Class ToggleBrailleCommand

Creates an instance of ToggleBrailleCommand.

Toggles the braille display when a trace is active and has something to encode, and otherwise offers the same key to a connected tactile display.

The two are one switch — "show me this by touch" — but only braille needs the data reduced to cells, and there are places it cannot be: the multi-panel lobby, where no series is selected yet, and the plot types with no braille table. A tactile display draws the chart's own geometry and needs none of that, so refusing on braille's behalf would hide the pins in exactly the cases they are most worth having — a scatter is the chart a pin grid draws best of all.

With no display connected there is nothing to offer, and the reader is better served by braille's own account of why it cannot open: a warning announcement and a warning tone, mirroring how l t warns when text mode is off. A trace with no data at all is left to braille for the same reason — "No info for braille" says more than pins that cannot change.