Contact State

<#4909#> The visual effect of a contact upon the user interface is controlled by the value of its <#429#>state<#429#> slot and is related to two factors^24.1.

<#432#>Mapping<#432#>: The concepts of <#433#>mapped<#433#>, <#435#>viewable<#435#>, and <#437#>visible<#437#> apply to any <#439#>xlib:window<#439#> object and therefore to contacts as well[#x-protocol##1###]. A contact is said to be ``mapped'' if <#441#>(xlib:map-window contact)<#441#> has been called. A contact is ``viewable'' if it and all of its ancestors are mapped. A contact is ``visible'' only if someone looking at the display screen can actually see some part of it; that is, the contact is viewable and is not completely occluded by any other windows.
<#445#>Geometry management<#445#>: A contact under geometry management control is said to be ``managed.'' As a result of CLUE geometry management, any changes to the position or size of a managed contact may affect the geometry of its managed siblings, its parent, and (in general) any other managed member of the contact subtree to which it belongs. Creating or destroying a managed contact can have a similar result. However, changes involving an unmanaged contact do not have this kind of ``ripple'' effect on the visible user interface.

These factors are not independent. In CLUE, it is invalid for a contact to be mapped but unmanaged, because this contradicts the purpose of geometry management^24.2. Thus, the <#451#>state<#451#> slot of a contact has one of three values.

`:withdrawn`	The contact is unmanaged and unmapped.
`:managed`	The contact is managed but unmapped.
`:mapped`	The contact is both managed and mapped.

The conditions corresponding to a contact's <#460#>state<#460#> are not guaranteed to be satisfied until the contact is realized. CLUE calls the <#463#>update-state<#463#> function in order to force consistency of the state of all contacts belonging to a <#465#>contact-display<#465#> (see Section~#ch:contact-display#466>).

<#4626#> <#4156#><#468#>update-state Function, contact-display<#468#><#4156#>

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<#4626#>

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The default <#488#>state<#488#> value is <#489#>:mapped<#489#>. As a result, unless specified otherwise, all contacts will automatically be viewable after <#490#>update-state<#490#> is called (in particular, after a call to <#491#>process-next-event<#491#>). After initialization and realization, the <#492#>(setf contact-state)<#492#> accessor method causes transitions in a contact's state and its visible effect. The most common usages are setting a contact's state to <#493#>:withdrawn<#493#> to withdraw it or to <#494#>:mapped<#494#> to present it.

=0 <#4919#>=0 <#4923#>