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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>
<p>The QCanvasView class provides an on-screen view of a QCanvas.
<a href="#details">More...</a>
<p><tt>#include <<a href="qcanvas-h.html">qcanvas.h</a>></tt>
<p>Inherits <a href="qscrollview.html">QScrollView</a>.
<p><a href="qcanvasview-members.html">List of all member functions.</a>
<h2>Public Members</h2>
<ul>
<li class=fn><a href="#QCanvasView"><b>QCanvasView</b></a> ( QWidget * parent = 0, const char * name = 0, WFlags f = 0 )</li>
<li class=fn><a href="#QCanvasView-2"><b>QCanvasView</b></a> ( QCanvas * canvas, QWidget * parent = 0, const char * name = 0, WFlags f = 0 )</li>
<li class=fn><a href="#~QCanvasView"><b>~QCanvasView</b></a> ()</li>
<li class=fn>QCanvas * <a href="#canvas"><b>canvas</b></a> () const</li>
<li class=fn>void <a href="#setCanvas"><b>setCanvas</b></a> ( QCanvas * canvas )</li>
<li class=fn>const QWMatrix & <a href="#worldMatrix"><b>worldMatrix</b></a> () const</li>
<li class=fn>const QWMatrix & <a href="#inverseWorldMatrix"><b>inverseWorldMatrix</b></a> () const</li>
<li class=fn>bool <a href="#setWorldMatrix"><b>setWorldMatrix</b></a> ( const QWMatrix & wm )</li>
</ul>
<h2>Protected Members</h2>
<ul>
<li class=fn>virtual void <a href="#drawContents"><b>drawContents</b></a> ( QPainter * p, int cx, int cy, int cw, int ch )</li>
<li class=fn>virtual QSize <a href="#sizeHint"><b>sizeHint</b></a> () const</li>
</ul>
<hr><a name="details"></a><h2>Detailed Description</h2>
The QCanvasView class provides an on-screen view of a <a href="qcanvas.html">QCanvas</a>.
<p>
<p> A QCanvasView is widget which provides a view of a QCanvas.
<p> If you want users to be able to interact with a canvas view,
subclass QCanvasView. You might then reimplement
<a href="qscrollview.html#contentsMousePressEvent">QScrollView::contentsMousePressEvent</a>(). For example, assuming no
<a href="qwmatrix.html#TransformationMode">transformation matrix</a> is set:
<p> <pre>
void MyCanvasView::contentsMousePressEvent( <a href="qmouseevent.html">QMouseEvent</a>* e )
{
<a href="qcanvasitemlist.html">QCanvasItemList</a> l = <a href="#canvas">canvas</a>()->collisions(e-><a href="qmouseevent.html#pos">pos</a>());
for (QCanvasItemList::Iterator it=l.<a href="qvaluelist.html#begin">begin</a>(); it!=l.<a href="qvaluelist.html#end">end</a>(); ++it) {
if ( (*it)->rtti() == QCanvasRectangle::RTTI )
<a href="qapplication.html#qDebug">qDebug</a>("A QCanvasRectangle lies somewhere at this point");
}
}
</pre>
<p> The canvas view shows canvas <a href="#canvas">canvas</a>(); this can be changed using
<a href="#setCanvas">setCanvas</a>().
<p> A transformation matrix can be used to transform the view of the
canvas in various ways, for example, zooming in or out or rotating.
For example:
<p> <pre>
<a href="qwmatrix.html">QWMatrix</a> wm;
wm.<a href="qwmatrix.html#scale">scale</a>( 2, 2 ); // Zooms in by 2 times
wm.<a href="qwmatrix.html#rotate">rotate</a>( 90 ); // Rotates 90 degrees counter clockwise
// around the origin.
wm.<a href="qwmatrix.html#translate">translate</a>( 0, -canvas->height() );
// moves the canvas down so what was visible
// before is still visible.
myCanvasView->setWorldMatrix( wm );
</pre>
<p> Use <a href="#setWorldMatrix">setWorldMatrix</a>() to set the canvas view's world matrix: you must
ensure that the world matrix is invertible. The current world matrix
is retrievable with <a href="#worldMatrix">worldMatrix</a>(), and its inversion is retrievable
with <a href="#inverseWorldMatrix">inverseWorldMatrix</a>().
<p> Example:
<p> The following code finds the part of the canvas that is visible in
this view, i.e. the bounding rectangle of the view in canvas coordinates.
