RibbonTabItem.IsSelected is briefly set to true for a tab that's not selected anymore, when a modal dialog is closed.

[HorpeHUN]

I have a very simple test app that has two ribbon tabs. The IsSelected property of these tabs are data bound to two properties. If the data bound property becomes true, a message box is displayed.

But if you close the message box, then the other tabs IsSelected property turns to true somehow, and the another message box gets displayed

MainWindow.xaml

        <Fluent:Ribbon>
            <Fluent:RibbonTabItem Header="First" IsSelected="{Binding ElementName=MyWindow, Path=IsFirstSelected}"/>
            <Fluent:RibbonTabItem Header="Second" IsSelected="{Binding ElementName=MyWindow, Path=IsSecondSelected}"/>
        </Fluent:Ribbon>

MainWindow.cs

bool isFirstSelected;
bool isSecondSelected;

public bool IsFirstSelected
{
    get { return isFirstSelected; }
    set
    {
        if (isFirstSelected != value)
        {
            isFirstSelected = value;

            if (value)
                MessageBox.Show("IsFirstSelected is now set to true.");
        }
    }
}


public bool IsSecondSelected
{
    get { return isSecondSelected; }
    set
    {
        if (isSecondSelected != value)
        {
            isSecondSelected = value;
            if (value)
                MessageBox.Show("IsSecondSelected is now set to true.");
        }
    }
}

Source code:
RibbonTest.zip

---

Environment

• Fluent.Ribbon v8.0.0
• Windows 10
• .NET Framework 4.7.2

[batzen]

Just had a look and first thought that it's a ribbon issue, but i think it's not.
Showing a messagebox, and thus causing a modal message loop, when setting a dependency property confuses the WPF input system somehow.
If you show the messagebox async like
this.Dispatcher.BeginInvoke(DispatcherPriority.Background, new Action(() => MessageBox.Show("IsFirstSelected is now set to true.")));
the issue is gone. If you set a breakpoint on the lines showing the messagebox you can see from the call stack that we get a WM_SETFOCUS window message when closing the messagebox which causes wpf the send a PreviewGotKeyboardFocus event to the other tab item.

[HorpeHUN]

We have switched from the Microsoft Ribbon (System.Windows.Controls.Ribbon) to this library, and we didn't have this problem with that. That doesn't set IsSelected to true in PreviewGotKeyboardFocus .

In our application, the main content changes when you change from one Tab to another. In some cases that takes a bit of time and a progress bar is displayed. And when the progress bar is closed, then the application starts switching back to the previous tab, and that causes problems.

We'll need to create a workaround, like ignoring the change of the IsSelected property when a change is already underway.
I still think this is a bug. Showing a dialog in one tab's IsSelected property setter sets another tab's IsSelected property to true as a side effect.

RibbonTest.exe!RibbonTest.MainWindow.IsFirstSelected.set(bool value = true) Line 17 C# Fluent.dll!Fluent.RibbonTabItem.OnPreviewGotKeyboardFocus(System.Windows.Input.KeyboardFocusChangedEventArgs e = {System.Windows.Input.KeyboardFocusChangedEventArgs}) Line 582 C# PresentationFramework.dll!System.Windows.MessageBox.Show(string messageBoxText) Line 135 C# RibbonTest.exe!RibbonTest.MainWindow.IsSecondSelected.set(bool value = true) Line 35 C#

[batzen]

I agree that it behaves a bit strange and I am not sure why that code, inside PreviewGotKeyboardFocus, exists.
Give me a few days to think about it.