/// <summary>
/// This function stores just the point data. Coordinates packing algorithm based on the Google/woff2 sources.
/// </summary>
/// <param name="writer"></param>
/// <param name="pointsCapacity"></param>
/// <param name="pointsLength"></param>
/// <returns>Returns true on success.</returns>
private bool PackPoints(WoffIndexer writer, uint pointsCapacity, ref uint pointsLength)
{
uint flagOffset = 0;
int lastFlag = -1;
int repeatCount = 0;
int lastX = 0;
int lastY = 0;
uint xBytes = 0;
uint yBytes = 0;
int nPoints = _contours.Count;
for (int i = 0; i < nPoints; ++i)
{
var point = _contours[i];
int flag = point.IsOnCurve ? kGlyfOnCurve : 0;
int dx = point.X - lastX;
int dy = point.Y - lastY;
if (dx == 0)
{
flag |= kGlyfThisXIsSame;
}
else if (dx > -256 && dx < 256)
{
flag |= kGlyfXShort | (dx > 0 ? kGlyfThisXIsSame : 0);
xBytes += 1;
}
else
{
xBytes += 2;
}
if (dy == 0)
{
flag |= kGlyfThisYIsSame;
}
else if (dy > -256 && dy < 256)
{
flag |= kGlyfYShort | (dy > 0 ? kGlyfThisYIsSame : 0);
yBytes += 1;
}
else
{
yBytes += 2;
}
if (flag == lastFlag && repeatCount != 255)
{
writer[flagOffset - 1] |= kGlyfRepeat;
repeatCount++;
}
else
{
if (repeatCount != 0)
{
if ((flagOffset >= pointsCapacity))
{
return(false);
}
writer[flagOffset++] = (byte)repeatCount;
}
if ((flagOffset >= pointsCapacity))
{
return(false);
}
writer[flagOffset++] = (byte)flag;
repeatCount = 0;
}
lastX = point.X;
lastY = point.Y;
lastFlag = flag;
}
if (repeatCount != 0)
{
if ((flagOffset >= pointsCapacity))
{
return(false);
}
writer[flagOffset++] = (byte)repeatCount;
}
uint xyBytes = xBytes + yBytes;
if ((xyBytes < xBytes || flagOffset + xyBytes < flagOffset || flagOffset + xyBytes > pointsCapacity))
{
return(false);
}
uint xOffset = flagOffset;
uint yOffset = flagOffset + xBytes;
lastX = 0;
lastY = 0;
for (int i = 0; i < nPoints; ++i)
{
int dx = _contours[i].X - lastX;
if (dx == 0)
{
// pass
}
else if (dx > -256 && dx < 256)
{
writer[xOffset++] = (byte)Math.Abs(dx);
}
else
{
// will always fit for valid input, but overflow is harmless
writer.WriteInt16(dx, ref xOffset);
}
lastX += dx;
int dy = _contours[i].Y - lastY;
if (dy == 0)
{
// pass
}
else if (dy > -256 && dy < 256)
{
writer[yOffset++] = (byte)Math.Abs(dy);
}
else
{
writer.WriteInt16(dy, ref yOffset);
}
lastY += dy;
}
pointsLength = yOffset;
return(true);
}
