Xvfb is a virtual X server that uses a plain file as framebuffer instead of a
physical screen. The 'xvfb' glue program makes an Xvfb session available to the
Linux version of Genode such that both native Genode programs and X clients can
run seamlessly integrated in one Nitpicker session. Using the 'xvfb' glue
program contained in this directory.  Because Xvfb is executed as Nitpicker
client, it is possible to integrate multiple instances of Xvfb into the same
Nitpicker session.


Preconditions for compiling
---------------------------

The 'xvfb' glue program is a hybrid process using the Genode interfaces and the
Linux interfaces directly. It tracks dirty screen regions using the X damage
extension and injects user-input events into the X server using the X test
extension. So you need the development package of both extensions to compile
it. The Debian package for the X damage extension is called 'libxdamage-dev'.
The X test extension is normally installed by default.  Furthermore you need to
enhance your 'SPECS' declaration in your
'<builddir>/etc/specs.conf' file as follows:

! SPECS += x11 xdamage xtest


Usage
-----

First start Xvfb using the following command-line arguments:

! Xvfb :1 -fbdir /tmp -screen 0 1024x768x16

While Xvfb is running, '/tmp/Xvfb_screen0' will contain the content of the X
server's frame buffer. This file must be specified for the 'xvfb' declaration
in the config file. In addition, the display of X server instance must be
declared via the 'display' tag. For example:

! <config>
!   <display>:1</display>
!   <xvfb>/tmp/Xvfb_screen0</xvfb>
! </config>


Known Limitations
-----------------

* With the current version, some keycodes are not mapped correctly.
* The screen mode of Nitpicker and the Xvfb session must be the same.
  Only modes with 16bit color depth are supported.
