Fix Airspace issue

[jeremyVignelles]

Many users have reported Airspace issues while using this library. One issue to rule them all and in the darkness bind them.

Sample code (taken from #41):

<Window
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:Wpf="clr-namespace:Vlc.DotNet.Wpf;assembly=Vlc.DotNet.Wpf" x:Class="LivestreamViewer.MainWindow"
        Title="MainWindow" Height="449" Width="753">
    <Grid>
        <Wpf:VlcControl x:Name="vlc" Margin="0,0,0,13" Panel.ZIndex="-1"/>
        <Grid x:Name="overlayGrid" HorizontalAlignment="Stretch" Height="25" Margin="0,0,0,0" VerticalAlignment="Bottom">
            <Rectangle Fill="Black" HorizontalAlignment="Stretch" Margin="0,0,0,0" Stroke="Black" VerticalAlignment="Stretch" IsHitTestVisible="False" Opacity="0.5"/>
        </Grid>
    </Grid>
</Window>

Technical explanations:

• https://msdn.microsoft.com/en-us/library/aa970688(v=vs.85).aspx
• https://blogs.msdn.microsoft.com/dwayneneed/2013/02/26/mitigating-airspace-issues-in-wpf-applications/
• https://msdn.microsoft.com/en-us/library/ms742522(v=vs.85).aspx

Following issues are impacted (and will be closed):

• The wpf VlcControl Have AirSpace problem #8
• WPF video is always on top #12
• Wpf VlcControl seems to ignore ZIndex #41
• VlcControl is always on the top of my window #143

Proposed workarounds/hacks (untested):

• https://stackoverflow.com/questions/5978917/render-wpf-control-on-top-of-windowsformshost/23662410#23662410
• https://github.com/kolorowezworki/Airhack (thanks @kolorowezworki)

[adamfierek]

https://github.com/kolorowezworki/Airhack
Try this. It's quite dirty, but it works ;)

[jeremyVignelles]

Thanks for providing a workaround! I'll keep this open until this is fixed or considered as an acceptable solution (I'd prefer the first option)

[adamfierek]

We cannot fix airspace. Maybe we can fix VLC control, but not general problem with Winforms. This is caused by the method of rendering WPF and Winforms controls and windows. I think, at the moment, we can base only on workarounds.

[jeremyVignelles]

This could be fixed by #249 : If there is no reference to winforms, then there is no airspace issue, am I wrong? the option I'm thinking of is using DirectX to do the rendering, rather than using WinForm/HWND. vlc-winrt is already using that technique for win10 apps

[adamfierek]

Sure. No Winforms/Win32Api == no airspace. DirectX is rendered the similar way to WPF. Avoiding problem is avoid, not solve ;) #249 is not about fixing airspace, rather about making something very new and different of current solution. We can use HWND of WPF Window directly and it will not need a reference to Windows.Forms, but airspace effect will not disappear. My workaround is for general mixing Winforms and WPF, not only for Vlc.DotNet control ;)

[jeremyVignelles]

A comment in #257 shows a workaround for the Airspace issue in stackoverflow : https://stackoverflow.com/questions/5978917/render-wpf-control-on-top-of-windowsformshost/23662410#23662410

[JUSTHassan]

A powerful workaround https://stackoverflow.com/a/43695349/1576027

<interop:AirspaceDecorator AirspaceMode="Redirect" Background="White" IsInputRedirectionEnabled="True" IsOutputRedirectionEnabled="True"> <Wpf:VlcControl x:Name="vlcControl" Margin="0,0,0,0"/> </interop:AirspaceDecorator>

[jeremyVignelles]

Will be solved in 3.0.0 when #365 gets merged

[jeremyVignelles]

Should be fixed in 3.0.0-develop250