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1 /**************************************************************************** |
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2 ** |
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3 ** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies). |
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4 ** All rights reserved. |
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5 ** Contact: Nokia Corporation (qt-info@nokia.com) |
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7 ** This file is part of the documentation of the Qt Toolkit. |
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9 ** $QT_BEGIN_LICENSE:LGPL$ |
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11 ** This file contains pre-release code and may not be distributed. |
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14 ** this package. |
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15 ** |
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16 ** GNU Lesser General Public License Usage |
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17 ** Alternatively, this file may be used under the terms of the GNU Lesser |
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18 ** General Public License version 2.1 as published by the Free Software |
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19 ** Foundation and appearing in the file LICENSE.LGPL included in the |
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21 ** ensure the GNU Lesser General Public License version 2.1 requirements |
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22 ** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html. |
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24 ** In addition, as a special exception, Nokia gives you certain additional |
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35 ** |
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36 ** |
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37 ** |
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38 ** $QT_END_LICENSE$ |
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39 ** |
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40 ****************************************************************************/ |
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41 |
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42 /*! |
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43 \page qt-embedded-displaymanagement.html |
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44 |
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45 \title Qt for Embedded Linux Display Management |
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46 \ingroup qt-embedded-linux |
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47 |
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48 When rendering, the default behavior for each Qt for Embedded Linux |
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49 client is to render its widgets into memory, while the server is |
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50 responsible for putting the contents of the memory onto the |
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51 screen. The server uses the screen driver to copy the content of |
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52 the memory to the display. |
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53 |
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54 The screen driver is loaded by the server application when it |
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55 starts running, using Qt's \l {How to Create Qt Plugins}{plugin |
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56 system}. |
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57 |
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58 Contents: |
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59 |
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60 \tableofcontents |
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61 |
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62 \section1 Available Drivers |
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63 |
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64 \l{Qt for Embedded Linux} provides drivers for the Linux framebuffer, the |
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65 virtual framebuffer, transformed screens, VNC servers and multi |
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66 screens. Run the \c configure script to list the available |
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67 drivers: |
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68 |
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69 \if defined(QTOPIA_DOCS) |
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70 \snippet doc/src/snippets/code/doc_src_qt-embedded-displaymanagement.qdoc 0 |
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71 \else |
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72 \snippet doc/src/snippets/code/doc_src_qt-embedded-displaymanagement.qdoc 1 |
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73 \endif |
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74 |
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75 \if defined(QTOPIA_DOCS) |
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76 In the default Qt Extended configuration, only an unaccelerated Linux |
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77 framebuffer driver (\c /dev/fb0) is enabled. The various drivers |
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78 can be enabled and disabled using the \c configure script. For |
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79 example: |
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80 |
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81 \snippet doc/src/snippets/code/doc_src_qt-embedded-displaymanagement.qdoc 2 |
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82 \else |
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83 In the default Qt configuration, only an unaccelerated Linux |
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84 framebuffer driver (\c /dev/fb0) is enabled. The various drivers |
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85 can be enabled and disabled using the \c configure script. For |
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86 example: |
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87 |
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88 \snippet doc/src/snippets/code/doc_src_qt-embedded-displaymanagement.qdoc 3 |
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89 \endif |
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90 |
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91 Custom screen drivers can be implemented by subclassing the |
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92 QScreen class and creating a screen driver plugin (derived from |
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93 the QScreenDriverPlugin class). The default implementation |
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94 of the QScreenDriverFactory class will automatically detect the |
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95 plugin, loading the driver into the server application at run-time. |
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96 |
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97 \section1 Specifying a Driver |
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98 |
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99 To specify which driver to use, set the QWS_DISPLAY environment |
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100 variable. For example (if the current shell is bash, ksh, zsh or |
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101 sh): |
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102 |
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103 \snippet doc/src/snippets/code/doc_src_qt-embedded-displaymanagement.qdoc 4 |
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104 |
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105 The valid values for the \c <driver> argument are \c LinuxFb, \c |
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106 QVFb, \c VNC, \c Transformed, \c Multi and \l |
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107 {QScreenDriverPlugin::keys()}{keys} identifying custom drivers, |
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108 and the \c {<display num>} argument is used to separate screens |
