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diff --git a/doc/src/examples/dbscreen.qdoc b/doc/src/examples/dbscreen.qdoc deleted file mode 100644 index bfecb9a3cb..0000000000 --- a/doc/src/examples/dbscreen.qdoc +++ /dev/null @@ -1,186 +0,0 @@ -/**************************************************************************** -** -** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies). -** Contact: http://www.qt-project.org/ -** -** This file is part of the documentation of the Qt Toolkit. -** -** $QT_BEGIN_LICENSE:FDL$ -** 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. -** -** -** -** -** -** $QT_END_LICENSE$ -** -****************************************************************************/ - -/*! - \example qws/dbscreen - \title Double Buffered Graphics Driver Example - - The Double Buffered Graphics Driver example shows how to write your own - double buffered graphics driver and add it to Qt for Embedded Linux. - - Similar to the \l{Accelerated Graphics Driver Example}, there are three steps - to writing and implementing this graphics driver: - - \list 1 - \li \l {Step 1: Creating a Custom Graphics Driver} - {Creating a Custom Graphics Driver} - - \li \l {Step 2: Implementing the Back Buffer} - {Implementing the Back Buffer} - - \li \l {Step 3: Creating the Driver Plugin} - {Creating the Driver Plugin} - - \endlist - - After compiling the example code, install the graphics driver plugin with - the command \c {make install}. To start an application using the graphics - driver, you can either set the environment variable \l QWS_DISPLAY and - then run the application, or you can just run the application using the - \c -display switch. - - Note that this is a minimal example and this driver will not work well - with widgets painting themself directly to the screen (e.g. widgets with - the Qt::WA_PaintOnScreen window attribute set). Also, the example requires - the Linux framebuffer to be set up correctly and with the correct device - permissions. For further information, refer to - \l{Testing the Linux Framebuffer}. - - \section1 Step 1: Creating a Custom Graphics Driver - - Usually, a custom graphics driver is created by subclassing the QScreen - class, the base class for implementing screen or graphics drivers in - Qt for Embedded Linux. In this example, however, we subclass the QLinuxFbScreen - class instead, to ensure that our driver uses the Linux framebuffer. - - For our graphics driver, the \c DBScreen class, we reimplement five - functions belonging to QScreen: - - \list - \li \l{QScreen::initDevice()}{initDevice()}, - \li \l{QScreen::shutdownDevice()}{shutdownDevice()}, - \li \l{QScreen::blit()}{blit()}, - \li \l{QScreen::solidFill()}{solidFill()}, and - \li \l{QScreen::exposeRegion()}{exposeRegion()}. - \endlist - - \snippet examples/qws/dbscreen/dbscreen.h 0 - - In addition to the abovementioned functions, there is a private instance - of QPainter and QImage - \c painter, used for drawing operations on - the back buffer, and \c image, the back buffer itself. - - \section1 Step 2: Implementing the Back Buffer - - The graphics driver must carry out three main functions: - - \list 1 - \li Allocate the back buffer on startup and deallocate it on shutdown. - \li Draw to the back buffer instead of directly to the screen - (which is what QLinuxFbScreen does). - \li Copy the back buffer to the screen whenever a screen update is - done. - \endlist - - \section2 Device initializing and shutdown - - We first reimplement \c initDevice() and \c shutdownDevice(). - - The \c initDevice() function initializes the framebuffer. We reimplement - this function to enable accelerated drivers to set up the graphic card. - For this example, we first call the super class' implementation to set up - the Linux framebuffer. If this call returns \c false, we return \c false. - Otherwise, we initialize the screen cursor with - QScreenCursor::initSoftwareCursor() as well as instantiate \c image and - \c painter. Then, we return \c true. - - \snippet examples/qws/dbscreen/dbscreen.cpp 0 - - The \c shutdownDevice() function's default implementation only hides the - mouse cursor. Hence, we reimplement it to carry out the necessary cleanup - before the Qt for Embedded Linux server exits. - - \snippet examples/qws/dbscreen/dbscreen.cpp 1 - - Again, we call the super class implementation to shutdown the Linux - framebuffer prior to deleting \c image and \c painter. - - \section2 Drawing to the back buffer - - We move on to the drawing functions - \c solidFill() and \c blit(). In - QLinuxFbScreen, these functions draw directly to the Linux framebuffer; - but in our driver we reimplement them to draw to the back buffer instead. - - \snippet examples/qws/dbscreen/dbscreen.cpp 2 - - The \c solidFill() function is called from \c exposeRegion() to fill the - given \c region of the screen with the specified \c color. In this - example, we use \c painter to fill rectangles in \c image, the back - buffer, according to the given region. - - \snippet examples/qws/dbscreen/dbscreen.cpp 3 - - The \c blit() function is also called from \c exposeRegion() to copy the - given QRegion object, \c region, in the given QImage object, \c image, to - the QPoint object specified by \c topLeft. Once again we use \c painter - to draw in the back buffer, \c image. - - \section2 Displaying the buffer on the screen - - The \c exposeRegion() function is called by the Qt for Embedded Linux server - whenever a screen update is required. The given \c region is the screen - region that needs to be updated and \c changing is is the index into - QWSServer::clientWindows() of the window that caused the update. - - \snippet examples/qws/dbscreen/dbscreen.cpp 4 - - In our implementation, we first call the super class implementation to - ensure that \c solidFill() and \c blit() will be called correctly. This - causes the changed areas to be updated in the back buffer. We then call - the super class' implementation of \c blit() to copy the updated region - from the back buffer into the Linux framebuffer. - - \section1 Step 3: Creating the Driver Plugin - - Qt provides a high level API for writing Qt extensions. One of the plugin - base classes provided is QScreenDriverPlugin, which we use in this example - to create our screen driver plugin. - - \snippet examples/qws/dbscreen/dbscreendriverplugin.cpp 0 - - There are only two functions to reimplement: - - \list - \li \l{QScreenDriverPlugin::create()}{create()} - creates a driver - matching the given key - \li \l{QScreenDriverPlugin::create()}{keys()} - returns a list of - valid keys representing the drivers supported by the plugin - \endlist - - \snippet examples/qws/dbscreen/dbscreendriverplugin.cpp 1 - \codeline - \snippet examples/qws/dbscreen/dbscreendriverplugin.cpp 2 - - Our plugin will only support one driver, \c dbscreen. - - Lastly, we export the plugin. - - \snippet examples/qws/dbscreen/dbscreendriverplugin.cpp 3 - - For detailed information about the Qt plugin system see - \l{How to Create Qt Plugins.} -*/ |