104 lines
3.8 KiB
XML
104 lines
3.8 KiB
XML
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<appendix id='Resource_Configuration_Management'>
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<title>Resource Configuration Management</title>
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<para>
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Setting and changing resources in X applications can be difficult for
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both the application programmer and the end user. <emphasis role='strong'>Resource
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Configuration Management (RCM)</emphasis> addresses this problem by changing
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the <function>X Intrinsics</function> to immediately modify a resource for a
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specified widget and each child widget in the hierarchy.
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In this context, immediate means: no sourcing of a resource
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file is required; the application does not need to be restarted for the
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new resource values to take effect; and the change
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occurs immediately.
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</para>
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<para>
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The main difference between <function>RCM</function> and the <function>Editres</function>
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protocol is that the <function>RCM</function>
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customizing hooks reside in the <function>Intrinsics</function> and thus are linked with
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other toolkits such as Motif and the Athena widgets. However, the
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<function>EditRes</function> protocol requires the application to link with the
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<function>EditRes</function>
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routines in the Xmu library and Xmu is not used by all applications that
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use Motif. Also, the <function>EditRes</function> protocol uses ClientMessage,
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whereas the
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<function>RCM</function> <function>Intrinsics</function> hooks use <function>PropertyNotify</function> events.
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</para>
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<para>
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X Properties and the <function>PropertyNotify</function> events are used
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to implement <function>RCM</function> and
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allow on-the-fly resource customization. When the X Toolkit is
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initialized, two atoms are interned with the strings
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<emphasis remap='I'>Custom Init</emphasis> and
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<emphasis remap='I'>Custom Data</emphasis>. Both
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<function>_XtCreatePopupShell</function>
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and
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<function>_XtAppCreateShell</function>
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register a <function>PropertyNotify</function> event handler to handle these properties.
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</para>
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<para>
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A customization tool uses the <emphasis remap='I'>Custom Init</emphasis> property to <emphasis remap='I'>ping</emphasis> an
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application to get the application's toplevel window. When the
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application's property notify event handler is invoked, the handler
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deletes the property. No data is transferred in this property.
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</para>
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<para>
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A customization tool uses the <emphasis remap='I'>Custom Data</emphasis> property to tell an
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application that it should change a resource's value. The data in
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the property contains the length of the resource name (the number
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of bytes in the resource name), the resource name and the new
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value for the resource. This property's type is <function>XA_STRING</function> and
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the format of the string is:
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</para>
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<orderedlist>
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<listitem>
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<para>
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The length of the resource name (the number of bytes in
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the resource name)
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</para>
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</listitem>
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<listitem>
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<para>
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One space character
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</para>
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</listitem>
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<listitem>
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<para>
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The resource name
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</para>
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</listitem>
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<listitem>
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<para>
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One space character
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</para>
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</listitem>
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<listitem>
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<para>
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The resource value
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</para>
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</listitem>
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</orderedlist>
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<para>
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When setting the application's resource, the event handler calls
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functions to walk the application's widget tree, determining which
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widgets are affected by the resource string, and then applying the value
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with
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<xref linkend='XtSetValues' xrefstyle='select: title'/>.
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As the widget tree is recursively descended, at
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each level in the widget tree a resource part is tested for a match.
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When the entire resource string has been matched, the value is applied
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to the widget or widgets.
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</para>
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<para>
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Before a value is set on a widget, it is first determined if the last
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part of the resource is a valid resource for that widget. It must also
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add the resource to the application's resource database and then query
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it using specific resource strings that is builds from the widget
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information.
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</para>
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</appendix>
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