RotateTransform,but arrow will point towards the original

[tomuGo]

Is there a way to solve this problem,Thanks!

Here is my code:

`

<TextBlock VerticalAlignment="Center" Grid.Row="1" Text="RotateTransform -90" x:Name="TextBlock" 
      MouseEnter="TextBlock_OnMouseMove" MouseLeave="TextBlock_OnMouseLeave" Height="22" Background="Beige" 
        Width="120">
    <TextBlock.RenderTransform>
        <RotateTransform Angle="-90"></RotateTransform>
    </TextBlock.RenderTransform>
</TextBlock>
<TextBlock VerticalAlignment="Center" Grid.Row="1" Text="RotateTransform   0"  Height="22" Background="Beige" Width="120">
    <TextBlock.RenderTransform>
        <RotateTransform Angle="0"></RotateTransform>
    </TextBlock.RenderTransform>
</TextBlock>
<Popup Grid.Row="1"
       AllowsTransparency="True"
       ClipToBounds="False"
       x:Name="Popup"
       Placement="Top"
       PlacementTarget="{Binding ElementName=TextBlock}">
    <Border Margin="150" ClipToBounds="False">
        <geometry:Balloon CornerRadius="10" PlacementOptions="Right, Center" PlacementTarget="{Binding PlacementTarget, RelativeSource={RelativeSource AncestorType={x:Type Popup}}}">
            <Grid Margin="5">
                <Grid.RowDefinitions>
                    <RowDefinition />
                    <RowDefinition />
                </Grid.RowDefinitions>
                <GroupBox Header="Stuff">
                    <TextBlock Text="RotateTransform -90" />
                </GroupBox>
                
            </Grid>
        </geometry:Balloon>
    </Border>
</Popup>

public partial class WaveToolTipTest : Window
    {
        public WaveToolTipTest()
        {
            InitializeComponent();
            
           
        }

        private void TextBlock_OnMouseMove(object sender, MouseEventArgs e)
        {
            Popup.IsOpen = true;
        }

        private void TextBlock_OnMouseLeave(object sender, MouseEventArgs e)
        {
            if (Popup.IsOpen && !TextBlock.IsMouseOver)
            {
                Popup.IsOpen = false;
            }
            
        }
    }