<p> <pre>
<a href="qrect.html">QRect</a> rc = QRect( myCanvasView->contentsX(), myCanvasView->contentsY(),
myCanvasView->visibleWidth(), myCanvasView->visibleHeight() );
<a href="qrect.html">QRect</a> canvasRect = myCanvasView->inverseWorldMatrix().mapRect(rc);
</pre>
<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>.
<p>
<hr><h2>Member Function Documentation</h2>
<h3 class=fn><a name="QCanvasView"></a>QCanvasView::QCanvasView ( <a href="qwidget.html">QWidget</a> * parent = 0, const char * name = 0, WFlags f = 0 )
</h3>
Constructs a QCanvasView with parent <em>parent</em>, and name <em>name</em>,
using the widget flags <em>f</em>. The canvas view is not associated
with a canvas, so you must to call <a href="#setCanvas">setCanvas</a>() to view a
canvas.
<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 )
</h3>
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
<p> Constructs a QCanvasView which views canvas <em>canvas</em>, with parent
<em>parent</em>, and name <em>name</em>, using the widget flags <em>f</em>.
<h3 class=fn><a name="~QCanvasView"></a>QCanvasView::~QCanvasView ()
</h3>
Destroys the canvas view. The associated canvas is <em>not</em> deleted.
<h3 class=fn><a href="qcanvas.html">QCanvas</a> * <a name="canvas"></a>QCanvasView::canvas () const
</h3>
<p> Returns a pointer to the canvas which the QCanvasView is currently
showing.
<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>
</h3>
Repaints part of the <a href="qcanvas.html">QCanvas</a> that the canvas view is showing
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>.
<p> <b>Warning:</b> When double buffering is enabled, <a href="#drawContents">drawContents</a>() will
not respect the current settings of the painter when setting up
the painter for the double buffer (e.g., <a href="qscrollview.html#viewport">viewport</a>() and
window()). Also, be aware that <a href="qcanvas.html#update">QCanvas::update</a>() bypasses
drawContents(), which means any reimplementation of
drawContents() is not called.
<p> <p>See also <a href="qcanvas.html#setDoubleBuffering">QCanvas::setDoubleBuffering</a>().
<p>Reimplemented from <a href="qscrollview.html#drawContents">QScrollView</a>.
<h3 class=fn>const <a href="qwmatrix.html">QWMatrix</a> & <a name="inverseWorldMatrix"></a>QCanvasView::inverseWorldMatrix () const
</h3>
Returns a reference to the inverse of the canvas view's current
<a href="qwmatrix.html#TransformationMode">transformation matrix</a>.
<p> <p>See also <a href="#setWorldMatrix">setWorldMatrix</a>() and <a href="#worldMatrix">worldMatrix</a>().
<h3 class=fn>void <a name="setCanvas"></a>QCanvasView::setCanvas ( <a href="qcanvas.html">QCanvas</a> * canvas )
</h3>
Sets the canvas that the QCanvasView is showing to the canvas <em>canvas</em>.
<h3 class=fn>bool <a name="setWorldMatrix"></a>QCanvasView::setWorldMatrix ( const <a href="qwmatrix.html">QWMatrix</a> & wm )
</h3>
Sets the <a href="qwmatrix.html#TransformationMode">transformation matrix</a> of the QCanvasView to <em>wm</em>. The
matrix must be invertible (i.e. if you create a world matrix that
zooms out by 2 times, then the inverse of this matrix is one that
will zoom in by 2 times).
<p> When you use this, you should note that the performance of the
QCanvasView will decrease considerably.
<p> Returns FALSE if <em>wm</em> is not invertable; otherwise returns TRUE.
<p> <p>See also <a href="#worldMatrix">worldMatrix</a>(), <a href="#inverseWorldMatrix">inverseWorldMatrix</a>(), and <a href="qwmatrix.html#isInvertible">QWMatrix::isInvertible</a>().
<p>Example: <a href="canvas-example.html#x2930">canvas/canvas.cpp</a>.
<h3 class=fn><a href="qsize.html">QSize</a> <a name="sizeHint"></a>QCanvasView::sizeHint () const<tt> [virtual protected]</tt>
</h3>
Suggests a size sufficient to view the entire canvas.
<h3 class=fn>const <a href="qwmatrix.html">QWMatrix</a> & <a name="worldMatrix"></a>QCanvasView::worldMatrix () const
</h3>
Returns a reference to the canvas view's current <a href="qwmatrix.html#TransformationMode">transformation matrix</a>.
<p> <p>See also <a href="#setWorldMatrix">setWorldMatrix</a>() and <a href="#inverseWorldMatrix">inverseWorldMatrix</a>().
<p>Example: <a href="canvas-example.html#x2931">canvas/canvas.cpp</a>.
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