Shrlalgo.RvKits/WPFluent/Controls/ContentDialog/ClientAreaBorder.cs

using WPFluent.Appearance;
using WPFluent.Hardware;

using System.Windows.Shell;

using Size = System.Windows.Size;

// ReSharper disable once CheckNamespace
namespace WPFluent.Controls;

/// <summary>
/// If you use <see cref="WindowChrome"/> to extend the UI elements to the non-client area, you can include this
/// container in the template of <see cref="Window"/> so that the content inside automatically fills the client area.
/// Using this container can let you get rid of various margin adaptations done in Setter/Trigger of the style of <see
/// cref="Window"/> when the window state changes.
/// </summary>
/// <example>
/// <code lang="xml"> &lt;Style x:Key="MyWindowCustomStyle" BasedOn="{StaticResource {x:Type Window}}"
/// TargetType="{x:Type controls:FluentWindow}"&gt; &lt;Setter Property="Template" &gt; &lt;Setter.Value&gt;
/// &lt;ControlTemplate TargetType="{x:Type Window}"&gt; &lt;AdornerDecorator&gt; &lt;controls:ClientAreaBorder
/// Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}"
/// BorderThickness="{TemplateBinding BorderThickness}"&gt; &lt;ContentPresenter x:Name="ContentPresenter" /&gt;
/// &lt;/controls:ClientAreaBorder&gt; &lt;/AdornerDecorator&gt; &lt;/ControlTemplate&gt; &lt;/Setter.Value&gt;
/// &lt;/Setter&gt; &lt;/Style&gt;</code>
/// </example>
public class ClientAreaBorder : System.Windows.Controls.Border, IThemeControl
{
    /*private const int SM_CXFRAME = 32;
    private const int SM_CYFRAME = 33;
    private const int SM_CXPADDEDBORDER = 92;*/
    private static Thickness? _paddedBorderThickness;
    private static Thickness? _resizeFrameBorderThickness;
    private static Thickness? _windowChromeNonClientFrameThickness;
    private bool _borderBrushApplied = false;
    private System.Windows.Window? _oldWindow;

    public ClientAreaBorder()
    {
        ApplicationTheme = Appearance.ApplicationThemeManager.GetAppTheme();
        Appearance.ApplicationThemeManager.Changed += OnThemeChanged;
    }

    private void ApplyDefaultWindowBorder()
    {
        if(Win32.Utilities.IsOSWindows11OrNewer || _oldWindow == null)
        {
            return;
        }

        _borderBrushApplied = true;

        // SystemParameters.WindowGlassBrush
        Color borderColor =
            ApplicationTheme == ApplicationTheme.Light
            ? Color.FromArgb(0xFF, 0x7A, 0x7A, 0x7A)
            : Color.FromArgb(0xFF, 0x3A, 0x3A, 0x3A);
        _oldWindow.SetCurrentValue(
            System.Windows.Controls.Control.BorderBrushProperty,
            new SolidColorBrush(borderColor));
        _oldWindow.SetCurrentValue(System.Windows.Controls.Control.BorderThicknessProperty, new Thickness(1));
    }

    private (double FactorX, double FactorY) GetDpi()
    {
        if(PresentationSource.FromVisual(this) is { } source)
        {
            return (
                source.CompositionTarget.TransformToDevice.M11, // Possible null reference
                source.CompositionTarget.TransformToDevice.M22
            );
        }

        DisplayDpi systemDPi = DpiHelper.GetSystemDpi();

        return (systemDPi.DpiScaleX, systemDPi.DpiScaleY);
    }

    private void OnThemeChanged(ApplicationTheme currentApplicationTheme, Color systemAccent)
    {
        ApplicationTheme = currentApplicationTheme;

        if(!_borderBrushApplied || _oldWindow == null)
        {
            return;
        }

