Deriving from WindowEx breaks bindings

[Slion]

When I derive from WindowEx scale of various UI elements are messed up on a 4K screen. Wierdly enough my icons are too big and my texts are too small. In any case it looks like it real messes the DPI awarness somehow.

[dotMorten]

Could you provide some more info? A reproducer and some screenshots would be helpful. I work on a 4K high dpi screen and have never seen this so would love to know more.

[Slion]

That is odd. It's on a closed source project which makes extensive use of Win32 APIs so maybe that's in combination with those API calls somehow.

[dotMorten]

If you’re able to distill the issue down to a smaller reproducer I would be able to take a look.

[Slion]

Yeah it's definitly not a DPI issue. Instead it somehow breaks access to some settings controlling the look and feel of the UI used by a derived class through XAML binding. Still really weird though.

[Slion]

The derived class has a list view with a data template for the list items and those list items are using binding to get some settings. Those bindings are broken somehow. Though it compiles and runs.

Here I name the class instance that now derives indirectly from WindowEx.

<local:WindowTaskbarBase
    x:Class="Taskbar.WindowTaskbar"
    x:Name="iMainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:Taskbar"
    xmlns:lib="using:Taskbar;assembly=Taskbar.Lib"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:muxc="using:Microsoft.UI.Xaml.Controls"
    mc:Ignorable="d"
    Activated="Window_Activated"
    Closed="Window_Closed"
    SizeChanged="iMainWindow_SizeChanged"    
    >

In the same XAML file I have the following to bind the settings:

        <Image                         
         Width ="{Binding ElementName=iMainWindow, Path=Settings.IconSize, Mode=OneWay}"
         Height="{Binding ElementName=iMainWindow, Path=Settings.IconSize, Mode=OneWay}"
         Margin="0"
         VerticalAlignment="Center"
         HorizontalAlignment="Center"
         Source="{x:Bind IconPath, Mode=OneWay}"
         />

[dotMorten]

What is iMainWindow? If it’s a window type that won’t work since it isn’t a dependency object. Try hardcoding the values in there just to rule out WinUIEx and confirm whether this is just a binding issue. Also does this happen if you don’t inherit from windowex but just from window?

[Slion]

I updated the post above. Everything works fine when not deriving from WindowEx.

To break it I just change:

internal class WindowBase : Microsoft.UI.Xaml.Window, INotifyPropertyChanged

to

internal class WindowBase : WindowEx, INotifyPropertyChanged

[Slion]

The settings class is using

ApplicationDataContainer iSettings = ApplicationData.Current.LocalSettings;

internally to store values. But the ones that are accessed from simplier bindings outside of the list items without having to use that iMainWindow are working fine.

[dotMorten]

@Slion If you could provide me with a small project that runs and reproduces the issue, I'd love to take a look.

[Slion]

Thanks, for now I've just postponed switching to WinUIEx until I find the time to investigate further.

[dotMorten]

Closing for now. If you get a chance to provide a repro, feel free to re-open.