<sect1 id="Viewport_Widget">
<title>Viewport Widget</title>
<para>
<!-- .LP -->
<!-- .XS -->
<!-- 	Viewport Widget -->
<!-- .XE -->
<indexterm significance="preferred"><primary>Viewport widget</primary></indexterm>
<literallayout class="monospaced">
<!-- .TA 2.0i -->
<!-- .ta 2.0i -->
<!-- .sp -->
Application Header file	&lt;X11/Xaw/Viewport.h&gt;
<indexterm><primary>Viewport.h</primary></indexterm>
Class Header file	&lt;X11/Xaw/ViewportP.h&gt;
<indexterm><primary>ViewportP.h</primary></indexterm>
Class		viewportWidgetClass
<indexterm><primary>viewportWidgetClass</primary></indexterm>
Class Name	Viewport
<indexterm><primary>Viewport widget</primary><secondary>class name</secondary></indexterm>
Superclass	Form
<!-- .sp -->
</literallayout>
</para>
<para>
<!-- .LP -->
The Viewport widget consists of a frame window, one or two Scrollbars,
and an inner window.  The size of the frame window is determined by the
viewing size of the data that is to be displayed and the dimensions to
which the Viewport is created.  The inner window is the full size of the
data that is to be displayed and is clipped by the frame window.  The
Viewport widget controls the scrolling of the data directly.  No
application callbacks are required for scrolling.
</para>
<para>
<!-- .LP -->
When the geometry of the frame window is equal in size to the inner
window, or when the data does not require scrolling, the Viewport widget
automatically removes any scrollbars.  The <function>forceBars</function> option causes
the Viewport widget to display all scrollbars permanently.
</para>
<sect2 id='Viewport::Resources'>
<title>Resources</title>
<para>
<!-- .LP -->
When creating a Viewport widget instance, the following resources are
retrieved from the argument list or the resource database:
</para>
<para>
<!-- .LP -->
<indexterm><primary>Viewport widget</primary><secondary>resources</secondary></indexterm>
<informaltable>
  <tgroup cols='5' align='center'>
  <colspec colname='c1'/>
  <colspec colname='c2'/>
  <colspec colname='c3'/>
  <colspec colname='c4'/>
  <colspec colname='c5'/>
  <thead>
    <row>
      <entry>Name</entry>
      <entry>Class</entry>
      <entry>Type</entry>
      <entry>Notes</entry>
      <entry>Default Value</entry>
    </row>
  </thead>
  <tbody>
    <row>
      <entry>accelerators</entry>
      <entry>Accelerators</entry>
      <entry>AcceleratorTable</entry>
      <entry></entry>
      <entry>NULL</entry>
    </row>
    <row>
      <entry>allowHoriz</entry>
      <entry>Boolean</entry>
      <entry>Boolean</entry>
      <entry></entry>
      <entry>False</entry>
    </row>
    <row>
      <entry>allowVert</entry>
      <entry>Boolean</entry>
      <entry>Boolean</entry>
      <entry></entry>
      <entry>False</entry>
    </row>
    <row>
      <entry>ancestorSensitive</entry>
      <entry>AncestorSensitive</entry>
      <entry>Boolean</entry>
      <entry>D</entry>
      <entry>True</entry>
    </row>
    <row>
      <entry>background</entry>
      <entry>Background</entry>
      <entry>Pixel</entry>
      <entry></entry>
      <entry>XtDefaultBackground</entry>
    </row>
    <row>
      <entry>backgroundPixmap</entry>
      <entry>Pixmap</entry>
      <entry>Pixmap</entry>
      <entry></entry>
      <entry>XtUnspecifiedPixmap</entry>
    </row>
    <row>
      <entry>borderColor</entry>
      <entry>BorderColor</entry>
      <entry>Pixel</entry>
      <entry></entry>
      <entry>XtDefaultForeground</entry>
    </row>
    <row>
      <entry>borderPixmap</entry>
      <entry>Pixmap</entry>
      <entry>Pixmap</entry>
      <entry></entry>
      <entry>XtUnspecifiedPixmap</entry>
