qlayoutitem.3qt

Linux 下的图形编程环境。

'\" t
.TH QLayoutItem 3qt "5 March 2001" "Trolltech AS" \" -*- nroff -*-
.\" Copyright 1992-2001 Trolltech AS.  All rights reserved.  See the
.\" license file included in the distribution for a complete license
.\" statement.
.\"
.ad l
.nh
.SH NAME
QLayoutItem \- The abstract items which a
.br
.PP
\fC#include <qabstractlayout.h>\fR
.PP
Inherited by QLayout, QSpacerItem and QWidgetItem.
.PP
.SS "Public Members"
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.BI "\fBQLayoutItem\fR ( int " "alignment" " = 0 ) "
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.BI "virtual \fB~QLayoutItem\fR () "
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.BI "virtual QSize \fBsizeHint\fR () const"
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.BI "virtual QSize \fBminimumSize\fR () const"
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.BI "virtual QSize \fBmaximumSize\fR () const"
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.BI "virtual QSizePolicy::ExpandData \fBexpanding\fR () const"
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.BI "virtual void \fBsetGeometry\fR ( const QRect & ) "
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.BI "virtual QRect \fBgeometry\fR () const"
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.BI "virtual bool \fBisEmpty\fR () const"
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.BI "virtual bool \fBhasHeightForWidth\fR () const"
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.BI "virtual int \fBheightForWidth\fR ( int ) const"
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.BI "virtual void \fBinvalidate\fR () "
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.BI "virtual QWidget* \fBwidget\fR () "
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.BI "virtual QLayoutIterator \fBiterator\fR () "
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.BI "virtual QLayout* \fBlayout\fR () "
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.BI "virtual QSpacerItem* \fBspacerItem\fR () "
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.BI "int \fBalignment\fR () const"
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.BI "virtual void \fBsetAlignment\fR ( int a ) "
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.SH DESCRIPTION
The abstract items which a QLayout manipulates.
.PP
For custom layouts.
.PP
See also QLayout.
.SH MEMBER FUNCTION DOCUMENTATION
.SH "QLayoutItem::QLayoutItem ( int alignment = 0 )"
Constructs a layout item with an \fIalignment\fR that is a bitwise OR of Qt::AlignmentFlags. Alignment may not be supported by all subclasses.
.SH "QLayoutItem::~QLayoutItem () \fC[virtual]\fR"
Destructs the QLayoutItem.
.SH "int QLayoutItem::alignment () const"
Returns the alignment of this item.
.SH "QSizePolicy::ExpandData QLayoutItem::expanding() const \fC[virtual]\fR"
Implemented in subclasses to return whether this item "wants" to expand.
.PP
Reimplemented in QSpacerItem, QWidgetItem, QBoxLayout, QGridLayout and QLayout.
.SH "QRect QLayoutItem::geometry () const \fC[virtual]\fR"
Returns the rectangle covered by this layout item.
.PP
Reimplemented in QWidgetItem, QLayout and QSpacerItem.
.SH "bool QLayoutItem::hasHeightForWidth () const \fC[virtual]\fR"
Returns TRUE if this layout's preferred height depends on its width. The default implementation returns FALSE;
.PP
Reimplement this function in layout managers that support height for width.
.PP
See also heightForWidth() and QWidget::heightForWidth().
.PP
Reimplemented in QBoxLayout, QGridLayout and QWidgetItem.
.SH "int QLayoutItem::heightForWidth ( int ) const \fC[virtual]\fR"
Returns the preferred height for this layout item, given the width \fIw.\fR
.PP
The default implementation returns -1, indicating that the preferred height is independent of the width of the item. Using the function hasHeightForWidth() will typically be much faster than calling this function and testing for -1.
