GSAnchor

Overview

Anchor names determine how an anchor is used. A base anchor such as top pairs with the corresponding mark anchor _top. Other naming schemes support ligatures, cursive attachment, component placement, and contextual mark attachment.

The position is expressed in layer coordinates. The inherited orientation can make the horizontal position relative to the layer width.

A layer identifies its anchors by name and can contain at most one anchor for each name. Use the layer anchor APIs to attach or detach an anchor, and use name to rename an attached anchor so that the layer lookup remains consistent.

Anchor Naming

Anchors are defined by their name. The following list covers naming schemes and names for which Glyphs provides specialized handling.

Built-in Naming Schemes

• Base anchors use names such as top; mark anchors use the same name with a leading underscore, such as _top.

• Ligature anchors append a one-based component index after an underscore, such as top_1 and top_2.

• Ligature caret anchors use caret_N, such as caret_1.

• Cursive attachment anchors use entry and exit. Cursive anchors can use the same suffix after each name to form separate cursive lookups, such as entry.medial and exit.medial. Use cursive attachment inside the Glyphs source file without exposing the anchors to the exported font files by prefixing the anchor name with #: #entry and #exit.

• Component connection anchors use connect on both the containing layer and the component glyph. Unlike mark attachment, the matching anchor on the component glyph has no leading underscore. Connection anchors are not treated as mark attachment anchors during anchor propagation.

• Context anchors are designated by prefixing the name with *, such as *top. A period suffix on a context anchor separates the mark class name from a local disambiguation suffix, such as *top.case.

• Mirrored components swap directional anchor names such as left and right, top and bottom, entry and exit, and ogonek and ogonekabove.

Well-known Anchor Names

• top, bottom, _top, and _bottom have special behavior during component anchor traversal.

• left, right, top, bottom, center, ogonek, ogonekabove, nukta, candra, imatra, and iimatra are recognized by built-in anchor placement.

• topleft, topright, bottomleft, bottomright, bindu, and candrabindu are recognized when generating Indic mark positioning.

• top_cantillation_final and bottom_cantillation have special handling for Hebrew mark positioning.

• LSB, RSB, TSB, BSB, HALT, VHAL, lfbd, and rtbd are used to generate spacing feature code.

• *origin is reserved for component origin adjustment and is not a context anchor.

• dotbelow and names containing bottom have special handling for Myanmar mark-to-mark positioning.

• Corner glyphs use fixed anchor names such as left, right, origin, node1, node2, start, end, and direction.