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191 lines
10 KiB
191 lines
10 KiB
14 years ago
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<!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/src/canvas/qcanvas.cpp:3456 -->
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>QCanvasView Class</title>
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<tr bgcolor="#E5E5E5">
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<td valign=center>
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<a href="index.html">
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<font color="#004faf">Home</font></a>
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<font color="#004faf">All Classes</font></a>
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<font color="#004faf">Main Classes</font></a>
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<font color="#004faf">Functions</font></a>
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</td>
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<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>QCanvasView Class Reference<br><small>[<a href="canvas.html">canvas module</a>]</small></h1>
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<p>The QCanvasView class provides an on-screen view of a QCanvas.
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<a href="#details">More...</a>
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<p><tt>#include <<a href="qcanvas-h.html">qcanvas.h</a>></tt>
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<p>Inherits <a href="qscrollview.html">QScrollView</a>.
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<p><a href="qcanvasview-members.html">List of all member functions.</a>
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<h2>Public Members</h2>
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<ul>
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<li class=fn><a href="#QCanvasView"><b>QCanvasView</b></a> ( QWidget * parent = 0, const char * name = 0, WFlags f = 0 )</li>
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<li class=fn><a href="#QCanvasView-2"><b>QCanvasView</b></a> ( QCanvas * canvas, QWidget * parent = 0, const char * name = 0, WFlags f = 0 )</li>
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<li class=fn><a href="#~QCanvasView"><b>~QCanvasView</b></a> ()</li>
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<li class=fn>QCanvas * <a href="#canvas"><b>canvas</b></a> () const</li>
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<li class=fn>void <a href="#setCanvas"><b>setCanvas</b></a> ( QCanvas * canvas )</li>
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<li class=fn>const QWMatrix & <a href="#worldMatrix"><b>worldMatrix</b></a> () const</li>
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<li class=fn>const QWMatrix & <a href="#inverseWorldMatrix"><b>inverseWorldMatrix</b></a> () const</li>
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<li class=fn>bool <a href="#setWorldMatrix"><b>setWorldMatrix</b></a> ( const QWMatrix & wm )</li>
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</ul>
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<h2>Protected Members</h2>
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<ul>
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<li class=fn>virtual void <a href="#drawContents"><b>drawContents</b></a> ( QPainter * p, int cx, int cy, int cw, int ch )</li>
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<li class=fn>virtual QSize <a href="#sizeHint"><b>sizeHint</b></a> () const</li>
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</ul>
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<hr><a name="details"></a><h2>Detailed Description</h2>
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The QCanvasView class provides an on-screen view of a <a href="qcanvas.html">QCanvas</a>.
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<p>
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<p> A QCanvasView is widget which provides a view of a QCanvas.
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<p> If you want users to be able to interact with a canvas view,
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subclass QCanvasView. You might then reimplement
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<a href="qscrollview.html#contentsMousePressEvent">QScrollView::contentsMousePressEvent</a>(). For example, assuming no
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<a href="qwmatrix.html#TransformationMode">transformation matrix</a> is set:
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<p> <pre>
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void MyCanvasView::contentsMousePressEvent( <a href="qmouseevent.html">QMouseEvent</a>* e )
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{
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<a href="qcanvasitemlist.html">QCanvasItemList</a> l = <a href="#canvas">canvas</a>()->collisions(e-><a href="qmouseevent.html#pos">pos</a>());
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for (QCanvasItemList::Iterator it=l.<a href="qvaluelist.html#begin">begin</a>(); it!=l.<a href="qvaluelist.html#end">end</a>(); ++it) {
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if ( (*it)->rtti() == QCanvasRectangle::RTTI )
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<a href="qapplication.html#qDebug">qDebug</a>("A QCanvasRectangle lies somewhere at this point");
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}
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}
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</pre>
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<p> The canvas view shows canvas <a href="#canvas">canvas</a>(); this can be changed using
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<a href="#setCanvas">setCanvas</a>().
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<p> A transformation matrix can be used to transform the view of the
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canvas in various ways, for example, zooming in or out or rotating.
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For example:
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<p> <pre>
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<a href="qwmatrix.html">QWMatrix</a> wm;
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wm.<a href="qwmatrix.html#scale">scale</a>( 2, 2 ); // Zooms in by 2 times
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wm.<a href="qwmatrix.html#rotate">rotate</a>( 90 ); // Rotates 90 degrees counter clockwise
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// around the origin.
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wm.<a href="qwmatrix.html#translate">translate</a>( 0, -canvas->height() );
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// moves the canvas down so what was visible
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// before is still visible.
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myCanvasView->setWorldMatrix( wm );
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</pre>
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<p> Use <a href="#setWorldMatrix">setWorldMatrix</a>() to set the canvas view's world matrix: you must
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ensure that the world matrix is invertible. The current world matrix
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is retrievable with <a href="#worldMatrix">worldMatrix</a>(), and its inversion is retrievable
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with <a href="#inverseWorldMatrix">inverseWorldMatrix</a>().
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<p> Example:
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<p> The following code finds the part of the canvas that is visible in
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this view, i.e. the bounding rectangle of the view in canvas coordinates.
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<p> <pre>
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<a href="qrect.html">QRect</a> rc = QRect( myCanvasView->contentsX(), myCanvasView->contentsY(),
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myCanvasView->visibleWidth(), myCanvasView->visibleHeight() );
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<a href="qrect.html">QRect</a> canvasRect = myCanvasView->inverseWorldMatrix().mapRect(rc);
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</pre>
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<p> <p>See also <a href="qwmatrix.html">QWMatrix</a>, <a href="qpainter.html#setWorldMatrix">QPainter::setWorldMatrix</a>(), <a href="graphics.html">Graphics Classes</a>, and <a href="images.html">Image Processing Classes</a>.