        ApplyDefaultWindowBorder();
    }

    private void OnWindowClosing(object? sender, CancelEventArgs e)
    {
        Appearance.ApplicationThemeManager.Changed -= OnThemeChanged;
        if(_oldWindow != null)
        {
            _oldWindow.Closing -= OnWindowClosing;
        }
    }

    private void OnWindowStateChanged(object? sender, EventArgs e)
    {
        if(sender is not System.Windows.Window window)
        {
            return;
        }

        Thickness padding =
            window.WindowState == WindowState.Maximized ? WindowChromeNonClientFrameThickness : default;
        SetCurrentValue(PaddingProperty, padding);
    }

    /// <inheritdoc/>
    protected override void OnVisualParentChanged(DependencyObject oldParent)
    {
        base.OnVisualParentChanged(oldParent);

        if(_oldWindow is { } oldWindow)
        {
            oldWindow.StateChanged -= OnWindowStateChanged;
            oldWindow.Closing -= OnWindowClosing;
        }

        var newWindow = System.Windows.Window.GetWindow(this);

        if(newWindow is not null)
        {
            newWindow.StateChanged -= OnWindowStateChanged; // Unsafe
            newWindow.StateChanged += OnWindowStateChanged;
            newWindow.Closing += OnWindowClosing;
        }

        _oldWindow = newWindow;

        ApplyDefaultWindowBorder();
    }

    public ApplicationTheme ApplicationTheme { get; set; } = ApplicationTheme.Unknown;

    /// <summary>
    /// Gets the system value for the padded border thickness (<see cref="User32.SM.CXPADDEDBORDER"/>) in WPF units.
    /// </summary>
    public Thickness PaddedBorderThickness
    {
        get
        {
            if(_paddedBorderThickness is not null)
            {
                return _paddedBorderThickness.Value;
            }

            var paddedBorder = Interop.User32.GetSystemMetrics(Interop.User32.SM.CXPADDEDBORDER);

            (double factorX, double factorY) = GetDpi();

            var frameSize = new Size(paddedBorder, paddedBorder);
            var frameSizeInDips = new Size(frameSize.Width / factorX, frameSize.Height / factorY);

            _paddedBorderThickness = new Thickness(
                frameSizeInDips.Width,
                frameSizeInDips.Height,
                frameSizeInDips.Width,
                frameSizeInDips.Height);

            return _paddedBorderThickness.Value;
        }
    }

    /// <summary>
    /// Gets the system <see cref="User32.SM.CXFRAME"/> and <see cref="User32.SM.CYFRAME"/> values in WPF units.
    /// </summary>
    public static Thickness ResizeFrameBorderThickness => _resizeFrameBorderThickness ??= new Thickness(
        SystemParameters.ResizeFrameVerticalBorderWidth,
        SystemParameters.ResizeFrameHorizontalBorderHeight,
        SystemParameters.ResizeFrameVerticalBorderWidth,
        SystemParameters.ResizeFrameHorizontalBorderHeight);

    /// <summary>
    /// Gets the thickness of the window's non-client frame used for maximizing the window with a custom chrome.
    /// </summary>
    /// <remarks>
    /// If you use a <see cref="WindowChrome"/> to extend the client area of a window to the non-client area, you need
    /// to handle the edge margin issue when the window is maximized. Use this property to get the correct margin value
    /// when the window is maximized, so that when the window is maximized, the client area can completely cover the
    /// screen client area by no less than a single pixel at any DPI. The<see cref="User32.GetSystemMetrics"/> method
    /// cannot obtain this value directly.
    /// </remarks>
    public Thickness WindowChromeNonClientFrameThickness => _windowChromeNonClientFrameThickness ??= new Thickness(
        ClientAreaBorder.ResizeFrameBorderThickness.Left + PaddedBorderThickness.Left,
        ClientAreaBorder.ResizeFrameBorderThickness.Top + PaddedBorderThickness.Top,
        ClientAreaBorder.ResizeFrameBorderThickness.Right + PaddedBorderThickness.Right,
        ClientAreaBorder.ResizeFrameBorderThickness.Bottom + PaddedBorderThickness.Bottom);
}