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111 lines
4.9 KiB
111 lines
4.9 KiB
14 years ago
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<!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/doc/qvfb.doc:36 -->
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<title>Qt/Embedded Virtual Framebuffer</title>
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<font color="#004faf">All Classes</font></a>
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<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>Qt/Embedded Virtual Framebuffer</h1>
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<p> The virtual framebuffer allows Qt/Embedded programs to be developed on
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a desktop machine, without switching between consoles and X11.
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<p> The virtual framebuffer is located in <tt>$QTDIR/tools/qvfb</tt>.
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<p> <h2> Using the Virtual Framebuffer
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</h2>
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<a name="1"></a><p> <ol type=1>
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<li> Configure Qt/Embedded with the <tt>-qvfb</tt> argument and compile the library:
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<pre>
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./configure -qvfb
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make
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</pre>
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<li> Compile <tt>qvfb</tt> as a normal Qt/X11 application and run it. Do <em>not</em>
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compile it as a Qt/Embedded application.
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<li> Start a Qt/Embedded master application (i.e., construct
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<a href="qapplication.html">QApplication</a> with the QApplication::GuiServer flag or use the <tt>-qws</tt> command line parameter). You can specify to the server that
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you wish to use the virtual framebuffer driver, e.g.:
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<pre>
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masterapp -qws -display QVFb:0
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</pre>
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<li> Qt/Embedded will autodetect qvfb, so you can omit the <tt>-display</tt>
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command line parameter if you know that qvfb is running, and that
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the Qt/Embedded library supports qvfb. (If this is not the case,
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Qt/Embedded will write to the real framebuffer, and your X11
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display will be corrupted.)
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<p> </ol>
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<p> <tt>qvfb</tt> supports the following command line options:
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<p> <center><table cellpadding="4" cellspacing="2" border="0">
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<tr bgcolor="#a2c511"> <th valign="top">Option <th valign="top">Meaning
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<tr bgcolor="#f0f0f0">
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<td valign="top"><tt>-width</tt> <em>width</em>
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<td valign="top">the width of the virtual framebuffer (default: 240).
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<tr bgcolor="#d0d0d0">
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<td valign="top"><tt>-height</tt> <em>height</em>
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<td valign="top">the height of the virtual framebuffer (default: 320).
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<tr bgcolor="#f0f0f0">
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<td valign="top"><tt>-depth</tt> <em>depth</em>
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<td valign="top">the depth of the virtual framebuffer (1, 8 or 32; default: 8).
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<tr bgcolor="#d0d0d0">
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<td valign="top"><tt>-nocursor</tt>
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<td valign="top">do not display the X11 cursor in the framebuffer window.
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<tr bgcolor="#f0f0f0">
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<td valign="top"><tt>-qwsdisplay</tt> <em>:id</em>
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<td valign="top">the Qt/Embedded display id to provide (default: :0).
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</table></center>
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<p> <h2> Virtual Framebuffer Design
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</h2>
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<a name="2"></a><p> The virtual framebuffer emulates a framebuffer using a shared memory region
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(the virtual frame buffer) and a utility to display the framebuffer in a
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window (<tt>qvfb</tt>). The regions of the display that have changed are updated
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periodically, so you will see discrete snapshots of the framebuffer rather
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than each individual drawing operation. For this reason drawing problems
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such as flickering may not be apparent until the program is run using a real
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framebuffer.
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<p> The target refresh rate can be set via the <b>View|Refresh Rate</b>
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menu item. This will cause <tt>qvfb</tt> to check for updated regions more
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frequently. The rate is a target only. If little drawing is being
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done, the framebuffer will not show any updates between drawing
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events. If an application is displaying an animation the updates will
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be frequent, then the application and <tt>qvfb</tt> will compete for
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processor time.
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<p> Mouse and keyboard events are passed to the Qt/Embedded master process via
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named pipes.
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<p> The virtual framebuffer is a development tool only. No security issues have
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been considered in the virtual framebuffer design. It should be avoided
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in a production environment; do not configure production libraries with <tt>-qvfb</tt>.
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<p>
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<p><address><hr><div align=center>
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<td>Copyright © 2007
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<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
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<td align=right><div align=right>Qt 3.3.8</div>
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</table></div></address></body>
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