# Hello, World

This example brings up the words "Hello, World" moving up and down, and in different colors.

    /****************************************************************************
    ** $Id: hello.h,v 1.4 1998/05/21 19:24:53 agulbra 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.
    **
    *****************************************************************************/

    #ifndef HELLO_H
    #define HELLO_H

    #include <qwidget.h>

    class Hello : public QWidget
    {
        Q_OBJECT
    public:
        Hello( const char *text, QWidget *parent=0, const char *name=0 );
    signals:
        void clicked();
    protected:
        void mouseReleaseEvent( QMouseEvent * );
        void paintEvent( QPaintEvent * );
    private slots:
        void animate();
    private:
        QString t;
        int     b;
    };

    #endif

    /****************************************************************************
    ** $Id: hello.cpp,v 2.5 1998/06/16 11:39:32 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 "hello.h"
    #include <qpushbutton.h>
    #include <qtimer.h>
    #include <qpainter.h>
    #include <qpixmap.h>

    /*
      Constructs a Hello widget. Starts a 40 ms animation timer.
    */

    Hello::Hello( const char *text, QWidget *parent, const char *name )
        : QWidget(parent,name), t(text), b(0)
    {
        QTimer *timer = new QTimer(this);
        connect( timer, SIGNAL(timeout()), SLOT(animate()) );
        timer->start( 40 );

        resize( 200, 100 );
    }

    /*
      This private slot is called each time the timer fires.
    */

    void Hello::animate()
    {
        b = (b + 1) & 15;
        repaint( FALSE );
    }

    /*
      Handles mouse button release events for the Hello widget.

      We emit the clicked() signal when the mouse is released inside
      the widget.
    */

    void Hello::mouseReleaseEvent( QMouseEvent *e )
    {
        if ( rect().contains( e->pos() ) )
            emit clicked();
    }

    /*
      Handles paint events for the Hello widget.

      Flicker-free update. The text is first drawn in the pixmap and the
      pixmap is then blt'ed to the screen.
    */

    void Hello::paintEvent( QPaintEvent * )
    {
        static int sin_tbl[16] = {
            0, 38, 71, 92, 100, 92, 71, 38, 0, -38, -71, -92, -100, -92, -71, -38};

        if ( t.isEmpty() )
            return;

        // 1: Compute some sizes, positions etc.
        QFontMetrics fm = fontMetrics();
        int w = fm.width(t) + 20;
        int h = fm.height() * 2;
        int pmx = width()/2 - w/2;
        int pmy = height()/2 - h/2;

        // 2: Create the pixmap and fill it with the widget's background
        QPixmap pm( w, h );
        pm.fill( this, pmx, pmy );

        // 3: Paint the pixmap. Cool wave effect
        QPainter p;
        int x = 10;
        int y = h/2 + fm.descent();
        int i = 0;
        p.begin( &pm );
        p.setFont( font() );
        while ( t[i] ) {
            int i16 = (b+i) & 15;
            p.setPen( QColor((15-i16)*16,255,255,QColor::Hsv) );
            p.drawText( x, y-sin_tbl[i16]*h/800, &t[i], 1 );
            x += fm.width( t[i] );
            i++;
        }
        p.end();

        // 4: Copy the pixmap to the Hello widget
        bitBlt( this, pmx, pmy, &pm );
    }