WPF WindowChrome: Edges of maximized Window are out of the screen

Question

I use WindowChrome to customize a Window. When I maximize the Window, then the edges are out of the screen. I use the following code to fix this:

Answer 1

Example of how to increase border thickness when a window is maximised. Otherwise, due to oddities of WindowChrome, part of the border will disappear.

This example also strips out the standard window header, so you have to add your own minimize/maximize/close buttons.

<Window ResizeMode="CanResizeWithGrip"
        WindowStyle="SingleBorderWindow">
    <!-- Remove window header and border. Use with ResizeMode="CanResizeWithGrip" and WindowStyle="SingleBorderWindow". -->
    <WindowChrome.WindowChrome>
        <WindowChrome     
            CaptionHeight="1"  
            CornerRadius ="0"
            ResizeBorderThickness="4"         
            GlassFrameThickness="0">
        </WindowChrome>
    </WindowChrome.WindowChrome>            
    <Border BorderThickness="1">     
        <Border.Style>
            <Style TargetType="{x:Type Border}">
                <Style.Triggers>
                    <!-- Add to avoid border disappearing when window is maximised -->
                    <DataTrigger Binding="{Binding WindowState, RelativeSource={RelativeSource AncestorType=Window}}" 
                                 Value="Maximized">
                        <Setter Property="Margin" Value="10"/>
                    </DataTrigger>
                    <DataTrigger Binding="{Binding WindowState, RelativeSource={RelativeSource AncestorType=Window}}" 
                                 Value="Normal">
                        <Setter Property="Margin" Value="0"/>
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </Border.Style>
        <Grid>
           <!-- Window XAML here. -->
        <Grid>
     </Border>
 </Window>

Answer 2

Based on the OP's original example, they were almost there...

When the window is maximised, Windows seems to ignore the ResizeBorderThickness value. Using <Setter Property="Margin" Value="7" /> seems to work, but this value may need to be changed depending on the operating system (I tested this on Windows 10).

I recommend making a couple of small tweaks (see code below), such as adding WindowStyle="None" and ResizeMode="CanResize" to Window, as well as moving the Style out into either Window.Resources, Application.Resources or even a ResourceDictionary, changing the style's TargetType to "{x:Type Panel}" and using a key name (eg: x:Key="WindowMainPanelStyle"), as this will prevent the style automatically being applied to any child Grid elements, as well as allowing the style to be used with any elements that inherit from Panel (such as Border, DockPanel, Grid, StackPanel, etc).

<Window x:Class="WpfApplication1.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    WindowStyle="None"
    ResizeMode="CanResize">

<WindowChrome.WindowChrome>
    <WindowChrome CaptionHeight="50" ResizeBorderThickness="5" />
</WindowChrome.WindowChrome>

<Window.Resources>
    <Style TargetType="{x:Type Panel}" x:Key="WindowMainPanelStyle">
        <Setter Property="Margin" Value="0" />
        <Style.Triggers>
            <DataTrigger Binding="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}, Path=WindowState}" Value="Maximized">
                <Setter Property="Margin" Value="7" />
            </DataTrigger>
        </Style.Triggers>
    </Style>
</Window.Resources>

<Grid Style="{StaticResource WindowMainPanelStyle}">
    <Border BorderThickness="2" BorderBrush="Blue" Background="Yellow" />
</Grid>

</Window>

Answer 3

The WindowChrome will basically overlap by the size of ResizeBorderThickness when maximized.

If you want your Window completely visible while maximized just use the WindowChrome ResizeBorderThickness (5px) as Margin in your Grid style:

<Setter Property="Margin" Value="5" />

---

Otherwise if you want your Border's BorderThickness not to be visible while the window is maximized, you should use your Border's BorderThickness (2px) as Margin in addition to the WindowChrome ResizeBorderThickness (5px) in your Grid style. Then the Margin would be 7px.