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This example shows very simple mouse-based user interaction and painting without any world transform matrix or other advanced features. Run the program, click the button, move the mouse, release the button, and watch the lines get drawn.
Implementation:
/**************************************************************************** ** $Id: qt/connect.cpp 3.1.2 edited Nov 8 10:35 $ ** ** Copyright (C) 1992-2000 Trolltech 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 <qwidget.h> #include <qpainter.h> #include <qapplication.h> #include <stdlib.h> const int MAXPOINTS = 2000; // maximum number of points const int MAXCOLORS = 40; // // ConnectWidget - draws connected lines // class ConnectWidget : public QWidget { public: ConnectWidget( QWidget *parent=0, const char *name=0 ); ~ConnectWidget(); protected: void paintEvent( QPaintEvent * ); void mousePressEvent( QMouseEvent *); void mouseReleaseEvent( QMouseEvent *); void mouseMoveEvent( QMouseEvent *); private: QPoint *points; // point array QColor *colors; // color array int count; // count = number of points bool down; // TRUE if mouse down }; // // Constructs a ConnectWidget. // ConnectWidget::ConnectWidget( QWidget *parent, const char *name ) : QWidget( parent, name, WStaticContents ) { setBackgroundColor( white ); // white background count = 0; down = FALSE; points = new QPoint[MAXPOINTS]; colors = new QColor[MAXCOLORS]; for ( int i=0; i<MAXCOLORS; i++ ) // init color array colors[i] = QColor( rand()&255, rand()&255, rand()&255 ); } ConnectWidget::~ConnectWidget() { delete[] points; // cleanup delete[] colors; } // // Handles paint events for the connect widget. // void ConnectWidget::paintEvent( QPaintEvent * ) { QPainter paint( this ); for ( int i=0; i<count-1; i++ ) { // connect all points for ( int j=i+1; j<count; j++ ) { paint.setPen( colors[rand()%MAXCOLORS] ); // set random pen color paint.drawLine( points[i], points[j] ); // draw line } } } // // Handles mouse press events for the connect widget. // void ConnectWidget::mousePressEvent( QMouseEvent * ) { down = TRUE; count = 0; // start recording points erase(); // erase widget contents } // // Handles mouse release events for the connect widget. // void ConnectWidget::mouseReleaseEvent( QMouseEvent * ) { down = FALSE; // done recording points update(); // draw the lines } // // Handles mouse move events for the connect widget. // void ConnectWidget::mouseMoveEvent( QMouseEvent *e ) { if ( down && count < MAXPOINTS ) { QPainter paint( this ); points[count++] = e->pos(); // add point paint.drawPoint( e->pos() ); // plot point } } // // Create and display a ConnectWidget. // int main( int argc, char **argv ) { QApplication a( argc, argv ); ConnectWidget connect; #ifndef QT_NO_WIDGET_TOPEXTRA // for Qt/Embedded minimal build connect.setCaption( "Qt Example - Draw lines"); #endif a.setMainWidget( &connect ); connect.show(); return a.exec(); }
See also Examples.
Copyright © 2003 Trolltech | Trademarks | Qt version 3.1.2
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