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| 32 | <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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| 33 |
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| 34 |
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| 35 | <p> The virtual framebuffer allows Qt/Embedded programs to be developed on
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| 36 | a desktop machine, without switching between consoles and X11.
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| 37 | <p> The virtual framebuffer is located in <tt>$QTDIR/tools/qvfb</tt>.
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| 38 | <p> <h2> Using the Virtual Framebuffer
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| 39 | </h2>
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| 40 | <a name="1"></a><p> <ol type=1>
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| 41 | <li> Configure Qt/Embedded with the <tt>-qvfb</tt> argument and compile the library:
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| 42 | <pre>
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| 43 | ./configure -qvfb
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| 44 | make
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| 45 | </pre>
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| 46 |
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| 47 | <li> Compile <tt>qvfb</tt> as a normal Qt/X11 application and run it. Do <em>not</em>
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| 48 | compile it as a Qt/Embedded application.
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| 49 | <li> Start a Qt/Embedded master application (i.e., construct
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| 50 | <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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| 51 | you wish to use the virtual framebuffer driver, e.g.:
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| 52 | <pre>
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| 53 | masterapp -qws -display QVFb:0
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| 54 | </pre>
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| 55 |
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| 56 | <li> Qt/Embedded will autodetect qvfb, so you can omit the <tt>-display</tt>
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| 57 | command line parameter if you know that qvfb is running, and that
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| 58 | the Qt/Embedded library supports qvfb. (If this is not the case,
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| 59 | Qt/Embedded will write to the real framebuffer, and your X11
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| 60 | display will be corrupted.)
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| 61 | <p> </ol>
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| 62 | <p> <tt>qvfb</tt> supports the following command line options:
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| 63 | <p> <center><table cellpadding="4" cellspacing="2" border="0">
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| 64 | <tr bgcolor="#a2c511"> <th valign="top">Option <th valign="top">Meaning
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| 65 | <tr bgcolor="#f0f0f0">
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| 66 | <td valign="top"><tt>-width</tt> <em>width</em>
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| 67 | <td valign="top">the width of the virtual framebuffer (default: 240).
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| 68 | <tr bgcolor="#d0d0d0">
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| 69 | <td valign="top"><tt>-height</tt> <em>height</em>
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| 70 | <td valign="top">the height of the virtual framebuffer (default: 320).
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| 71 | <tr bgcolor="#f0f0f0">
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| 72 | <td valign="top"><tt>-depth</tt> <em>depth</em>
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| 73 | <td valign="top">the depth of the virtual framebuffer (1, 8 or 32; default: 8).
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| 74 | <tr bgcolor="#d0d0d0">
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| 75 | <td valign="top"><tt>-nocursor</tt>
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| 76 | <td valign="top">do not display the X11 cursor in the framebuffer window.
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| 77 | <tr bgcolor="#f0f0f0">
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| 78 | <td valign="top"><tt>-qwsdisplay</tt> <em>:id</em>
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| 79 | <td valign="top">the Qt/Embedded display id to provide (default: :0).
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| 80 | </table></center>
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| 81 | <p> <h2> Virtual Framebuffer Design
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| 82 | </h2>
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| 83 | <a name="2"></a><p> The virtual framebuffer emulates a framebuffer using a shared memory region
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| 84 | (the virtual frame buffer) and a utility to display the framebuffer in a
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| 85 | window (<tt>qvfb</tt>). The regions of the display that have changed are updated
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| 86 | periodically, so you will see discrete snapshots of the framebuffer rather
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| 87 | than each individual drawing operation. For this reason drawing problems
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| 88 | such as flickering may not be apparent until the program is run using a real
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| 89 | framebuffer.
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| 90 | <p> The target refresh rate can be set via the <b>View|Refresh Rate</b>
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| 91 | menu item. This will cause <tt>qvfb</tt> to check for updated regions more
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| 92 | frequently. The rate is a target only. If little drawing is being
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| 93 | done, the framebuffer will not show any updates between drawing
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| 94 | events. If an application is displaying an animation the updates will
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| 95 | be frequent, then the application and <tt>qvfb</tt> will compete for
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| 96 | processor time.
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| 97 | <p> Mouse and keyboard events are passed to the Qt/Embedded master process via
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| 98 | named pipes.
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| 99 | <p> The virtual framebuffer is a development tool only. No security issues have
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| 100 | been considered in the virtual framebuffer design. It should be avoided
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| 101 | in a production environment; do not configure production libraries with <tt>-qvfb</tt>.
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| 102 | <p>
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| 103 | <!-- eof -->
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| 108 | <td align=right><div align=right>Qt 3.3.8</div>
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