File: canvas.doc

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/****************************************************************************
**
** Documentation for the canvas module
**
** Copyright (C) 2000-2008 Trolltech ASA.  All rights reserved.
**
** This file is part of the Qt GUI Toolkit.
**
** This file may be used under the terms of the GNU General
** Public License versions 2.0 or 3.0 as published by the Free
** Software Foundation and appearing in the files LICENSE.GPL2
** and LICENSE.GPL3 included in the packaging of this file.
** Alternatively you may (at your option) use any later version
** of the GNU General Public License if such license has been
** publicly approved by Trolltech ASA (or its successors, if any)
** and the KDE Free Qt Foundation.
**
** Please review the following information to ensure GNU General
** Public Licensing requirements will be met:
** http://trolltech.com/products/qt/licenses/licensing/opensource/.
** If you are unsure which license is appropriate for your use, please
** review the following information:
** http://trolltech.com/products/qt/licenses/licensing/licensingoverview
** or contact the sales department at sales@trolltech.com.
**
** This file may be used under the terms of the Q Public License as
** defined by Trolltech ASA and appearing in the file LICENSE.QPL
** included in the packaging of this file.  Licensees holding valid Qt
** Commercial licenses may use this file in accordance with the Qt
** Commercial License Agreement provided with the Software.
**
** This file is provided "AS IS" with NO WARRANTY OF ANY KIND,
** INCLUDING THE WARRANTIES OF DESIGN, MERCHANTABILITY AND FITNESS FOR
** A PARTICULAR PURPOSE. Trolltech reserves all rights not granted
** herein.
**
**********************************************************************/

/*!
\page canvas.html

\title Canvas Module

\if defined(commercial)
This module is part of the \link commercialeditions.html Qt Enterprise Edition
\endlink.
\endif

The canvas module provides a highly optimized 2D graphic area called
\l QCanvas. The canvas can contain an arbitrary number of \link
QCanvasItem QCanvasItems \endlink. Canvas items can have an arbitrary
shape, size and content, can be freely moved around in the canvas,
and can be checked for collisions. Canvas items can be set to move
across the canvas automatically and animated canvas items are
supported with QCanvasSprite. (If you require 3D graphics see Qt's
\link opengl.html OpenGL module \endlink.)

The canvas module uses a document/view model. The \l QCanvasView class
is used to show a particular view of a canvas. Multiple views can operate
on the same canvas at the same time. Every view can use an arbitrary
transformation matrix on the canvas which makes it easy to implement
features such as zooming.

<center><a href="qcanvas.html">
<img src="qcanvas.png" alt="Screenshot of a canvas"></a></center>

Qt provides a number of predefined \l QCanvas items as listed below.

\list
\i QCanvasItem -- An abstract base class for all canvas items.
\i QCanvasEllipse -- An ellipse or "pie segment".
\i QCanvasLine -- A line segment.
\i QCanvasPolygon -- A polygon.
\i QCanvasPolygonalItem -- A base class for items that have a
non-rectangular shape. Most canvas items derive from this class.
\i QCanvasRectangle -- A rectangle. The rectangle cannot be tilted or
rotated. Rotated rectangles can be drawn using QCanvasPolygon.
\i QCanvasSpline -- A multi-bezier spline.
\i QCanvasSprite -- An animated pixmap.
\i QCanvasText -- A text string.
\endlist

The two classes \l QCanvasPixmap and \l QCanvasPixmapArray are used
by \l QCanvasSprite to show animated and moving pixmaps on the
canvas.

More specialized items can be created by inheriting from one of the
canvas item classes. It is easiest to inherit from one of
QCanvasItem's derived classes (usually \l QCanvasPolygonalItem) rather
than inherit QCanvasItem directly.

See \c examples/canvas for an example that shows off some of QCanvas's
capabilities.

*/