1<sect1 id="Viewport_Widget">
2<title>Viewport Widget</title>
3<para>
4<!-- .LP -->
5<!-- .XS -->
6<!-- 	Viewport Widget -->
7<!-- .XE -->
8<indexterm significance="preferred"><primary>Viewport widget</primary></indexterm>
9<literallayout class="monospaced">
10<!-- .TA 2.0i -->
11<!-- .ta 2.0i -->
12<!-- .sp -->
13Application Header file	&lt;X11/Xaw/Viewport.h&gt;
14<indexterm><primary>Viewport.h</primary></indexterm>
15Class Header file	&lt;X11/Xaw/ViewportP.h&gt;
16<indexterm><primary>ViewportP.h</primary></indexterm>
17Class		viewportWidgetClass
18<indexterm><primary>viewportWidgetClass</primary></indexterm>
19Class Name	Viewport
20<indexterm><primary>Viewport widget</primary><secondary>class name</secondary></indexterm>
21Superclass	Form
22<!-- .sp -->
23</literallayout>
24</para>
25<para>
26<!-- .LP -->
27The Viewport widget consists of a frame window, one or two Scrollbars,
28and an inner window.  The size of the frame window is determined by the
29viewing size of the data that is to be displayed and the dimensions to
30which the Viewport is created.  The inner window is the full size of the
31data that is to be displayed and is clipped by the frame window.  The
32Viewport widget controls the scrolling of the data directly.  No
33application callbacks are required for scrolling.
34</para>
35<para>
36<!-- .LP -->
37When the geometry of the frame window is equal in size to the inner
38window, or when the data does not require scrolling, the Viewport widget
39automatically removes any scrollbars.  The <function>forceBars</function> option causes
40the Viewport widget to display all scrollbars permanently.
41</para>
42<sect2 id='Viewport::Resources'>
43<title>Resources</title>
44<para>
45<!-- .LP -->
46When creating a Viewport widget instance, the following resources are
47retrieved from the argument list or the resource database:
48</para>
49<para>
50<!-- .LP -->
51<indexterm><primary>Viewport widget</primary><secondary>resources</secondary></indexterm>
52<informaltable>
53  <tgroup cols='5' align='center'>
54  <colspec colname='c1'/>
55  <colspec colname='c2'/>
56  <colspec colname='c3'/>
57  <colspec colname='c4'/>
58  <colspec colname='c5'/>
59  <thead>
60    <row>
61      <entry>Name</entry>
62      <entry>Class</entry>
63      <entry>Type</entry>
64      <entry>Notes</entry>
65      <entry>Default Value</entry>
66    </row>
67  </thead>
68  <tbody>
69    <row>
70      <entry>accelerators</entry>
71      <entry>Accelerators</entry>
72      <entry>AcceleratorTable</entry>
73      <entry></entry>
74      <entry>NULL</entry>
75    </row>
76    <row>
77      <entry>allowHoriz</entry>
78      <entry>Boolean</entry>
79      <entry>Boolean</entry>
80      <entry></entry>
81      <entry>False</entry>
82    </row>
83    <row>
84      <entry>allowVert</entry>
85      <entry>Boolean</entry>
86      <entry>Boolean</entry>
87      <entry></entry>
88      <entry>False</entry>
89    </row>
90    <row>
91      <entry>ancestorSensitive</entry>
92      <entry>AncestorSensitive</entry>
93      <entry>Boolean</entry>
94      <entry>D</entry>
95      <entry>True</entry>
96    </row>
97    <row>
98      <entry>background</entry>
99      <entry>Background</entry>
100      <entry>Pixel</entry>
101      <entry></entry>
102      <entry>XtDefaultBackground</entry>
103    </row>
104    <row>
105      <entry>backgroundPixmap</entry>
106      <entry>Pixmap</entry>
107      <entry>Pixmap</entry>
108      <entry></entry>
109      <entry>XtUnspecifiedPixmap</entry>
110    </row>
111    <row>
112      <entry>borderColor</entry>
113      <entry>BorderColor</entry>
114      <entry>Pixel</entry>
115      <entry></entry>
116      <entry>XtDefaultForeground</entry>
117    </row>
118    <row>
119      <entry>borderPixmap</entry>
120      <entry>Pixmap</entry>
121      <entry>Pixmap</entry>
122      <entry></entry>
123      <entry>XtUnspecifiedPixmap</entry>
124    </row>
125    <row>
126      <entry>borderWidth</entry>
127      <entry>BorderWidth</entry>
