source: trunk/doc/html/drawlines-example.html

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2<!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/examples/drawlines/drawlines.doc:5 -->
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6<title>Connect the Points</title>
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31</td>
32<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>Connect the Points</h1>
33
34
35<p>
36This example shows very simple mouse-based user interaction and
37painting without any world transform matrix or other advanced
38features. Run the program, click the button, move the mouse,
39release the button, and watch the lines get drawn.
40<p> <hr>
41<p> Implementation:
42<p> <pre>/****************************************************************************
43** $Id: drawlines-example.html 2051 2007-02-21 10:04:20Z chehrlic $
44**
45** Copyright (C) 1992-2007 Trolltech ASA. All rights reserved.
46**
47** This file is part of an example program for Qt. This example
48** program may be used, distributed and modified without limitation.
49**
50*****************************************************************************/
51
52#include &lt;<a href="qwidget-h.html">qwidget.h</a>&gt;
53#include &lt;<a href="qpainter-h.html">qpainter.h</a>&gt;
54#include &lt;<a href="qapplication-h.html">qapplication.h</a>&gt;
55#include &lt;stdlib.h&gt;
56
57
58const int MAXPOINTS = 2000; // maximum number of points
59const int MAXCOLORS = 40;
60
61
62//
63// ConnectWidget - draws connected lines
64//
65
66class ConnectWidget : public <a href="qwidget.html">QWidget</a>
67{
68public:
69 ConnectWidget( <a href="qwidget.html">QWidget</a> *parent=0, const char *name=0 );
70 ~ConnectWidget();
71protected:
72 void paintEvent( <a href="qpaintevent.html">QPaintEvent</a> * );
73 void mousePressEvent( <a href="qmouseevent.html">QMouseEvent</a> *);
74 void mouseReleaseEvent( <a href="qmouseevent.html">QMouseEvent</a> *);
75 void mouseMoveEvent( <a href="qmouseevent.html">QMouseEvent</a> *);
76private:
77 <a href="qpoint.html">QPoint</a> *points; // point array
78 <a href="qcolor.html">QColor</a> *colors; // color array
79 int count; // count = number of points
80 bool down; // TRUE if mouse down
81};
82
83
84//
85// Constructs a ConnectWidget.
86//
87
88<a name="f475"></a>ConnectWidget::ConnectWidget( <a href="qwidget.html">QWidget</a> *parent, const char *name )
89 : <a href="qwidget.html">QWidget</a>( parent, name, WStaticContents )
90{
91 <a href="qwidget.html#setBackgroundColor">setBackgroundColor</a>( white ); // white background
92 count = 0;
93 down = FALSE;
94 points = new <a href="qpoint.html">QPoint</a>[MAXPOINTS];
95 colors = new <a href="qcolor.html">QColor</a>[MAXCOLORS];
96 for ( int i=0; i&lt;MAXCOLORS; i++ ) // init color array
97 colors[i] = QColor( rand()&amp;255, rand()&amp;255, rand()&amp;255 );
98}
99
100ConnectWidget::~ConnectWidget()
101{
102 delete[] points; // cleanup
103 delete[] colors;
104}
105
106
107//
108// Handles paint events for the connect widget.
109//
110
111<a name="x1661"></a>void ConnectWidget::<a href="qwidget.html#paintEvent">paintEvent</a>( <a href="qpaintevent.html">QPaintEvent</a> * )
112{
113 <a href="qpainter.html">QPainter</a> paint( this );
114 for ( int i=0; i&lt;count-1; i++ ) { // connect all points
115 for ( int j=i+1; j&lt;count; j++ ) {
116 paint.<a href="qpainter.html#setPen">setPen</a>( colors[rand()%MAXCOLORS] ); // set random pen color
117<a name="x1655"></a> paint.<a href="qpainter.html#drawLine">drawLine</a>( points[i], points[j] ); // draw line
118 }
119 }
120}
121
122
123//
124// Handles mouse press events for the connect widget.
125//
126
127<a name="x1659"></a>void ConnectWidget::<a href="qwidget.html#mousePressEvent">mousePressEvent</a>( <a href="qmouseevent.html">QMouseEvent</a> * )
128{
129 down = TRUE;
130 count = 0; // start recording points
131 <a href="qwidget.html#erase">erase</a>(); // erase widget contents
132}
133
134
135//
136// Handles mouse release events for the connect widget.
137//
138
139<a name="x1660"></a>void ConnectWidget::<a href="qwidget.html#mouseReleaseEvent">mouseReleaseEvent</a>( <a href="qmouseevent.html">QMouseEvent</a> * )
140{
141 down = FALSE; // done recording points
142 <a href="qwidget.html#update">update</a>(); // draw the lines
143}
144
145
146//
147// Handles mouse move events for the connect widget.
148//
149
150<a name="x1658"></a>void ConnectWidget::<a href="qwidget.html#mouseMoveEvent">mouseMoveEvent</a>( <a href="qmouseevent.html">QMouseEvent</a> *e )
151{
152 if ( down &amp;&amp; count &lt; MAXPOINTS ) {
153 <a href="qpainter.html">QPainter</a> paint( this );
154<a name="x1654"></a> points[count++] = e-&gt;<a href="qmouseevent.html#pos">pos</a>(); // add point
155<a name="x1656"></a> paint.<a href="qpainter.html#drawPoint">drawPoint</a>( e-&gt;<a href="qmouseevent.html#pos">pos</a>() ); // plot point
156 }
157}
158
159
160//
161// Create and display a ConnectWidget.
162//
163
164int main( int argc, char **argv )
165{
166 <a href="qapplication.html">QApplication</a> a( argc, argv );
167 ConnectWidget connect;
168#ifndef QT_NO_WIDGET_TOPEXTRA // for Qt/Embedded minimal build
169 connect.<a href="qwidget.html#setCaption">setCaption</a>( "Qt Example - Draw lines");
170#endif
171 a.<a href="qapplication.html#setMainWidget">setMainWidget</a>( &amp;connect );
172 connect.<a href="qwidget.html#show">show</a>();
173 return a.<a href="qapplication.html#exec">exec</a>();
174}
175</pre>
176
177<p>See also <a href="examples.html">Examples</a>.
178
179<!-- eof -->
180<p><address><hr><div align=center>
181<table width=100% cellspacing=0 border=0><tr>
182<td>Copyright &copy; 2007
183<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
184<td align=right><div align=right>Qt 3.3.8</div>
185</table></div></address></body>
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