Initial import from the monolithic Qt.

This is the beginning of revision history for this module. If you
want to look at revision history older than this, please refer to the
Qt Git wiki for how to use Git history grafting. At the time of
writing, this wiki is located here:

http://qt.gitorious.org/qt/pages/GitIntroductionWithQt

If you have already performed the grafting and you don't see any
history beyond this commit, try running "git log" with the "--follow"
argument.

Branched from the monolithic repo, Qt master branch, at commit
896db169ea224deb96c59ce8af800d019de63f12

1 files changed, 210 insertions, 0 deletions

diff --git a/doc/src/examples/2dpainting.qdoc b/doc/src/examples/2dpainting.qdoc
new file mode 100644
index 0000000000..e90788e38c
--- /dev/null
+++ b/doc/src/examples/2dpainting.qdoc
@@ -0,0 +1,210 @@
+/****************************************************************************
+**
+** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the documentation of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:FDL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** GNU Free Documentation License
+** Alternatively, this file may be used under the terms of the GNU Free
+** Documentation License version 1.3 as published by the Free Software
+** Foundation and appearing in the file included in the packaging of this
+** file.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+/*!
+    \example opengl/2dpainting
+    \title 2D Painting Example
+
+    The 2D Painting example shows how QPainter and QGLWidget can be used
+    together to display accelerated 2D graphics on supported hardware.
+
+    \image 2dpainting-example.png
+
+    The QPainter class is used to draw 2D graphics primitives onto
+    paint devices provided by QPaintDevice subclasses, such as QWidget
+    and QImage.
+
+    Since QGLWidget is a subclass of QWidget, it is possible
+    to reimplement its \l{QWidget::paintEvent()}{paintEvent()} and use
+    QPainter to draw on the device, just as you would with a QWidget.
+    The only difference is that the painting operations will be accelerated
+    in hardware if it is supported by your system's OpenGL drivers.
+
+    In this example, we perform the same painting operations on a
+    QWidget and a QGLWidget. The QWidget is shown with anti-aliasing
+    enabled, and the QGLWidget will also use anti-aliasing if the
+    required extensions are supported by your system's OpenGL driver.
+
+    \section1 Overview
+
+    To be able to compare the results of painting onto a QGLWidget subclass
+    with native drawing in a QWidget subclass, we want to show both kinds
+    of widget side by side. To do this, we derive subclasses of QWidget and
+    QGLWidget, using a separate \c Helper class to perform the same painting
+    operations for each, and lay them out in a top-level widget, itself
+    provided a the \c Window class.
+
+    \section1 Helper Class Definition
+
+    In this example, the painting operations are performed by a helper class.
+    We do this because we want the same painting operations to be performed
+    for both our QWidget subclass and the QGLWidget subclass.
+
+    The \c Helper class is minimal:
+
+    \snippet examples/opengl/2dpainting/helper.h 0
+
+    Apart from the constructor, it only provides a \c paint() function to paint
+    using a painter supplied by one of our widget subclasses.
+
+    \section1 Helper Class Implementation
+
+    The constructor of the class sets up the resources it needs to paint
+    content onto a widget:
+
+    \snippet examples/opengl/2dpainting/helper.cpp 0
+
+    The actual painting is performed in the \c paint() function. This takes
+    a QPainter that has already been set up to paint onto a paint device
+    (either a QWidget or a QGLWidget), a QPaintEvent that provides information
+    about the region to be painted, and a measure of the elapsed time (in
+    milliseconds) since the paint device was last updated.
+
+    \snippet examples/opengl/2dpainting/helper.cpp 1
+
+    We begin painting by filling in the region contained in the paint event
+    before translating the origin of the coordinate system so that the rest
+    of the painting operations will be displaced towards the center of the
+    paint device.
+
+    We draw a spiral pattern of circles, using the elapsed time specified to
+    animate them so that they appear to move outward and around the coordinate
+    system's origin:
+
+    \snippet examples/opengl/2dpainting/helper.cpp 2
+
