Progress bar

ui.Progress creates a progress bar filled to a value between 0 and 1; a negative value shows activity of unknown length, a segment sliding across.

ui.Progress(c, float64(app.done)/float64(app.total)).Label("Uploading")
ui.Progress(c, -1).Label("Connecting")

Reverse fills it from the right, for interfaces laid out from right to left. It stretches across its column; give it a Width in a row.

A bar of unknown length moves only while it is in view, and costs only its painting: the window paints the last frame again at the display's rate, without running the view.

For a spinning indicator that takes less room, use a spinner; for a level that is no progress, as a disk's use, a meter.

Accessibility

Assistive technology sees a progress indicator of the value, or of unknown length, named by its Label.