Home | All Classes | Main Classes | Annotated | Grouped Classes | Functions |

# Layout Managers

This example shows simple and intermediate use of Qt's layout classes, QGridLayout, QBoxLayout etc.

Implementation:

    /****************************************************************************
    ** $Id: qt/layout.cpp   3.3.8   edited Jan 11 14:37 $
    **
    ** Copyright (C) 1992-2007 Trolltech ASA.  All rights reserved.
    **
    ** This file is part of an example program for Qt.  This example
    ** program may be used, distributed and modified without limitation.
    **
    *****************************************************************************/

    #include <qapplication.h>
    #include <qlabel.h>
    #include <qcolor.h>
    #include <qpushbutton.h>
    #include <qlayout.h>
    #include <qlineedit.h>
    #include <qmultilineedit.h>
    #include <qmenubar.h>
    #include <qpopupmenu.h>

    class ExampleWidget : public QWidget
    {
    public:
        ExampleWidget( QWidget *parent = 0, const char *name = 0 );
        ~ExampleWidget();
    };

    ExampleWidget::ExampleWidget( QWidget *parent, const char *name )
        : QWidget( parent, name )
    {
        // Make the top-level layout; a vertical box to contain all widgets
        // and sub-layouts.
        QBoxLayout *topLayout = new QVBoxLayout( this, 5 );

        // Create a menubar...
        QMenuBar *menubar = new QMenuBar( this );
        menubar->setSeparator( QMenuBar::InWindowsStyle );
        QPopupMenu* popup;
        popup = new QPopupMenu( this );
        popup->insertItem( "&Quit", qApp, SLOT(quit()) );
        menubar->insertItem( "&File", popup );

        // ...and tell the layout about it.
        topLayout->setMenuBar( menubar );

        // Make an hbox that will hold a row of buttons.
        QBoxLayout *buttons = new QHBoxLayout( topLayout );
        int i;
        for ( i = 1; i <= 4; i++ ) {
            QPushButton* but = new QPushButton( this );
            QString s;
            s.sprintf( "Button %d", i );
            but->setText( s );

            // Set horizontal stretch factor to 10 to let the buttons
            // stretch horizontally. The buttons will not stretch
            // vertically, since bigWidget below will take up vertical
            // stretch.
            buttons->addWidget( but, 10 );
            // (Actually, the result would have been the same with a
            // stretch factor of 0; if no items in a layout have non-zero
            // stretch, the space is divided equally between members.)
        }

        // Make another hbox that will hold a left-justified row of buttons.
        QBoxLayout *buttons2 = new QHBoxLayout( topLayout );

        QPushButton* but = new QPushButton( "Button five", this );
        buttons2->addWidget( but );

        but = new QPushButton( "Button 6", this );
        buttons2->addWidget( but );

        // Fill up the rest of the hbox with stretchable space, so that
        // the buttons get their minimum width and are pushed to the left.
        buttons2->addStretch( 10 );

        // Make  a big widget that will grab all space in the middle.
        QMultiLineEdit *bigWidget = new QMultiLineEdit( this );
        bigWidget->setText( "This widget will get all the remaining space" );
        bigWidget->setFrameStyle( QFrame::Panel | QFrame::Plain );

        // Set vertical stretch factor to 10 to let the bigWidget stretch
        // vertically. It will stretch horizontally because there are no
        // widgets beside it to take up horizontal stretch.
        //    topLayout->addWidget( bigWidget, 10 );
        topLayout->addWidget( bigWidget );

        // Make a grid that will hold a vertical table of QLabel/QLineEdit
        // pairs next to a large QMultiLineEdit.

        // Don't use hard-coded row/column numbers in QGridLayout, you'll
        // regret it when you have to change the layout.
        const int numRows = 3;
        const int labelCol = 0;
        const int linedCol = 1;
        const int multiCol = 2;

        // Let the grid-layout have a spacing of 10 pixels between
        // widgets, overriding the default from topLayout.
        QGridLayout *grid = new QGridLayout( topLayout, 0, 0, 10 );
        int row;

        for ( row = 0; row < numRows; row++ ) {
            QLineEdit *ed = new QLineEdit( this );
            // The line edit goes in the second column
            grid->addWidget( ed, row, linedCol );

            // Make a label that is a buddy of the line edit
            QString s;
            s.sprintf( "Line &%d", row+1 );
            QLabel *label = new QLabel( ed, s, this );
            // The label goes in the first column.
            grid->addWidget( label, row, labelCol );
        }

        // The multiline edit will cover the entire vertical range of the
        // grid (rows 0 to numRows) and stay in column 2.

        QMultiLineEdit *med = new QMultiLineEdit( this );
        grid->addMultiCellWidget( med, 0, -1, multiCol, multiCol );

        // The labels will take the space they need. Let the remaining
        // horizontal space be shared so that the multiline edit gets
        // twice as much as the line edit.
        grid->setColStretch( linedCol, 10 );
        grid->setColStretch( multiCol, 20 );

        // Add a widget at the bottom.
        QLabel* sb = new QLabel( this );
        sb->setText( "Let's pretend this is a status bar" );
        sb->setFrameStyle( QFrame::Panel | QFrame::Sunken );
        // This widget will use all horizontal space, and have a fixed height.

        // we should have made a subclass and implemented sizePolicy there...
        sb->setFixedHeight( sb->sizeHint().height() );

        sb->setAlignment( AlignVCenter | AlignLeft );
        topLayout->addWidget( sb );

        topLayout->activate();
    }

    ExampleWidget::~ExampleWidget()
    {
        // All child widgets are deleted by Qt.
        // The top-level layout and all its sub-layouts are deleted by Qt.
    }

    int main( int argc, char **argv )
    {
        QApplication a( argc, argv );

        ExampleWidget f;
        a.setMainWidget(&f);
        f.setCaption("Qt Example - Layouts");
        f.show();

        return a.exec();
    }

See also Examples.