WPF form of arbitrary shape

ArbitraryShapeForm.xaml

<Window x:Class="Test.ArbitraryShapeForm"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="ArbitraryShapeForm"
        AllowsTransparency="True"
        Background="Transparent"
        WindowStyle="None">
    
    <Canvas Width="300" Height="300">
        <Path Stroke="Gray" StrokeThickness="2">
            <Path.Data>
                <PathGeometry>
                    <PathFigure StartPoint="0,0">
                        <LineSegment Point="0,260"  />
                        <LineSegment Point="180,260" />
                        <LineSegment Point="220,300" />
                        <LineSegment Point="260,260" />
                        <LineSegment Point="300,260" />
                        <LineSegment Point="300,0" />
                        <LineSegment Point="0,0" />
                    </PathFigure>
                </PathGeometry>
            </Path.Data>
            <Path.Fill>
                <LinearGradientBrush StartPoint="0, 0" EndPoint="0, 1">
                    <GradientStop Color="Yellow" Offset="0" />
                    <GradientStop Color="Red" Offset="1.2" />
                </LinearGradientBrush>
            </Path.Fill>
        </Path>
        
        <Grid Canvas.Top="0" Canvas.Left="0" Height="260" Width="300">
            <Grid.RowDefinitions>
                <RowDefinition Height="auto" />
                <RowDefinition />
            </Grid.RowDefinitions>
            
            <TextBlock Grid.Row="0" Text="Ololo! Where have you been?" TextAlignment="Center" Margin="0 20" />
            <Button Grid.Row="1" Name="justButton" Content="Ok" Height="24" Width="50" VerticalAlignment="Bottom" HorizontalAlignment="Right" Margin="6" />
        </Grid>

        <CheckBox Canvas.Bottom="20" Canvas.Right="74" >
            <CheckBox.RenderTransform>
                <RotateTransform x:Name="rotate" Angle="0" CenterX="7" CenterY="7" />
            </CheckBox.RenderTransform>
            <CheckBox.Triggers>
                <EventTrigger RoutedEvent="CheckBox.Loaded">
                    <BeginStoryboard>
                        <Storyboard Storyboard.TargetName="rotate" Storyboard.TargetProperty="Angle">
                            <DoubleAnimation From="0" To="360" Duration="0:0:3" RepeatBehavior="Forever" />
                        </Storyboard>
                    </BeginStoryboard>
                </EventTrigger>
            </CheckBox.Triggers>
        </CheckBox>
    </Canvas>
</Window>

ArbitraryShapeForm.xaml.cs

using System;
using System.Windows;

namespace Test
{
    /// <summary>
    /// Interaction logic for ArbitraryShapeForm.xaml
    /// </summary>
    public partial class ArbitraryShapeForm : Window
    {
        public ArbitraryShapeForm()
        {
            InitializeComponent();

            this.justButton.Click += (sender, e) => this.Close();
        }
    }
}