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RedHat 9 (Linux i386) - man page for qcanvasview (redhat section 3qt)

QCanvasView(3qt)								 QCanvasView(3qt)

NAME
       QCanvasView - On-screen view of a QCanvas

SYNOPSIS
       #include <qcanvas.h>

       Inherits QScrollView.

   Public Members
       QCanvasView ( QWidget * parent = 0, const char * name = 0, WFlags f = 0 )
       QCanvasView ( QCanvas * canvas, QWidget * parent = 0, const char * name = 0, WFlags f = 0
	   )
       ~QCanvasView ()
       QCanvas * canvas () const
       void setCanvas ( QCanvas * canvas )
       const QWMatrix & worldMatrix () const
       const QWMatrix & inverseWorldMatrix () const
       bool setWorldMatrix ( const QWMatrix & wm )

   Protected Members
       virtual void drawContents ( QPainter * p, int cx, int cy, int cw, int ch )
       virtual QSize sizeHint () const

DESCRIPTION
       The QCanvasView class provides an on-screen view of a QCanvas.

       A QCanvasView is widget which provides a view of a QCanvas.

       If you want users to be able to interact with a canvas view, subclass QCanvasView. You
       might then reimplement QScrollView::contentsMousePressEvent() for example:

	   void MyCanvasView::contentsMousePressEvent( QMouseEvent* e )
	   {
	       QCanvasItemList l = canvas()->collisions(e->pos());
	       for (QCanvasItemList::Iterator it=l.begin(); it!=l.end(); ++it) {
		   if ( (*it)->rtti() == QCanvasRectangle::RTTI )
		       qDebug("A QCanvasRectangle lies somewhere at this point");
	       }
	   }

       Set the canvas that the view shows with setCanvas() and retrieve the canvas which the view
       is showing with canvas().

       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:

	   QWMatrix wm;
	   wm.scale( 2, 2 );   // Zooms in by 2 times
	   wm.rotate( 90 );    // Rotates 90 degrees counter clockwise
			       // around the origin.
	   wm.translate( 0, -canvas->height() );
			       // moves the canvas down so what was visible
			       // before is still visible.
	   myCanvasView->setWorldMatrix( wm );

       Use setWorldMatrix() to set the canvas view's world matrix: you must ensure that the world
       matrix is invertible. The current world matrix is retrievable with worldMatrix(), and its
       inversion is retrievable with inverseWorldMatrix().

       Example:

       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.

	   QRect rc = QRect( myCanvasView->contentsX(), myCanvasView->contentsY(),
			     myCanvasView->visibleWidth(), myCanvasView->visibleHeight() );
	   QRect canvasRect = myCanvasView->inverseWorldMatrix().mapRect(rc);

       See also QWMatrix, QPainter::setWorldMatrix(), Graphics Classes, and Image Processing
       Classes.

MEMBER FUNCTION DOCUMENTATION
QCanvasView::QCanvasView ( QWidget * parent = 0, const char * name = 0, WFlags f = 0 )
       Constructs a QCanvasView with parent parent, and name name, using the widget flags f. The
       canvas view is not associated with a canvas, so you will need to call setCanvas() to
       display a canvas.

QCanvasView::QCanvasView ( QCanvas * canvas, QWidget * parent = 0, const char * name = 0, WFlags
       f = 0 )
       This is an overloaded member function, provided for convenience. It behaves essentially
       like the above function.

       Constructs a QCanvasView which views canvas canvas, with parent parent, and name name,
       using the widget flags f.

QCanvasView::~QCanvasView ()
       Destroys the canvas view. The associated canvas is not deleted.

QCanvas * QCanvasView::canvas () const
       Returns a pointer to the canvas which the QCanvasView is currently showing.

void QCanvasView::drawContents ( QPainter * p, int cx, int cy, int cw, int ch ) [virtual
       protected]
       Repaints part of the QCanvas that the canvas view is showing starting at cx by cy, with a
       width of cw and a height of ch using the painter p.

       Reimplemented from QScrollView.

const QWMatrix &; QCanvasView::inverseWorldMatrix () const
       Returns a reference to the inverse of the canvas view's current transformation matrix.

       See also setWorldMatrix() and worldMatrix().

void QCanvasView::setCanvas ( QCanvas * canvas )
       Sets the canvas that the QCanvasView is showing to the canvas canvas.

bool QCanvasView::setWorldMatrix ( const QWMatrix & wm )
       Sets the transformation matrix of the QCanvasView to wm. 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).

       When you use this, you should note that the performance of the QCanvasView will decrease
       considerably.

       Returns FALSE if wm is not invertable; otherwise returns TRUE.

       See also worldMatrix(), inverseWorldMatrix(), and QWMatrix::isInvertible().

       Example: canvas/canvas.cpp.

QSize QCanvasView::sizeHint () const [virtual protected]
       Suggests a size sufficient to view the entire canvas.

const QWMatrix &; QCanvasView::worldMatrix () const
       Returns a reference to the canvas view's current transformation matrix.

       See also setWorldMatrix() and inverseWorldMatrix().

       Example: canvas/canvas.cpp.

SEE ALSO
       http://doc.trolltech.com/qcanvasview.html http://www.trolltech.com/faq/tech.html

COPYRIGHT
       Copyright 1992-2001 Trolltech AS, http://www.trolltech.com.  See the license file included
       in the distribution for a complete license statement.

AUTHOR
       Generated automatically from the source code.

BUGS
       If you find a bug in Qt, please report it as described in
       http://doc.trolltech.com/bughowto.html.	Good bug reports help us to help you. Thank you.

       The definitive Qt documentation is provided in HTML format; it is located at
       $QTDIR/doc/html and can be read using Qt Assistant or with a web browser. This man page is
       provided as a convenience for those users who prefer man pages, although this format is
       not officially supported by Trolltech.

       If you find errors in this manual page, please report them to qt-bugs@trolltech.com.
       Please include the name of the manual page (qcanvasview.3qt) and the Qt version (3.1.1).

Trolltech AS				 9 December 2002			 QCanvasView(3qt)


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