Accessibility

A Caliper widget is a single drawn image as far as macOS is concerned, which would make it invisible to VoiceOver. So each one carries its own words.

VoiceOver

Menu bar items have the widget’s name as their label, and as their value what every cell shows — “CPU 23%, Memory Used 61% and Download 1.2 MB/s” — rebuilt whenever the picture is.

• An alerting cell says so: “CPU critical at 95%”.
• A cell of many readings, like a core matrix, is summarised as an average and a peak rather than read out core by core.
• A cell with no reading says “no reading”.

Desktop widgets and the editor’s preview say the same.

The detail panel is drawn rather than built from controls, so it gives VoiceOver an element for every line it draws, and its group chips are buttons that press.

Not colour alone

An alert is never only a colour. A cell past its warning threshold is underlined with a dashed line, and past its critical one with a solid line. The line sits under the cell, where no style draws, so it costs no width. See Alerts.

Reduce Motion

Nothing in Caliper animates. A number that eases between values is a number you cannot read, so there is nothing for Reduce Motion to turn off.