128      <entry>Dimension</entry>
129      <entry></entry>
130      <entry>1</entry>
131    </row>
132    <row>
133      <entry>children</entry>
134      <entry>ReadOnly</entry>
135      <entry>WidgetList</entry>
136      <entry>R</entry>
137      <entry>NULL</entry>
138    </row>
139    <row>
140      <entry>colormap</entry>
141      <entry>Colormap</entry>
142      <entry>Colormap</entry>
143      <entry></entry>
144      <entry>Parent's Colormap</entry>
145    </row>
146    <row>
147      <entry>depth</entry>
148      <entry>Depth</entry>
149      <entry>int</entry>
150      <entry>C</entry>
151      <entry>Parent's Depth</entry>
152    </row>
153    <row>
154      <entry>destroyCallback</entry>
155      <entry>Callback</entry>
156      <entry>XtCallbackList</entry>
157      <entry></entry>
158      <entry>NULL</entry>
159    </row>
160    <row>
161      <entry>forceBars</entry>
162      <entry>Boolean</entry>
163      <entry>Boolean</entry>
164      <entry></entry>
165      <entry>False</entry>
166    </row>
167    <row>
168      <entry>height</entry>
169      <entry>Height</entry>
170      <entry>Dimension</entry>
171      <entry></entry>
172      <entry>height of the child</entry>
173    </row>
174    <row>
175      <entry>mappedWhenManaged</entry>
176      <entry>MappedWhenManaged</entry>
177      <entry>Boolean</entry>
178      <entry></entry>
179      <entry>True</entry>
180    </row>
181    <row>
182      <entry>numChildren</entry>
183      <entry>ReadOnly</entry>
184      <entry>Cardinal</entry>
185      <entry>R</entry>
186      <entry>0</entry>
187    </row>
188    <row>
189      <entry>reportCallback</entry>
190      <entry>ReportCallback</entry>
191      <entry>XtCallbackList</entry>
192      <entry></entry>
193      <entry>NULL</entry>
194    </row>
195    <row>
196      <entry>screen</entry>
197      <entry>Screen</entry>
198      <entry>Screen</entry>
199      <entry>R</entry>
200      <entry>Parent's Screen</entry>
201    </row>
202    <row>
203      <entry>sensitive</entry>
204      <entry>Sensitive</entry>
205      <entry>Boolean</entry>
206      <entry></entry>
207      <entry>True</entry>
208    </row>
209    <row>
210      <entry>translations</entry>
211      <entry>Translations</entry>
212      <entry>TranslationTable</entry>
213      <entry></entry>
214      <entry>NULL</entry>
215    </row>
216    <row>
217      <entry>useBottom</entry>
218      <entry>Boolean</entry>
219      <entry>Boolean</entry>
220      <entry></entry>
221      <entry>False</entry>
222    </row>
223    <row>
224      <entry>useRight</entry>
225      <entry>Boolean</entry>
226      <entry>Boolean</entry>
227      <entry></entry>
228      <entry>False</entry>
229    </row>
230    <row>
231      <entry>width</entry>
232      <entry>Width</entry>
233      <entry>Dimension</entry>
234      <entry></entry>
235      <entry>width of the child</entry>
236    </row>
237    <row>
238      <entry>x</entry>
239      <entry>Position</entry>
240      <entry>Position</entry>
241      <entry></entry>
242      <entry>0</entry>
243    </row>
244    <row>
245      <entry>y</entry>
246      <entry>Position</entry>
247      <entry>Position</entry>
248      <entry></entry>
249      <entry>0</entry>
250    </row>
251    <row>
252      <entry>_</entry>
253    </row>
254  </tbody>
255  </tgroup>
256</informaltable>
257<!-- .Ac -->
258<variablelist>
259  <varlistentry>
260    <term>
261      <function>allowHoriz</function>
262    </term>
263    <listitem>
264      <para>
265<!-- .br -->
266<!-- .ns -->
267      </para>
268    </listitem>
269  </varlistentry>
270  <varlistentry>
271    <term>
272      <function>allowVert</function>
273    </term>
274    <listitem>
275      <para>
276If these resources are <function>False</function> then the Viewport will never create
277a scrollbar in this direction.  If it is <function>True</function> then the scrollbar will
278only appear when it is needed, unless <function>forceBars</function> is <function>True</function>.
