2019-04-30 06:20
ReporternokolaAssigned Tosfernandez 
Status closedResolutionfixed 
Product Version2.1.0b17 
Target Version2.2.0Fixed in Version2.2.0b6 
Summary0001222: VisualTreeHelper.HitTest returns element with IsHitTestVisible == false
DescriptionThe issue is that Noesis returns a "hit test success" for an element with IsHitTestVisible == false:
Steps To Reproduce1. Setup XAML like this:
_mainContent (Grid)
       UserControl IsHitTestVisible == false
            <-- mysterious border that doesn't exist in xaml -->
            Canvas IsHitTestVisible == false

2. Call with some point inside the canvas
            HitTestResult result = VisualTreeHelper.HitTest(_mainContent, new Point(x, y));
            DependencyObject visualHit = result.VisualHit;
            FrameworkElement fe = visualHit as FrameworkElement;
            bool isHitTestVisible = fe.IsHitTestVisible;

no hit test on canvas
Actual: hit test on mysterious border that is not in XAML and has IsHitTestVisible == false (see screenshot.)
Additional InformationI don't have the border in my XAML. It looks like it's coming from a template or something new from Noesis.
The border background is #00FFFFFF.
I have no such brush anywhere in my solution.
TagsNo tags attached.




2018-01-20 11:24

manager   ~0005032

Last edited: 2018-01-20 11:24

View 2 revisions

A couple of questions:

- Is the Canvas the direct logical child of the UserControl? I mean: UserControl.Content = Canvas?

- Does the UserControl have its Background = Transparent? Because UserControl default template looks as follows:

    Background="{TemplateBinding Background}"
    BorderBrush="{TemplateBinding BorderBrush}"
    BorderThickness="{TemplateBinding BorderThickness}"
    Padding="{TemplateBinding Padding}">
        HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
        VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>

By default UserControl has a null Background, so its template Border shouldn't return in a hit test.

Apart from that our default templates have a default Background = Transparent in the following controls: Label, RadioButton, CheckBox, ScrollViewer, ListBoxItem, MenuItem, ComboBoxItem, TreeViewItem, StatusBarItem, and ListViewItem. But these are required to properly click them with the mouse.

If you can attach a minimal project where this can be reproduced we can debug it and find what is occurring.

Thanks for your collaboration.



2018-01-20 16:47

reporter   ~0005035

Thanks! yes - it was a background=transparent causing the hit test to occur. Removing it canceled hit testing as well. Note that the behavior where hit testing is being ignored looks like a WPF bug: ... ?forum=wpf
I propose to deviate from WPF on this one since it's obviously an issue if hit testing returns elements with IsHitTestVisible == false. It's great that you value compatibility so much. In this case, perhaps it's a good idea to fix the bug and have a list of "Fixed in Noesis" differences somewhere compared to WPF. What do you think?


2018-01-20 16:47

reporter   ~0005036

And yes, the Canvas is a direct logical child of the UserControl


2018-01-20 16:48

reporter   ~0005037

For completeness:
<UserControl x:Class="FantasiaPhone.UnityImageFrame"
             Background="Transparent" IsHitTestVisible="False">
    <Canvas x:Name="frameRoot" IsHitTestVisible="False">


2018-01-27 02:31

reporter   ~0005054

ai_enabled has good suggestion in the forums: add a HitTest overload with boolean flag to allow IsHitTestVisible = false to work.

In addition, can be mentioned somewhere in docs as "beneficial deviation from WPF behavior".
What do you think?


2018-01-29 14:48

manager   ~0005058

We decided to implement in C# the callback version of the HitTest function.
This will work for any situation and makes code compatible with WPF.


2018-01-29 18:28

reporter   ~0005062

Thanks, sounds good! hopefully not too taxing on the system due to pinvoke-s (can't really tell without profiling)


2018-06-02 08:59

updater   ~0005213

Please give higher priority to the implementation of the C# HitTest method with the callback delegate for the next update.
Without it, we have to rely on a very problematic and complex workaround code.


2018-06-02 18:28

reporter   ~0005214

Note: having a callback, while good idea, may have significant performance implications if we have to switch from managed to native code.
In addition (or instead of) to callback, can we have a boolean parameter e.g. "emulateWpfBehavior" that is true by default and mimics the WPF bug, and false otherwise?

(to be fair, I think the WPF behavior is just a bug, ideally Noesis fixes it in your implementation and you work better than WPF on this one. There's no reason why an IsHitTestVisible==false should ever hit)


2018-06-02 18:38

updater   ~0005215

Yes, having a parameter or simply another method will be good enough for our needs. When it was discussed on the forums, I've also supported this much more efficient approach.


2018-12-28 13:25

updater   ~0005379

Any updates on this?

> We decided to implement in C# the callback version of the HitTest function. This will work for any situation and makes code compatible with WPF.


2018-12-31 11:21

manager   ~0005380

Haven't work on this yet but is something we are going to address before releasing the final 2.2 version.


2019-04-30 06:20

reporter   ~0005653

Thanks for the fix!

Issue History

Date Modified Username Field Change
2018-01-20 04:46 nokola New Issue
2018-01-20 04:46 nokola File Added: NoesisHitTestFail.jpg
2018-01-20 11:24 sfernandez Assigned To => sfernandez
2018-01-20 11:24 sfernandez Status new => feedback
2018-01-20 11:24 sfernandez Note Added: 0005032
2018-01-20 11:24 sfernandez Note Edited: 0005032 View Revisions
2018-01-20 16:47 nokola Note Added: 0005035
2018-01-20 16:47 nokola Status feedback => assigned
2018-01-20 16:47 nokola Note Added: 0005036
2018-01-20 16:48 nokola Note Added: 0005037
2018-01-27 02:31 nokola Note Added: 0005054
2018-01-29 14:48 sfernandez Note Added: 0005058
2018-01-29 18:28 nokola Note Added: 0005062
2018-06-02 08:59 ai_enabled Note Added: 0005213
2018-06-02 18:28 nokola Note Added: 0005214
2018-06-02 18:38 ai_enabled Note Added: 0005215
2018-11-01 02:14 jsantos View Status public => private
2018-11-22 12:00 sfernandez Target Version => 2.2.0
2018-11-22 12:00 sfernandez View Status private => public
2018-11-22 12:00 sfernandez Platform => Any
2018-12-28 13:25 ai_enabled Note Added: 0005379
2018-12-31 11:21 sfernandez Note Added: 0005380
2019-01-16 13:15 sfernandez Status assigned => resolved
2019-01-16 13:15 sfernandez Resolution open => fixed
2019-01-16 13:15 sfernandez Fixed in Version => 2.2.0b6
2019-04-30 06:20 nokola Status resolved => closed
2019-04-30 06:20 nokola Note Added: 0005653
2019-04-30 18:19 sfernandez File Deleted: NoesisHitTestFail.jpg