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/****************************************************************************
**
** Copyright (C) 2018 Pelagicore AG
** Contact: https://www.qt.io/licensing/
**
** This file is part of the documentation of the Pelagicore Application Manager.
**
** $QT_BEGIN_LICENSE:FDL-QTAS$
** Commercial License Usage
** Licensees holding valid commercial Qt Automotive Suite 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 Free Documentation License Usage
** 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. Please review the following information to ensure
** the GNU Free Documentation License version 1.3 requirements
** will be met: https://www.gnu.org/licenses/fdl-1.3.html.
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\example applicationmanager/custom-appman
\title Implementing a Custom Application-Manager Example
\image custom-appman.png Screenshot
\brief Basic structure and starting point for a custom application-manager executable.
\ingroup applicationmanager-examples
\section1 Introduction
The application-manager is compiled as a self-contained executable that can be configured
in large parts through the YAML based config file system and startup plugins. However it may still
be necessary to implement a custom application-manager executable to have more influence over the
startup behavior.
\note Please note however, that all C++ classes in the application-manager modules are considered private
API at the moment, so there are no compatibility guarantees at all.
If you still desire to go down that road however, this example will provide you with an starting
point to build your custom implementation upon.
Keep in mind though, that this custom application-manager executable will need a System-UI to
display something on the screen, just as the standard \c appman executable.
\section1 Walkthrough
Following is a breakdown of the minimal code needed for such a custom implementation:
\quotefromfile applicationmanager/custom-appman/custom-appman.cpp
\skipto #include
\printuntil QT_USE_NAMESPACE_AM
The application-manager is split into functional building blocks/libraries. These includes will
pull in the basic set of classes needed.
In order to avoid possible clashes with QML plugins, all of the application-manager's symbols are
namespaced - \c QT_USE_NAMESPACE_AM will expand to the matching \c using statement.
\skipto QCoreApplication::setApplicationName
\printuntil QCoreApplication::setApplicationVersion
Not application-manager specific, but having an application name and version set is generally
a good idea.
\printline Logging::init
We want the logging part of the application-manager initialized as early as possible, especially
when dealing with DLT logging.
\printline Package::ensure
If you are using the installer part of the application-manager, this function needs to be called
\e before the QApplication constructor to make sure your C locale is an UTF-8 variant (this is a
requirement in order to get deterministic results when using \c libarchive with non-ASCII filenames).
\printto try
Again, for the installer part only, an additional setup step is necessary before running the
QApplication constructor: if the executable is setuid-root, this call will \c fork of a child
process which keeps the root privileges while the main process permanently drop them.
\printuntil return 2
\printline }
This \c try block is the heart of the custom application-manager. You need to create a \c Main
(which is a class derived from QGuiApplication) object plus a suitable configuration object: in
this simple case we just use the application-manager's default YAML parsing, so we instantiate
a \c DefaultConfiguration object.
The rest of the function consists of parsing the configuration and then calling the relevant
setup routines on the \c Main object.
Since \c Main can be derived differently depending on your application-manager configuration
(headless, with widgets or standard), you would need to know the correct base-class for the exec()
call - the \c MainBase typedef will circumvent that problem though.
Keep in mind that most functions in the application-manager will throw exceptions that are
derived from \c std::exception, so a \c catch handler is a must.
*/
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