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Fix Tracking of Last Line Break #447

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Fix Tracking of Last Line Break #447

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23c9a43
Fix #446
JimBobSquarePants Jan 30, 2025
fb83c12
Revert unnecessary changes
JimBobSquarePants Jan 30, 2025
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67 changes: 39 additions & 28 deletions src/SixLabors.Fonts/TextLayout.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1182,42 +1182,40 @@ VerticalOrientationType.Rotate or
lineBreaks.Add(lineBreakEnumerator.Current);
}

int usedOffset = 0;
int processed = 0;
while (textLine.Count > 0)
{
LineBreak? bestBreak = null;
foreach (LineBreak lineBreak in lineBreaks)
{
// Adjust the break index relative to the current position in the original line
int measureAt = lineBreak.PositionMeasure - usedOffset;

// Skip breaks that are already behind the trimmed portion
if (measureAt < 0)
// Skip breaks that are already behind the processed portion
if (lineBreak.PositionWrap <= processed)
{
continue;
}

// Measure the text up to the adjusted break point
float measure = textLine.MeasureAt(measureAt);
if (measure > wrappingLength)
float advance = textLine.MeasureAt(lineBreak.PositionMeasure - processed);
if (advance >= wrappingLength)
{
// Stop and use the best break so far
bestBreak ??= lineBreak;
break;
}

// Update the best break
bestBreak = lineBreak;

// If it's a mandatory break, stop immediately
if (lineBreak.Required)
{
bestBreak = lineBreak;
break;
}

// Update the best break
bestBreak = lineBreak;
}

if (bestBreak != null)
{
LineBreak breakAt = bestBreak.Value;
if (breakAll)
{
// Break-all works differently to the other modes.
Expand All @@ -1226,30 +1224,34 @@ VerticalOrientationType.Rotate or
TextLine? remaining;
if (bestBreak.Value.Required)
{
if (textLine.TrySplitAt(bestBreak.Value, keepAll, out remaining))
if (textLine.TrySplitAt(breakAt, keepAll, out remaining))
{
usedOffset += textLine.Count;
processed = breakAt.PositionWrap;
textLines.Add(textLine.Finalize(options));
textLine = remaining;
}
}
else if (textLine.TrySplitAt(wrappingLength, out remaining))
{
usedOffset += textLine.Count;
processed += textLine.Count;
textLines.Add(textLine.Finalize(options));
textLine = remaining;
}
else
{
usedOffset += textLine.Count;
processed += textLine.Count;
}
}
else
{
// Split the current line at the adjusted break index
if (textLine.TrySplitAt(bestBreak.Value, keepAll, out TextLine? remaining))
if (textLine.TrySplitAt(breakAt, keepAll, out TextLine? remaining))
{
usedOffset += textLine.Count;
// If 'keepAll' is true then the break could be later than expected.
processed = keepAll
? processed + Math.Max(textLine.Count, breakAt.PositionWrap - processed)
: breakAt.PositionWrap;

if (breakWord)
{
// A break was found, but we need to check if the line is too long
Expand All @@ -1258,7 +1260,7 @@ VerticalOrientationType.Rotate or
textLine.TrySplitAt(wrappingLength, out TextLine? overflow))
{
// Reinsert the overflow at the beginning of the remaining line
usedOffset -= overflow.Count;
processed -= overflow.Count;
remaining.InsertAt(0, overflow);
}
}
Expand All @@ -1269,13 +1271,14 @@ VerticalOrientationType.Rotate or
}
else
{
usedOffset += textLine.Count;
processed += textLine.Count;
}
}
}
else
{
// If no valid break is found, add the remaining line and exit
// We're at the last line break which should be at the end of the
// text. We can break here and finalize the line.
if (breakWord || breakAll)
{
while (textLine.ScaledLineAdvance > wrappingLength)
Expand Down Expand Up @@ -1316,6 +1319,7 @@ public float ScaledMaxAdvance()
internal sealed class TextLine
{
private readonly List<GlyphLayoutData> data;
private readonly Dictionary<int, float> advances = new();

public TextLine() => this.data = new(16);