    </row>
    <row>
      <entry>borderWidth</entry>
      <entry>BorderWidth</entry>
      <entry>Dimension</entry>
      <entry></entry>
      <entry>1</entry>
    </row>
    <row>
      <entry>children</entry>
      <entry>ReadOnly</entry>
      <entry>WidgetList</entry>
      <entry>R</entry>
      <entry>NULL</entry>
    </row>
    <row>
      <entry>colormap</entry>
      <entry>Colormap</entry>
      <entry>Colormap</entry>
      <entry></entry>
      <entry>Parent's Colormap</entry>
    </row>
    <row>
      <entry>depth</entry>
      <entry>Depth</entry>
      <entry>int</entry>
      <entry>C</entry>
      <entry>Parent's Depth</entry>
    </row>
    <row>
      <entry>destroyCallback</entry>
      <entry>Callback</entry>
      <entry>XtCallbackList</entry>
      <entry></entry>
      <entry>NULL</entry>
    </row>
    <row>
      <entry>forceBars</entry>
      <entry>Boolean</entry>
      <entry>Boolean</entry>
      <entry></entry>
      <entry>False</entry>
    </row>
    <row>
      <entry>height</entry>
      <entry>Height</entry>
      <entry>Dimension</entry>
      <entry></entry>
      <entry>height of the child</entry>
    </row>
    <row>
      <entry>mappedWhenManaged</entry>
      <entry>MappedWhenManaged</entry>
      <entry>Boolean</entry>
      <entry></entry>
      <entry>True</entry>
    </row>
    <row>
      <entry>numChildren</entry>
      <entry>ReadOnly</entry>
      <entry>Cardinal</entry>
      <entry>R</entry>
      <entry>0</entry>
    </row>
    <row>
      <entry>reportCallback</entry>
      <entry>ReportCallback</entry>
      <entry>XtCallbackList</entry>
      <entry></entry>
      <entry>NULL</entry>
    </row>
    <row>
      <entry>screen</entry>
      <entry>Screen</entry>
      <entry>Screen</entry>
      <entry>R</entry>
      <entry>Parent's Screen</entry>
    </row>
    <row>
      <entry>sensitive</entry>
      <entry>Sensitive</entry>
      <entry>Boolean</entry>
      <entry></entry>
      <entry>True</entry>
    </row>
    <row>
      <entry>translations</entry>
      <entry>Translations</entry>
      <entry>TranslationTable</entry>
      <entry></entry>
      <entry>NULL</entry>
    </row>
    <row>
      <entry>useBottom</entry>
      <entry>Boolean</entry>
      <entry>Boolean</entry>
      <entry></entry>
      <entry>False</entry>
    </row>
    <row>
      <entry>useRight</entry>
      <entry>Boolean</entry>
      <entry>Boolean</entry>
      <entry></entry>
      <entry>False</entry>
    </row>
    <row>
      <entry>width</entry>
      <entry>Width</entry>
      <entry>Dimension</entry>
      <entry></entry>
      <entry>width of the child</entry>
    </row>
    <row>
      <entry>x</entry>
      <entry>Position</entry>
      <entry>Position</entry>
      <entry></entry>
      <entry>0</entry>
    </row>
    <row>
      <entry>y</entry>
      <entry>Position</entry>
      <entry>Position</entry>
      <entry></entry>
      <entry>0</entry>
    </row>
    <row>
      <entry>_</entry>
    </row>
  </tbody>
  </tgroup>
</informaltable>
<!-- .Ac -->
<variablelist>
  <varlistentry>
    <term>
      <function>allowHoriz</function>
    </term>
    <listitem>
      <para>
<!-- .br -->
<!-- .ns -->
      </para>
    </listitem>
  </varlistentry>
  <varlistentry>
    <term>
      <function>allowVert</function>
    </term>
    <listitem>
      <para>
If these resources are <function>False</function> then the Viewport will never create
a scrollbar in this direction.  If it is <function>True</function> then the scrollbar will
only appear when it is needed, unless <function>forceBars</function> is <function>True</function>.
