KDE Visual Design Group/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 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
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- Add the unit to the current value caption, if appropriate.
Slider with few steps
eg screen size, symbol-size
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- 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
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- 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
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