[2] | 1 | /****************************************************************************
|
---|
| 2 | **
|
---|
[846] | 3 | ** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
|
---|
[561] | 4 | ** All rights reserved.
|
---|
| 5 | ** Contact: Nokia Corporation ([email protected])
|
---|
[2] | 6 | **
|
---|
| 7 | ** This file is part of the documentation of the Qt Toolkit.
|
---|
| 8 | **
|
---|
[846] | 9 | ** $QT_BEGIN_LICENSE:FDL$
|
---|
[2] | 10 | ** Commercial Usage
|
---|
| 11 | ** Licensees holding valid Qt Commercial licenses may use this file in
|
---|
| 12 | ** accordance with the Qt Commercial License Agreement provided with the
|
---|
[846] | 13 | ** Software or, alternatively, in accordance with the terms contained in a
|
---|
| 14 | ** written agreement between you and Nokia.
|
---|
[2] | 15 | **
|
---|
[846] | 16 | ** GNU Free Documentation License
|
---|
| 17 | ** Alternatively, this file may be used under the terms of the GNU Free
|
---|
| 18 | ** Documentation License version 1.3 as published by the Free Software
|
---|
| 19 | ** Foundation and appearing in the file included in the packaging of this
|
---|
| 20 | ** file.
|
---|
[2] | 21 | **
|
---|
[561] | 22 | ** If you have questions regarding the use of this file, please contact
|
---|
| 23 | ** Nokia at [email protected].
|
---|
[2] | 24 | ** $QT_END_LICENSE$
|
---|
| 25 | **
|
---|
| 26 | ****************************************************************************/
|
---|
| 27 |
|
---|
| 28 | /*!
|
---|
| 29 | \example qws/svgalib
|
---|
| 30 | \title Accelerated Graphics Driver Example
|
---|
| 31 |
|
---|
| 32 | The Accelerated Graphics Driver example shows how you can write
|
---|
| 33 | your own accelerated graphics driver and \l {add your graphics
|
---|
| 34 | driver to Qt for Embedded Linux}. In \l{Qt for Embedded Linux},
|
---|
| 35 | painting is a pure software implementation and is normally performed
|
---|
| 36 | in two steps:
|
---|
| 37 | The clients render each window onto a corresponding surface
|
---|
| 38 | (stored in memory) using a paint engine, and then the server uses
|
---|
| 39 | the graphics driver to compose the surface images and copy them to
|
---|
| 40 | the screen. (See the \l{Qt for Embedded Linux Architecture} documentation
|
---|
| 41 | for details.)
|
---|
| 42 |
|
---|
| 43 | The rendering can be accelerated in two ways: Either by
|
---|
| 44 | accelerating the copying of pixels to the screen, or by
|
---|
| 45 | accelerating the explicit painting operations. The first is done
|
---|
| 46 | in the graphics driver implementation, the latter is performed by
|
---|
| 47 | the paint engine implementation. Typically, both the pixel copying
|
---|
| 48 | and the painting operations are accelerated using the following
|
---|
| 49 | approach:
|
---|
| 50 |
|
---|
| 51 | \list 1
|
---|
| 52 | \o \l {Step 1: Creating a Custom Graphics Driver}
|
---|
| 53 | {Creating a Custom Graphics Driver}
|
---|
| 54 |
|
---|
| 55 | \o \l {Step 2: Implementing a Custom Raster Paint Engine}
|
---|
| 56 | {Implementing a Custom Paint Engine}
|
---|
| 57 |
|
---|
| 58 | \o \l {Step 3: Making the Widgets Aware of the Custom Paint
|
---|
| 59 | Engine}{Making the Widgets Aware of the Custom Paint Engine}
|
---|
| 60 |
|
---|
| 61 | \endlist
|
---|
| 62 |
|
---|
| 63 | After compiling the example code, install the graphics driver
|
---|
| 64 | plugin with the command \c {make install}. To start an application
|
---|
| 65 | using the graphics driver, you can either set the environment
|
---|
| 66 | variable \l QWS_DISPLAY and then run the application, or you can
|
---|
| 67 | just run the application using the \c -display switch:
|
---|
| 68 |
|
---|
| 69 | \snippet doc/src/snippets/code/doc_src_examples_svgalib.qdoc 0
|
---|
| 70 |
|
---|
| 71 | \table
|
---|
| 72 | \header \o SVGAlib
|
---|
| 73 | \row \o
|
---|
| 74 |
|
---|
| 75 | Instead of interfacing the graphics hardware directly, this
|
---|
| 76 | example relies on \l {http://www.svgalib.org}{SVGAlib} being
|
---|
| 77 | installed on your system. \l {http://www.svgalib.org}{SVGAlib} is
|
---|
| 78 | a small graphics library which provides acceleration for many
|
---|
| 79 | common graphics cards used on desktop computers. It should work on
|
---|
| 80 | most workstations and has a small and simple API.
|
---|
| 81 |
|
---|
| 82 | \endtable
|
---|
| 83 |
|
---|
| 84 | \section1 Step 1: Creating a Custom Graphics Driver
|
---|
| 85 |
|
---|
| 86 | The custom graphics driver is created by deriving from the QScreen
|
---|
| 87 | class. QScreen is the base class for implementing screen/graphics
|
---|
| 88 | drivers in Qt for Embedded Linux.
|
---|
| 89 |
|
---|
| 90 | \snippet examples/qws/svgalib/svgalibscreen.h 0
|
---|
| 91 | \codeline
|
---|
| 92 | \snippet examples/qws/svgalib/svgalibscreen.h 1
|
---|
| 93 |
|
---|
| 94 | The \l {QScreen::}{connect()}, \l {QScreen::}{disconnect()}, \l
|
---|
| 95 | {QScreen::}{initDevice()} and \l {QScreen::}{shutdownDevice()}
|
---|
| 96 | functions are declared as pure virtual functions in QScreen and
|
---|
| 97 | must be implemented. They are used to configure the hardware, or
|
---|
| 98 | query its configuration: \l {QScreen::}{connect()} and \l
|
---|
| 99 | {QScreen::}{disconnect()} are called by both the server and client
|
---|
| 100 | processes, while the \l {QScreen::}{initDevice()} and \l
|
---|
| 101 | {QScreen::}{shutdownDevice()} functions are only called by the
|
---|
| 102 | server process.
|
---|
| 103 |
|
---|
| 104 | QScreen's \l {QScreen::}{setMode()} and \l {QScreen::}{blank()}
|
---|
| 105 | functions are also pure virtual, but our driver's implementations
|
---|
| 106 | are trivial. The last two functions (\l {QScreen::}{blit()} and \l
|
---|
| 107 | {QScreen::}{solidFill()}) are the ones involved in putting pixels
|
---|
| 108 | on the screen, i.e., we reimplement these functions to perform the
|
---|
| 109 | pixel copying acceleration.
|
---|
| 110 |
|
---|
| 111 | Finally, the \c context variable is a pointer to a \l
|
---|
| 112 | {http://www.svgalib.org}{SVGAlib} specific type. Note that the
|
---|
| 113 | details of using the \l {http://www.svgalib.org}{SVGAlib} library
|
---|
| 114 | is beyond the scope of this example.
|
---|
| 115 |
|
---|
| 116 | \section2 SvgalibScreen Class Implementation
|
---|
| 117 |
|
---|
| 118 | The \l {QScreen::}{connect()} function is the first function that
|
---|
| |
---|