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235 lines
7.6 KiB
235 lines
7.6 KiB
14 years ago
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/doc/framebuffer-howto.doc:36 -->
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>Enabling the Linux Framebuffer</title>
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<tr bgcolor="#E5E5E5">
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<td valign=center>
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<a href="index.html">
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<font color="#004faf">Home</font></a>
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<font color="#004faf">All Classes</font></a>
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<font color="#004faf">Main Classes</font></a>
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<font color="#004faf">Annotated</font></a>
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<font color="#004faf">Grouped Classes</font></a>
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<font color="#004faf">Functions</font></a>
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</td>
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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>Enabling the Linux Framebuffer</h1>
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<p> This is only a short guide.
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See <a href="file:/usr/src/linux/README">/usr/src/linux/README</a> and
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<a href="file:/usr/src/linux/Documentation/fb/">/usr/src/linux/Documentation/fb/</a> for detailed information.
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There is also a detailed explanation at
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<a href="http://www.linuxdoc.org/HOWTO/Framebuffer-HOWTO.html">http://www.linuxdoc.org/HOWTO/Framebuffer-HOWTO.html</a>.
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<p> <ol type=1>
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<li> Make sure that you have the Linux kernel source code in
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<a href="file:/usr/src/linux/">/usr/src/linux/</a>.
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<p> <li> Log in as root and <tt>cd</tt> <tt>/usr/src/linux</tt>
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<p> <li> Configure the kernel:
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<p> Run:
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<pre>
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make menuconfig
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</pre>
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<p> Select "Code maturity level options" and set "Prompt for
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development and/or incomplete code/drivers".
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<p> Then select "Console drivers" and set "Support for frame buffer
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devices" to built-in (even if it says EXPERIMENTAL). Then configure
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the driver. Most modern graphics cards can use the "VESA VGA
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graphics console"; use that or a driver that specifically matches
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your video card. Finally, enable "Advanced low level driver options"
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and make sure that 16 and 32 bpp packed pixel support are enabled.
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<p> When you are finished, chose exit and save.
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<p> <li> Compile the kernel
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<p> First do:
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<pre>
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make dep
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</pre>
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then:
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<pre>
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make bzImage
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</pre>
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<p> The new kernel should now be in arch/i386/boot/bzImage.
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<p> <li> Copy the kernel to the boot directory:
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<pre>
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cp arch/i386/boot/bzImage /boot/linux.vesafb
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</pre>
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<p> <li> Edit /etc/lilo.conf.
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<p> <b>Warning:</b> Keep a backup of <a href="file:/etc/lilo.conf">/etc/lilo.conf</a>, and have a rescue disk
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available. If you make a mistake, the machine may not boot.
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<p> The file <a href="file:/etc/lilo.conf">/etc/lilo.conf</a> specifies how the system boots. The
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precise contents of the file varies from system to system. Here is
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an example:
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<pre>
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# LILO configuration file
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boot = /dev/hda3
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delay = 30
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image = /boot/vmlinuz
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root = /dev/hda3
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label = Linux
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read-only # Non-UMSDOS filesystems should be mounted read-only for checking
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other=/dev/hda1
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label=nt
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table=/dev/hda
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</pre>
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<p> Make a new "image" section that is a copy of the first one, but with
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<pre>
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image = /boot/linux.vesafb
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</pre>
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and
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<pre>
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label = Linux-vesafb
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</pre>
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Place it just above the first image section.
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<p> Add a line before the image section saying <tt>vga = 791</tt>. (Meaning
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1024x768, 16 bpp.)
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<p> With the above example, lilo.conf would now be:
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<pre>
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# LILO configuration file
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boot = /dev/hda3
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delay = 30
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vga = 791
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image = /boot/linux.vesafb
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root = /dev/hda3
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label = Linux-vesafb
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read-only # Non-UMSDOS filesystems should be mounted read-only for checking
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image = /boot/vmlinuz
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root = /dev/hda3
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label = Linux
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read-only # Non-UMSDOS filesystems should be mounted read-only for checking
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other=/dev/hda1
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label=nt
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table=/dev/hda
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</pre>
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<p> Do not change any existing lines in the file; just add new ones.
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<p> <li> To make the new changes take effect, run the lilo program:
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<pre>
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lilo
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</pre>
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<p> <li> Reboot the system. You should now see a penguin logo while the
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system is booting.
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(Or more than one on a multi-processor machine.)
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<p> <li> If it does not boot properly with the new kernel, you can boot with
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the old kernel by entering the label of the old image section at
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the LILO prompt. (with the example lilo.conf file, the old label is
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Linux.)
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<p> If that does not work (probably because of an error in lilo.conf),
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boot the machine using your rescue disk, restore <a href="file:/etc/lilo.conf">/etc/lilo.conf</a> from backup and re-run lilo.
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<p> <li> Testing: Here's a short program that opens the frame buffer and draws a
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gradient-filled red square.
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<p> <pre>
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#include <unistd.h>
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#include <stdio.h>
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#include <fcntl.h>
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#include <linux/fb.h>
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#include <sys/mman.h>
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int main()
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{
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int fbfd = 0;
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struct fb_var_screeninfo vinfo;
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struct fb_fix_screeninfo finfo;
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long int screensize = 0;
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char *fbp = 0;
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int x = 0, y = 0;
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long int location = 0;
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// Open the file for reading and writing
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fbfd = open("/dev/fb0", O_RDWR);
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if (!fbfd) {
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printf("Error: cannot open framebuffer device.\n");
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exit(1);
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}
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printf("The framebuffer device was opened successfully.\n");
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// Get fixed screen information
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if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) {
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printf("Error reading fixed information.\n");
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exit(2);
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}
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// Get variable screen information
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if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) {
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printf("Error reading variable information.\n");
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exit(3);
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}
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printf("%dx%d, %dbpp\n", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel );
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// Figure out the size of the screen in bytes
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screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;
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// Map the device to memory
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fbp = (char *)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED,
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fbfd, 0);
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if ((int)fbp == -1) {
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printf("Error: failed to map framebuffer device to memory.\n");
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exit(4);
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}
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printf("The framebuffer device was mapped to memory successfully.\n");
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x = 100; y = 100; // Where we are going to put the pixel
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// Figure out where in memory to put the pixel
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for ( y = 100; y < 300; y++ )
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for ( x = 100; x < 300; x++ ) {
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location = (x+vinfo.xoffset) * (vinfo.bits_per_pixel/8) +
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(y+vinfo.yoffset) * finfo.line_length;
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if ( vinfo.bits_per_pixel == 32 ) {
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*(fbp + location) = 100; // Some blue
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*(fbp + location + 1) = 15+(x-100)/2; // A little green
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*(fbp + location + 2) = 200-(y-100)/5; // A lot of red
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*(fbp + location + 3) = 0; // No transparency
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} else { //assume 16bpp
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int b = 10;
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int g = (x-100)/6; // A little green
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int r = 31-(y-100)/16; // A lot of red
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unsigned short int t = r<<11 | g << 5 | b;
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*((unsigned short int*)(fbp + location)) = t;
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}
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}
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munmap(fbp, screensize);
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close(fbfd);
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return 0;
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}
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</pre>
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</ol>
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<p>
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<!-- eof -->
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<p><address><hr><div align=center>
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<table width=100% cellspacing=0 border=0><tr>
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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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</html>
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