279<!-- .As -->
280<!-- .Bg -->
281<!-- .Gp -->
282<!-- .Bc -->
283<!-- .Bp -->
284<!-- .Bw -->
285<!-- .Ch -->
286<!-- .Cm -->
287<!-- .Dp -->
288<!-- .Dc -->
289      </para>
290    </listitem>
291  </varlistentry>
292  <varlistentry>
293    <term>
294      <function>forceBars</function>
295    </term>
296    <listitem>
297      <para>
298When <function>True</function> the scrollbars that have been <emphasis remap='I'>allowed</emphasis> will always be
299visible on the screen.  If <function>False</function> the scrollbars will be visible only
300when the inner window is larger than the frame.
301<!-- .Hw -->
302<!-- .Mm -->
303<!-- .Nc -->
304      </para>
305    </listitem>
306  </varlistentry>
307  <varlistentry>
308    <term>
309      <function>reportCallback</function>
310    </term>
311    <listitem>
312      <para>
313These callbacks will be executed whenever the Viewport adjusts the viewed
314area of the child.  The call_data parameter is a pointer to an XawPannerReport
315structure.
316<!-- .Sc -->
317<!-- .Se -->
318<!-- .Tr -->
319      </para>
320    </listitem>
321  </varlistentry>
322  <varlistentry>
323    <term>
324      <function>useBottom</function>
325    </term>
326    <listitem>
327      <para>
328<!-- .br -->
329<!-- .ns -->
330      </para>
331    </listitem>
332  </varlistentry>
333  <varlistentry>
334    <term>
335      <function>useRight</function>
336    </term>
337    <listitem>
338      <para>
339By default the scrollbars appear on the left and top of the screen.
340These resources allow the vertical scrollbar to be placed on the right
341edge of the Viewport, and the horizontal scrollbar on the bottom edge of
342the Viewport.
343<!-- .Xy -->
344    </para>
345  </listitem>
346  </varlistentry>
347</variablelist>
348</para>
349</sect2>
350<sect2 id='Viewport::Layout_Semantics'>
351<title>Layout Semantics</title>
352<para>
353<!-- .LP -->
354<indexterm><primary>Viewport widget</primary><secondary>layout semantics</secondary></indexterm>
355The Viewport widget manages a single child widget.  When the size of the
356child is larger than the size of the Viewport, the user can interactively
357move the child within the Viewport by repositioning the scrollbars.
358</para>
359<para>
360<!-- .LP -->
361The default size of the Viewport before it is realized is the width and/or
362height of the child.  After it is realized, the Viewport will allow its
363child to grow vertically or horizontally if <function>allowVert</function> or
364<function>allowHoriz</function> are set, respectively.  If the corresponding vertical
365or horizontal scrollbar is not enabled, the Viewport will propagate the
366geometry request to its own parent and the child will be allowed to change
367size only if the Viewport's parent allows it.  Regardless of whether or not
368scrollbars are enabled in the corresponding direction, if the child requests
369a new size smaller than the Viewport size, the change will be allowed only
370if the parent of the Viewport allows the Viewport to shrink to the
371appropriate dimension.
372</para>
373<para>
374<!-- .LP -->
375The scrollbar children of the Viewport are named <function>horizontal</function> and
376<function>vertical</function>.  By using these names the programmer can specify resources
377for the individual scrollbars.  <xref linkend='XtSetValues' xrefstyle='select: title'/> can be used to modify
378the resources dynamically once the widget ID has been obtained with
379<function>XtNameToWidget</function>.
380<indexterm><primary>XtNameToWidget</primary></indexterm>
381<!-- .NT -->
382</para>
383<note><para>
384Although the Viewport is a Subclass of the Form, no resources for the Form
385may be supplied for any of the children of the Viewport.  These constraints
386are managed internally and are not meant for public consumption.
387</para></note>
388<!-- .NE -->
389
390</sect2>
391</sect1>
392