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Including External Code

The following commands enable you to include code snippets from external files. You can make QDoc include the complete contents of a file, or you can quote specific parts of the file and skip others. The typical use of the latter is to quote a file chunk by chunk.

Note: Although all these commands can be used for rendering C++ code, the \snippet and \codeline commands are preferred over the others. These commands allow equivalent code snippets for other Qt language bindings to be substituted for the C++ snippets in the documentation.

\quotefile

The \quotefile command expands to the complete contents of the file given as argument.

The command considers the rest of the line as part of its argument, make sure to follow the file name with a line break.

The file's contents is rendered in a separate paragraph, using a monospace font and the standard indentation. The code is shown verbatim.

/ *!
    This is a simple "Hello world" example:

    \quotefile examples/main.cpp

    It contains only the bare minimum you need
    to get a Qt application up and running.
* /

QDoc renders this as:

This is a simple "Hello world" example:

/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the tools applications of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:GPL-EXCEPT$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3 as published by the Free Software
** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/

#include <QApplication>
#include <QPushButton>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    QPushButton hello("Hello world!");
    hello.resize(100, 30);

    hello.show();
    return app.exec();
}

It contains only the bare minimum you need to get a Qt application up and running.

See also \quotefromfile and \code.

\quotefromfile

The \quotefromfile command opens the file given as argument for quoting.

The command considers the rest of the line as part of its argument, make sure to follow the file name with a line break.

The command is intended for use when quoting parts from file with the walkthrough commands: \printline, \printto, \printuntil, \skipline, \skipto, \skipuntil. This enables you to quote specific portions of a file.

/ *!
    The whole application is contained within
    the \c main() function:

    \quotefromfile examples/main.cpp

    \skipto main
    \printuntil app(argc, argv)

    First we create a QApplication object using
    the \c argc and \c argv parameters.

    \skipto QPushButton
    \printuntil resize

    Then we create a QPushButton, and give it a reasonable
    size using the QWidget::resize() function.

    ...
* /

QDoc renders this as:

The whole application is contained within the main() function:

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

First we create a QApplication object using the argc and argv parameters.

    QPushButton hello("Hello world!");
    hello.resize(100, 30);

Then we create a QPushButton, and give it a reasonable size using the QWidget::resize() function.

...

QDoc remembers which file it is quoting from, and the current position in that file (see \printline for more information). There is no need to "close" the file.

See also \quotefile, \code and \dots.

\printline

The \printline command expands to the line from the current position to the next non-blank line of the current source file.

To ensure that the documentation remains synchronized with the source file, a substring of the line must be specified as an argument to the command. Note that the command considers the rest of the line as part of its argument, make sure to follow the substring with a line break.

The line from the source file is rendered as a separate paragraph, using a monospace font and the standard indentation. The code is shown verbatim.

/ *!
    There has to be exactly one QApplication object
    in every GUI application that uses Qt.

    \quotefromfile examples/main.cpp

    \printline QApplication

    This line includes the QApplication class
    definition. QApplication manages various
    application-wide resources, such as the
    default font and cursor.

    \printline QPushButton

    This line includes the QPushButton class
    definition. The QPushButton widget provides a command
    button.

    \printline main

    The main function...
* /

QDoc renders this as:

There has to be exactly one QApplication object in every GUI application that uses Qt.

#include <QApplication>

This line includes the QApplication class definition. QApplication manages various application-wide resources, such as the default font and cursor.

#include <QPushButton>

This line includes the QPushButton class definition. The QPushButton widget provides a command button.

int main(int argc, char *argv[])

The main function...

QDoc reads the file sequentially. To move the current position forward you can use either of the \skip... commands. To move the current position backward, you can use the \quotefromfile command again.

If the substring argument is surrounded by slashes it is interpreted as a regular expression.

