CH6.xml revision 5ec34c4c 
1<chapter id='Composite_and_Constraint_Widgets'>
2<title>Composite and Constraint Widgets</title>
3<para>
4These widgets may contain arbitrary widget children.  They implement a
5policy for the size and location of their children.
6</para>
7<para>
8<variablelist>
9  <varlistentry>
10    <term>Box</term>
11    <listitem>
12      <para>
13This widget will pack its children as tightly as possible in non-overlapping rows.
14      </para>
15    </listitem>
16  </varlistentry>
17  <varlistentry>
18    <term>Dialog</term>
19    <listitem>
20      <para>
21An implementation of a commonly used interaction semantic to prompt for
22auxiliary input from the user, such as a filename.
23      </para>
24    </listitem>
25  </varlistentry>
26  <varlistentry>
27    <term>Form</term>
28    <listitem>
29      <para>
30A more sophisticated layout widget that allows the children to specify
31their positions relative to the other children, or to the edges of the Form.
32      </para>
33    </listitem>
34  </varlistentry>
35  <varlistentry>
36    <term>Paned</term>
37    <listitem>
38      <para>
39Allows children to be tiled vertically or horizontally.  Controls are
40also provided to allow the user to dynamically resize the individual panes.
41      </para>
42    </listitem>
43  </varlistentry>
44  <varlistentry>
45    <term>Porthole</term>
46    <listitem>
47      <para>
48Allows viewing of a managed child which is as large as, or larger than its
49parent, typically under control of a Panner widget.
50      </para>
51    </listitem>
52  </varlistentry>
53  <varlistentry>
54    <term>Tree</term>
55    <listitem>
56      <para>
57Provides geometry management of widgets arranged in a directed, acyclic graph.
58      </para>
59    </listitem>
60  </varlistentry>
61  <varlistentry>
62    <term>Viewport</term>
63    <listitem>
64      <para>
65Consists of a frame, one or two scrollbars, and an inner window.  The
66inner window can contain all the data that is to be displayed.  This inner
67window will be clipped by the frame with the scrollbars controlling
68which section of the inner window is currently visible.
69      </para>
70    </listitem>
71  </varlistentry>
72</variablelist>
73</para>
74<note>
75<para>
76<!-- .LP -->
77The geometry management semantics provided by the X Toolkit give full
78control of the size and position of a widget to the parent of that
79widget.  While the children are allowed to request a certain size or
80location, it is the parent who makes the final decision.  Many of the
81composite widgets here will deny any geometry request from their
82children by default.  If a child widget is not getting the expected size
83or location, it is most likely the parent disallowing a request, or
84implementing semantics slightly different than those expected by the
85application programmer.
86</para>
87<para>
88<!-- .LP -->
89If the application wishes to change the size or location of
90any widget it should make a call to <xref linkend='XtSetValues' xrefstyle='select: title'/>.  This will
91<indexterm><primary>XtSetValues</primary></indexterm>
92allow the widget to ask its parent for the new size or location.
93As noted above the parent is allowed to refuse this request,
94and the child must live with the result.  If the
95application is unable to achieve the desired semantics, then perhaps it
96should use a different composite widget.  Under no circumstances
97should an application programmer resort to <function>XtMoveWidget</function> or
98<indexterm><primary>XtMoveWidget</primary></indexterm>
99<function>XtResizeWidget</function>; these functions are exclusively for the use of
100<indexterm><primary>XtResizeWidget</primary></indexterm>
101Composite widget implementors.
102</para>
103<para>
104<!-- .LP -->
105For more information on geometry management consult the
106<olink targetdoc='intrinsics' targetptr='Geometry_Management'
107><citetitle>X Toolkit Intrinsics - C Language Interface</citetitle></olink>.
108</para>
109</note>
110
111<xi:include xmlns:xi="http://www.w3.org/2001/XInclude"  href="Box.xml"/>
112<xi:include xmlns:xi="http://www.w3.org/2001/XInclude"  href="Dialog.xml"/>
113<xi:include xmlns:xi="http://www.w3.org/2001/XInclude"  href="Form.xml"/>
114<xi:include xmlns:xi="http://www.w3.org/2001/XInclude"  href="Paned.xml"/>
115<xi:include xmlns:xi="http://www.w3.org/2001/XInclude"  href="Porthole.xml"/>
116<xi:include xmlns:xi="http://www.w3.org/2001/XInclude"  href="Tree.xml"/>
117<xi:include xmlns:xi="http://www.w3.org/2001/XInclude"  href="Viewport.xml"/>
118
119</chapter>
120