Number input

ui.NumberInput creates a text input editing a *float64 as a number between two bounds, which Up and Down, and the buttons beside it, change by a step. What is typed applies as soon as it is a number in range, and shows rounded to the decimals of the step once the input loses the focus. Changed reports a new value.

ui.NumberInput(c, &app.copies, 1, 99, 1).Label("Copies")
ui.NumberInput(c, &app.opacity, 0, 1, 0.05).Label("Opacity")

For a value the user only steps, use a stepper; for one chosen roughly, a slider.

Accessibility

Assistive technology sees a spin button of the value, named by its Label or its field, which it increments and decrements by the step.