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6<title>QLayoutItem Class</title>
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32<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>QLayoutItem Class Reference</h1>
33
34<p>The QLayoutItem class provides an abstract item that a
35QLayout manipulates.
36<a href="#details">More...</a>
37<p><tt>#include &lt;<a href="qlayout-h.html">qlayout.h</a>&gt;</tt>
38<p>Inherited by <a href="qlayout.html">QLayout</a>, <a href="qspaceritem.html">QSpacerItem</a>, and <a href="qwidgetitem.html">QWidgetItem</a>.
39<p><a href="qlayoutitem-members.html">List of all member functions.</a>
40<h2>Public Members</h2>
41<ul>
42<li class=fn><a href="#QLayoutItem"><b>QLayoutItem</b></a> ( int&nbsp;alignment = 0 )</li>
43<li class=fn>virtual <a href="#~QLayoutItem"><b>~QLayoutItem</b></a> ()</li>
44<li class=fn>virtual QSize <a href="#sizeHint"><b>sizeHint</b></a> () const = 0</li>
45<li class=fn>virtual QSize <a href="#minimumSize"><b>minimumSize</b></a> () const = 0</li>
46<li class=fn>virtual QSize <a href="#maximumSize"><b>maximumSize</b></a> () const = 0</li>
47<li class=fn>virtual QSizePolicy::ExpandData <a href="#expanding"><b>expanding</b></a> () const = 0</li>
48<li class=fn>virtual void <a href="#setGeometry"><b>setGeometry</b></a> ( const&nbsp;QRect&nbsp;&amp;&nbsp;r ) = 0</li>
49<li class=fn>virtual QRect <a href="#geometry"><b>geometry</b></a> () const = 0</li>
50<li class=fn>virtual bool <a href="#isEmpty"><b>isEmpty</b></a> () const = 0</li>
51<li class=fn>virtual bool <a href="#hasHeightForWidth"><b>hasHeightForWidth</b></a> () const</li>
52<li class=fn>virtual int <a href="#heightForWidth"><b>heightForWidth</b></a> ( int&nbsp;w ) const</li>
53<li class=fn>virtual void <a href="#invalidate"><b>invalidate</b></a> ()</li>
54<li class=fn>virtual QWidget * <a href="#widget"><b>widget</b></a> ()</li>
55<li class=fn>virtual QLayoutIterator <a href="#iterator"><b>iterator</b></a> ()</li>
56<li class=fn>virtual QLayout * <a href="#layout"><b>layout</b></a> ()</li>
57<li class=fn>virtual QSpacerItem * <a href="#spacerItem"><b>spacerItem</b></a> ()</li>
58<li class=fn>int <a href="#alignment"><b>alignment</b></a> () const</li>
59<li class=fn>virtual void <a href="#setAlignment"><b>setAlignment</b></a> ( int&nbsp;a )</li>
60</ul>
61<hr><a name="details"></a><h2>Detailed Description</h2>
62
63
64
65
66The QLayoutItem class provides an abstract item that a
67<a href="qlayout.html">QLayout</a> manipulates.
68<p> This is used by custom layouts.
69<p> Pure virtual functions are provided to return information about
70the layout, including, <a href="#sizeHint">sizeHint</a>(), <a href="#minimumSize">minimumSize</a>(), <a href="#maximumSize">maximumSize</a>()
71and <a href="#expanding">expanding</a>().
72<p> The layout's geometry can be set and retrieved with <a href="#setGeometry">setGeometry</a>()
73and <a href="#geometry">geometry</a>(), and its alignment with <a href="#setAlignment">setAlignment</a>() and
74<a href="#alignment">alignment</a>().
75<p> <a href="#isEmpty">isEmpty</a>() returns whether the layout is empty. <a href="#iterator">iterator</a>() returns
76an iterator for the layout's children. If the concrete item is a
77<a href="qwidget.html">QWidget</a>, it can be retrieved using <a href="#widget">widget</a>(). Similarly for
78<a href="#layout">layout</a>() and <a href="#spacerItem">spacerItem</a>().
79<p> <p>See also <a href="qlayout.html">QLayout</a>, <a href="appearance.html">Widget Appearance and Style</a>, and <a href="geomanagement.html">Layout Management</a>.
80
81<hr><h2>Member Function Documentation</h2>
82<h3 class=fn><a name="QLayoutItem"></a>QLayoutItem::QLayoutItem ( int&nbsp;alignment = 0 )
83</h3>
84
85<p> Constructs a layout item with an <em>alignment</em> that is a bitwise OR
86of the <a href="qt.html#AlignmentFlags-enum">Qt::AlignmentFlags</a>. Not all subclasses support
87alignment.