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109 that are using the same screen driver and to enable multiple |
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110 displays (see the \l {Running Qt for Embedded Linux Applications} |
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111 documentation for more details). The driver specific options are |
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112 described in the table below. |
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113 |
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114 \table |
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115 \header |
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116 \o Driver Specific Option \o Available For \o Description |
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117 \row |
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118 \o \c tty=<device> |
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119 \o LinuxFb |
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120 \o Passes the device file to the console the application is |
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121 running on. |
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122 \row |
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123 \o \c nographicsmodeswitch |
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124 \o LinuxFb |
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125 \o Ensures that the application is not in graphics mode. |
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126 \row |
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127 \o \c littleendian |
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128 \o LinuxFb |
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129 \o Tells the driver it must handle a little-endian frame |
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130 buffer in a big-endian system. |
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131 \row |
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132 \o \c mmWidth=<value> \target mmWidth |
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133 \o LinuxFb, QVFb |
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134 \o The screen's physical width (used to calculate DPI). |
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135 \row |
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136 \o \c mmHeight=<value> \target mmHeight |
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137 \o LinuxFb, QVFb |
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138 \o The screen's physical height (used to calculate DPI). |
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139 \row |
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140 \o \c <device> |
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141 \o LinuxFb |
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142 \o |
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143 \row |
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144 \o \c <subdriver> |
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145 \o VNC, Transformed, Multi |
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146 \o Specifies a subdriver. |
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147 \row |
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148 \o \c <RotX> |
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149 \o Transformed |
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150 \o Specifies the rotation of the screen. The valid values of |
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151 \c X are 90, 180 and 270. |
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152 \row |
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153 \o \c offset=<x,y> |
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154 \o Multi |
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155 \o Specifies the coordinates of a subscreen's top-left corner |
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156 (by default 0,0). |
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157 |
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158 \endtable |
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159 |
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160 The QWS_DISPLAY environment variable can also be set using the \c |
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161 -display option when running an application. For example: |
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162 |
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163 \snippet doc/src/snippets/code/doc_src_qt-embedded-displaymanagement.qdoc 5 |
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164 |
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165 \section1 Subdrivers and Multiple Drivers |
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166 |
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167 The VNC, Transformed and Multi screen drivers depend on |
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168 subdrivers. The general syntax for specifying a driver is as |
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169 follows: |
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170 |
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171 \snippet doc/src/snippets/code/doc_src_qt-embedded-displaymanagement.qdoc 6 |
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172 |
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173 In the case of subdrivers, it is important to add a space between |
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174 each subdriver and before the display number to separate the |
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175 various drivers and displays. Note that \c Multi screen drivers |
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176 can have several subdrivers. For example: |
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177 |
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178 \snippet doc/src/snippets/code/doc_src_qt-embedded-displaymanagement.qdoc 7 |
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179 |
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180 Note also that the VNC screen driver defaults to a virtual screen |
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181 driver if no subdriver is specified. In this case the VNC driver accepts a |
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182 few additional (optional) arguments specifying the size and depth |
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183 of the default virtual screen: |
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184 |
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185 \list |
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186 \o \c {size=<width x height>} |
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187 \o \c {depth=<value>} |
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188 \o \c {mmHeight=<physical height in millimeters>} |
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189 \o \c {mmWidth=<physical width in millimeters>} |
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190 \endlist |
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191 |
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192 Example running the VNC screen driver with a virtual screen of size |
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193 720x480 with 32 bits per pixel: |
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194 |
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195 \snippet doc/src/snippets/code/doc_src_qt-embedded-displaymanagement.qdoc 8 |
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196 |
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197 Example running the VNC screen driver on top of the Linux framebuffer |
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198 driver: |
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199 |
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200 \snippet doc/src/snippets/code/doc_src_qt-embedded-displaymanagement.qdoc 9 |
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201 |
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202 In this last example, Qt is using two screen drivers simultaneously, |
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203 displaying output on both the device's screen and across a network on |
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204 VNC client displays. |
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205 */ |