Updated: XDM, GDM, KDM, WDM shootout :-)

[Osamu Aoki <osamu@debian.org>]

Update reflecting people's comments:

On Sun, Sep 26, 2004 at 01:11:32AM +0200, Osamu Aoki wrote:

The result of comparison is (+ is yes, - is no):

       1) Use of     2) Choice 3) Choice    4) Non ~/.xsession  5) User
          Xsession.d    of WM     of locale    custom           List
                                  by user      startup script
  XDM     ++            --        --           -                -
  GDM     +             +         ++           only gnome       ++
  KDM     ++            +         +(restart)   -                ++
  WDM     ++            +-        --           -                -

(KDM listing is anticipated situation for next unstable version.)

Conclusion:

  In short, for most cases GDM seems to be the most featureful but KDM
  and WDM offers similar functionality.  Linked library is the major
  difference.  They all offer custom start but that is with one WM
  specified in ~/.xsession .  ~/.xsession mode is presented as "Default
  System session" in GDM and confusing.  "default" mode is for different
  thing. 

>   Also, I realized as CJK user that there is no standard way to set up
>   start up script under menu chosen WM.  This is major problem for CJK
>   user who needs to set up keyboard input set up (sometimes daemon).  I
>   hear that Mandrake uses ~/.i18n and SUSE uses ~/.xim.  There is no
>   hook script in /etc/X11/Xsession.d/ to read this kind of files.
>   Something needs to be done.

    This start up script concern is basically for CJK user.  No wonder
    others do not feel so bothered and no comments made on this most
    important thing.

> Here, the verbose meaning of above comparison are:
>   1) Use of /etc/X11/Xsession.d/
>   2) Choice of session/window manager by menu
>   3) Choice of locales by menu
>   4) Customizable start up like ~/.xsession
>   5) User list (if customized, default can be on/off)
> ======================================================================
> Detailed review results.
> 
> * XDM: Simplest, light and works.
> 
>   This is reference DM.  Not much menu as expected.  
> 
> * GDM: The best of all and flashy graphics (even for KDE).
> 
>   Its start up script does not call /etc/X11/Xsession, but practically
>   the same code with GDM specific enhancement is executed to run scripts
>   in /etc/X11/Xsession.d/.
>   
>   For the choice of WM, I did not see xfce.  But it was OK.
>   
>   For custom startup, ~/.gnomerc is run.  This is only for
>   gnome-session.  

The use of ~/.xsession allows custom mode. Use "Default System session"
in GDM.  ("default" means different thing.)

>   For non gnome-session, I do not see easy
>   way to provide user customization with default install. 
>   
>   Default start mode is user selectable. (Can be annoying)
>   
>   Linked to gnome and many library.  Can be heavy.
> 
> * KDM: Good
> 
>   Its start up script does not call /etc/X11/Xsession nor bother to use
>   /etc/X11/Xsession.d/.  Thus out of lack with ssh-agent. (Bug #265865)

    Once this is fixed, it should be as above.  Pretty much same as GDM.
    Main difference is you that you need to restart system to get
    different locale or just edit ~/.dmrc from console.

?   (The authentic way to run start up script such as kinput2 / scim is 
?    not clear.)  (Need to wait next dinstall to test it.)

> * WDM: Simple but gives you choice of WM
> 
>   For the choice of WM, I saw false listing of metacity which itself is
>   useless.  But it was OK.  

(It is mostly issue with other package setting questionable alternative
values but consistency with freedesktop system standard is desirable in
the long run.)

You need to be root to change locale easily for the menu entry (for 
non ~/.xsession choices).  The same situation for keyboard input method
start up script.

For ~/.xsession, use "default" menu entry for WDM.

>   It looks lightest as WM selectable DM.
> 
> * General
>   It looks like auto listing of available WM are tricky.  Despite some
>   glitches I saw, it was usable.  I think if there is a standard way to
>   list available session manager / display manager, it can be better, I
>   think.

    No consistent user customizable start-up script location exist which
    works will all the menu shown session/window managers in non-XDM DM.

    Here, I repeat that ~/.xsession does not give solution to my problem
    since I can not choose WM from menu.  So far my local solution of
    ~/.i18n hook script seems to be the only usable one:

----------------------------------
# /etc/X11/Xsession.d/80xfree86-common_i18n
# source ~/.i18n for internationalization of X

I18NRC=$HOME/.i18n
if grep -qs ^allow-i18n "$OPTIONFILE"; then
  if [ -r "$I18NRC" ]; then
    if [ -x "$I18NRC" ]; then
      "$I18NRC"
     else
      . "$I18NRC"
    fi
  fi
fi
-------------------------------------

Cheers,

Osamu