Projects/Usability/HIG/Slider

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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 with simple descriptions because the precise value is read from the caption. For instance, 'min' and 'max' instead of '640x480' and '1280x1024' in case of screen resolution.
  • 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 min/max captions of the slider. Do not center align it with both the slider and the value caption.
  • 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


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