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Xvfb - virtual framebuffer X server for X Version
11
Xvfb [ option ] ...
Xvfb is an X server that can run
on machines with no display hardware and no physical input devices. It
emulates a dumb framebuffer using virtual memory.
The primary use of this
server was intended to be server testing. The mfb or cfb code for any depth
can be exercised with this server without the need for real hardware that
supports the desired depths. The X community has found many other novel
uses for Xvfb, including testing clients against unusual depths and screen
configurations, doing batch processing with Xvfb as a background rendering
engine, load testing, as an aid to porting the X server to a new platform,
and providing an unobtrusive way to run applications that don't really need
an X server but insist on having one anyway.
To build Xvfb, put
the following in your host.def and remake.
In addition to the normal server options described in the Xserver(1)
manual page, Xvfb accepts the following command line switches:
- -screen screennum
WxHxD
- This option creates screen screennum and sets its width, height,
and depth to W, H, and D respectively. By default, only screen 0 exists
and has the dimensions 1280x1024x8.
- -pixdepths list-of-depths
- This option specifies
a list of pixmap depths that the server should support in addition to the
depths implied by the supported screens. list-of-depths is a space-separated
list of integers that can have values from 1 to 32.
- -fbdir framebuffer-directory
- This option specifies the directory in which the memory mapped files containing
the framebuffer memory should be created. See FILES. This option only exists
on machines that have the mmap and msync system calls.
- -shmem
- This option
specifies that the framebuffer should be put in shared memory. The shared
memory ID for each screen will be printed by the server. The shared memory
is in xwd format. This option only exists on machines that support the System
V shared memory interface.
If neither -shmem nor -fbdir is specified, the
framebuffer memory will be allocated with malloc().
- -linebias n
- This option
specifies how to adjust the pixelization of thin lines. The value n is a
bitmask of octants in which to prefer an axial step when the Bresenham
error term is exactly zero. See the file Xserver/mi/miline.h for more information.
This option is probably only useful to server developers to experiment
with the range of line pixelization possible with the cfb and mfb code.
- -blackpixel pixel-value, -whitepixel pixel-value
- These options specify the
black and white pixel values the server should use.
The following files
are created if the -fbdir option is given.
- framebuffer-directory/Xvfb_screen<n>
- Memory mapped file containing screen n's framebuffer memory, one file per
screen. The file is in xwd format. Thus, taking a full-screen snapshot can
be done with a file copy command, and the resulting snapshot will even
contain the cursor image.
- Xvfb :1 -screen 0 1600x1200x32
- The server
will listen for connections as server number 1, and screen 0 will be depth
32 1600x1200.
- Xvfb :1 -screen 1 1600x1200x16
- The server will listen for connections
as server number 1, will have the default screen configuration (one screen,
1280x1024x8), and screen 1 will be depth 16 1600x1200.
- Xvfb -pixdepths 3
27 -fbdir /usr/tmp
- The server will listen for connections as server number
0, will have the default screen configuration (one screen, 1280x1024x8),
will also support pixmap depths of 3 and 27, and will use memory mapped
files in /usr/tmp for the framebuffer.
- xwud -in /usr/tmp/Xvfb_screen0
- Displays
screen 0 of the server started by the preceding example.
X(7)
, Xserver(1)
,
xwd(1)
, xwud(1)
, XWDFile.h
David P. Wiggins, The Open Group, Inc.
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