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svgalib.faq(7)                Svgalib User Manual               svgalib.faq(7)



NAME
       svgalib.faq - frequently asked questions about svgalib


INTRODUCTION
       I  (Matan  Ziv-Av),  added/changed some of the answers in this file, so
       some answers are mine, and some are Michael's.

       List of (recently) frequently asked questions about svgalib. Esp. about
       it's status and future. Please note that as of now all answers are just
       written by me, Michael Weller <eowmobATexp-math.de>. I'd  like
       this to change. So email your suggestion (best of all: question and the
       answer).

       Also, most questions deal with the status and future and my ideas about
       it.  Necessarily  they  contain my own private opinions on this. People
       may disagree and I'm sure I don't have the best ideas about it  or  may
       even  be  completely  wrong. I don't want to force anyone to agree with
       me.

       Also, I was asked about MY opinions, so I'm just presenting them here.


CONTENTS
       Q 1)   I want to write some svgalib application. Where is the  documen-
              tation?

       Q 2)   My board is not supported. What now?

       Q 3)   I get:

              You must be the owner of the current console to use svgalib.
              Not  running  in  a graphics capable console, and unable to find
              one.

              However, though logged in not directly from the linux console, I
              am the owner of the console.

       Q 4)   Is svgalib dead?

       Q 5)   There are so many Xfree drivers, why not just use them.

       Q 6)   Why not just use the VGA BIOS?.

       Q 7)   What about GGI?

       Q 8)   Why not just use X11?

       Q 9)   Now, again, what about the future of svgalib?

       Q 10)  Ok,  just  for  completeness,  what are your plans about svgalib
              anyway?

       Q 11)  Nice plan. But will it become true?

THE QUESTIONS
   Q 1)
       I want to write some svgalib application. Where is the documentation?


   A a)
       Well, did you really look at everything? The 0-README file in  the  top
       level  directory  contains  all function prototypes and explanations on
       how to call them.

       Yes, the documentation is short and/or confusing. Sorry, English is not
       my  native  tongue.  Many people complain and want to write some better
       documentation. You are welcome to do so! However,  up  to  now,  either
       people  found the documentation sufficient once they looked at the cor-
       rect files or they just gave up. At least, I  never  heard  from  these
       people again.

       Also, svgalib comes with source. If in doubt: read it.

       Finally:  Linux  distributions  include svgalib, but not the source and
       README's (or hide them so good noone finds them). Well, no problem, get
       full svgalib source, demos, readme's from svgalib-*.tar.gz on any Linux
       FTP server in your vicinity. Even if you don't dare to install or  com-
       pile it, it contains the readme's.

       Oh  yes,  there are some simple demos in the demos/ subdir. They should
       get you started.

       When someone writes man(1) manual  pages,  a  distribution  might  just
       install them. Please do not complain, write them, mail them to me.


   A b)
       Finally,  I,  Michael  Weller wrote the manpages. Looking at svgalib(7)
       should get you started. Additions and corrections are still welcome, of
       course.


   Q 2)
       My board is not supported. What now?


   A)
       Simple:


       a)     Contact  the  maintainers  (see other README's) and check out if
              someone is working on a driver.


       b)     If so, contact them if you like and announce you'd be willing to
              test things or even help coding.


       c)     If  not,  write  a  driver. Get as many docs on your card as you
              can, then read and understand the internals  of  svgalib  (again
              read the README's carefully!).

       Please  understand that this is a free project. I will not go and buy a
       similar card and write a driver for you. I already  wrote  support  for
       the  hardware  I  have!  I just do this as a hobby. Because I don't get
       paid for this I can not just buy card & docu and spend much  much  time
       supporting whatever graphics card on earth exists.

       Also read below on the future of svgalib.

       If you don't feel able to write a driver for whatever reason, please do
       not complain if other people don't do it for you (because you  are  not
       better than they are).


   Q 3)
       I get:

       You must be the owner of the current console to use svgalib.
       Not running in a graphics capable console, and unable to find one.

       However, though logged in not directly from the linux console, I am the
       owner of the console.


   A)
       Alas, some programs use their suid root privilege  and  become  a  full
       root  owned process. svgalib thinks they are run by root which does not
       own the current console.  Defining ROOT_VC_SHORTCUT in Makefile.cfg and
       recompiling  will  allow svgalib to allocate a new VC. However, it will
       allow any person which is able to exec that program to start  in  on  a
       new  console.  Even if not logged in from the console at all. Thus, for
       security, you need to explicitly enable that root feature.


   Q 4)
       Is svgalib dead?


   A)
       This question comes up frequently esp. in recent times.

       The answer is, of course, no.


   Q 5)
       There are so many Xfree drivers, why not just use them.


   A)
       Well, actually much of the code in there is actually  already  used  by
       svgalib.  Xfree  coders worked on svgalib and vice versa. But honestly,
       do not expect that a driver from Xfree can just be  used  for  svgalib.
       The  internal  structures  of  Xfree and svgalib (and GGI) are just too
       different. As a source of knowledge and for one or  the  other  subrou-
       tine, the Xfree sources are invaluable however.


   Q 6)
       Why not just use the VGA BIOS?.


   A)
       Actually,  we  do.  There  is  now,  thanks  to Josh Vanderhoof, a VESA
       driver.  The VESA driver does not work on all  cards,  even  though  it
       should.   It  does  not  even work on all cards where vbetest works. If
       vbetest does not work it means the bios writers assumed it would always
       run  in  DOS,  and  used tricks (for delay, etc.) that can't work under
       Linux. If vbetest works, but the VESA driver does not, I (Matan Ziv-Av)
       believe it is due to the following reason: The driver use VESA function
       4 (save/restore video state). This function can't be used in a  single-
       tasking  environment  (DOS)  and  as  such, some bios writers failed to
       implement it properly, and all the tests  (which  are  run  under  DOS)
       failed to discover this.

