DesktopClock/DesktopClock/OutlinedTextBlock.cs

using System;
using System.ComponentModel;
using System.Globalization;
using System.Windows;
using System.Windows.Documents;
using System.Windows.Markup;
using System.Windows.Media;

namespace DesktopClock;

// https://stackoverflow.com/a/35262509
[ContentProperty("Text")]
public class OutlinedTextBlock : FrameworkElement
{
    private void UpdatePen()
    {
        _Pen = new Pen(Stroke, StrokeThickness)
        {
            DashCap = PenLineCap.Round,
            EndLineCap = PenLineCap.Round,
            LineJoin = PenLineJoin.Round,
            StartLineCap = PenLineCap.Round
        };

        InvalidateVisual();
    }

    public static readonly DependencyProperty FillProperty = DependencyProperty.Register(
      "Fill",
      typeof(Brush),
      typeof(OutlinedTextBlock),
      new FrameworkPropertyMetadata(Brushes.Black, FrameworkPropertyMetadataOptions.AffectsRender));

    public static readonly DependencyProperty StrokeProperty = DependencyProperty.Register(
      "Stroke",
      typeof(Brush),
      typeof(OutlinedTextBlock),
      new FrameworkPropertyMetadata(Brushes.Black, FrameworkPropertyMetadataOptions.AffectsRender, StrokePropertyChangedCallback));

    private static void StrokePropertyChangedCallback(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
    {
        (dependencyObject as OutlinedTextBlock)?.UpdatePen();
    }

    public static readonly DependencyProperty StrokeThicknessProperty = DependencyProperty.Register(
      "StrokeThickness",
      typeof(double),
      typeof(OutlinedTextBlock),
      new FrameworkPropertyMetadata(1d, FrameworkPropertyMetadataOptions.AffectsRender, StrokePropertyChangedCallback));

    public static readonly DependencyProperty FontFamilyProperty = TextElement.FontFamilyProperty.AddOwner(
      typeof(OutlinedTextBlock),
      new FrameworkPropertyMetadata(OnFormattedTextUpdated));

    public static readonly DependencyProperty FontSizeProperty = TextElement.FontSizeProperty.AddOwner(
      typeof(OutlinedTextBlock),
      new FrameworkPropertyMetadata(OnFormattedTextUpdated));

    public static readonly DependencyProperty FontStretchProperty = TextElement.FontStretchProperty.AddOwner(
      typeof(OutlinedTextBlock),
      new FrameworkPropertyMetadata(OnFormattedTextUpdated));

    public static readonly DependencyProperty FontStyleProperty = TextElement.FontStyleProperty.AddOwner(
      typeof(OutlinedTextBlock),
      new FrameworkPropertyMetadata(OnFormattedTextUpdated));

    public static readonly DependencyProperty FontWeightProperty = TextElement.FontWeightProperty.AddOwner(
      typeof(OutlinedTextBlock),
      new FrameworkPropertyMetadata(OnFormattedTextUpdated));

    public static readonly DependencyProperty TextProperty = DependencyProperty.Register(
      "Text",
      typeof(string),
      typeof(OutlinedTextBlock),
      new FrameworkPropertyMetadata(OnFormattedTextInvalidated));

    public static readonly DependencyProperty TextAlignmentProperty = DependencyProperty.Register(
      "TextAlignment",
      typeof(TextAlignment),
      typeof(OutlinedTextBlock),
      new FrameworkPropertyMetadata(OnFormattedTextUpdated));

    public static readonly DependencyProperty TextDecorationsProperty = DependencyProperty.Register(
      "TextDecorations",
      typeof(TextDecorationCollection),
      typeof(OutlinedTextBlock),
      new FrameworkPropertyMetadata(OnFormattedTextUpdated));

    public static readonly DependencyProperty TextTrimmingProperty = DependencyProperty.Register(
      "TextTrimming",
      typeof(TextTrimming),
      typeof(OutlinedTextBlock),
      new FrameworkPropertyMetadata(OnFormattedTextUpdated));

    public static readonly DependencyProperty TextWrappingProperty = DependencyProperty.Register(
      "TextWrapping",
      typeof(TextWrapping),
      typeof(OutlinedTextBlock),
      new FrameworkPropertyMetadata(TextWrapping.NoWrap, OnFormattedTextUpdated));

    private FormattedText _FormattedText;
    private Geometry _TextGeometry;
    private Pen _Pen;

    public Brush Fill
    {
        get => (Brush)GetValue(FillProperty);
        set => SetValue(FillProperty, value);
    }

    public FontFamily FontFamily
    {
        get => (FontFamily)GetValue(FontFamilyProperty);
        set => SetValue(FontFamilyProperty, value);
    }

