// AddPathPositionedRun
public void AddPathPositionedRun(ReadOnlySpan <ushort> glyphs, SKFont font, ReadOnlySpan <float> glyphWidths, ReadOnlySpan <SKPoint> glyphOffsets, SKPath path, SKTextAlign textAlign = SKTextAlign.Left)
{
using var pathMeasure = new SKPathMeasure(path);
var contourLength = pathMeasure.Length;
var textLength = glyphOffsets[glyphs.Length - 1].X + glyphWidths[glyphs.Length - 1];
var alignment = (int)textAlign * 0.5f;
var startOffset = glyphOffsets[0].X + (contourLength - textLength) * alignment;
var firstGlyphIndex = 0;
var pathGlyphCount = 0;
using var glyphTransforms = Utils.RentArray <SKRotationScaleMatrix> (glyphs.Length);
// TODO: deal with multiple contours?
for (var index = 0; index < glyphOffsets.Length; index++)
{
var glyphOffset = glyphOffsets[index];
var halfWidth = glyphWidths[index] * 0.5f;
var pathOffset = startOffset + glyphOffset.X + halfWidth;
// TODO: clip glyphs on both ends of paths
if (pathOffset >= 0 && pathOffset < contourLength && pathMeasure.GetPositionAndTangent(pathOffset, out var position, out var tangent))
{
if (pathGlyphCount == 0)
{
firstGlyphIndex = index;
}
var tx = tangent.X;
var ty = tangent.Y;
var px = position.X;
var py = position.Y;
// horizontally offset the position using the tangent vector
px -= tx * halfWidth;
py -= ty * halfWidth;
// vertically offset the position using the normal vector (-ty, tx)
var dy = glyphOffset.Y;
px -= dy * ty;
py += dy * tx;
glyphTransforms.Span[pathGlyphCount++] = new SKRotationScaleMatrix(tx, ty, px, py);
}
}
var glyphSubset = glyphs.Slice(firstGlyphIndex, pathGlyphCount);
var positions = glyphTransforms.Span.Slice(0, pathGlyphCount);
AddRotationScaleRun(glyphSubset, font, positions);
}
public extern static bool sk_pathmeasure_get_matrix(sk_pathmeasure_t pathMeasure, float distance, out SKMatrix matrix, SKPathMeasure.MatrixFlags flags);