/ *!
    \quotefromfile examples/mainwindow.cpp

    \skipto closeEvent
    \printuntil /^\}/

    Close events are sent to widgets that the users want to
    close, usually by clicking \c File|Exit or by clicking
    the \c X title bar button. By reimplementing the event
    handler, we can intercept attempts to close the
    application.
* /

QDoc renders this as:

void MainWindow::closeEvent(QCloseEvent *event)
//! [1] //! [2]
{
    if (maybeSave()) {
        event->accept();
    } else {
        event->ignore();
    }
}

Close events are sent to widgets that the users want to close, usually by clicking File|Exit or by clicking the X title bar button. By reimplementing the event handler, we can intercept attempts to close the application.

(The complete example file...)

The regular expression /^\}/ makes QDoc print until the first '}' character occurring at the beginning of the line without indentation. /.../ encloses the regular expression, and '^' means the beginning of the line. The '}' character must be escaped since it is a special character in regular expressions.

QDoc will emit a warning if the specified substring or regular expression cannot be located, i.e. if the source code has changed.

See also \printto and \printuntil.

\printto

The \printto command expands to all the lines from the current position up to and excluding the next line containing a given substring.

The command considers the rest of the line as part of its argument, make sure to follow the substring with a line break. The command also follows the same conventions for positioning and argument as the \printline command.

The lines from the source file are rendered in a separate paragraph, using a monospace font and the standard indentation. The code is shown verbatim.

/ *!
    The whole application is contained within the
    \c main() function:

    \quotefromfile examples/main.cpp
    \printto hello

    First we create a QApplication object using the \c argc and
    \c argv parameters...
* /

QDoc renders this as:

The whole application is contained within the main() function:

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

First we create a QApplication object using the argc and argv parameters...

See also \printline and \printuntil.

\printuntil

The \printuntil command expands to all the lines from the current position up to and including the next line containing a given substring.

The command considers the rest of the line as part of its argument, make sure to follow the substring with a line break. The command also follows the same conventions for positioning and argument as the \printline command.

If \printuntil is used without an argument, it expands to all the lines from the current position to the end of the quoted file.

The lines from the source file are rendered in a separate paragraph, using a monospace font and the standard indentation. The code is shown verbatim.

/ *!
    The whole application is contained within the
    \c main() function:

    \quotefromfile examples/main.cpp
    \skipto main
    \printuntil hello

    First we create a QApplication object using the
    \c argc and \c argv parameters, then we create
    a QPushButton.
* /

QDoc renders this as:

The whole application is contained within the main() function:

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    QPushButton hello("Hello world!");

First we create a QApplication object using the argc and argv parameters, then we create a QPushButton.

See also \printline and \printto.

\skipline

The \skipline command ignores the next non-blank line in the current source file.

Doc reads the file sequentially, and the \skipline command is used to move the current position (omitting a line of the source file). See the remark about file positioning above.

The command considers the rest of the line as part of its argument, make sure to follow the substring with a line break. The command also follows the same conventions for argument as the \printline command, and it is used in conjunction with the \quotefromfile command.

/ *!
    QPushButton is a GUI push button that the user
    can press and release.

    \quotefromfile examples/main.cpp
    \skipline QApplication
    \printline QPushButton

    This line includes the QPushButton class
    definition. For each class that is part of the
    public Qt API, there exists a header file of
    the same name that contains its definition.
* /

QDoc renders this as:

QPushButton is a GUI push button that the user can press and release.

#include <QPushButton>

This line includes the QPushButton class definition. For each class that is part of the public Qt API, there exists a header file of the same name that contains its definition.

See also \skipto, \skipuntil and \dots.

\skipto

The \skipto command ignores all the lines from the current position up to and excluding the next line containing a given substring.

QDoc reads the file sequentially, and the \skipto command is used to move the current position (omitting one or several lines of the source file). See the remark about file positioning above.

The command considers the rest of the line as part of its argument, make sure to follow the substring with a line break.

The command also follows the same conventions for argument as the \printline command, and it is used in conjunction with the \quotefromfile command.

