WPF minimized owned windows should stay minimized, if Parent is minimized and then restored-CodePudding

I have a Main window and a child window. The owner of the child window is main window. The child window is not a dialog. I have used the following code in the constructor of the child window:

this.Owner = Application.Current.MainWindow;
this.WindowStartupLocation = WindowStartupLocation.CenterOwner;
this.ShowInTaskbar = false;

I have set this.ShowInTaskbar = false because I want the child window to be displayed in the bottom of the screen when minimized(and not in the taskbar). When I minimize the Main window, child window should also minimize(this is working). But when the child window is already minimized and then if I minimize and restore the main window the child window is also restoring. I want the child window to stay minimized if it was already minimized.

CodePudding user response：

This behavior is by design but you can override it by checking for the child's WindowState property in the parent's StateChanged event. Set a flag if it was minimized, and manually minimize the child window when it's going to switch to normal while the flag is set.

In this sample I put a button for creating and opening a new child Window, and set the child's properties and event listeners in the parent class. So there are no XAML and code-behind files for the child window. The code looks like this:

XAML:

<Window x:Class="WpfApp1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp1"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <Button Content="Button" HorizontalAlignment="Left" Margin="407,157,0,0" VerticalAlignment="Top" Width="75" Click="Button_Click"/>
    </Grid>
</Window>

Code-Behind:

public partial class MainWindow : Window
{
    private Window childWindow;
    private bool ignoreStateChange = false;

    public MainWindow()
    {
        InitializeComponent();
        this.StateChanged  = MainWindow_StateChanged;
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        childWindow = new Window() { Owner = this, WindowStartupLocation = WindowStartupLocation.CenterOwner, ShowInTaskbar = false };
        childWindow.StateChanged  = ChildWindow_StateChanged;
        childWindow.Show();
    }


    private void MainWindow_StateChanged(object sender, EventArgs e)
    {
        if (WindowState == WindowState.Normal && childWindow?.WindowState == WindowState.Minimized)
            ignoreStateChange = true;
    }

    private void ChildWindow_StateChanged(object sender, EventArgs e)
    {
        if (ignoreStateChange)
        {
            ignoreStateChange = false;
            childWindow.WindowState = WindowState.Minimized;
            return;
        }
    }
}