ProgressScope

The receiver of an asyncWithProgress block: a CoroutineScope that can report progress and split the bar into slices.

Each ProgressScope owns a window, which is a part of the whole bar. The block's own scope owns the whole bar. A slice owns a part of its parent's window. A report of 0.5f in a slice fills half of that slice, not half of the bar.

The phase is the label of the current step. It is sticky: a report without a phase keeps the last phase.

You cannot implement this interface. Only asyncWithProgress creates it.

Threading

• report is safe from any thread, for example from parallel workers.

• Call slice and change the phase only from the block's own sequential code.

Watch out

• Reports from parallel workers can arrive out of order, so the bar can move back a little. Count finished units in one shared counter and report it with report(done, total). For a bar that never moves back, filter at the collector.

• After the operation completes, fails or is cancelled, reports do nothing.