.PP
Reimplement this function in layout managers that support height for width. A typical implementation will look like this:
.PP
.nf
.br
  int MyLayout::heightForWidth( int w ) const
.br
  {
.br
      if ( cache_dirty || cached_width != w ) {
.br
          //Not all C++ compilers support "mutable" yet:
.br
          MyLayout * mthis = (MyLayout*)this;
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          int h = calculateHeightForWidth( w );
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          mthis->cached_hfw = h;
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          return h;
.br
      }
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      return cached_hfw;
.br
  }
.fi
.PP
Caching is strongly recommended, without it layout will take exponential time.
.PP
See also hasHeightForWidth().
.PP
Reimplemented in QGridLayout, QWidgetItem and QBoxLayout.
.SH "void QLayoutItem::invalidate () \fC[virtual]\fR"
Invalidates any cached information in this layout item.
.PP
Reimplemented in QBoxLayout, QLayout and QGridLayout.
.SH "virtual bool QLayoutItem::isEmpty () const \fC[virtual]\fR"
Implemented in subclasses to return whether this item is empty, i.e. whether it contains any widgets.
.PP
Reimplemented in QLayout, QWidgetItem and QSpacerItem.
.SH "QLayoutIterator QLayoutItem::iterator () \fC[virtual]\fR"
Returns an iterator over this item's QLayoutItem children. The default implementation returns an empty iterator.
.PP
Reimplement this function in subclasses that can have children.
.PP
Reimplemented in QGridLayout, QLayout and QBoxLayout.
.SH "QLayout * QLayoutItem::layout () \fC[virtual]\fR"
If this item is a QLayout, return it as a QLayout, otherwise return 0. This function provides type-safe casting.
.PP
Reimplemented in QLayout.
.SH "QSize QLayoutItem::maximumSize () const \fC[virtual]\fR"
Implemented in subclasses to return the maximum size of this item.
.PP
Reimplemented in QLayout, QSpacerItem, QGridLayout, QWidgetItem and QBoxLayout.
.SH "QSize QLayoutItem::minimumSize () const \fC[virtual]\fR"
Implemented in subclasses to return the minimum size of this item.
.PP
Reimplemented in QSpacerItem, QGridLayout, QBoxLayout, QLayout and QWidgetItem.
.SH "void QLayoutItem::setAlignment ( int a ) \fC[virtual]\fR"
Sets the alignment of this item to \fIa,\fR which is a bitwise OR of Qt::AlignmentFlags.
.SH "void QLayoutItem::setGeometry ( const QRect & r ) \fC[virtual]\fR"
Implemented in subclasses to set this item's geometry to \fIr.\fR
.PP
Reimplemented in QWidgetItem, QBoxLayout, QGridLayout, QLayout and QSpacerItem.
.SH "QSize QLayoutItem::sizeHint () const \fC[virtual]\fR"
Implemented in subclasses to return the preferred size of this item.
.PP
Reimplemented in QWidgetItem, QBoxLayout, QSpacerItem and QGridLayout.
.SH "QSpacerItem * QLayoutItem::spacerItem () \fC[virtual]\fR"
If this item is a QSpacerItem, return it as a QSpacerItem, otherwise return 0. This function provides type-safe casting.
.PP
Reimplemented in QSpacerItem.
.SH "QWidget * QLayoutItem::widget () \fC[virtual]\fR"
If this item is a QWidgetItem, the managed widget is returned.
The default implementation returns 0;.
.SH "SEE ALSO"
.BR http://doc.trolltech.com/qlayoutitem.html
.BR http://www.trolltech.com/faq/tech.html
.SH COPYRIGHT
Copyright 1992-2001 Trolltech AS, http://www.trolltech.com.  See the
license file included in the distribution for a complete license
statement.
.SH AUTHOR
Generated automatically from the source code.
.SH BUGS
If you find a bug in Qt, please report it as described in
.BR http://doc.trolltech.com/bughowto.html .
Good bug reports make our job much simpler. Thank you.
.P
In case of content or formattting problems with this manual page, please
report them to
.BR [e-mail] .
Please include the name of the manual page (qlayoutitem.3qt) and the Qt
version (2.3.0).