[Sussex] DirectFB

[Geoff Teale]

SLUGS,

At the weekend I got DirectFB up and running with a rootless X server
sitting on it (effectively putting an X compatibility layer around
framebuffer rendered graphics).

On Gentoo this was as simple as:

emerge dev-libs/directfb x11-misc/xdirectfb

(Nice :) )

All hardware detection is done automagically so there is no need to go
through any config to start the thing.  Whaddya know, startxdfb turn the
screen blue and brings up a mouse pointer.  After a unusually lengthy delay
a Gnome2 splash screen appeared, seconds later it crashed.

Ho hum thought I.  A quick nose on the web told me that GTK+2, and Qt3
aren't supported under DirectFB, but earlier version are.  After about 15
minutes of scanning the directories for setup files I worked out that
X-DirectFB was using the $XSESSION variable to determine which window
manager to load.   In Gentoo this variable is set in /etc/rc.conf, I vim'd
that file and seconds later I found myself in a fully operational fluxbox
(my favourite window manager by a mile) environment running directly in the
framebuffer.  Another quick vim on /etc/fb.modes and I had it running at a
respectable 1280x1024 at 75hz

So what did this all achieve... well, not a lot really.  I put in about 30
minutes work to free up a few CPU cycles and about 60MB of memory.  

For this gain there is an equal tradeoff - DirectFB doesn't allow you to
swap terms with ctrl-alt-Fn or shift resolution with
ctrl-alt-keypad_plus/minus.  More importantly a lot of software won't run
under DirectFB's rootless X server, although most non-KDE software of note
seems to run fine.  Gnome 1.4, Fluxbox, Gimp, OpenOffice.org, Mozilla, Dillo
etc. all run well and in OpenOffice especially you notice a significant
speed increase.

The real clincher on this deal though is the ability to vary the
transparancy of any window on the fly clicking on it's handle, holding down
the Caps-lock key and scrolling the wheel on your wheelmouse.  This is
seriously impressive and is a good mechanism for saying "Anything they Mac
stand at LINUX Expo can do on OS X 10.2 I can do on my LINUX box too!".

-- 
GJT
geoff.teale at claybrook.co.uk




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