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<p>
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<hr><h2>Member Function Documentation</h2>
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<h3 class=fn><a name="QCanvasView"></a>QCanvasView::QCanvasView ( <a href="qwidget.html">QWidget</a> * parent = 0, const char * name = 0, WFlags f = 0 )
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</h3>
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Constructs a QCanvasView with parent <em>parent</em>, and name <em>name</em>,
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using the widget flags <em>f</em>. The canvas view is not associated
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with a canvas, so you must to call <a href="#setCanvas">setCanvas</a>() to view a
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canvas.
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<h3 class=fn><a name="QCanvasView-2"></a>QCanvasView::QCanvasView ( <a href="qcanvas.html">QCanvas</a> * canvas, <a href="qwidget.html">QWidget</a> * parent = 0, const char * name = 0, WFlags f = 0 )
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</h3>
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This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
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<p> Constructs a QCanvasView which views canvas <em>canvas</em>, with parent
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<em>parent</em>, and name <em>name</em>, using the widget flags <em>f</em>.
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<h3 class=fn><a name="~QCanvasView"></a>QCanvasView::~QCanvasView ()
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</h3>
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Destroys the canvas view. The associated canvas is <em>not</em> deleted.
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<h3 class=fn><a href="qcanvas.html">QCanvas</a> * <a name="canvas"></a>QCanvasView::canvas () const
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</h3>
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<p> Returns a pointer to the canvas which the QCanvasView is currently
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showing.
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<h3 class=fn>void <a name="drawContents"></a>QCanvasView::drawContents ( <a href="qpainter.html">QPainter</a> * p, int cx, int cy, int cw, int ch )<tt> [virtual protected]</tt>
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</h3>
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Repaints part of the <a href="qcanvas.html">QCanvas</a> that the canvas view is showing
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starting at <em>cx</em> by <em>cy</em>, with a width of <em>cw</em> and a height of <em>ch</em> using the painter <em>p</em>.
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<p> <b>Warning:</b> When double buffering is enabled, <a href="#drawContents">drawContents</a>() will
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not respect the current settings of the painter when setting up
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the painter for the double buffer (e.g., <a href="qscrollview.html#viewport">viewport</a>() and
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window()). Also, be aware that <a href="qcanvas.html#update">QCanvas::update</a>() bypasses
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drawContents(), which means any reimplementation of
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drawContents() is not called.
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<p> <p>See also <a href="qcanvas.html#setDoubleBuffering">QCanvas::setDoubleBuffering</a>().
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<p>Reimplemented from <a href="qscrollview.html#drawContents">QScrollView</a>.
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<h3 class=fn>const <a href="qwmatrix.html">QWMatrix</a> & <a name="inverseWorldMatrix"></a>QCanvasView::inverseWorldMatrix () const
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</h3>
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Returns a reference to the inverse of the canvas view's current
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<a href="qwmatrix.html#TransformationMode">transformation matrix</a>.
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<p> <p>See also <a href="#setWorldMatrix">setWorldMatrix</a>() and <a href="#worldMatrix">worldMatrix</a>().
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<h3 class=fn>void <a name="setCanvas"></a>QCanvasView::setCanvas ( <a href="qcanvas.html">QCanvas</a> * canvas )
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</h3>
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Sets the canvas that the QCanvasView is showing to the canvas <em>canvas</em>.
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<h3 class=fn>bool <a name="setWorldMatrix"></a>QCanvasView::setWorldMatrix ( const <a href="qwmatrix.html">QWMatrix</a> & wm )
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</h3>
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Sets the <a href="qwmatrix.html#TransformationMode">transformation matrix</a> of the QCanvasView to <em>wm</em>. The
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matrix must be invertible (i.e. if you create a world matrix that
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zooms out by 2 times, then the inverse of this matrix is one that
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will zoom in by 2 times).
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<p> When you use this, you should note that the performance of the
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QCanvasView will decrease considerably.
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<p> Returns FALSE if <em>wm</em> is not invertable; otherwise returns TRUE.
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<p> <p>See also <a href="#worldMatrix">worldMatrix</a>(), <a href="#inverseWorldMatrix">inverseWorldMatrix</a>(), and <a href="qwmatrix.html#isInvertible">QWMatrix::isInvertible</a>().
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<p>Example: <a href="canvas-example.html#x2930">canvas/canvas.cpp</a>.
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<h3 class=fn><a href="qsize.html">QSize</a> <a name="sizeHint"></a>QCanvasView::sizeHint () const<tt> [virtual protected]</tt>
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</h3>
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Suggests a size sufficient to view the entire canvas.
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<h3 class=fn>const <a href="qwmatrix.html">QWMatrix</a> & <a name="worldMatrix"></a>QCanvasView::worldMatrix () const
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</h3>
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Returns a reference to the canvas view's current <a href="qwmatrix.html#TransformationMode">transformation matrix</a>.
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<p> <p>See also <a href="#setWorldMatrix">setWorldMatrix</a>() and <a href="#inverseWorldMatrix">inverseWorldMatrix</a>().
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<p>Example: <a href="canvas-example.html#x2931">canvas/canvas.cpp</a>.
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<!-- eof -->
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<hr><p>
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This file is part of the <a href="index.html">Qt toolkit</a>.
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Copyright © 1995-2007
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<a href="http://www.trolltech.com/">Trolltech</a>. All Rights Reserved.<p><address><hr><div align=center>
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<table width=100% cellspacing=0 border=0><tr>
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<td>Copyright © 2007
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<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
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<td align=right><div align=right>Qt 3.3.8</div>
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</table></div></address></body>
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</html>
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