88
89<h3 class=fn><a name="~QLayoutItem"></a>QLayoutItem::~QLayoutItem ()<tt> [virtual]</tt>
90</h3>
91Destroys the QLayoutItem.
92
93<h3 class=fn>int <a name="alignment"></a>QLayoutItem::alignment () const
94</h3>
95
96<p> Returns the alignment of this item.
97
98<h3 class=fn><a href="qsizepolicy.html#ExpandData-enum">QSizePolicy::ExpandData</a> <a name="expanding"></a>QLayoutItem::expanding () const<tt> [pure virtual]</tt>
99</h3>
100
101<p> Implemented in subclasses to return the direction(s) this item
102"wants" to expand in (if any).
103
104<p>Reimplemented in <a href="qlayout.html#expanding">QLayout</a>, <a href="qspaceritem.html#expanding">QSpacerItem</a>, and <a href="qwidgetitem.html#expanding">QWidgetItem</a>.
105<h3 class=fn><a href="qrect.html">QRect</a> <a name="geometry"></a>QLayoutItem::geometry () const<tt> [pure virtual]</tt>
106</h3>
107
108<p> Returns the rectangle covered by this layout item.
109
110<p>Example: <a href="customlayout-example.html#x1495">customlayout/border.cpp</a>.
111<h3 class=fn>bool <a name="hasHeightForWidth"></a>QLayoutItem::hasHeightForWidth () const<tt> [virtual]</tt>
112</h3>
113Returns TRUE if this layout's preferred height depends on its
114width; otherwise returns FALSE. The default implementation returns
115FALSE.
116<p> Reimplement this function in layout managers that support height
117for width.
118<p> <p>See also <a href="#heightForWidth">heightForWidth</a>() and <a href="qwidget.html#heightForWidth">QWidget::heightForWidth</a>().
119
120<p>Examples: <a href="customlayout-example.html#x1496">customlayout/border.cpp</a> and <a href="customlayout-example.html#x1472">customlayout/flow.cpp</a>.
121<p>Reimplemented in <a href="qgridlayout.html#hasHeightForWidth">QGridLayout</a> and <a href="qboxlayout.html#hasHeightForWidth">QBoxLayout</a>.
122<h3 class=fn>int <a name="heightForWidth"></a>QLayoutItem::heightForWidth ( int&nbsp;w ) const<tt> [virtual]</tt>
123</h3>
124Returns the preferred height for this layout item, given the width
125<em>w</em>.
126<p> The default implementation returns -1, indicating that the
127preferred height is independent of the width of the item. Using
128the function <a href="#hasHeightForWidth">hasHeightForWidth</a>() will typically be much faster
129than calling this function and testing for -1.
130<p> Reimplement this function in layout managers that support height
131for width. A typical implementation will look like this:
132<pre>
133 int MyLayout::heightForWidth( int w ) const
134 {
135 if ( cache_dirty || cached_width != w ) {
136 // not all C++ compilers support "mutable"
137 MyLayout *that = (MyLayout*)this;
138 int h = calculateHeightForWidth( w );
139 that-&gt;cached_hfw = h;
140 return h;
141 }
142 return cached_hfw;
143 }
144 </pre>
145
146<p> Caching is strongly recommended; without it layout will take
147exponential time.
148<p> <p>See also <a href="#hasHeightForWidth">hasHeightForWidth</a>().
149
150<p>Example: <a href="customlayout-example.html#x1473">customlayout/flow.cpp</a>.
151<p>Reimplemented in <a href="qgridlayout.html#heightForWidth">QGridLayout</a> and <a href="qboxlayout.html#heightForWidth">QBoxLayout</a>.
152<h3 class=fn>void <a name="invalidate"></a>QLayoutItem::invalidate ()<tt> [virtual]</tt>
153</h3>
154Invalidates any cached information in this layout item.
155
156<p>Reimplemented in <a href="qlayout.html#invalidate">QLayout</a>.
157<h3 class=fn>bool <a name="isEmpty"></a>QLayoutItem::isEmpty () const<tt> [pure virtual]</tt>
158</h3>
159
160<p> Implemented in subclasses to return whether this item is empty,
161i.e. whether it contains any widgets.
162
163<p>Reimplemented in <a href="qlayout.html#isEmpty">QLayout</a>, <a href="qspaceritem.html#isEmpty">QSpacerItem</a>, and <a href="qwidgetitem.html#isEmpty">QWidgetItem</a>.
164<h3 class=fn><a href="qlayoutiterator.html">QLayoutIterator</a> <a name="iterator"></a>QLayoutItem::iterator ()<tt> [virtual]</tt>
165</h3>
166Returns an iterator over this item's QLayoutItem children. The
167default implementation returns an empty iterator.
168<p> Reimplement this function in subclasses that can have children.
