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Fix vertical alignment of non-vertical glyphs #435

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Dec 18, 2024
Merged

Fix vertical alignment of non-vertical glyphs #435

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76 changes: 39 additions & 37 deletions src/SixLabors.Fonts/TextLayout.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -537,7 +537,18 @@ private static IEnumerable<GlyphLayout> LayoutLineVertical(
{
// Align the glyph horizontally and vertically centering vertically around the baseline.
Vector2 scale = new Vector2(data.PointSize) / metric.ScaleFactor;
Vector2 offset = new(0, (metric.Bounds.Max.Y + metric.TopSideBearing) * scale.Y);

float alignX = 0;
if (data.IsTransformed)
{
// Calculate the horizontal alignment offset:
// - Normalize lsb to zero
// - Center the glyph horizontally within the max line height.
alignX -= metric.LeftSideBearing * scale.X;
alignX += (scaledMaxLineHeight - (metric.Bounds.Size().X * scale.X)) * .5F;
}

Vector2 offset = new(alignX, (metric.Bounds.Max.Y + metric.TopSideBearing) * scale.Y);

glyphs.Add(new GlyphLayout(
new Glyph(metric, data.PointSize),
Expand Down Expand Up @@ -668,7 +679,7 @@ private static IEnumerable<GlyphLayout> LayoutLineVerticalMixed(
continue;
}

if (data.IsRotated)
if (data.IsTransformed)
{
int j = 0;
foreach (GlyphMetrics metric in data.Metrics)
Expand Down Expand Up @@ -887,6 +898,7 @@ private static TextBox BreakLines(
bool keepAll = options.WordBreaking == WordBreaking.KeepAll;
bool breakWord = options.WordBreaking == WordBreaking.BreakWord;
bool isHorizontalLayout = layoutMode.IsHorizontal();
bool isVerticalLayout = layoutMode.IsVertical();
bool isVerticalMixedLayout = layoutMode.IsVerticalMixed();

// Calculate the position of potential line breaks.
Expand Down Expand Up @@ -955,12 +967,19 @@ private static TextBox BreakLines(
// Determine whether the glyph advance should be calculated using vertical or horizontal metrics
// For vertical mixed layout we will rotate glyphs with the vertical orientation type R or TR
// which do not already have a vertical substitution.
bool isRotated = isVerticalMixedLayout &&
bool shouldRotate = isVerticalMixedLayout &&
!isVerticalSubstitution &&
CodePoint.GetVerticalOrientationType(codePoint) is
VerticalOrientationType.Rotate or
VerticalOrientationType.TransformRotate;

// Determine whether the glyph advance should be offset for vertical layout.
bool shouldOffset = isVerticalLayout &&
!isVerticalSubstitution &&
CodePoint.GetVerticalOrientationType(codePoint) is
VerticalOrientationType.Rotate or
VerticalOrientationType.TransformRotate;

if (CodePoint.IsVariationSelector(codePoint))
{
codePointIndex++;
Expand All @@ -977,7 +996,7 @@ VerticalOrientationType.Rotate or
? new float[metrics.Count]
: decomposedAdvancesBuffer[..(isDecomposed ? metrics.Count : 1)];

if (isHorizontalLayout || isRotated)
if (isHorizontalLayout || shouldRotate)
{
glyphAdvance = glyph.AdvanceWidth;
}
Expand Down Expand Up @@ -1005,7 +1024,7 @@ VerticalOrientationType.Rotate or
layoutMode,
options.ColorFontSupport)[0];

if (isHorizontalLayout || isRotated)
if (isHorizontalLayout || shouldRotate)
{
glyphAdvance = spaceMetrics.AdvanceWidth * options.TabWidth;
glyph.SetAdvanceWidth((ushort)glyphAdvance);
Expand All @@ -1031,7 +1050,7 @@ VerticalOrientationType.Rotate or
{
// Standard text.
// If decomposed we need to add the advance; otherwise, use the largest advance for the metrics.
if (isHorizontalLayout || isRotated)
if (isHorizontalLayout || shouldRotate)
{
for (int i = 1; i < metrics.Count; i++)
{
Expand Down Expand Up @@ -1066,7 +1085,7 @@ VerticalOrientationType.Rotate or
}