/ *!
    The whole application is contained within
    the \c main() function:

    \quotefromfile examples/main.cpp
    \skipto main
    \printuntil }

    First we create a QApplication object. There
    has to be exactly one such object in
    every GUI application that uses Qt. Then
    we create a QPushButton, resize it to a reasonable
    size...
* /

QDoc renders this as:

The whole application is contained within the main() function:

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    QPushButton hello("Hello world!");
    hello.resize(100, 30);

    hello.show();
    return app.exec();
}

First we create a QApplication object. There has to be exactly one such object in every GUI application that uses Qt. Then we create a QPushButton, resize it to a reasonable size ...

See also \skipline, \skipuntil and \dots.

\skipuntil

The \skipuntil command ignores all the lines from the current position up to and including the next line containing a given substring.

QDoc reads the file sequentially, and the \skipuntil command is used to move the current position (omitting one or several lines of the source file). See the remark about file positioning above.

The command considers the rest of the line as part of its argument, make sure to follow the substring with a line break.

The command also follows the same conventions for argument as the \printline command, and it is used in conjunction with the \quotefromfile command.

/ *!
    The first thing we did in the \c main() function
    was to create a QApplication object \c app.

    \quotefromfile examples/main.cpp
    \skipuntil show
    \dots
    \printuntil }

    In the end we must remember to make \c main() pass the
    control to Qt. QCoreApplication::exec() will return when
    the application exits...
* /

QDoc renders this as:

The first thing we did in the main() function was to create a QApplication object app.

    ...
    return app.exec();
}

In the end we must remember to make main() pass the control to Qt. QCoreApplication::exec() will return when the application exits...

See also \skipline, \skipto and \dots.

\dots

The \dots command indicates that parts of the source file have been omitted when quoting a file.

The command is used in conjunction with the \quotefromfile command, and should be stated on its own line. The dots are rendered on a new line, using a monospace font.

/ *!
    \quotefromfile examples/main.cpp
    \skipto main
    \printuntil {
    \dots
    \skipuntil exec
    \printline }
* /

QDoc renders this as:

int main(int argc, char *argv[])
{
    ...
}

The default indentation is 4 spaces, but this can be adjusted using the command's optional argument.

/ *!
    \dots 0
    \dots
    \dots 8
    \dots 12
    \dots 16
* /

QDoc renders this as:

...
    ...
        ...
            ...
                ...

See also \skipline, \skipto and \skipuntil.

\snippet

The \snippet command causes a code snippet to be included verbatim as preformatted text, which may be syntax highlighted.

Each code snippet is referenced by the file that holds it and by a unique identifier for that file. Snippet files are typically stored in a snippets directory inside the documentation directory (for example, $QTDIR/doc/src/snippets).

For example, the following documentation references a snippet in a file residing in a subdirectory of the documentation directory:

\snippet snippets/textdocument-resources/main.cpp Adding a resource

The text following the file name is the unique identifier for the snippet. This is used to delimit the quoted code in the relevant snippet file, as shown in the following example that corresponds to the above \snippet command:

    ...
    QImage image(64, 64, QImage::Format_RGB32);
    image.fill(qRgb(255, 160, 128));

//! [Adding a resource]
    document->addResource(QTextDocument::ImageResource,
        QUrl("mydata://image.png"), QVariant(image));
//! [Adding a resource]
    ...

By default, QDoc looks for //! as a code snippet marker. For .pro, .py, .cmake, and CMakeLists.txt files, #! is detected. Finally, <!-- is accepted in .html, .qrc, .ui, .xml, and .xq files.

\codeline

The \codeline command inserts a blank line of preformatted text. It is used to insert gaps between snippets without closing the current preformatted text area and opening a new one.

© The Qt Company Ltd
Licensed under the GNU Free Documentation License, Version 1.3.
https://doc.qt.io/qt-6.2/07-0-qdoc-commands-includingexternalcode.html