Comment faire pour centrer un menu contextuel dans la fenêtre (Windows store)

J'ai un contextuel personnalisé (comme un contrôle utilisateur) dont j'ai la charge par programmation. Je ne suis pas en mesure de le centrer sur l'axe x, uniquement sur la verticale. Le popup n'est pas ajouté à un fichier xaml, mais elle est ajoutée à la fenêtre racine.

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;
using System.Windows;
using Windows.UI.Core;
//The User Control item template is documented at http://go.microsoft.com/fwlink/?LinkId=234236
namespace QSTLibrary.WIN8.Tools
{
public sealed partial class CustomProgressRingPopup : UserControl
{
public CustomProgressRingPopup()
{
this.InitializeComponent();
}
public string Text
{
get { return (string)GetValue(TextProperty); }
set { SetValue(TextProperty, value); }
}
//Using a DependencyProperty as the backing store for Text.  This enables animation, styling, binding, etc...
public static readonly DependencyProperty TextProperty = DependencyProperty.Register(
"Text", 
typeof(string), 
typeof(CustomProgressRingPopup),
new PropertyMetadata("", OnTextChanged));
public void OpenPopup()
{
this.ParentPopup.IsOpen = true;
}
public void ClosePopup()
{
this.ParentPopup.IsOpen = false;
}
private static void OnTextChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var instance = d as CustomProgressRingPopup;
var newValue = e.NewValue as string;
if (instance != null && newValue != null)
{
instance.CustomTextBlock.Text = newValue;
}
}
private void OnPopupLoaded(object sender, RoutedEventArgs e)
{
this.ParentPopup.HorizontalOffset = (Window.Current.Bounds.Width - gdChild.ActualWidth) / 2;
this.ParentPopup.VerticalOffset = (Window.Current.Bounds.Height - gdChild.ActualHeight) / 2;
}
}
}

userControl xaml:

<UserControl
x:Class="QSTLibrary.WIN8.Tools.CustomProgressRingPopup"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:QSTLibrary.WIN8.Tools"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
d:DesignHeight="300"
d:DesignWidth="400">
<Popup x:Name="ParentPopup" HorizontalAlignment="Center" VerticalAlignment="Center" Loaded="OnPopupLoaded">
<Grid x:Name="gdChild" Height="auto" Width="auto" Background="Blue" Margin="20">
<Grid.RowDefinitions>
<RowDefinition/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<ProgressRing x:Name="CustomProgressRing" Height="40" Width="40" IsActive="true" Grid.Column="0" Margin="20"/>
<TextBlock x:Name="CustomTextBlock" Height="auto" Width="auto" FontSize="25" Grid.Column="1" Margin="20"/>
</Grid>
</Popup>    
</UserControl>

Voici comment je l'utilise: externe:

_loginProgressRingPopup.Text = "Logging in";
_loginProgressRingPopup.OpenPopup();

OriginalL'auteur Alexandru Circus | 2013-09-26