Bracket Layers

Not every design change should be a continuous transformation. A glyph can need one construction in light weights and another in heavy weights, even while the rest of the family changes smoothly. Bracket layers let you choose a point where one design gives way to another, then interpolate each side using its own ordinary master layers.

Why a Design May Need a Break

Consider a dollar sign ($). In a light design, two fine vertical strokes through the S may be clear and well separated. As the weight increases, those strokes can crowd the counters and intersections. For the heavier part of the family, you might choose a single vertical stroke, or a stroke that is interrupted through the middle of the S. The right choice depends on the typeface; neither is an automatic correction that FontLab makes for you.

This is a change of construction, not just a request for more weight. A continuous morph may squeeze two strokes together or gradually shrink an unwanted piece. That can produce a narrow dark seam, a disappearing sliver, or an awkward intermediate form. Even when you can force the outlines into compatible point structures, the resulting transition may not be the design you want.

A bracket break lets you make a different decision: use the two-stroke construction up to a chosen weight, and the alternative construction above it. Each design can develop smoothly within its own range. The switch changes the dollar sign while the other glyphs continue through the same weight axis normally.

Other useful cases follow the same principle:

  • Upright and italic constructions. Where a design deliberately transitions between upright and italic forms, a letter may need a structural replacement, such as a double-storey a giving way to a single-storey form. Changing its slant alone does not make that replacement. A bracket can locate the structural switch on the chosen axis; it is not required merely because a family includes italics.
  • Small optical sizes. A detail that works at display sizes may need a simpler construction at text sizes: an opening may need to remain clear, or a small internal feature may be omitted. If the intended change is discrete, an optical-size bracket can separate the constructions.
  • Narrow or heavy extremes. A junction or terminal can require a different arrangement where space becomes scarce. Use a break when the alternative changes the design’s structure; use a continuous correction when the same structure can still develop satisfactorily.

A bracket does not remove a visible discontinuity: it makes that discontinuity intentional and locates it precisely. Choose a break where the replacement makes design sense, and inspect its rhythm and spacing in text. Changes in advance width can also change line lengths. Keep the advances consistent across the break when a width jump is not part of the intended design.

Two Designs at One Location

Suppose the family has Air, Regular, and Black masters, with Regular at Weight 400. In the dollar-sign glyph, keep the two-stroke design from Air through Regular and use a single-stroke design from Regular toward Black. Adding a bracket at Regular gives that glyph four master layers:

Air
Regular [<400]
Regular [>400]
Black

FontLab renames the original Regular layer and creates one independent copy at the same location. Edit Regular [<400] as the two-stroke design and Regular [>400] as the single-stroke design. Air interpolates toward the lower Regular variant; the upper Regular variant interpolates toward Black.

The two Regular variants may have different contour structures. Match Air with Regular [<400] and match Regular [>400] with Black. Compatibility is needed within each range, not across the break. You do not need to give the two-stroke and single-stroke dollar signs an artificial point correspondence.

This creates one additional glyph master layer. It does not create groups, duplicate Air and Black, or add a font-wide master. The alternative remains part of the same editable glyph, rather than a separately named glyph that you must manage throughout the source font.

In bracket-layer names, <400 denotes the lower side below 400. The >400 design takes over at 400 and above, matching the minimum-boundary behavior of Glyphs alternate layers. Both drawings stay at location 400; do not move one slightly along the axis to separate them. The two Regular layers are the endpoint drawings for different ranges, not two sources to blend together.

You may also leave one layer named simply Regular. With Regular [<400] and Regular at the same master location, the bracket drawing applies below 400 and plain Regular fills the remaining range, starting at 400. With Regular and Regular [>400], plain Regular fills the lower range instead. Both forms keep two independent drawings and the same interpolation behavior as the fully named pair.

FontLab infers one ordinary fallback for one bracket cut at a shared master location. The layers must share the same base name, and the bracket must contain one axis condition. Keep explicit bracket names for more complex ranges. An ordinary Regular source at another location remains a separate source. Add Bracket Layer still supplies both explicit names; you can remove the suffix from either one when this simpler naming is useful.

Add and Edit a Bracket

  1. Preview the glyph and decide whether the problem needs a structural switch. If the same construction should remain continuous, first consider a corrective master or The Sigma Tool.
  2. In Layers & Masters, select the master layer at the intended break. In the example, select the dollar sign’s Regular layer at 400.
  3. Click the Duplicate layer button and choose Add Bracket Layer from its popup. Choose the axis when the font has several axes. Duplicate Layer makes an ordinary copy instead; the Layers list has no context menu.
  4. Edit the two bracket variants for their respective constructions, and check their compatibility with the masters in their own ranges.
  5. Preview below the break, at it, and just above it. Then inspect several positions within each range. Check outlines, advances, sidebearings, and attachments, followed by the glyph in representative text.

You can also choose Add Bracket from the Variations widget’s context menu. With several axes, names identify the conditions explicitly, for example Regular [Weight>400&Width<100]. The ampersand means both conditions apply. Axis names are case-insensitive and may use the font’s shortnames: [wt>400&wd<100] has the same meaning when wt and wd are the shortnames for Weight and Width.

Select and Preview a Range

Bracket masters appear in bold and sort at the position of their base master. The lower Regular variant precedes the upper one. When you activate the font’s Regular master, FontLab chooses the bracket nearest the previously active master: from Black it chooses Regular [>400], and from Air it chooses Regular [<400]. With no usable previous state, it chooses the lower range. Clicking a particular bracket variant selects that variant directly.

In the Variations widget, a line in the selection color marks the active range beneath the previews, from the left sidebearing of its left master to the right sidebearing of its right master. Both endpoint masters are included. Inactive ranges are gray. Activate a range, then click its left or right master to edit the corresponding variant. Switching ranges keeps the preview positions fixed. When you move the axis to exactly 400, the upper range becomes active. Clicking the lower boundary master explicitly still lets you edit Regular [<400] at its original location; it does not change which design the exported font uses at 400. Compatibility indications in the Layers panel and the Glyph window’s master selector compare masters only within the active range.

Choose Layers or Separate Glyphs

Use bracket layers when you want to edit a glyph’s regional designs together, with the normal layer and master controls. Use separate replacement glyphs and conditional tags when those alternatives belong in a broader layout workflow or require control over when substitution runs; see Beyond the Uniform Blend.

Neither a bracket nor Sigma is a replacement for a corrective master in every situation. A master supplies a drawing to interpolate through; Sigma shapes the continuous trajectories between drawings; a bracket separates drawings that should not interpolate into each other. Choose the one that expresses the intended design change, then test the delivered font at its boundaries and in text. Export and import are covered in OpenType, Variable, and Web Fonts.