refactor(text): drop IFont.Shape direction-guessing overload

Shaping should shape a run of known direction; guessing direction from script is a
layout concern, not a font capability, and it forced every IFont backend to
replicate HarfBuzz's GuessSegmentProperties direction inference. The only caller was
the legacy non-bidi Run.Segments/ParsedText path (superseded by UnicodeText); it now
passes the run's own FlowDirection to the explicit Shape(text, direction) overload,
dropping the per-segment shaper guess and the spaces-only RTL hack that compensated
for it. SkiaFont/ManagedFont collapse ShapeCore into the single Shape (GuessSegment-
Properties stays — it also sets script/language — with direction set explicitly).

Validated: text + acrylic runtime tests unchanged (the one Given_TextBlock gripper
failure is pre-existing — fails identically on baseline without this change).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: ramezgerges

src/Uno.UI.Composition.Drawing/IFont.cs

@@ -25,13 +25,6 @@ public interface IFont
 	/// </summary>
 	GlyphRun Shape(ReadOnlySpan<char> text, TextDirection direction, bool enableLigatures = true);
 
-	/// <summary>
-	/// Shapes a run, letting the shaper guess the run's direction from its script (used by the segment itemizer that
-	/// hasn't resolved bidi itself) and reporting it back via <paramref name="resolvedDirection"/>. Otherwise
-	/// identical to <see cref="Shape(ReadOnlySpan{char}, TextDirection, bool)"/>.
-	/// </summary>
-	GlyphRun Shape(ReadOnlySpan<char> text, out TextDirection resolvedDirection, bool enableLigatures = true);
-
 	/// <summary>
 	/// Builds the combined filled outline of the run's outline glyphs (color glyphs are excluded — draw those
 	/// via <see cref="AppendColorGlyphImages"/>). Each glyph is placed at its position, shifted by <paramref name="baselineY"/>.

src/Uno.UI.Composition.Skia/Composition/Uno/Drawing/SkiaFont.cs

@@ -65,21 +65,11 @@ public float GetGlyphAdvance(ushort glyph)
 	public string FamilyName => _font.Typeface?.FamilyName ?? string.Empty;
 
 	public GlyphRun Shape(ReadOnlySpan<char> text, TextDirection direction, bool enableLigatures = true)
-		=> ShapeCore(text, direction, enableLigatures, out _);
-
-	public GlyphRun Shape(ReadOnlySpan<char> text, out TextDirection resolvedDirection, bool enableLigatures = true)
-		=> ShapeCore(text, null, enableLigatures, out resolvedDirection);
-
-	private GlyphRun ShapeCore(ReadOnlySpan<char> text, TextDirection? direction, bool enableLigatures, out TextDirection resolvedDirection)
 	{
 		using var buffer = new HbBuffer();
 		buffer.AddUtf16(text);
-		buffer.GuessSegmentProperties();
-		if (direction is { } requested)
-		{
-			buffer.Direction = requested == TextDirection.RightToLeft ? HarfBuzzSharp.Direction.RightToLeft : HarfBuzzSharp.Direction.LeftToRight;
-		}
-		resolvedDirection = buffer.Direction == HarfBuzzSharp.Direction.RightToLeft ? TextDirection.RightToLeft : TextDirection.LeftToRight;
+		buffer.GuessSegmentProperties(); // sets the run's script/language for the shaper; direction is set explicitly below
+		buffer.Direction = direction == TextDirection.RightToLeft ? HarfBuzzSharp.Direction.RightToLeft : HarfBuzzSharp.Direction.LeftToRight;
 
 		if (enableLigatures)
 		{

src/Uno.UI.Composition/Composition/Uno/Drawing/ManagedFont.cs

@@ -149,21 +149,11 @@ public int GetAdvanceWidth(ushort glyph)
 	public string FamilyName => _familyName ??= ParseFamilyName(_data, _name);
 
 	public GlyphRun Shape(ReadOnlySpan<char> text, TextDirection direction, bool enableLigatures = true)
-		=> ShapeCore(text, direction, enableLigatures, out _);
-
-	public GlyphRun Shape(ReadOnlySpan<char> text, out TextDirection resolvedDirection, bool enableLigatures = true)
-		=> ShapeCore(text, null, enableLigatures, out resolvedDirection);
-
-	private GlyphRun ShapeCore(ReadOnlySpan<char> text, TextDirection? direction, bool enableLigatures, out TextDirection resolvedDirection)
 	{
 		using var buffer = new HbBuffer();
 		buffer.AddUtf16(text);
-		buffer.GuessSegmentProperties();
-		if (direction is { } requested)
-		{
-			buffer.Direction = requested == TextDirection.RightToLeft ? HarfBuzzSharp.Direction.RightToLeft : HarfBuzzSharp.Direction.LeftToRight;
-		}
-		resolvedDirection = buffer.Direction == HarfBuzzSharp.Direction.RightToLeft ? TextDirection.RightToLeft : TextDirection.LeftToRight;
+		buffer.GuessSegmentProperties(); // sets the run's script/language for the shaper; direction is set explicitly below
+		buffer.Direction = direction == TextDirection.RightToLeft ? HarfBuzzSharp.Direction.RightToLeft : HarfBuzzSharp.Direction.LeftToRight;
 
 		if (enableLigatures)
 		{

src/Uno.UI/UI/Xaml/Documents/Run.skia.cs

@@ -215,22 +215,13 @@ private List<Segment> GetSegments()
 					// Skip the second line break char so it stays part of the same cluster as the first.
 					var shapedLength = lineBreakLength == 2 ? length - 1 : length;
 
-					// The direction is guessed by the shaper from the run's script (bidi itemization isn't done here
-					// yet — see the TODO above). Ligatures are disabled because a TextBox needs each source char to
-					// stay separately addressable (uno#15528, uno#16788).
-					var glyphRun = segmentFont.Shape(text.Slice(i, shapedLength), out var resolvedDirection, enableLigatures: false);
-					var direction = resolvedDirection is TextDirection.LeftToRight ? FlowDirection.LeftToRight : FlowDirection.RightToLeft;
-					if (direction == FlowDirection.LeftToRight &&
-						segments.Count > 0 && segments[segments.Count - 1].Direction == FlowDirection.RightToLeft &&
-						trailingSpaces + leadingSpaces == length)
-					{
-						// If the current segment consists of spaces only, it will be considered LeftToRight.
-						// But if the previous segment was RightToLeft, we want the current segment to also be RTL.
-						// This is quite hacky, it feels like GetRenderOrderedSegmentSpans is buggy and a real fix needs to go there.
-						direction = FlowDirection.RightToLeft;
-					}
-
-					var glyphs = GetGlyphs(glyphRun, i, resolvedDirection is TextDirection.RightToLeft);
+					// Legacy non-bidi path (superseded by UnicodeText): shape each segment in the run's own
+					// FlowDirection rather than resolving bidi. Ligatures are disabled because a TextBox needs each
+					// source char to stay separately addressable (uno#15528, uno#16788).
+					var direction = this.FlowDirection;
+					var textDirection = direction == FlowDirection.RightToLeft ? TextDirection.RightToLeft : TextDirection.LeftToRight;
+					var glyphRun = segmentFont.Shape(text.Slice(i, shapedLength), textDirection, enableLigatures: false);
+					var glyphs = GetGlyphs(glyphRun, i, textDirection is TextDirection.RightToLeft);
 
 					Debug.Assert(!(Text.AsSpan(i, length).Contains('\t')) || length == 1);
 					if (length == 1 && text[i] == '\t')