public static LookupType3Format1SubTable Load(BigEndianBinaryReader reader, long offset, LookupFlags lookupFlags)
{
// Cursive Attachment Positioning Format1.
// +--------------------+---------------------------------+------------------------------------------------------+
// | Type | Name | Description |
// +====================+=================================+======================================================+
// | uint16 | posFormat | Format identifier: format = 1 |
// +--------------------+---------------------------------+------------------------------------------------------+
// | Offset16 | coverageOffset | Offset to Coverage table, |
// | | | from beginning of CursivePos subtable. |
// +--------------------+---------------------------------+------------------------------------------------------+
// | uint16 | entryExitCount | Number of EntryExit records. |
// +--------------------+---------------------------------+------------------------------------------------------+
// | EntryExitRecord | entryExitRecord[entryExitCount] | Array of EntryExit records, in Coverage index order. |
// +--------------------+---------------------------------+------------------------------------------------------+
ushort coverageOffset = reader.ReadOffset16();
ushort entryExitCount = reader.ReadUInt16();
var entryExitRecords = new EntryExitRecord[entryExitCount];
for (int i = 0; i < entryExitCount; i++)
{
entryExitRecords[i] = new EntryExitRecord(reader, offset);
}
var entryExitAnchors = new EntryExitAnchors[entryExitCount];
for (int i = 0; i < entryExitCount; i++)
{
entryExitAnchors[i] = new EntryExitAnchors(reader, offset, entryExitRecords[i]);
}
var coverageTable = CoverageTable.Load(reader, offset + coverageOffset);
return(new LookupType3Format1SubTable(coverageTable, entryExitAnchors, lookupFlags));
}
public override bool TryUpdatePosition(
FontMetrics fontMetrics,
GPosTable table,
GlyphPositioningCollection collection,
Tag feature,
ushort index,
int count)
{
if (count <= 1)
{
return(false);
}
// Implements Cursive Attachment Positioning Subtable:
// https://docs.microsoft.com/en-us/typography/opentype/spec/gpos#lookup-type-3-cursive-attachment-positioning-subtable
ushort glyphId = collection[index][0];
if (glyphId == 0)
{
return(false);
}
ushort nextIndex = (ushort)(index + 1);
ushort nextGlyphId = collection[nextIndex][0];
if (nextGlyphId == 0)
{
return(false);
}
int coverageNext = this.coverageTable.CoverageIndexOf(nextGlyphId);
if (coverageNext < 0)
{
return(false);
}
EntryExitAnchors nextRecord = this.entryExitAnchors[coverageNext];
AnchorTable? entry = nextRecord.EntryAnchor;
if (entry is null)
{
return(false);
}
int coverage = this.coverageTable.CoverageIndexOf(glyphId);
if (coverage < 0)
{
return(false);
}
EntryExitAnchors curRecord = this.entryExitAnchors[coverage];
AnchorTable? exit = curRecord.ExitAnchor;
if (exit is null)
{
return(false);
}
GlyphShapingData current = collection.GetGlyphShapingData(index);
GlyphShapingData next = collection.GetGlyphShapingData(nextIndex);
// TODO: Vertical.
if (current.Direction == TextDirection.LeftToRight)
{
current.Bounds.Width = exit.XCoordinate + current.Bounds.X;
int delta = entry.XCoordinate + next.Bounds.X;
next.Bounds.Width -= delta;
next.Bounds.X -= delta;
}
else
{
int delta = exit.XCoordinate + current.Bounds.X;
current.Bounds.Width -= delta;
current.Bounds.X -= delta;
next.Bounds.Width = entry.XCoordinate + next.Bounds.X;
}
int child = index;
int parent = nextIndex;
int xOffset = entry.XCoordinate - exit.XCoordinate;
int yOffset = entry.YCoordinate - exit.YCoordinate;
if (this.LookupFlags.HasFlag(LookupFlags.RightToLeft))
{
int temp = child;
child = parent;
parent = temp;
xOffset = -xOffset;
yOffset = -yOffset;
}
// If child was already connected to someone else, walk through its old
// chain and reverse the link direction, such that the whole tree of its
// previous connection now attaches to new parent.Watch out for case
// where new parent is on the path from old chain...
bool horizontal = !collection.IsVerticalLayoutMode;
ReverseCursiveMinorOffset(collection, index, child, horizontal, parent);
GlyphShapingData c = collection.GetGlyphShapingData(child);
c.CursiveAttachment = parent - child;
if (horizontal)
{
c.Bounds.Y = yOffset;
}
else
{
c.Bounds.X = xOffset;
}
// If parent was attached to child, separate them.
GlyphShapingData p = collection.GetGlyphShapingData(parent);
if (p.CursiveAttachment == -c.CursiveAttachment)
{
p.CursiveAttachment = 0;
}
return(true);
}
