Segments should not carry actions

What it is

Each segment is “which way we are looking now,” not “do that thing.” Save, share, delete, send, and new do not belong on the track. When an action is drawn as a segment, the shape promises an exclusive mode: tapping Delete looks as if the current mode became delete and the Save mode switched off. What actually fires is a command, maybe with a confirm, and from then on the lit segment and the system state disagree.

Actions may sit beside the segmented control as ordinary buttons; they must not become a segment.

Why it happens

A segmented control trains this model: the lit segment describes the current world, and tapping another rewrites the description rather than emitting a side effect. A command button trains the opposite: press produces an event, then the button usually returns to unpressed even if the world changed. Crowding both models onto one track makes people guess buttons with the segment model: after Share they wait for the view to become a share pane and for List to dim; if share is only a card and the segment stays on List, they think it failed and tap again.

Exclusion also forces a false single-choice on commands: you cannot save and share because the track will not light two segments. Parallel commands become fake modes. A destructive command drawn as a segment also inherits the same visual weight as Preview; danger is washed out by the track’s tidy look.

Where it stops holding

“Edit / Preview” looks like actions but is a mode: while Edit is lit the canvas is writable; while Preview is lit it is read-only. The test is whether after the tap the segment stays lit and describes a lasting state. If it blinks off or opens a one-shot dialog, it is an action. Toolbar bold and alignment are toggle buttons that can stay pressed, but they are stackable states, not one exclusive track — do not tidy them into segments. Wizard Back / Next are navigation commands, so use buttons; drawing them as two segments implies two exclusive views rather than a walkable path.

Applying it

• Audit every segment: after lighting, does it keep describing the current view? If not, take it off the track and make it a button.
• Keep destructive commands off the track, with their own visual weight; do not borrow the track’s tidiness to lower alarm.
• When you need a current mode plus a one-shot action, the mode is the segmented control and the action is a button beside it, not a third segment.
• How to check: tap each segment and watch whether the lit state stays and the content becomes that face. A blink-and-off, or a side effect with no view change, is an action that snuck in.

Related

• Within the group: E3.07.1 Segments fit a few parallel, exclusive view switches · E3.07.2 More segments squeeze labels until they cannot be read
• Adjacent: E1.01 Button Hierarchy · E1.12 Toggle and State Buttons · E1.14 Button Groups and Split Buttons
• Search terms: segment versus button · mode not action · segmented control misuse