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diff --git a/doc/src/examples/2dpainting.qdoc b/doc/src/examples/2dpainting.qdoc deleted file mode 100644 index d2d19b6e3b..0000000000 --- a/doc/src/examples/2dpainting.qdoc +++ /dev/null @@ -1,210 +0,0 @@ -/**************************************************************************** -** -** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies). -** Contact: http://www.qt-project.org/ -** -** This file is part of the documentation of the Qt Toolkit. -** -** $QT_BEGIN_LICENSE:FDL$ -** 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. -** -** Other Usage -** Alternatively, this file may be used in accordance with the terms -** and conditions contained in a signed written agreement between you -** and Nokia. -** -** -** -** -** -** $QT_END_LICENSE$ -** -****************************************************************************/ - -/*! - \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. -*/ |