Advanced use of tool tips

/****************************************************************************
** $Id: tooltip.cpp,v 1.6 1998/06/16 11:39:35 warwick Exp $
**
** Copyright (C) 1992-1998 Troll Tech AS.  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 "tooltip.h"
#include <qapplication.h>
#include <qpainter.h>
#include <stdlib.h>

DynamicTip::DynamicTip( QWidget * parent )
    : QToolTip( parent )
{
    // no explicit initialization needed
}

void DynamicTip::maybeTip( const QPoint &pos )
{
    if ( !parentWidget()->inherits( "TellMe" ) )
        return;

    QRect r( ((TellMe*)parentWidget())->tip(pos) );
    if ( !r.isValid() )
        return;

    QString s;
    s.sprintf( "position: %d,%d", r.center().x(), r.center().y() );
    tip( r, s );
}

TellMe::TellMe( QWidget * parent , const char * name  )
    : QWidget( parent, name )
{
    setMinimumSize( 30, 30 );
    r1 = randomRect();
    r2 = randomRect();
    r3 = randomRect();

    t = new DynamicTip( this );

    QToolTip::add( this, r3, "this color is called red" ); // <- helpful
}

TellMe::~TellMe()
{
    delete t;
    t = 0;
}

void TellMe::paintEvent( QPaintEvent * e )
{
    QPainter p( this );

    // I try to be efficient here, and repaint only what's needed

    if ( e->rect().intersects( r1 ) ) {
        p.setBrush( blue );
        p.drawRect( r1 );
    }

    if ( e->rect().intersects( r2 ) ) {
        p.setBrush( blue );
        p.drawRect( r2 );
    }

    if ( e->rect().intersects( r3 ) ) {
        p.setBrush( red );
        p.drawRect( r3 );
    }
}

void TellMe::mousePressEvent( QMouseEvent * e )
{
    if ( r1.contains( e->pos() ) )
        r1 = randomRect();
    if ( r2.contains( e->pos() ) )
        r2 = randomRect();
    repaint();
}

void TellMe::resizeEvent( QResizeEvent * )
{
    if ( !rect().contains( r1 ) )
         r1 = randomRect();
    if ( !rect().contains( r2 ) )
         r2 = randomRect();
}

QRect TellMe::randomRect()
{
    return QRect( ::rand() % (width() - 20), ::rand() % (height() - 20),
                  20, 20 );
}

QRect TellMe::tip( const QPoint & p )
{
    if ( r1.contains( p ) )
        return r1;
    else if ( r2.contains( p ) )
        return r2;
    else
        return QRect( 0,0, -1,-1 );
}