[patch] Measure a titled BorderElement wide enough to draw its title

TUI.Test/BorderElementRenderTests.cs

@@ -2,6 +2,7 @@
 
 namespace ktsu.TUI.Test;
 
+using ktsu.TUI.Core.Elements.Layouts;
 using ktsu.TUI.Core.Elements.Primitives;
 using ktsu.TUI.Core.Models;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
@@ -230,4 +231,44 @@ public void TitleWithALineBreakIsDrawnOnOneRow(string title)
 		Assert.IsFalse(provider.Writes.Any(w => w.Text.Contains('\r') || w.Text.Contains('\n')), "A write carried a line break");
 		Assert.AreEqual(0, provider.WritesOf(" ab cd ").Single().Position.Y);
 	}
+
+	/// <summary>
+	/// A border sized by a layout is measured wide enough for its title, so a title longer than
+	/// the content is drawn in full rather than cut short or dropped (ktsu-dev/TUI#157).
+	/// </summary>
+	[TestMethod]
+	public void TitleLongerThanTheContentIsDrawnInFullInsideAStackPanel()
+	{
+		// Arrange
+		StackPanel panel = new(Orientation.Horizontal) { Spacing = 1 };
+		panel.AddChild(new BorderElement { Title = "Single", Child = new TextElement { Text = "Content" } });
+		panel.AddChild(new BorderElement { Title = "Status", Child = new TextElement { Text = "OK" } });
+		panel.Position = Position.Origin;
+		panel.Dimensions = new Dimensions(80, 24);
+		RecordingConsoleProvider provider = new();
+
+		// Act
+		panel.ArrangeChildren();
+		panel.Render(provider);
+
+		// Assert
+		Assert.ContainsSingle(provider.WritesOf(" Single "));
+		Assert.ContainsSingle(provider.WritesOf(" Status "));
+	}
+
+	/// <summary>
+	/// The measure reserves room for the title only when a title is drawn: an untitled border, and a
+	/// <see cref="BorderStyle.None"/> border, are still exactly as wide as their content.
+	/// </summary>
+	[TestMethod]
+	public void MeasuredWidthMakesRoomForTheTitleOnlyWhenOneIsDrawn()
+	{
+		BorderElement titled = new() { Title = "Status", Child = new TextElement { Text = "OK" } };
+		BorderElement untitled = new() { Child = new TextElement { Text = "OK" } };
+		BorderElement borderless = new(BorderStyle.None) { Title = "Status", Child = new TextElement { Text = "OK" } };
+
+		Assert.AreEqual(" Status ".Length + 2, titled.CalculateRequiredDimensions().Width);
+		Assert.AreEqual("OK".Length + 2, untitled.CalculateRequiredDimensions().Width);
+		Assert.AreEqual("OK".Length + 2, borderless.CalculateRequiredDimensions().Width);
+	}
 }

TUI/Elements/Primitives/BorderElement.cs

@@ -151,9 +151,7 @@ protected override void OnRender(IConsoleProvider provider)
 		{
 			int maxTitleWidth = dimensions.Width - 4; // Leave space for border and padding
 
-			// A line break written to the terminal would move the rest of the title off the top
-			// border row and over the left edge, so each break becomes a space (ktsu-dev/TUI#151).
-			string singleLineTitle = Title.Replace("\r\n", " ", StringComparison.Ordinal).Replace('\r', ' ').Replace('\n', ' ');
+			string singleLineTitle = GetSingleLineTitle();
 			string displayTitle = singleLineTitle.Length > maxTitleWidth ? singleLineTitle[..maxTitleWidth] : singleLineTitle;
 			string titleWithPadding = $" {displayTitle} ";
 
@@ -186,9 +184,24 @@ protected override void OnArrangeChildren()
 
 	/// <inheritdoc />
 	// The border itself is reserved by the Padding(1) set in the constructor, which the base
-	// class adds to this result, so only the child's own size belongs here (ktsu-dev/TUI#132)
-	protected override Dimensions OnCalculateRequiredDimensionsForChildren() =>
-		Children.Count == 0 ? Dimensions.Empty : Children.First().CalculateRequiredDimensions();
+	// class adds to this result, so only the child's own size belongs here (ktsu-dev/TUI#132).
+	// A title is drawn as " title " between the corners, so the content area must be at least
+	// two wider than the title or a layout sizes the border too narrow to show it (ktsu-dev/TUI#157).
+	protected override Dimensions OnCalculateRequiredDimensionsForChildren()
+	{
+		Dimensions childDimensions = Children.Count == 0 ? Dimensions.Empty : Children.First().CalculateRequiredDimensions();
+		if (BorderStyle == BorderStyle.None || string.IsNullOrEmpty(Title))
+		{
+			return childDimensions;
+		}
+
+		return new Dimensions(Math.Max(childDimensions.Width, GetSingleLineTitle().Length + 2), childDimensions.Height);
+	}
+
+	// A line break written to the terminal would move the rest of the title off the top
+	// border row and over the left edge, so each break becomes a space (ktsu-dev/TUI#151).
+	private string GetSingleLineTitle() =>
+		Title.Replace("\r\n", " ", StringComparison.Ordinal).Replace('\r', ' ').Replace('\n', ' ');
 
 	private static BorderCharacters GetBorderCharacters(BorderStyle style)
 	{