169
170<p>Reimplemented in <a href="qlayout.html#iterator">QLayout</a>.
171<h3 class=fn><a href="qlayout.html">QLayout</a>&nbsp;* <a name="layout"></a>QLayoutItem::layout ()<tt> [virtual]</tt>
172</h3>
173If this item is a <a href="qlayout.html">QLayout</a>, it is returned as a QLayout; otherwise
1740 is returned. This function provides type-safe casting.
175
176<h3 class=fn><a href="qsize.html">QSize</a> <a name="maximumSize"></a>QLayoutItem::maximumSize () const<tt> [pure virtual]</tt>
177</h3>
178
179<p> Implemented in subclasses to return the maximum size of this item.
180
181<p>Reimplemented in <a href="qlayout.html#maximumSize">QLayout</a>, <a href="qspaceritem.html#maximumSize">QSpacerItem</a>, and <a href="qwidgetitem.html#maximumSize">QWidgetItem</a>.
182<h3 class=fn><a href="qsize.html">QSize</a> <a name="minimumSize"></a>QLayoutItem::minimumSize () const<tt> [pure virtual]</tt>
183</h3>
184
185<p> Implemented in subclasses to return the minimum size of this item.
186
187<p>Examples: <a href="customlayout-example.html#x1497">customlayout/border.cpp</a>, <a href="customlayout-example.html#x1515">customlayout/card.cpp</a>, and <a href="customlayout-example.html#x1474">customlayout/flow.cpp</a>.
188<p>Reimplemented in <a href="qlayout.html#minimumSize">QLayout</a>, <a href="qspaceritem.html#minimumSize">QSpacerItem</a>, and <a href="qwidgetitem.html#minimumSize">QWidgetItem</a>.
189<h3 class=fn>void <a name="setAlignment"></a>QLayoutItem::setAlignment ( int&nbsp;a )<tt> [virtual]</tt>
190</h3>
191Sets the alignment of this item to <em>a</em>, which is a bitwise OR of
192the <a href="qt.html#AlignmentFlags-enum">Qt::AlignmentFlags</a>. Not all subclasses support alignment.
193
194<p>Example: <a href="tutorial2-09.html#x2644">chart/optionsform.cpp</a>.
195<h3 class=fn>void <a name="setGeometry"></a>QLayoutItem::setGeometry ( const&nbsp;<a href="qrect.html">QRect</a>&nbsp;&amp;&nbsp;r )<tt> [pure virtual]</tt>
196</h3>
197
198<p> Implemented in subclasses to set this item's geometry to <em>r</em>.
199
200<p>Examples: <a href="customlayout-example.html#x1498">customlayout/border.cpp</a>, <a href="customlayout-example.html#x1516">customlayout/card.cpp</a>, and <a href="customlayout-example.html#x1475">customlayout/flow.cpp</a>.
201<p>Reimplemented in <a href="qlayout.html#setGeometry">QLayout</a>, <a href="qspaceritem.html#setGeometry">QSpacerItem</a>, and <a href="qwidgetitem.html#setGeometry">QWidgetItem</a>.
202<h3 class=fn><a href="qsize.html">QSize</a> <a name="sizeHint"></a>QLayoutItem::sizeHint () const<tt> [pure virtual]</tt>
203</h3>
204
205<p> Implemented in subclasses to return the preferred size of this item.
206
207<p>Examples: <a href="customlayout-example.html#x1499">customlayout/border.cpp</a>, <a href="customlayout-example.html#x1517">customlayout/card.cpp</a>, and <a href="customlayout-example.html#x1476">customlayout/flow.cpp</a>.
208<p>Reimplemented in <a href="qspaceritem.html#sizeHint">QSpacerItem</a>, <a href="qwidgetitem.html#sizeHint">QWidgetItem</a>, <a href="qgridlayout.html#sizeHint">QGridLayout</a>, and <a href="qboxlayout.html#sizeHint">QBoxLayout</a>.
209<h3 class=fn><a href="qspaceritem.html">QSpacerItem</a>&nbsp;* <a name="spacerItem"></a>QLayoutItem::spacerItem ()<tt> [virtual]</tt>
210</h3>
211If this item is a <a href="qspaceritem.html">QSpacerItem</a>, it is returned as a QSpacerItem;
212otherwise 0 is returned. This function provides type-safe casting.
213
214<h3 class=fn><a href="qwidget.html">QWidget</a>&nbsp;* <a name="widget"></a>QLayoutItem::widget ()<tt> [virtual]</tt>
215</h3>
216If this item is a <a href="qwidget.html">QWidget</a>, it is returned as a QWidget; otherwise
2170 is returned. This function provides type-safe casting.
218
219<p>Reimplemented in <a href="qwidgetitem.html#widget">QWidgetItem</a>.
220<!-- eof -->
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