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/****************************************************************************
**
** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
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/*!
\example widgets/maemovibration
\group all-examples
\title Maemo Vibration Example
\brief The Maemo Vibration example shows how to tell the Maemo Mode Control Entity
(MCE) to vibrate a maemo device.
The MCE is a system service on Maemo that, among other things, provides an
D-Bus interface to trigger vibrations. The vibrations are specified as
patterns and are defined in a system configuration file.
The example program reads the configuration file to look for possible
vibration patterns and display a button for each. Pressing a button will
make the device vibrate accordingly, until the application closes, or
another pattern is started.
\image maemovibration-example.png Screenshot of the Maemo Vibration Example
The code makes use of two classes:
\list
\o \c MceVibrator connects to the MCE service and can start a certain
vibrator pattern. It also is responsible to parse the configuration
file.
\o \c ButtonWidget provides a button for each pattern. Pressing the button
activates the pattern in question.
\endlist
\section1 MceVibrator Class Definition
\snippet examples/widgets/maemovibration/mcevibrator.h 0
The \c MceVibrator class inherits from QObject and provides a specialized
and Qt friendly interface to the MCE vibration facilty. The slot \c vibrate()
can be called to make the device vibrate according to a specific pattern
name. We will connect it to a signal of a \c ButtonWidget object later. The
static method \c ParsePatternNames() can be called to find out which patterns
are available to us.
\list
\o \c mceInterface is our D-Bus handle to the MCE service. We use it to
invoke methods on the MCE request object.
\o \c lastPatternName contains the pattern that was activated last time. We
have to keep track of this, because the last pattern has to be
deactivated before activating a new pattern.
\endlist
\section1 MceVibrator Class Implementation
To connect to the service, we initialize the D-Bus interface handle. The
system header \c "mce/dbus-names.h" contains definitions of the D-Bus
service name and request object path and interface. These are passed to the
constructor of the handle, and Qt will automatically establish a connection
to it, if it is possible.
The MCE expects us to first enable the vibrator before we can use it. This
is done with the call to the \c MCE_ENABLE_VIBRATOR D-Bus method.
\snippet examples/widgets/maemovibration/mcevibrator.cpp 0
From now on we can activate vibration patterns. Each time a vibration
pattern is activated, the last pattern has to be deactivated first. In the
vibrate slot we use the MCE interface to call the activation method.
\snippet examples/widgets/maemovibration/mcevibrator.cpp 1
The calls to the private method deactivate simply makes sure to deactivate
the last pattern used, if there was one.
\snippet examples/widgets/maemovibration/mcevibrator.cpp 2
Calling either the activate or deactivate MCE D-Bus method with invalid
pattern names are ignored.
Finally, the destructor disables the vibrator. When the destructor of the
MCE interface handle is called, the connection is also closed.
\snippet examples/widgets/maemovibration/mcevibrator.cpp 3
The MCE configuration file contains options for many different things. We
are only interested in one line that contains the vibration patterns. It
has the following format:
\code
VibratorPatterns=semicolon;separated;list;of;values
\endcode
The static method \c ParsePatternNames looks for this line and returns a
QStringList containing the values, which are the pattern names we can use.
\snippet examples/widgets/maemovibration/mcevibrator.cpp 4
The helper function \c checkError() saves us some code duplication. None of the
called methods return anything of use to us, so we're only interested in
getting error messages for debugging.
\snippet examples/widgets/maemovibration/mcevibrator.cpp 5
\section1 ButtonWidget Class Definition
\snippet examples/widgets/maemovibration/buttonwidget.h 0
The \c ButtonWidget class inherits from QWidget and provides the main user
interface for the application. It creates a grid of buttons, one for each
string in the stringlist passed to the constructor. Pressing a button emits
the \c clicked() signal, where the string is the text of the button that
was pressed.
This class is taken from the QSignalMapper documentation. The only change
is the number of columns in the grid from three to two, to make the button
labels fit.
\section1 ButtonWidget Class Implementation
\snippet examples/widgets/maemovibration/buttonwidget.cpp 0
\section1 \c main() Function
The main function begins with looking up the patterns available to us.
\snippet examples/widgets/maemovibration/main.cpp 0
Then we create one instance of both classes, and connects the
\c ButtonWidget's clicked signal to the \c MceVibrator's \c vibrate() slot.
This works, since the button texts are the same as the pattern names.
\snippet examples/widgets/maemovibration/main.cpp 1
*/
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