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Add setting border color + fix background extending inside FluentWindow #1508

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Add setting border color + fix background extending inside FluentWindow #1508

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32467e1
Add setting border color
Nuklon Aug 8, 2025
957eb0a
Update FluentWindow.cs
Nuklon Aug 8, 2025
b697a68
Update FluentWindow.cs
Nuklon Aug 8, 2025
22b84f7
Update UnsafeNativeMethods.cs
Nuklon Aug 8, 2025
52cf5ba
Use border only when active, similar to WinUI
Nuklon Aug 8, 2025
b9bb8cf
Update UnsafeNativeMethods.cs
Nuklon Aug 11, 2025
e1a5f34
Listen for theme changes
Nuklon Aug 14, 2025
90f9231
Ensure desktop composition is enabled before changing WindowChrome
Nuklon Sep 28, 2025
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60 changes: 46 additions & 14 deletions src/Wpf.Ui/Controls/FluentWindow/FluentWindow.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,9 @@
// All Rights Reserved.

using System.Windows.Shell;
using Wpf.Ui.Appearance;
using Wpf.Ui.Interop;
using Wpf.Ui.Win32;

// ReSharper disable once CheckNamespace
namespace Wpf.Ui.Controls;
Expand Down Expand Up @@ -103,12 +105,35 @@ static FluentWindow()
protected override void OnSourceInitialized(EventArgs e)
{
OnCornerPreferenceChanged(default, WindowCornerPreference);
OnExtendsContentIntoTitleBarChanged(default, ExtendsContentIntoTitleBar);
OnExtendsContentIntoTitleBarChanged(false, ExtendsContentIntoTitleBar);
OnBackdropTypeChanged(default, WindowBackdropType);

base.OnSourceInitialized(e);
}

/// <inheritdoc />
protected override void OnActivated(EventArgs e)
{
base.OnActivated(e);

if (Utilities.IsOSWindows11OrNewer)
{
UnsafeNativeMethods.ApplyBorderColor(this, ApplicationAccentColorManager.SystemAccent);
}
}

/// <inheritdoc />
protected override void OnDeactivated(EventArgs e)
{
base.OnDeactivated(e);

if (Utilities.IsOSWindows11OrNewer)
{
// DWMWA_COLOR_DEFAULT.
UnsafeNativeMethods.ApplyBorderColor(this, unchecked((int)0xFFFFFFFF));
}
}

/// <summary>
/// Private <see cref="WindowCornerPreference"/> property callback.
/// </summary>
Expand Down Expand Up @@ -182,10 +207,11 @@ protected virtual void OnBackdropTypeChanged(WindowBackdropType oldValue, Window
return;
}

SetWindowChrome();

if (newValue == WindowBackdropType.None)
{
_ = WindowBackdrop.RemoveBackdrop(this);

return;
}

Expand Down Expand Up @@ -233,20 +259,26 @@ protected virtual void OnExtendsContentIntoTitleBarChanged(bool oldValue, bool n
// AllowsTransparency = true;
SetCurrentValue(WindowStyleProperty, WindowStyle.SingleBorderWindow);

WindowChrome.SetWindowChrome(
this,
new WindowChrome
{
CaptionHeight = 0,
CornerRadius = default,
GlassFrameThickness = new Thickness(-1),
ResizeBorderThickness = ResizeMode == ResizeMode.NoResize ? default : new Thickness(4),
UseAeroCaptionButtons = false,
}
);

// WindowStyleProperty.OverrideMetadata(typeof(FluentWindow), new FrameworkPropertyMetadata(WindowStyle.SingleBorderWindow));
// AllowsTransparencyProperty.OverrideMetadata(typeof(FluentWindow), new FrameworkPropertyMetadata(false));
_ = UnsafeNativeMethods.RemoveWindowTitlebarContents(this);
}

/// <summary>
/// This virtual method is called when <see cref="WindowBackdropType"/> is changed.
/// </summary>
protected virtual void SetWindowChrome()
{
WindowChrome.SetWindowChrome(
this,
new WindowChrome
{
CaptionHeight = 0,
CornerRadius = default,
GlassFrameThickness = WindowBackdropType == WindowBackdropType.None ? new Thickness(0.00001) : new Thickness(-1), // 0.00001 so there's no glass frame drawn around the window, but the border is still drawn.
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This is the fix for FluentWindow. -1 cannot be used if None is specified, otherwise the background of the window is rendered 1 pixel inside, which is obviously wrong.

