Button groups
Controls joined into one. Only the outer corners round.
Button welded to a field
Segmented choice
Vertical, with a group nested in it
Toolbar toggles - primary on, outline off
Use it for
- A field with its one action welded on: a spanning group, the field grows, then a secondary IconButton.
- Groups nest. A corner only rounds where both groups agree it's an outer one.
- A segmented choice: fill the group, chosen one primary, the rest secondary, labels centred.
- Editor toolbar toggles: primary when on, outline when off.
Dont
- Leave a segmented control shrunk to its labels. It should span its field.
- Mix the primary-on toggle pattern and Toggle on the same surface.
- Use a secondary off state unless its a master switch whose off state matters.