KDE Visual Design Group/HIG/Slider

Note
This page is now on [https://hig.kde.org/]

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 the 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

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 with the slider.
You can show the current value on the right of the slider or if space is very dense show it only as a tooltip when the slider is moved

Add the unit to the current value caption, if appropriate.

Slider with few steps

eg screen size, symbol-size

Mark significant values along the length of the slider with text or checkmarks. Checkmark have a height of 4 px or 8 if you want to emphasize them.
Min/max labels are optional. Label min/max with real values, eg '640x480' and '5120×2880' in case of screen resolution.
Label the range of values; use checkmark and value label; don't label every checkmark.

Slider with many steps

eg volume control, mouse speed, brightness

Don't show checkmarks if the exact value is not important
Don't show min/max label if the values don't give the user additional information, eg. don't label them 0%, 100%
If the exact value might be important to the user offer an input field instead of the current value label

Implementation

QSlider