Projects/Usability/HIG/Slider

Purpose

A slider is a widget with which a user may set a value by moving an indicator, usually in a horizontal fashion. The user may also click on a point on the slider to change the setting. It is different from a scrollbar in that it is typically used to adjust a value without changing the format of the display or the other information on the screen. A slider is used to set defined, contiguous values or a range of discrete values. It is a good choice when values have a relative quantity, not a numeric value. Usually, changes made on the slider are shown immediately. That instant feedback supports input that is not necessarily precise. Compared with spin controls a slider provides faster changes within a larger range but with lower accuracy. Sliders are almost solely operable by mouse.

Guidelines

Is this the right control

• Use a slider when adjusting the value relative to its current value is more important than choosing an absolute value.
• Use a slider when it is useful for the user to control the rate of change of the value in real time.
• If the value is open-ended on one or both ends, consider using a Spin Box instead.

Behavior

• Try to give immediate feedback while user makes a selection.
• Size the control so that a user can easily set the desired value.
• Do not use a non-linear scale, e.g. logarithmic.

Appearance

• Mark significant values along the length of the slider with text or tick marks.
• Label the minimum and the maximum.
• Label the slider with a text label to its left, using sentence capitalization. Provide an access key in the label that allows the user to give focus directly to the slider.
• Align the label horizontally in line the slider.
• Add the unit to the current value caption, if appropriate.
• Label the range of values; use tick marks and value label; don't label every tick mark.

Implementation

• QSlider