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diff --git a/doc/src/examples/mousecalibration.qdoc b/doc/src/examples/mousecalibration.qdoc new file mode 100644 index 0000000000..9edc11b823 --- /dev/null +++ b/doc/src/examples/mousecalibration.qdoc @@ -0,0 +1,193 @@ +/**************************************************************************** +** +** 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 qws/mousecalibration + \title Mouse Calibration Example + + The Mouse Calibration example demonstrates how to write a simple + program using the mechanisms provided by the QWSMouseHandler class + to calibrate the mouse handler in \l{Qt for Embedded Linux}. + + Calibration is the process of mapping between physical + (i.e. device) coordinates and logical coordinates. + + The example consists of two classes in addition to the main program: + + \list + \o \c Calibration is a dialog widget that retrieves the device coordinates. + \o \c ScribbleWidget is a minimal drawing program used to let the user + test the new mouse settings. + \endlist + + First we will review the main program, then we will take a look at + the \c Calibration class. The \c ScribbleWidget class is only a + help tool in this context, and will not be covered here. + + \section1 The Main Program + + The program starts by presenting a message box informing the user + of what is going to happen: + + \snippet examples/qws/mousecalibration/main.cpp 0 + + The QMessageBox class provides a modal dialog with a range of + different messages, roughly arranged along two axes: severity and + complexity. The message box has a different icon for each of the + severity levels, but the icon must be specified explicitly. In our + case we use the default QMessageBox::NoIcon value. In addition we + use the default complexity, i.e. a message box showing the given + text and an \gui OK button. + + At this stage in the program, the mouse could be completely + uncalibrated, making the user unable to press the \gui OK button. For + that reason we use the static QTimer::singleShot() function to + make the message box disappear after 10 seconds. The QTimer class + provides repetitive and single-shot timers: The single shot + function calls the given slot after the specified interval. + + \snippet examples/qws/mousecalibration/main.cpp 1 + + Next, we create an instance of the \c Calibration class which is a + dialog widget retrieving the required sample coordinates: The + dialog sequentially presents five marks for the user to press, + storing the device coordinates for the mouse press events. + + \snippet examples/qws/mousecalibration/main.cpp 2 + + When the calibration dialog returns, we let the user test the new + mouse settings by drawing onto a \c ScribbleWidget object. Since + the mouse still can be uncalibrated, we continue to use the + QMessageBox and QTimer classes to inform the user about the + program's progress. + + An improved calibration tool would let the user choose between + accepting the new calibration, reverting to the old one, and + restarting the calibration. + + \section1 Calibration Class Definition + + The \c Calibration class inherits from QDialog and is responsible + for retrieving the device coordinates from the user. + + \snippet examples/qws/mousecalibration/calibration.h 0 + + We reimplement QDialog's \l {QDialog::exec()}{exec()} and \l + {QDialog::accept()}{accept()} slots, and QWidget's \l + {QWidget::paintEvent()}{paintEvent()} and \l + {QWidget::mouseReleaseEvent()}{mouseReleaseEvent()} functions. + + In addition, we declare a couple of private variables, \c data and + \c pressCount, holding the \c Calibration object's number of mouse + press events and current calibration data. The \c pressCount + variable is a convenience variable, while the \c data is a + QWSPointerCalibrationData object (storing the physical and logical + coordinates) that is passed to the mouse handler. The + QWSPointerCalibrationData class is simply a container for + calibration data. + + \section1 Calibration Class Implementation + + In the constructor we first ensure that the \c Calibration dialog + fills up the entire screen, has focus and will receive mouse + events (the latter by making the dialog modal): + + \snippet examples/qws/mousecalibration/calibration.cpp 0 + + Then we initialize the \l{QWSPointerCalibrationData::}{screenPoints} + array: + + \snippet examples/qws/mousecalibration/calibration.cpp 1 + + In order to specify the calibration, the + \l{QWSPointerCalibrationData::screenPoints}{screenPoints} array must + contain the screen coordinates for the logical positions + represented by the QWSPointerCalibrationData::Location enum + (e.g. QWSPointerCalibrationData::TopLeft). Since non-linearity is + expected to increase on the edge of the screen, all points are + kept 10 percent within the screen. The \c qt_screen pointer is a + reference to the screen device. There can only be one screen + device per application. + + \snippet examples/qws/mousecalibration/calibration.cpp 2 + + Finally, we initialize the variable which keeps track of the number of + mouse press events we have received. + + \snippet examples/qws/mousecalibration/calibration.cpp 3 + + The destructor is trivial. + + \snippet examples/qws/mousecalibration/calibration.cpp 4 + + The reimplementation of the QDialog::exec() slot is called from + the main program. + + First we clear the current calibration making the following mouse + event delivered in raw device coordinates. Then we call the + QWidget::grabMouse() function to make sure no mouse events are + lost, and the QWidget::activateWindow() function to make the + top-level widget containing this dialog, the active window. When + the call to the QDialog::exec() base function returns, we call + QWidget::releaseMouse() to release the mouse grab before the + function returns. + + \snippet examples/qws/mousecalibration/calibration.cpp 5 + + The QWidget::paintEvent() function is reimplemented to receive the + widget's paint events. A paint event is a request to repaint all + or parts of the widget. It can happen as a result of + QWidget::repaint() or QWidget::update(), or because the widget was + obscured and has now been uncovered, or for many other reasons. + In our reimplementation of the function we simply draw a cross at + the next point the user should press. + + \snippet examples/qws/mousecalibration/calibration.cpp 6 + + We then reimplement the QWidget::mouseReleaseEvent() function to + receive the widget's move events, using the QMouseEvent object + passed as parameter to find the coordinates the user pressed, and + update the QWSPointerCalibrationData::devPoints array. + + In order to complete the mapping between logical and physical + coordinates, the \l + {QWSPointerCalibrationData::devPoints}{devPoints} array must + contain the raw device coordinates for the logical positions + represented by the QWSPointerCalibrationData::Location enum + (e.g. QWSPointerCalibrationData::TopLeft) + + We continue by drawing the next cross, or close the dialog by + calling the QDialog::accept() slot if we have collected all the + required coordinate samples. + + \snippet examples/qws/mousecalibration/calibration.cpp 7 + + Our reimplementation of the QDialog::accept() slot simply activate + the new calibration data using the QWSMouseHandler::calibrate() + function. We also use the Q_ASSERT() macro to ensure that the number + of required samples are present. +*/ |