Segment components are a great way to unify recurring shape edges. Think cupped serifs, tapered stems, ornamental sides of Tuscan-style typefaces, and the like.
In short, a segment glyph is a glyph with a special name containing an open path, which then can be injected as a segment component into a host path.
Step 1 Create the _segment glyph
Choose Glyph > Add Glyphs (Cmd-Shift-G) and type the name of our new segment glyph. For my example, I will choose the name
_segment.spike. The name of a segment glyph must start with
_segment, followed by an arbitrary dot suffix.
Draw an open outline along the baseline, and put a
start anchor on the first node, and an
end anchor on the last node, perhaps like this:
You can choose Glyph > Set Anchors (Cmd-U) to add the two anchors to your segment glyph. Make sure your
end anchors snap exactly onto the first and last points. And do keep them on a horizontal stretch. How high exactly does not matter, but I guess keeping them on or around the baseline makes the handling easier.
Step 2 Insert the segment component
Now that we have set up our segment, it is time to put it to good use. Bring up one of your letters, let’s say an H, then select a segment, right-click and pick Add Segment Component from the context menu:
You will be presented with all segment components in the font. In case you have many already because you got carried away with creating segment components, you can quickly search in their glyph names by typing a search term:
Repeat with other segments you want it to use it for, and do not forget to add it to all masters in case you have a multiple-master setup in front of you. Congratulations, your segment components are live!
Good to know Behavior of segment components
The cool thing is, the segment component will be squeezed or stretched onto the receiving segment, no matter what its length is. So, depending on what exactly your segment glyph looks like, it may be a good idea to have different versions for different sizes, think of
_segment.spike.capHeight, you get the idea. On the other hand, if it is just a simple bend, e.g., for a cupped serif or a tapered stem, you might just as well get away with just one segment component for all applications.
And, at least to some degree, a segment component even gets bent onto a curve, ta-daaa:
Caution: Glyphs will not add nodes to keep the shape bending as authentic as possible. Rather, the number of nodes is kept the same to keep outline compatibility as much as possible. (Otherwise it would not work in variable fonts.) So each node will keep its individual perpendicular offset to the segment. That means that point triplets (e.g., handle-node-handle) may change their angle through the bend, because each of the three points (i.e., not the triplet as a whole) keeps its own distance to the curve, and the curvature causes different, non-linear displacements for each node.
So if you plan to apply your segment component to curve segments as well, perhaps avoid node triplets. Sounds complicated? Yeah, but don’t worry, just experiment a little, and you will get the hang of it in no time.