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+** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
+** Contact:
+** This file is part of the documentation of the Qt Toolkit.
+** 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.
+ \group printing
+ \title Printer and Printing APIs
+ \brief Classes for producing printed output
+ \ingroup groups
+ \page printing.html
+ \title Printing with Qt
+ \ingroup qt-graphics
+ \previouspage Styling
+ \contentspage The Paint System
+ \brief A guide to producing printed output with Qt's paint system and widgets.
+ Qt provides extensive cross-platform support for printing. Using the printing
+ systems on each platform, Qt applications can print to attached printers and
+ across networks to remote printers. Qt's printing system also enables PostScript
+ and PDF files to be generated, providing the foundation for basic report
+ generation facilities.
+ \tableofcontents
+ \section1 Classes Supporting Printing
+ The following classes support the selecting and setting up of printers and
+ printing output.
+ \annotatedlist printing
+ \section1 Paint Devices and Printing
+ In Qt, printers are represented by QPrinter, a paint device that provides
+ functionality specific to printing, such as support for multiple pages and
+ double-sided output. As a result, printing involves using a QPainter to paint
+ onto a series of pages in the same way that you would paint onto a custom
+ widget or image.
+ \section2 Creating a QPrinter
+ Although QPrinter objects can be constructed and set up without requiring user
+ input, printing is often performed as a result of a request by the user;
+ for example, when the user selects the \gui{File|Print...} menu item in a GUI
+ application. In such cases, a newly-constructed QPrinter object is supplied to
+ a QPrintDialog, allowing the user to specify the printer to use, paper size, and
+ other printing properties.
+ \snippet richtext/orderform/mainwindow.cpp 18
+ It is also possible to set certain default properties by modifying the QPrinter
+ before it is supplied to the print dialog. For example, applications that
+ generate batches of reports for printing may set up the QPrinter to
+ \l{QPrinter::setOutputFileName()}{write to a local file} by default rather than
+ to a printer.
+ \section2 Painting onto a Page
+ Once a QPrinter object has been constructed and set up, a QPainter can be used
+ to perform painting operations on it. We can construct and set up a painter in
+ the following way:
+ \snippet printing-qprinter/object.cpp 0
+ Since the QPrinter starts with a blank page, we only need to call the
+ \l{QPrinter::}{newPage()} function after drawing each page, except for the
+ last page.
+ The document is sent to the printer, or written to a local file, when we call
+ \l{QPainter::}{end()}.
+ \section2 Coordinate Systems
+ QPrinter provides functions that can be used to obtain information about the
+ dimensions of the paper (the paper rectangle) and the dimensions of the
+ printable area (the page rectangle). These are given in logical device
+ coordinates that may differ from the physical coordinates used by the device
+ itself, indicating that the printer is able to render text and graphics at a
+ (typically higher) resolution than the user's display.
+ Although we do not need to handle the conversion between logical and physical
+ coordinates ourselves, we still need to apply transformations to painting
+ operations because the pixel measurements used to draw on screen are often
+ too small for the higher resolutions of typical printers.
+ \table
+ \row \li \b{Printer and Painter Coordinate Systems}
+ The \l{QPrinter::}{paperRect()} and \l{QPrinter::}{pageRect()} functions
+ provide information about the size of the paper used for printing and the
+ area on it that can be painted on.
+ The rectangle returned by \l{QPrinter::}{pageRect()} usually lies inside
+ the rectangle returned by \l{QPrinter::}{paperRect()}. You do not need to
+ take the positions and sizes of these area into account when using a QPainter
+ with a QPrinter as the underlying paint device; the origin of the painter's
+ coordinate system will coincide with the top-left corner of the page
+ rectangle, and painting operations will be clipped to the bounds of the
+ drawable part of the page.
+ \li \inlineimage printer-rects.png
+ \endtable
+ The paint system automatically uses the correct device metrics when painting
+ text but, if you need to position text using information obtained from
+ font metrics, you need to ensure that the print device is specified when
+ you construct QFontMetrics and QFontMetricsF objects, or ensure that each QFont
+ used is constructed using the form of the constructor that accepts a
+ QPaintDevice argument.
+ \section1 Printing Widgets
+ To print a widget, you can use the QWidget::render() function. As mentioned,
+ the printer's resolution is usually higher than the screen resolution, so you
+ will have to scale the painter. You may also want to position the widget on the
+ page. The following code sample shows how this may look.
+ \snippet widgetprinting.cpp 0
+ This will center the widget on the page and scale it so that it fits the page.
+ \section1 Printing from Complex Widgets
+ Certain widgets, such as QTextEdit and QGraphicsView, display rich content
+ that is typically managed by instances of other classes, such as QTextDocument
+ and QGraphicsScene. As a result, it is these content handling classes that
+ usually provide printing functionality, either via a function that can be used
+ to perform the complete task, or via a function that accepts an existing
+ QPainter object. Some widgets provide convenience functions to expose underlying
+ printing features, avoiding the need to obtain the content handler just to call
+ a single function.
+ The following table shows which class and function are responsible for
+ printing from a selection of different widgets. For widgets that do not expose
+ printing functionality directly, the content handling classes containing this
+ functionality can be obtained via a function in the corresponding widget's API.
+ \table
+ \header \li Widget \li Printing function \li Accepts
+ \row \li QGraphicsView \li QGraphicsView::render() \li QPainter
+ \row \li QSvgWidget \li QSvgRenderer::render() \li QPainter
+ \row \li QTextEdit \li QTextDocument::print() \li QPrinter
+ \row \li QTextLayout \li QTextLayout::draw() \li QPainter
+ \row \li QTextLine \li QTextLine::draw() \li QPainter
+ \endtable
+ QTextEdit requires a QPrinter rather than a QPainter because it uses information
+ about the configured page dimensions in order to insert page breaks at the most
+ appropriate places in printed documents.
+ \page pdf-licensing.html
+ \title Notes about PDF Licensing
+ \ingroup licensing
+ \brief Details of restrictions on the use of PDF-related trademarks.
+ Please note that Adobe\reg places restrictions on the use of its trademarks
+ (including logos) in conjunction with PDF; e.g. "Adobe PDF". Please refer
+ to \l{}{} for guidelines.