ResizeBorderThickness = ResizeMode == ResizeMode.NoResize ? default : new Thickness(4),
UseAeroCaptionButtons = false,
}
);
}
}
81 changes: 59 additions & 22 deletions src/Wpf.Ui/Interop/UnsafeNativeMethods.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -49,15 +49,64 @@ public static bool ApplyWindowCornerPreference(IntPtr handle, WindowCornerPrefer

int pvAttribute = (int)UnsafeReflection.Cast(cornerPreference);

// TODO: Validate HRESULT
_ = Dwmapi.DwmSetWindowAttribute(
return Dwmapi.DwmSetWindowAttribute(
handle,
Dwmapi.DWMWINDOWATTRIBUTE.DWMWA_WINDOW_CORNER_PREFERENCE,
ref pvAttribute,
Marshal.SizeOf(typeof(int))
);
) == 0;
}

return true;
/// <summary>
/// Tries to apply the color of the border.
/// </summary>
/// <param name="window">The window.</param>
/// <param name="color">The color.</param>
/// <returns><see langword="true" /> if invocation of native Windows function succeeds.</returns>
public static bool ApplyBorderColor(Window window, Color color) =>
GetHandle(window, out IntPtr windowHandle)
&& ApplyBorderColor(windowHandle, color);

/// <summary>
/// Tries to apply the color of the border.
/// </summary>
/// <param name="window">The window.</param>
/// <param name="color">The color.</param>
/// <returns><see langword="true" /> if invocation of native Windows function succeeds.</returns>
public static bool ApplyBorderColor(Window window, int color) =>
GetHandle(window, out IntPtr windowHandle)
&& ApplyBorderColor(windowHandle, color);

/// <summary>
/// Tries to apply the color of the border.
/// </summary>
/// <param name="handle">The handle.</param>
/// <param name="color">The color.</param>
/// <returns><see langword="true"/> if invocation of native Windows function succeeds.</returns>
public static bool ApplyBorderColor(IntPtr handle, Color color)
{
return ApplyBorderColor(handle, (color.B << 16) | (color.G << 8) | color.R);
}

/// <summary>
/// Tries to apply the color of the border.
/// </summary>
/// <param name="handle">The handle.</param>
/// <param name="color">The color.</param>
/// <returns><see langword="true"/> if invocation of native Windows function succeeds.</returns>
public static bool ApplyBorderColor(IntPtr handle, int color)
{
if (handle == IntPtr.Zero)
{
return false;
}

if (!User32.IsWindow(handle))
{
return false;
}

return Dwmapi.DwmSetWindowAttribute(handle, Dwmapi.DWMWINDOWATTRIBUTE.DWMWA_BORDER_COLOR, ref color, sizeof(int)) == 0;
}

/// <summary>
Expand Down Expand Up @@ -93,10 +142,7 @@ public static bool RemoveWindowDarkMode(IntPtr handle)
dwAttribute = Dwmapi.DWMWINDOWATTRIBUTE.DMWA_USE_IMMERSIVE_DARK_MODE_OLD;
}

// TODO: Validate HRESULT
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I also corrected this, it's only returning 0 on success.

_ = Dwmapi.DwmSetWindowAttribute(handle, dwAttribute, ref pvAttribute, Marshal.SizeOf(typeof(int)));

return true;
return Dwmapi.DwmSetWindowAttribute(handle, dwAttribute, ref pvAttribute, Marshal.SizeOf(typeof(int))) == 0;
}

/// <summary>
Expand Down Expand Up @@ -132,10 +178,7 @@ public static bool ApplyWindowDarkMode(IntPtr handle)
dwAttribute = Dwmapi.DWMWINDOWATTRIBUTE.DMWA_USE_IMMERSIVE_DARK_MODE_OLD;
}

// TODO: Validate HRESULT
_ = Dwmapi.DwmSetWindowAttribute(handle, dwAttribute, ref pvAttribute, Marshal.SizeOf(typeof(int)));

return true;
return Dwmapi.DwmSetWindowAttribute(handle, dwAttribute, ref pvAttribute, Marshal.SizeOf(typeof(int))) == 0;
}

/// <summary>
Expand Down Expand Up @@ -214,15 +257,12 @@ public static bool ApplyWindowBackdrop(IntPtr handle, WindowBackdropType backgro
return false;
}

// TODO: Validate HRESULT
_ = Dwmapi.DwmSetWindowAttribute(
return Dwmapi.DwmSetWindowAttribute(
handle,
Dwmapi.DWMWINDOWATTRIBUTE.DWMWA_SYSTEMBACKDROP_TYPE,
ref backdropPvAttribute,
Marshal.SizeOf(typeof(int))
);

return true;
) == 0;
}

/// <summary>
Expand Down Expand Up @@ -296,15 +336,12 @@ public static bool ApplyWindowLegacyMicaEffect(IntPtr handle)
{
var backdropPvAttribute = 0x1; // Enable

// TODO: Validate HRESULT
_ = Dwmapi.DwmSetWindowAttribute(
return Dwmapi.DwmSetWindowAttribute(
handle,
Dwmapi.DWMWINDOWATTRIBUTE.DWMWA_MICA_EFFECT,
ref backdropPvAttribute,
Marshal.SizeOf(typeof(int))
);

return true;
) == 0;
}

/// <summary>
Expand Down