CentralizedControl/HandyControl/HandyControl_Shared/Controls/Other/Watermark.cs

using System.Windows;
using System.Windows.Controls;
using System.Windows.Markup;
using System.Windows.Media;
using System.Windows.Shapes;
using HandyControl.Data;

namespace HandyControl.Controls;

[TemplatePart(Name = ElementRoot, Type = typeof(Border))]
[ContentProperty(nameof(Content))]
public class Watermark : Control
{
    private const string ElementRoot = "PART_Root";

    private Border _borderRoot;

    private DrawingBrush _brush;

    public static readonly DependencyProperty AngleProperty = DependencyProperty.Register(
        nameof(Angle), typeof(double), typeof(Watermark), new FrameworkPropertyMetadata(ValueBoxes.Double0Box, FrameworkPropertyMetadataOptions.AffectsRender));

    public double Angle
    {
        get => (double) GetValue(AngleProperty);
        set => SetValue(AngleProperty, value);
    }

    public static readonly DependencyProperty ContentProperty = DependencyProperty.Register(
        nameof(Content), typeof(object), typeof(Watermark), new PropertyMetadata(default));

    public object Content
    {
        get => GetValue(ContentProperty);
        set => SetValue(ContentProperty, value);
    }

    public static readonly DependencyProperty MarkProperty = DependencyProperty.Register(
        nameof(Mark), typeof(object), typeof(Watermark), new FrameworkPropertyMetadata(default, FrameworkPropertyMetadataOptions.AffectsRender));

    public object Mark
    {
        get => GetValue(MarkProperty);
        set => SetValue(MarkProperty, value);
    }

    public static readonly DependencyProperty MarkWidthProperty = DependencyProperty.Register(
        nameof(MarkWidth), typeof(double), typeof(Watermark), new FrameworkPropertyMetadata(ValueBoxes.Double0Box, FrameworkPropertyMetadataOptions.AffectsRender));

    public double MarkWidth
    {
        get => (double) GetValue(MarkWidthProperty);
        set => SetValue(MarkWidthProperty, value);
    }

    public static readonly DependencyProperty MarkHeightProperty = DependencyProperty.Register(
        nameof(MarkHeight), typeof(double), typeof(Watermark), new FrameworkPropertyMetadata(ValueBoxes.Double0Box, FrameworkPropertyMetadataOptions.AffectsRender));

    public double MarkHeight
    {
        get => (double) GetValue(MarkHeightProperty);
        set => SetValue(MarkHeightProperty, value);
    }

    public static readonly DependencyProperty MarkBrushProperty = DependencyProperty.Register(
        nameof(MarkBrush), typeof(Brush), typeof(Watermark), new FrameworkPropertyMetadata(default(Brush), FrameworkPropertyMetadataOptions.AffectsRender));

    public Brush MarkBrush
    {
        get => (Brush) GetValue(MarkBrushProperty);
        set => SetValue(MarkBrushProperty, value);
    }

    public static readonly DependencyProperty AutoSizeEnabledProperty = DependencyProperty.Register(
        nameof(AutoSizeEnabled), typeof(bool), typeof(Watermark), new FrameworkPropertyMetadata(ValueBoxes.TrueBox, FrameworkPropertyMetadataOptions.AffectsRender));

    public bool AutoSizeEnabled
    {
        get => (bool) GetValue(AutoSizeEnabledProperty);
        set => SetValue(AutoSizeEnabledProperty, ValueBoxes.BooleanBox(value));
    }

    public static readonly DependencyProperty MarkMarginProperty = DependencyProperty.Register(
        nameof(MarkMargin), typeof(Thickness), typeof(Watermark), new FrameworkPropertyMetadata(default(Thickness), FrameworkPropertyMetadataOptions.AffectsRender));

    public Thickness MarkMargin
    {
        get => (Thickness) GetValue(MarkMarginProperty);
        set => SetValue(MarkMarginProperty, value);
    }

    public override void OnApplyTemplate() => _borderRoot = GetTemplateChild(ElementRoot) as Border;

    private void EnsureBrush()
    {
        var presenter = new ContentPresenter();

        if (Mark is Geometry geometry)
        {
            presenter.Content = new Path
            {
                Width = MarkWidth,
                Height = MarkHeight,
                Fill = MarkBrush,
                Stretch = Stretch.Uniform,
                Data = geometry
            };
        }
        else if (Mark is string str)
        {
            presenter.Content = new TextBlock
            {
                Text = str,
                FontSize = FontSize,
                Foreground = MarkBrush
            };
        }
        else
        {
            presenter.Content = Mark;
        }

        Size markSize;
        if (AutoSizeEnabled)
        {
            presenter.Measure(new Size(double.MaxValue, double.MaxValue));
            markSize = presenter.DesiredSize;
        }
        else
        {
            markSize = new Size(MarkWidth, MarkHeight);
        }

        _brush = new DrawingBrush
        {
            ViewportUnits = BrushMappingMode.Absolute,
            Stretch = Stretch.Uniform,
            TileMode = TileMode.Tile,
            Transform = new RotateTransform(Angle),
            Drawing = new GeometryDrawing
            {
                Brush = new VisualBrush(new Border
                {
                    Background = Brushes.Transparent,
                    Padding = MarkMargin,
                    Child = presenter
                }),
                Geometry = new RectangleGeometry(new Rect(markSize))
            },
            Viewport = new Rect(markSize)
        };

        RenderOptions.SetCacheInvalidationThresholdMinimum(_brush, 0.5);
        RenderOptions.SetCacheInvalidationThresholdMaximum(_brush, 2);
        RenderOptions.SetCachingHint(_brush, CachingHint.Cache);

        if (_borderRoot != null)
        {
            _borderRoot.Background = _brush;
        }
    }

    protected override void OnRender(DrawingContext drawingContext) => EnsureBrush();
}