Difference between revisions of "Projects/Usability/HIG/Toggle Buttons"

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==Purpose==
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A toggle button is a button which stays down when clicked once and goes up when clicked a second time.
 
A toggle button is a button which stays down when clicked once and goes up when clicked a second time.
  
==When to use==
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==Guidelines==
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===When to Use===
  
 
Use a toggle button to indicate a '''state'''.
 
Use a toggle button to indicate a '''state'''.
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Example: A word processor should use toggle buttons to indicate the state of "Bold", "Italic" or "Underline" formatting.
 
Example: A word processor should use toggle buttons to indicate the state of "Bold", "Italic" or "Underline" formatting.
  
==When not to use==
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[[File:Toggle-button-formatting.png]]
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(Toggle buttons used in a rich text editor)
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===When not to Use===
  
 
Do not use a toggle button to indicate an '''action'''.
 
Do not use a toggle button to indicate an '''action'''.
  
Example: A music player should not use a toggle button to implement a Play/Pause button. It should use a normal button and adjust the icon and label to represent the '''action''' which would be performed when clicked.
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Example: A music player should not use a toggle button to implement a combined Play/Pause button. It should use a normal button and adjust the icon and label to represent the action which would be performed when clicked.
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[[File:Toggle-button-media-player.png]]
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==Icon and Label==
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There are two ways to label a toggle button. You can either describe the state reached when the button is down or describe the current state.
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===First option: Describe the state reached when the button is down===
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In this case the icon and label should not change when the button is down.
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Example: We create a toggle button to toggle the visibility of a sidebar. The label of this button is "Show Sidebar". When the button is toggled down, it should still say "Show Sidebar": it should not be changed to "Hide Sidebar".
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Think of the button as a check box: when you click a check box you do not expect its label to change. If it makes more sense to change the button text to "Hide Sidebar" when the sidebar is shown then you should use a normal button, not a toggle button.
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It is worth noting that unlike normal buttons, the label of a toggle button does not need to contain a verb, as long as there is no ambiguity. In this example the label can be reduced to "Sidebar".
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[[File:Toggle-button-summary.png]]
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===Second option: Describe the current state===
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In this case the label will often include a passive verb. For example a button to lock or unlock an element would say "Unlocked" when it is up and "Locked" when it is down. The icon should also change to match the label.
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[[File:Toggle-button-unlocked-locked.png]]
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===Which option to use===
  
==How to use==
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There is no strict rule to decide which option is the best, it depends on the context of your application. Note however that the second option has one drawback: since the label change, the button width will change as well. This can be annoying if the button is in the middle of a toolbar as it will cause all buttons after it to shift horizontally.
  
Never change the icon or label of a toggle button. The fact that it is pressed down is enough to indicate the current state of the element it represents.
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== Implementation ==
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* [http://api.kde.org/4.10-api/kdelibs-apidocs/kdeui/html/classKPushButton.html KPushButton] for generic buttons.
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* [http://api.kde.org/4.10-api/kdelibs-apidocs/kdeui/html/classKAction.html KAction] is used to generate buttons in toolbars.
  
Since a toggle button represents a state, in most cases the label should be a noun rather than a verb.
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Both classes have a <code>checkable</code> property which must be set to <code>true</code> to turn them into toggle buttons. You can then use the <code>checked</code> property to get and set the state of the button.

Revision as of 16:53, 27 June 2013

Contents

Purpose

A toggle button is a button which stays down when clicked once and goes up when clicked a second time.

Guidelines

When to Use

Use a toggle button to indicate a state.

Example: A word processor should use toggle buttons to indicate the state of "Bold", "Italic" or "Underline" formatting.

Toggle-button-formatting.png (Toggle buttons used in a rich text editor)

When not to Use

Do not use a toggle button to indicate an action.

Example: A music player should not use a toggle button to implement a combined Play/Pause button. It should use a normal button and adjust the icon and label to represent the action which would be performed when clicked.

Toggle-button-media-player.png

Icon and Label

There are two ways to label a toggle button. You can either describe the state reached when the button is down or describe the current state.

First option: Describe the state reached when the button is down

In this case the icon and label should not change when the button is down.

Example: We create a toggle button to toggle the visibility of a sidebar. The label of this button is "Show Sidebar". When the button is toggled down, it should still say "Show Sidebar": it should not be changed to "Hide Sidebar".

Think of the button as a check box: when you click a check box you do not expect its label to change. If it makes more sense to change the button text to "Hide Sidebar" when the sidebar is shown then you should use a normal button, not a toggle button.

It is worth noting that unlike normal buttons, the label of a toggle button does not need to contain a verb, as long as there is no ambiguity. In this example the label can be reduced to "Sidebar".

Toggle-button-summary.png

Second option: Describe the current state

In this case the label will often include a passive verb. For example a button to lock or unlock an element would say "Unlocked" when it is up and "Locked" when it is down. The icon should also change to match the label.

Toggle-button-unlocked-locked.png

Which option to use

There is no strict rule to decide which option is the best, it depends on the context of your application. Note however that the second option has one drawback: since the label change, the button width will change as well. This can be annoying if the button is in the middle of a toolbar as it will cause all buttons after it to shift horizontally.

Implementation

Both classes have a checkable property which must be set to true to turn them into toggle buttons. You can then use the checked property to get and set the state of the button.


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