qlayoutitem.3qt

linux下GUI编程工具qt的在线连接帮助手册

'\" t
.TH QLayoutItem 3qt "11 October 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 \- Abstract item that a QLayout manipulates
.PP
\fC#include <qlayout.h>\fR
.PP
Inherited by QLayout, QSpacerItem and QWidgetItem.
.PP
.SS "Public Members"
.in +1c
.ti -1c
.BI "\fBQLayoutItem\fR ( int alignment = 0 )"
.br
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.BI "virtual \fB~QLayoutItem\fR ()"
.br
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.BI "virtual QSize \fBsizeHint\fR () const"
.br
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.BI "virtual QSize \fBminimumSize\fR () const"
.br
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.BI "virtual QSize \fBmaximumSize\fR () const"
.br
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.BI "virtual QSizePolicy::ExpandData \fBexpanding\fR () const"
.br
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.BI "virtual void \fBsetGeometry\fR ( const QRect & r )"
.br
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.BI "virtual QRect \fBgeometry\fR () const"
.br
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.BI "virtual bool \fBisEmpty\fR () const"
.br
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.BI "virtual bool \fBhasHeightForWidth\fR () const"
.br
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.BI "virtual int \fBheightForWidth\fR ( int w ) const"
.br
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.BI "virtual void \fBinvalidate\fR ()"
.br
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.BI "virtual QWidget * \fBwidget\fR ()"
.br
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.BI "virtual QLayoutIterator \fBiterator\fR ()"
.br
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.BI "virtual QLayout * \fBlayout\fR ()"
.br
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.BI "virtual QSpacerItem * \fBspacerItem\fR ()"
.br
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.BI "int \fBalignment\fR () const"
.br
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.BI "virtual void \fBsetAlignment\fR ( int a )"
.br
.in -1c
.SH DESCRIPTION
The QLayoutItem class provides an abstract item that a QLayout manipulates.
.PP
This is used by custom layouts.
.PP
See also QLayout, Widget Appearance and Style and Layout Management.
.SH MEMBER FUNCTION DOCUMENTATION
.SH "QLayoutItem::QLayoutItem ( int alignment = 0 )"
Constructs a layout item with an \fIalignment\fR that is a bitwise OR of the Qt::AlignmentFlags. Not all subclasses support alignment.
.SH "QLayoutItem::~QLayoutItem ()\fC [virtual]\fR"
Destroys 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 QLayout, QSpacerItem and QWidgetItem.
.SH "QRect QLayoutItem::geometry () const\fC [virtual]\fR"
Returns the rectangle covered by this layout item.
.PP
Example: customlayout/border.cpp.
.SH "bool QLayoutItem::hasHeightForWidth () const\fC [virtual]\fR"
Returns TRUE if this layout's preferred height depends on its width; otherwise returns FALSE. 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
Examples:
.)l customlayout/border.cpp and customlayout/flow.cpp.
.PP
Reimplemented in QGridLayout and QBoxLayout.
.SH "int QLayoutItem::heightForWidth ( int w ) 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"
.br
            MyLayout *that = (MyLayout*)this;
.br
            int h = calculateHeightForWidth( w );
.br
            that->cached_hfw = h;
.br
            return h;
.br
        }
.br
        return cached_hfw;
.br
    }
.br
.fi
.PP
Caching is strongly recommended; without it layout will take exponential time.
.PP
See also hasHeightForWidth().
.PP
Example: customlayout/flow.cpp.
.PP
Reimplemented in QGridLayout and QBoxLayout.
.SH "void QLayoutItem::invalidate ()\fC [virtual]\fR"
Invalidates any cached information in this layout item.
.PP
Reimplemented in QLayout.
.SH "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, QSpacerItem and QWidgetItem.
.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 QLayout.
.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.
.SH "QSize QLayoutItem::maximumSize () const\fC [virtual]\fR"
Implemented in subclasses to return the maximum size of this item.
.PP
Reimplemented in QLayout, QSpacerItem and QWidgetItem.
.SH "QSize QLayoutItem::minimumSize () const\fC [virtual]\fR"
Implemented in subclasses to return the minimum size of this item.
.PP
Examples:
.)l customlayout/border.cpp, customlayout/card.cpp and customlayout/flow.cpp.
.PP
Reimplemented in QLayout, QSpacerItem 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 the Qt::AlignmentFlags. Not all subclasses support alignment.
.SH "void QLayoutItem::setGeometry ( const QRect & r )\fC [virtual]\fR"
Implemented in subclasses to set this item's geometry to \fIr\fR.
.PP
Examples:
.)l customlayout/border.cpp, customlayout/card.cpp and customlayout/flow.cpp.
.PP
Reimplemented in QLayout, QSpacerItem and QWidgetItem.
.SH "QSize QLayoutItem::sizeHint () const\fC [virtual]\fR"
Implemented in subclasses to return the preferred size of this item.
.PP
Examples:
.)l customlayout/border.cpp, customlayout/card.cpp and customlayout/flow.cpp.
.PP
Reimplemented in QSpacerItem, QWidgetItem, QGridLayout and QBoxLayout.
.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.
.SH "QWidget * QLayoutItem::widget ()\fC [virtual]\fR"
If this item is a QWidgetItem, the managed widget is returned. The default implementation returns 0.
.PP
Reimplemented in QWidgetItem.

.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 help us to help you. Thank you.
.P
The definitive Qt documentation is provided in HTML format; it is
located at $QTDIR/doc/html and can be read using Qt Assistant or with
a web browser. This man page is provided as a convenience for those
users who prefer man pages, although this format is not officially
supported by Trolltech. 
.P
If you find errors in this manual page, please report them to
.BR [e-mail] .
Please include the name of the manual page (qlayoutitem.3qt) and the Qt
version (3.0.0).