NAME

Xvfb - virtual framebuffer X server for X Version 11

SYNOPSIS

Xvfb [ option ] ...

DESCRIPTION

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 fb 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 _X_v_f_b, including testing clients against unusual depths and screen configurations, doing batch processing with _X_v_f_b 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.

OPTIONS

In addition to the normal server options described in the _X_s_e_r_v_e_r_(_1_) manual page, _X_v_f_b accepts the following command line switches:

-screen _s_c_r_e_e_n_n_u_m _W_x_H_x_D
This option creates screen _s_c_r_e_e_n_n_u_m 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 _l_i_s_t_-_o_f_-_d_e_p_t_h_s
This option specifies a list of pixmap depths that the server should support in addition to the depths implied by the supported screens. _l_i_s_t_-_o_f_-_d_e_p_t_h_s is a space-separated list of integers that can have values from 1 to 32.
-fbdir _f_r_a_m_e_b_u_f_f_e_r_-_d_i_r_e_c_t_o_r_y
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 --sshhmmeemm nor --ffbbddiirr 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 fb code.
-blackpixel _p_i_x_e_l_-_v_a_l_u_e, -whitepixel _p_i_x_e_l_-_v_a_l_u_e
These options specify the black and white pixel values the server should use.

FILES

The following files are created if the -fbdir option is given.
_f_r_a_m_e_b_u_f_f_e_r_-_d_i_r_e_c_t_o_r_y/Xvfb_screen
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.

EXAMPLES

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 /var/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 /var/tmp for the framebuffer.
xwud -in /var/tmp/Xvfb_screen0
Displays screen 0 of the server started by the preceding example.

SEE ALSO

X(7), Xserver(1), xwd(1), xwud(1), XWDFile.h

AUTHORS

David P. Wiggins, The Open Group, Inc.