// Now scale the advance.
if (isHorizontalLayout || isRotated)
if (isHorizontalLayout || shouldRotate)
{
float scaleAX = pointSize / glyph.ScaleFactor.X;
glyphAdvance *= scaleAX;
Expand All @@ -1093,14 +1112,11 @@ VerticalOrientationType.Rotate or
// Mandatory wrap at index.
if (currentLineBreak.PositionWrap == codePointIndex && currentLineBreak.Required)
{
if (textLine.Count > 0)
{
textLines.Add(textLine.Finalize());
glyphCount += textLine.Count;
textLine = new();
lineAdvance = 0;
requiredBreak = true;
}
textLines.Add(textLine.Finalize());
glyphCount += textLine.Count;
textLine = new();
lineAdvance = 0;
requiredBreak = true;
}
else if (shouldWrap && lineAdvance + glyphAdvance >= wrappingLength)
{
Expand Down Expand Up @@ -1181,7 +1197,6 @@ VerticalOrientationType.Rotate or
}

// Find the next line break.
bool lastMandatory = lastLineBreak.Required;
if (currentLineBreak.PositionWrap == codePointIndex)
{
lastLineBreak = currentLineBreak;
Expand All @@ -1203,22 +1218,9 @@ VerticalOrientationType.Rotate or
continue;
}

// The previous line ended with a non-mandatory break at the wrapping length but the new line starts
// with a mandatory line break. We should not add a new line in this case as the line break has
// already been synthesized.
if (textLine.Count == 0
&& textLines.Count > 0
&& !lastMandatory
&& CodePoint.IsNewLine(codePoint))
{
codePointIndex++;
graphemeCodePointIndex++;
continue;
}

// Do not add new lines unless at position zero.
if (textLine.Count > 0 && CodePoint.IsNewLine(codePoint))
{
// Do not add new lines unless at position zero.
codePointIndex++;
graphemeCodePointIndex++;
continue;
Expand All @@ -1232,7 +1234,7 @@ VerticalOrientationType.Rotate or
// Work out the scaled metrics for the glyph.
GlyphMetrics metric = metrics[i];
float scaleY = pointSize / metric.ScaleFactor.Y;
IMetricsHeader metricsHeader = isHorizontalLayout || isRotated
IMetricsHeader metricsHeader = isHorizontalLayout || shouldRotate
? metric.FontMetrics.HorizontalMetrics
: metric.FontMetrics.VerticalMetrics;
float ascender = metricsHeader.Ascender * scaleY;
Expand All @@ -1257,7 +1259,7 @@ VerticalOrientationType.Rotate or
bidiRuns[bidiMap[codePointIndex]],
graphemeIndex,
codePointIndex,
isRotated,
shouldRotate || shouldOffset,
isDecomposed,
stringIndex);
}
Expand Down Expand Up @@ -1323,7 +1325,7 @@ public void Add(
BidiRun bidiRun,
int graphemeIndex,
int offset,
bool isRotated,
bool isTransformed,
bool isDecomposed,
int stringIndex)
{
Expand All @@ -1344,7 +1346,7 @@ public void Add(
bidiRun,
graphemeIndex,
offset,
isRotated,
isTransformed,
isDecomposed,
stringIndex));
}
Expand Down Expand Up @@ -1695,7 +1697,7 @@ public GlyphLayoutData(
BidiRun bidiRun,
int graphemeIndex,
int offset,
bool isRotated,
bool isTransformed,
bool isDecomposed,
int stringIndex)
{
Expand All @@ -1708,7 +1710,7 @@ public GlyphLayoutData(
this.BidiRun = bidiRun;
this.GraphemeIndex = graphemeIndex;
this.Offset = offset;
this.IsRotated = isRotated;
this.IsTransformed = isTransformed;
this.IsDecomposed = isDecomposed;
this.StringIndex = stringIndex;
}
Expand All @@ -1735,7 +1737,7 @@ public GlyphLayoutData(

public int Offset { get; }

public bool IsRotated { get; }
public bool IsTransformed { get; }

public bool IsDecomposed { get; }

Expand Down
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