       The VESA driver does work with many cards though.


   Q 7)
       What about GGI?


   A)
       Yes,  GGI.  Another long story. At first: Yes, I like the idea of an in
       kernel graphics driver. I like it very much. And, yes, this  is  a  bit
       weird  because  I am the svgalib maintainer and a working GGI will make
       svgalib obsolete. Again, I already said above: I did not invent svgalib
       nor  do I promote it as the solution (now compare this to GGI). It just
       does what it does and works for me and some other people.

       I liked this idea so much, I even started coding a frame buffer  device
       once.  After  a  short  time,  other people came out with the GGI idea.
       Right from their beginning they claimed to be the only source  of  wis-
       dom.  I  tried  to join our efforts, but failed. In general we have the
       same goals (read the GGI project pages for that).

       Anyhow, at that time a flame war started. I don't really  know  why.  I
       don't see I did anything else than offering my opinions, work and expe-
       rience. But that should be judged by others.

       Well, after some time I stopped bothering  them.  I  was  satisfied  to
       learn  later  though that they actually came up with some conclusions I
       proposed first but weeks or months later. But let  us  leave  the  past
       alone.


       When  intending  to  contribute to svgalib, you should think about what
       you really want. I don't see that GGI is becoming available  soon.  GGI
       people  told me the opposite again and again, ok, I still don't see it.
       Still out of a sudden, everything might be GGI infested, so  you  might
       consider contributing to GGI instead.

       With  svgalib  you might be able to use your fruits earlier. And anyone
       (with supported hardware) can just use  it  right  away  without  rein-
       stalling  kernel/X11  what else (maybe being unable to use something he
       did before).


   Q 8)
       Why not just use X11?

       Yes, this is what many people say. This is the common Unix  way  to  do
       it.  X does it.

       But X has some drawbacks:


       i)     It  uses  many  resources. Admittedly this is becoming of lesser
              importance now, where you can run a sensible X11 Linux system on
              8MB  (16  MB  for heaven like performance) which is the absolute
              minimum to get a simple text editor running under M$ windows.

              Still, an advantage of Linux is the ability to use old  hardware
              for    mission    critical    background   jobs   on   the   net
              (servers/routers/firewalls) on low price or otherwise even unus-
              able hardware.


       ii)    X  has  a  nice  API with draw commands for any kind of 'command
              oriented' screen output. I mean with that: Select a color,  draw
              a line, polygon, etc.

              This imposes a bunch of overhead. If you just want access to the
              screen memory, it slows things down as hell. If you want just to
              use above's draw commands, it is ok!


       iii)   One  can  now  circumvent the API restrictions by getting direct
              screen access using a special Xfree extension.  Basically  Xfree
              just setups the screen and gives you shared memory access to the
              screen memory. IMHO, this is not much different from the  shared
              memory  X11 extension by MIT (which is probably why it was added
              so easily).  Still it needs quite some overhead, at  least  when
              the card does not allow for a linear frame buffer.

              However,  you cannot change screen modes and rez as easily. This
              is IMHO THE drawback of X. For a picture viewer,  you  want  256
              color high/true color modes on a per picture basis (also, insert
              any other application you like: movie viewers, a special game, a
              drawing  program).  Also, you want a small picture use a low rez
              s.t. it does not appear as a thumbnail, maybe  use  a  high  rez
              mode  for a huge picture which you don't want to use on a perma-
              nent basis because it flickers like hell (and you don't want  to
              use a panning virtual desktop too, I hated them at best).

              This latter restriction can of course be circumvented by enlarg-
              ing the picture. But this will need  much  time  for  a  picture
              viewer  already  and certainly too much for smooth video or game
              animations.


       iv)    Finally, the problem how X11 itself accesses the screen  is  not
              solved.   Security is usually no concern because X11 does it, is
              a trusted executable and a firewall between applications and the
              hardware.

              Alas, there might be security holes, also the stability and per-
              formance issues (IRQ driven accelerator queue, CPU  support  for
              VGA memory paging) still exist, though one can expect an Xserver
              to be a generally well coded application.


   Q 9)
       Now, again, what about the future of svgalib?

       For console graphics, svgalib is still the only solution for most  peo-
       ple, and as such it should go on for a while. Compared to the othe con-
       sole graphics options (kgi  and  kernel  fb  device),  writing  svgalib
       driver  is  the  simplest  (at least, this is my experience), and so it
       makes sense to believe that svgalib will work on all cards where  there
       is someone interested enough in that support.


   Q 10)
       Ok, just for completeness, what are your plans about svgalib anyway?

       First,  make  svgalib cooperate nicely with kernel fb device. Then (and
       it should be very similar) make svgalib work on a secondary vga card.

       A rewrite of the code for memory handling and virtual console  handling
       is  necessary  for the previous goals, but is also necessary in itself,
       and so will be done also.

       I do intend to maintain complete binary compatibility,  so  that  older
       programs will go on working.

       As  internal  changes are made, the drivers have to be changed as well.
       For some of the older drivers (ali, ark,  ati,  et3000,  et4000,  gvga,
       oak),  I no longer get any reports, so I don't know if they still work.
       Some features are also lost, for example, linear frame buffer  on  non-
       PCI  cards.  This  should not be a very big problem, as users with such
       cards can go on using 1.3.1, as most changes  are  not  applicable  for
       older machines.


SEE ALSO
       svgalib(7), libvga.config(5).


AUTHOR
       This file was written by Michael Weller <eowmobATexp-math.de>,
       And later changed by Matan Ziv-Av.



Svgalib 1.4.1                     10 Jun 1999                   svgalib.faq(7)