<!-- .As -->
<!-- .Bg -->
<!-- .Gp -->
<!-- .Bc -->
<!-- .Bp -->
<!-- .Bw -->
<!-- .Ch -->
<!-- .Cm -->
<!-- .Dp -->
<!-- .Dc -->
      </para>
    </listitem>
  </varlistentry>
  <varlistentry>
    <term>
      <function>forceBars</function>
    </term>
    <listitem>
      <para>
When <function>True</function> the scrollbars that have been <emphasis remap='I'>allowed</emphasis> will always be
visible on the screen.  If <function>False</function> the scrollbars will be visible only
when the inner window is larger than the frame.
<!-- .Hw -->
<!-- .Mm -->
<!-- .Nc -->
      </para>
    </listitem>
  </varlistentry>
  <varlistentry>
    <term>
      <function>reportCallback</function>
    </term>
    <listitem>
      <para>
These callbacks will be executed whenever the Viewport adjusts the viewed
area of the child.  The call_data parameter is a pointer to an XawPannerReport
structure.
<!-- .Sc -->
<!-- .Se -->
<!-- .Tr -->
      </para>
    </listitem>
  </varlistentry>
  <varlistentry>
    <term>
      <function>useBottom</function>
    </term>
    <listitem>
      <para>
<!-- .br -->
<!-- .ns -->
      </para>
    </listitem>
  </varlistentry>
  <varlistentry>
    <term>
      <function>useRight</function>
    </term>
    <listitem>
      <para>
By default the scrollbars appear on the left and top of the screen.
These resources allow the vertical scrollbar to be placed on the right
edge of the Viewport, and the horizontal scrollbar on the bottom edge of
the Viewport.
<!-- .Xy -->
    </para>
  </listitem>
  </varlistentry>
</variablelist>
</para>
</sect2>
<sect2 id='Viewport::Layout_Semantics'>
<title>Layout Semantics</title>
<para>
<!-- .LP -->
<indexterm><primary>Viewport widget</primary><secondary>layout semantics</secondary></indexterm>
The Viewport widget manages a single child widget.  When the size of the
child is larger than the size of the Viewport, the user can interactively
move the child within the Viewport by repositioning the scrollbars.
</para>
<para>
<!-- .LP -->
The default size of the Viewport before it is realized is the width and/or
height of the child.  After it is realized, the Viewport will allow its
child to grow vertically or horizontally if <function>allowVert</function> or
<function>allowHoriz</function> are set, respectively.  If the corresponding vertical
or horizontal scrollbar is not enabled, the Viewport will propagate the
geometry request to its own parent and the child will be allowed to change
size only if the Viewport's parent allows it.  Regardless of whether or not
scrollbars are enabled in the corresponding direction, if the child requests
a new size smaller than the Viewport size, the change will be allowed only
if the parent of the Viewport allows the Viewport to shrink to the
appropriate dimension.
</para>
<para>
<!-- .LP -->
The scrollbar children of the Viewport are named <function>horizontal</function> and
<function>vertical</function>.  By using these names the programmer can specify resources
for the individual scrollbars.  <xref linkend='XtSetValues' xrefstyle='select: title'/> can be used to modify
the resources dynamically once the widget ID has been obtained with
<function>XtNameToWidget</function>.
<indexterm><primary>XtNameToWidget</primary></indexterm>
<!-- .NT -->
</para>
<note><para>
Although the Viewport is a Subclass of the Form, no resources for the Form
may be supplied for any of the children of the Viewport.  These constraints
are managed internally and are not meant for public consumption.
</para></note>
<!-- .NE -->

</sect2>
</sect1>