+    Since the coordinate system is rotated many times during
+    this process, we \l{QPainter::save()}{save()} the QPainter's state
+    beforehand and \l{QPainter::restore()}{restore()} it afterwards.
+
+    \snippet examples/opengl/2dpainting/helper.cpp 3
+
+    We draw some text at the origin to complete the effect.
+
+    \section1 Widget Class Definition
+
+    The \c Widget class provides a basic custom widget that we use to
+    display the simple animation painted by the \c Helper class.
+
+    \snippet examples/opengl/2dpainting/widget.h 0
+
+    Apart from the constructor, it only contains a
+    \l{QWidget::paintEvent()}{paintEvent()} function, that lets us draw
+    customized content, and a slot that is used to animate its contents.
+    One member variable keeps track of the \c Helper that the widget uses
+    to paint its contents, and the other records the elapsed time since
+    it was last updated.
+
+    \section1 Widget Class Implementation
+
+    The constructor only initializes the member variables, storing the
+    \c Helper object supplied and calling the base class's constructor,
+    and enforces a fixed size for the widget:
+
+    \snippet examples/opengl/2dpainting/widget.cpp 0
+
+    The \c animate() slot is called whenever a timer, which we define later, times
+    out:
+
+    \snippet examples/opengl/2dpainting/widget.cpp 1
+
+    Here, we determine the interval that has elapsed since the timer last
+    timed out, and we add it to any existing value before repainting the
+    widget. Since the animation used in the \c Helper class loops every second,
+    we can use the modulo operator to ensure that the \c elapsed variable is
+    always less than 1000.
+
+    Since the \c Helper class does all of the actual painting, we only have
+    to implement a paint event that sets up a QPainter for the widget and calls
+    the helper's \c paint() function:
+
+    \snippet examples/opengl/2dpainting/widget.cpp 2
+
+    \section1 GLWidget Class Definition
+
+    The \c GLWidget class definition is basically the same as the \c Widget
+    class except that it is derived from QGLWidget.
+
+    \snippet examples/opengl/2dpainting/glwidget.h 0
+
+    Again, the member variables record the \c Helper used to paint the
+    widget and the elapsed time since the previous update.
+
+    \section1 GLWidget Class Implementation
+
+    The constructor differs a little from the \c Widget class's constructor:
+
+    \snippet examples/opengl/2dpainting/glwidget.cpp 0
+
+    As well as initializing the \c elapsed member variable and storing the
+    \c Helper object used to paint the widget, the base class's constructor
+    is called with the format that specifies the \l QGL::SampleBuffers flag.
+    This enables anti-aliasing if it is supported by your system's OpenGL
+    driver.
+
+    The \c animate() slot is exactly the same as that provided by the \c Widget
+    class:
+
+    \snippet examples/opengl/2dpainting/glwidget.cpp 1
+
+    The \c paintEvent() is almost the same as that found in the \c Widget class:
+
+    \snippet examples/opengl/2dpainting/glwidget.cpp 2
+
+    Since anti-aliasing will be enabled if available, we only need to set up
+    a QPainter on the widget and call the helper's \c paint() function to display
+    the widget's contents.
+
+    \section1 Window Class Definition
+
+    The \c Window class has a basic, minimal definition:
+
+    \snippet examples/opengl/2dpainting/window.h 0
+
+    It contains a single \c Helper object that will be shared between all
+    widgets.
+
+    \section1 Window Class Implementation
+
+    The constructor does all the work, creating a widget of each type and
+    inserting them with labels into a layout:
+
+    \snippet examples/opengl/2dpainting/window.cpp 0
+
+    A timer with a 50 millisecond time out is constructed for animation purposes,
+    and connected to the \c animate() slots of the \c Widget and \c GLWidget objects.
+    Once started, the widgets should be updated at around 20 frames per second.
+
+    \section1 Running the Example
+
+    The example shows the same painting operations performed at the same time
+    in a \c Widget and a \c GLWidget. The quality and speed of rendering in the
+    \c GLWidget depends on the level of support for multisampling and hardware
+    acceleration that your system's OpenGL driver provides. If support for either
+    of these is lacking, the driver may fall back on a software renderer that
+    may trade quality for speed.
+*/