Expand Down Expand Up @@ -1383,6 +1387,11 @@ public void InsertAt(int index, TextLine textLine)

public float MeasureAt(int index)
{
if (this.advances.TryGetValue(index, out float advance))
{
return advance;
}

if (index >= this.data.Count)
{
index = this.data.Count - 1;
Expand All @@ -1395,12 +1404,13 @@ public float MeasureAt(int index)
index--;
}

float advance = 0;
advance = 0;
for (int i = 0; i <= index; i++)
{
advance += this.data[i].ScaledAdvance;
}

this.advances[index] = advance;
return advance;
}

Expand Down Expand Up @@ -1440,11 +1450,11 @@ public bool TrySplitAt(float length, [NotNullWhen(true)] out TextLine? result)
public bool TrySplitAt(LineBreak lineBreak, bool keepAll, [NotNullWhen(true)] out TextLine? result)
{
int index = this.data.Count;
GlyphLayoutData glyphWrap = default;
GlyphLayoutData glyphData = default;
while (index > 0)
{
glyphWrap = this.data[--index];
if (glyphWrap.CodePointIndex == lineBreak.PositionWrap)
glyphData = this.data[--index];
if (glyphData.CodePointIndex == lineBreak.PositionWrap)
{
break;
}
Expand All @@ -1455,14 +1465,14 @@ public bool TrySplitAt(LineBreak lineBreak, bool keepAll, [NotNullWhen(true)] ou
if (index > 0
&& !lineBreak.Required
&& keepAll
&& UnicodeUtility.IsCJKCodePoint((uint)glyphWrap.CodePoint.Value))
&& UnicodeUtility.IsCJKCodePoint((uint)glyphData.CodePoint.Value))
{
// Loop through previous glyphs to see if there is
// a non CJK codepoint we can break at.
while (index > 0)
{
glyphWrap = this.data[--index];
if (!UnicodeUtility.IsCJKCodePoint((uint)glyphWrap.CodePoint.Value))
glyphData = this.data[--index];
if (!UnicodeUtility.IsCJKCodePoint((uint)glyphData.CodePoint.Value))
{
index++;
break;
Expand Down Expand Up @@ -1694,6 +1704,7 @@ private static void RecalculateLineMetrics(TextLine textLine)
textLine.ScaledMaxAscender = ascender;
textLine.ScaledMaxDescender = descender;
textLine.ScaledMaxLineHeight = lineHeight;
textLine.advances.Clear();
}

/// <summary>
Expand Down
3 changes: 3 additions & 0 deletions tests/Images/ReferenceOutput/Issue_446_A__WrappingLength_860_.png
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3 changes: 3 additions & 0 deletions tests/Images/ReferenceOutput/Issue_446_B__WrappingLength_860_.png
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37 changes: 37 additions & 0 deletions tests/SixLabors.Fonts.Tests/Issues/Issues_446.cs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,37 @@
// Copyright (c) Six Labors.
// Licensed under the Six Labors Split License.

using System.Numerics;

namespace SixLabors.Fonts.Tests.Issues;

public class Issues_446
{
private readonly FontFamily charisSIL = new FontCollection().Add(TestFonts.CharisSILRegular);

[Fact]
public void Issue_446_A()
{
Font font = this.charisSIL.CreateFont(85);
TextLayoutTestUtilities.TestLayout(
"⇒ Tim Cook\n⇒ Jef Bezos\n⇒ Steve Jobs\n⇒ Mark Zuckerberg",
new TextOptions(font)
{
Origin = new Vector2(50, 20),
WrappingLength = 860,
});
}

[Fact]
public void Issue_446_B()
{
Font font = this.charisSIL.CreateFont(85);
TextLayoutTestUtilities.TestLayout(
"⇒ Tim Cook\n⇒ Jeff Bezos\n⇒ Steve Jobs\n⇒ Mark Zuckerberg",
new TextOptions(font)
{
Origin = new Vector2(50, 20),
WrappingLength = 860,
});
}
}
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