By default, when selecting through the tab items, the first focusable element within each RadTabItem will gain focus. This is the behavior of the standard  RadTabItem as well. Provide an option to disable this default selection through a boolean property.

The workaround is to set the IsContentPreserved of the RadTabControl to True.

When you select the RadTabItems via Keyboard or Mouse, Narrator or other Accessibility tools like NVDA do no read the selected tab.

This is a bug in the RadTabControlAutomaitonPeer / RadTabItemAutomationPeer's code.

Usually screen readers read "Selected Tab One", "Selected Tab 2". This is how MS TabControl is read actually.

TabControl's TabItems aren't properly updated on attempt to change the theme palette variation runtime until any of the items is selected. Check the following video - https://www.screencast.com/t/jMj0EZqFfy.

There are several possible workarounds which include:

• Clearing all merged resource dictionaries and re-merging them
• Increasing and decreasing the height of the MainWindow by 1 after loading the chosen palette to force the refresh
  

Currently, when scrolling tabs in a TabControl using the mouse wheel, the direction of the scroll is the opposite as tab controls of many other applications, for example all web browsers scroll tabs in the opposite direction as the Telerik RadTabControl.

This behaviour may cause frustration in the end user and damages the user experience. I think it's necessary to expose a way to allow inverting the RadTabControl mouse wheel scroll direction.

Tabcontrol doesn't work correctly when we set the properties TabOrientation="Vertical" and AllTabsEqualHeight="False". The Header are always Aligned left no matter the value align property.

DECLINED: This issue cannot be reproduced with R3 2016 release version.

When a RadDocking is located inside a RadTabControl and the RadPaneGroup contains only one RadPane the content is scrolled(if located inside a ScrollViewer)

When a TabItem has a width (and the TabControl - don't) and if you try to resize the window so that the width of the window is less than the width of the TabItem - the TabItems start jumping

The SelectedTabContent is not added when the control is loaded in memory and a we try to create a ImageSource out of the UserControl hosting the TabControl

Workaround:
Use the PreviewMouseLeftButtonUp and PreviewMouseLeftButtonDown events of the DropDownMenuItem. Handle the first event and invoke DropDownMenuItem.MouseLeftButtonUpEvent in the second in order to workaround the MouseLeftButtonUp event fired from the DropDownMenuButton and to call the logic for selecting the tabitem only when the dropdown menuitem is clicked (not just hovered). 

<Style TargetType="telerikTabControl:DropDownMenuItem">		
        <EventSetter Event="PreviewMouseLeftButtonUp" Handler="DropDownMenuItem_PreviewMouseLeftButtonUp" />
        <EventSetter Event="PreviewMouseLeftButtonDown" Handler="DropDownMenuItem_PreviewMouseLeftButtonDown" />
</Style>

private void DropDownMenuItem_PreviewMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{		
		e.Handled = true;
}

private void DropDownMenuItem_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
	var item = (sender as DropDownMenuItem);
	MouseButtonEventArgs mouseEventArgs = new MouseButtonEventArgs(Mouse.PrimaryDevice, 0, MouseButton.Left);
	mouseEventArgs.RoutedEvent = DropDownMenuItem.MouseLeftButtonUpEvent;
	item.RaiseEvent(mouseEventArgs);
}

In version 2016.2.613.45 of the Office2013 Theme, there is a problem in the control template for the RadTabControl. The ContentBorder element properly gets it's BorderThickness from the TemplatedParent, but the PlacementStates VisualStates override it with hard-coded Thickness (0,1,1,1 in the case of the "Left" Visual State) in their storyboards rather than doing an appropriate transform of the Thickness. This makes it impossible to override the BorderThickness for the control in any state other than the default layout without copying and replacing the entire control template. This appears to be a change in behavior since the (Februray 2016?) release, but I cannot be sure as the old theme files were uninstalled during the upgrade and the telerik.windows.controls.navigation.baml file is not properly decompiled in JustDecompile.

Workaround: Set HorizontalScrollBarVisibility property to Visible in order to show the scrollbar: 
<telerik:RadTabControl ScrollViewer.HorizontalScrollBarVisibility="Visible" .../>

or use Loaded event of TabControl and change the Height in order to trigger SizeChanged:
private void xTab_Loaded(object sender, RoutedEventArgs e)
{
    this.Height++;
    this.Height--;
}

RadTabControlBase expose a protected method called OnPreviewSelectionChanged that should raise the event PreviewSelectionChanged event. This means that you should be able to override it and implement additional logic if necessary.

However, the method is never used in the code and therefore it is not fired when the PreviewSelectionChanged event raises. 

Use the method to raise the event.

Drag and drop from Visual Studio Toolbox to the designer area doesn't allow you to drop the corresponding control inside the content of the selected tab item. 

To work this around, add a Grid panel with transparent background inside the RadTabItem's in XAML. You can do this also  through the toolbox.

 <telerik:RadTabItem x:Name="RadTabItem1" Header="Tab item 1">
	<Grid Background="Transparent" />
 </telerik:RadTabItem>