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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Qt Toolkit - Qt/Embedded Virtual Framebuffer</title><style type="text/css"><!--h3.fn,span.fn { margin-left: 1cm; text-indent: -1cm; }a:link { color: #004faf; text-decoration: none }a:visited { color: #672967; text-decoration: none }body { background: white; color: black; }--></style></head><body bgcolor="#ffffff"><p><table width="100%"><tr><td><a href="index.html"><img width="100" height="100" src="qtlogo.png"alt="Home" border="0"><img width="100"height="100" src="face.png" alt="Home" border="0"></a><td valign="top"><div align="right"><img src="dochead.png" width="472" height="27"><br><a href="classes.html"><b>Classes</b></a>- <a href="annotated.html">Annotated</a>- <a href="hierarchy.html">Tree</a>- <a href="functions.html">Functions</a>- <a href="index.html">Home</a>- <a href="topicals.html"><b>Structure</b> <font face="Arial,Helvetica,Geneva,Swiss,SunSans-Regular" align="center" size=32>Qte</font></a></div></table><h1 align="center"> Qt/Embedded Virtual Framebuffer</h1><br clear="all">The virtual framebuffer allows Qt/Embedded programs to be developed on yourdesktop machine, without switching between consoles and X11.<p>The virtual framebuffer is located in $QTDIR/tools/qvfb<p><h3>Using the virtual framebuffer</h3><ol> <li>Make sure QT_NO_QWS_VFB in $QTDIR/src/tools/qconfig.h is not defined and compile the Qt/Embedded library.<li>Compile qvfb as a <i>normal Qt/X11 application</i> and run it - do not compile it as a Qt/Embedded application.<li>Start a Qt/Embedded master application (i.e. construct QApplication with QApplication::GuiServer flag or use the -qws command line parameter). You will need to specify to the server that you wish to use the virtual framebuffer driver, e.g.:<p> <tt>widgets -qws -display QVFb:0</tt><li>You may prefer to set the QWS_DISPLAY environment variable to be <tt>QVFb:0</tt>.</ol><p>qvfb supports the following command line options:<p><table><tr><td><tt>-width width</tt></td> <td>the width of the virtual framebuffer (default: 240).</td></tr><tr><td><tt>-height height</tt></td> <td>the height of the virtual framebuffer (default: 320).</td></tr><tr><td><tt>-depth depth</tt></td> <td>the depth of the virtual framebuffer (1, 4, 8 or 32, default: 8).</td></tr><tr><td><tt>-nocursor</tt></td> <td>do not display the X11 cursor in the framebuffer window.</td></tr><tr><td><tt>-qwsdisplay :id</tt></td> <td>the Qt/Embedded display id to provide (default :0).</td></tr></table><p><h3>Virtual Framebuffer Design</h3><p>The virtual framebuffer emulates a framebuffer using a shared memory region(the virtual frame buffer) and a utility to display the framebuffer in awindow (qvfb). The regions of the display that have changed are updatedperiodically, so you will see discrete snapshots of the framebuffer ratherthan each individual drawing operation. For this reason drawing problemssuch as flickering may not be apparent until the program is run using a realframebuffer.<p>The target refresh rate can be set via the View->Refresh Rate menu item.This will cause qvfb to check for updated regions more quickly. The rateis a target only. If little drawing is being done, the framebuffer willnot show any updates between drawing events. If an application is displayingan animation the updates will be frequent, and the application andqvfb will compete for processor time.<p>Mouse and keyboard events are passed to the Qt/Embedded master process vianamed pipes.<p>The virtual framebuffer is a development tool only. No security issues havebeen considered in the virtual framebuffer design. It should not be usedin a production environment and QT_NO_QWS_VFB should always be definedin production libraries.<p><address><hr><div align="center"><table width="100%" cellspacing="0" border="0"><tr><td>Copyright ⌨️ 快捷键说明
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