tqt3/doc/canvas.doc

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** Documentation for the canvas module
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/*!
\page canvas.html

\title Canvas Module

\if defined(commercial)
This module is part of the \link commercialeditions.html TQt 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="ntqcanvas.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.

*/