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authorQt by Nokia <qt-info@nokia.com>2011-04-27 12:05:43 +0200
committeraxis <qt-info@nokia.com>2011-04-27 12:05:43 +0200
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downloadqtsvg-983a4b61f1da719dac647a7190533d1edf2b2159.tar.gz
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+/****************************************************************************
+**
+** 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 painting/svggenerator
+ \title SVG Generator Example
+
+ The SVG Generator example shows how to add SVG file export to applications.
+
+ \image svggenerator-example.png
+
+ Scalable Vector Graphics (SVG) is an XML-based language for describing
+ two-dimensional vector graphics. Qt provides classes for rendering and
+ generating SVG drawings. This example allows the user to create a simple
+ picture and save it to an SVG file.
+
+ The example consists of two classes: \c Window and \c DisplayWidget.
+
+ The \c Window class contains the application logic and constructs the user
+ interface from a Qt Designer UI file as described in the
+ \l{Using a Designer UI File in Your Application#The Multiple Inheritance Approach}{Qt Designer manual}.
+ It also contains the code to write an SVG file.
+
+ The \c DisplayWidget class performs all the work of painting a picture on
+ screen. Since we want the SVG to resemble this picture as closely as
+ possible, we make this code available to the \c Window class so that it can
+ be used to generate SVG files.
+
+ \section1 The DisplayWidget Class
+
+ The \c DisplayWidget class displays a drawing consisting of a selection of
+ elements chosen by the user. These are defined using \c Shape and
+ \c Background enums that are included within the class definition:
+
+ \snippet examples/painting/svggenerator/displaywidget.h DisplayWidget class definition
+
+ Much of this class is used to configure the appearance of the drawing. The
+ \c paintEvent() and \c paint() functions are most relevant to the purpose
+ of this example, so we will describe these here and leave the reader to
+ look at the source code for the example to see how shapes and colors are
+ handled.
+
+ We reimplement the QWidget::paintEvent() function to display the drawing
+ on screen:
+
+ \snippet examples/painting/svggenerator/displaywidget.cpp paint event
+
+ Here, we only construct a QPainter object, begin painting on the device
+ and set a render hint for improved output quality before calling the
+ \c paint() function to perform the painting itself. When this returns,
+ we close the painter and return.
+
+ The \c paint() function is designed to be used for different painting
+ tasks. In this example, we use it to draw on a \c DisplayWidget instance
+ and on a QSvgGenerator object. We show how the painting is performed to
+ demonstrate that there is nothing device-specific about the process:
+
+ \snippet examples/painting/svggenerator/displaywidget.cpp paint function
+
+ \section1 The Window Class
+
+ The \c Window class represents the example's window, containing the user
+ interface, which has been created using Qt Designer:
+
+ \snippet examples/painting/svggenerator/window.h Window class definition
+
+ As with the \c DisplayWidget class, we concentrate on the parts of the code
+ which are concerned with painting and SVG generation. In the \c Window
+ class, the \c saveSvg() function is called whenever the \gui{Save As...}
+ button is clicked; this connection was defined in the \c{window.ui} file
+ using Qt Designer.
+
+ The start of the \c saveSvg() function performs the task of showing a file
+ dialog so that the user can specify a SVG file to save the drawing to.
+
+ \snippet examples/painting/svggenerator/window.cpp save SVG
+
+ In the rest of the function, we set up the generator and configure it to
+ generate output with the appropriate dimensions and write to the
+ user-specified file. We paint on the QSvgGenerator object in the same way
+ that we paint on a widget, calling the \c DisplayWidget::paint() function
+ so that we use exactly the same code that we used to display the drawing.
+
+ The generation process itself begins with the call to the painter's
+ \l{QPainter::}{begin()} function and ends with call to its
+ \l{QPainter::}{end()} function. The QSvgGenerator paint device relies on
+ the explicit use of these functions to ensure that output is written to
+ the file.
+
+ \section1 Further Reading
+
+ The \l{SVG Viewer Example} shows how to display SVG drawings in an
+ application, and can be used to show the contents of SVG files created
+ by this example.
+
+ See the QtSvg module documentation for more information about SVG and Qt's
+ SVG classes.
+*/