    [TypeConverter(typeof(FontSizeConverter))]
    public double FontSize
    {
        get => (double)GetValue(FontSizeProperty);
        set => SetValue(FontSizeProperty, value);
    }

    public FontStretch FontStretch
    {
        get => (FontStretch)GetValue(FontStretchProperty);
        set => SetValue(FontStretchProperty, value);
    }

    public FontStyle FontStyle
    {
        get => (FontStyle)GetValue(FontStyleProperty);
        set => SetValue(FontStyleProperty, value);
    }

    public FontWeight FontWeight
    {
        get => (FontWeight)GetValue(FontWeightProperty);
        set => SetValue(FontWeightProperty, value);
    }

    public Brush Stroke
    {
        get => (Brush)GetValue(StrokeProperty);
        set => SetValue(StrokeProperty, value);
    }

    public double StrokeThickness
    {
        get => (double)GetValue(StrokeThicknessProperty);
        set => SetValue(StrokeThicknessProperty, value);
    }

    public string Text
    {
        get => (string)GetValue(TextProperty);
        set => SetValue(TextProperty, value);
    }

    public TextAlignment TextAlignment
    {
        get => (TextAlignment)GetValue(TextAlignmentProperty);
        set => SetValue(TextAlignmentProperty, value);
    }

    public TextDecorationCollection TextDecorations
    {
        get => (TextDecorationCollection)GetValue(TextDecorationsProperty);
        set => SetValue(TextDecorationsProperty, value);
    }

    public TextTrimming TextTrimming
    {
        get => (TextTrimming)GetValue(TextTrimmingProperty);
        set => SetValue(TextTrimmingProperty, value);
    }

    public TextWrapping TextWrapping
    {
        get => (TextWrapping)GetValue(TextWrappingProperty);
        set => SetValue(TextWrappingProperty, value);
    }

    public OutlinedTextBlock()
    {
        UpdatePen();
        TextDecorations = new TextDecorationCollection();
    }

    protected override void OnRender(DrawingContext drawingContext)
    {
        EnsureGeometry();

        drawingContext.DrawGeometry(null, _Pen, _TextGeometry);
        drawingContext.DrawGeometry(Fill, null, _TextGeometry);
    }

    protected override Size MeasureOverride(Size availableSize)
    {
        EnsureFormattedText();

        // constrain the formatted text according to the available size

        var w = availableSize.Width;
        var h = availableSize.Height;

        // the Math.Min call is important - without this constraint (which seems arbitrary, but is the maximum allowable text width), things blow up when availableSize is infinite in both directions
        // the Math.Max call is to ensure we don't hit zero, which will cause MaxTextHeight to throw
        _FormattedText.MaxTextWidth = Math.Min(3579139, w);
        _FormattedText.MaxTextHeight = Math.Max(0.0001d, h);

        // return the desired size
        return new Size(Math.Ceiling(_FormattedText.Width), Math.Ceiling(_FormattedText.Height));
    }

    protected override Size ArrangeOverride(Size finalSize)
    {
        EnsureFormattedText();

        // update the formatted text with the final size
        _FormattedText.MaxTextWidth = finalSize.Width;
        _FormattedText.MaxTextHeight = Math.Max(0.0001d, finalSize.Height);

        // need to re-generate the geometry now that the dimensions have changed
        _TextGeometry = null;

        return finalSize;
    }

    private static void OnFormattedTextInvalidated(DependencyObject dependencyObject,
      DependencyPropertyChangedEventArgs e)
    {
        var outlinedTextBlock = (OutlinedTextBlock)dependencyObject;
        outlinedTextBlock._FormattedText = null;
        outlinedTextBlock._TextGeometry = null;

        outlinedTextBlock.InvalidateMeasure();
        outlinedTextBlock.InvalidateVisual();
    }

    private static void OnFormattedTextUpdated(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs e)
    {
        var outlinedTextBlock = (OutlinedTextBlock)dependencyObject;
        outlinedTextBlock.UpdateFormattedText();
        outlinedTextBlock._TextGeometry = null;

        outlinedTextBlock.InvalidateMeasure();
        outlinedTextBlock.InvalidateVisual();
    }

    private void EnsureFormattedText()
    {
        if (_FormattedText != null)
        {
            return;
        }

#pragma warning disable CS0618 // Type or member is obsolete
        _FormattedText = new FormattedText(
            Text ?? "",
            CultureInfo.CurrentUICulture,
            FlowDirection,
            new Typeface(FontFamily, FontStyle, FontWeight, FontStretch),
            FontSize,
            Brushes.Black);
#pragma warning restore CS0618 // Type or member is obsolete

        UpdateFormattedText();
    }

    private void UpdateFormattedText()
    {
        if (_FormattedText == null)
        {
            return;
        }

        _FormattedText.MaxLineCount = TextWrapping == TextWrapping.NoWrap ? 1 : int.MaxValue;
        _FormattedText.TextAlignment = TextAlignment;
        _FormattedText.Trimming = TextTrimming;

        _FormattedText.SetFontSize(FontSize);
        _FormattedText.SetFontStyle(FontStyle);
        _FormattedText.SetFontWeight(FontWeight);
        _FormattedText.SetFontFamily(FontFamily);
        _FormattedText.SetFontStretch(FontStretch);
        _FormattedText.SetTextDecorations(TextDecorations);
    }

    private void EnsureGeometry()
    {
        if (_TextGeometry != null)
        {
            return;
        }

        EnsureFormattedText();
        _TextGeometry = _FormattedText.BuildGeometry(new Point(0, 0));
    }
}