Well here is a little description of how DrakX can be modified or extended.
Please refer to README file for getting DrakX code source and to known more
exactly how it works and what it can do.


********************************************************************************
* Execution of DrakX ***********************************************************
********************************************************************************
DrakX has originally be written by pixel in perl and C.
entry point for stage2 is /usr/bin/runinstall2 which is typically a link to
/usr/bin/install2 which simply load module install2.pm and execute
install2::main with @ARGV.

install2::main parse command line arguments, prepare installation, find the right
install/interactive class (take a look at gi/docs/object_class.fig) according to
command line, memory available and if the interactive chosen is initializing
correctly, else it will try a less-demanding interactive object.
Once done, $::o is set to this install & interactive object and main runs the
various step of install2 defined in $o->{steps}, starting with $o->{steps}{first}
and iterating with method install::any::getNextStep().
while running step, it trap any errors that may arise and use perl exception to
change step.

********************************************************************************
* DrakX modules descriptions ***************************************************
********************************************************************************
Here is a brief description of what each modules of DrakX is doing.

install2: main module of DrakX as described above, main loop execution of DrakX.

install/steps: generic installation module containing steps definition, all steps
  should always be defined here as some methods may be used on automatic mode.
  there is no interactivity available. typically are defined base operation for
  configuring each step according to $o.

install/steps_interactive: generic installation module with generic interative
  methods. typically are found all interactive code of DrakX for each steps.

install/steps_auto_install: implementation installation module without interactive
  methods to match auto_install mode. this is the simplest as almost no method are
  redefined (inherit module install/steps only, compared to other implementation
  modules described below).

install/steps_stdio: implementation installation module with interactive stdio
  methods to match stdio mode. inherit modules install/steps_interactive and
  interactive_stdio.

install/steps_newt: implementation installation module with interactive newt
  methods to match newt mode. inherit modules install/steps_interactive and
  interactive_newt.

install/steps_gtk: implementation installation module with interactive gtk
  methods to match gtk mode. inherit modules install/steps_interactive and
  interactive_gtk.

install/any: contains various methods using generic interactive interface but
  not used by standalone tools.

install/gtk: contains various methods using gtk interface but not used by
  standalone tools.

interactive_stdio: implementation methods for interactivity in stdio mode.
  inherit module interactive.

interactive_newt: implementation methods for interactivity in newt mode.
  inherit module interactive.

interactive_gtk: implementation methods for interactivity in gtk mode.
  inherit module interactive.

my_gtk: basic gtk access methods.

any: contains various methods using generic interactive interface. to compare
  against install/any module as this one is available for standalone tools.

class_discard: simple module that implement every methods undefined to return
  nothing. this trick is used to ensure no undefined method can arise when using
  code that reference interactive method which are not defined.

common: contains very simple and very usefull (common) methods to do various task.
  some methods inspired by functionnal language.

c: contains wrapper to C definition of methods used by DrakX, use of C is necessary
  for C extern libraries interface (rpmlib, ldetect), kernel interface, XFree
  interface.

commands: implement some un*x commands, conflicting name with perl contains
  trailing underscore (_). this module is used by commands perl script that
  determine which command to run according to $0 (this is used this way when DrakX
  is running).

run_program: allow running a program with redirection but without using a shell.
  allow rooted execution.

help: contains all help message displayed by DrakX.

log: log facility methods.

lang: language manipulation methods, get and set sysconfig file, load po.

keyboard: keyboard manipulation methods, get and set sysconfig file, set console
  keyboard mapping.

mouse: mouse manipulation methods, get and set sysconfig file, change mouse.

timezone: time zone manipulation methods, get and set timezone.

services: services manipulation methods, activate or delete services (see
  /etc/rc.d/init.d directories).

detect_devices: manage detection of various class of hardware.

devices: manage device file, create device special according device name.

partition_table: base partition table management methods, it manages
  appriopriate partition_table_XXX object according to what has been read
  as XXX partition table type.

partition_table::bsd: matches a BSD partition table.

partition_table::dos: matches a DOS partition table.

partition_table::emtpy: matches an empty partition table.

partition_table::mac: matches an Apple partition table.

partition_table::raw: generic class for the following partition_table::XXX.

partition_table::sun: matches a Sun Label partition table.

fs: read and write /etc/fstab file, mount and umount, format.

fsedit: manage (modyfy, edit) mount point associated to partition (like editing
  /etc/fstab).

swap: swap management methods, format and mount (activation).

raid: raid (software only) management methods.

lvm: lvm (Logical Volume Manager) management methods.

loopback: loopback management methods, used for lnx4win type installation or using
  a file as a partition.

diskdrake: diskdrake itself, disk graphical (using gtk) manipulation tools.

ftp: ftp mangement methods, used when using ftp install.

http: http management methods, used when using http install.

modparm: kernel modules options management, allow building nice dialog with each
  module parameter available.

modules: kernel modules management, allow loading or unloading (ala modprobe or
  insmod).

printer: printer management methods, read and write both LPR or CUPS configuration.

printerdrake: interactive printer management methods.

network: network management methods, get and set sysconfig file.

netconnect: network configuration wizard.

netconnect_const: network configuration wirard data.

Xconfig: X configuration (monitor + already existing config file) management.

Xconfigurator: X configuration wizard.

Xconfigurator_const: X configuration wizard data.

booloader: bootloader (LILO, GRUB, LOADLIN, SILO) configuration management methods.

pkgs: rpm package and hdlist, depslist management methods, allow selecting or
  unselecting packages, manage rpmsrate file and select group, installation and
  removal methods of rpm file.

crypto: *obsoleted* module to manage crypto site and rpm file.

standalone: standalone only, allow defining a standalone tools.

bootlook: standalone only, interface with DrakConf to configure bootloader options.

drakfirewall: standalone only, interface with DrakConf to configure a tiny firewall.

********************************************************************************
* DrakX FAT resizer module description *****************************************
********************************************************************************
here is a fat resizer written in perl and C used by DrakX (diskdrake) to resize
FAT16/FAT32 partition. it moves clusters to make sure a shrink can be done on the
limit of the partition itself, if no cluster need to be moved, only boot sector
partition limit are modified.

any: various methods to flag cluster, compute min size.

boot_sector: boot sector management methods.

c_rewritten: originally resize_fat was only perl, this contains code section that
  are the most sensible to speed or memory contraints and have been rewritten to C
  using perl extension.

dir_entry: manage directory structure.

directory: traverse directory recursively, needed to move correctly cluster.

fat: manage fat structure.

info_sector: manage info sector.

io: manage I/O on disk (need to take care of big file as partition size may be
  larger than 2GB).

main: main resizer algortihm. if needed allocate new clusters, copy files, copy
  directories. update boot sector info.

********************************************************************************
* Adding a new step to DrakX ***************************************************
********************************************************************************
Say we want to add a question for setting "alawindows" option.
We put it pretty early in the install, let's say after "Select Installation
Class".

1. in install2.pm

add

  selectAlawindows => [ __("A la windows or not"), 0, 1, '' ],

after

  selectInstallClass => [ __("Select installation class"), 1, 1, '' ],

the 0, 1, '' means not "redoable", "skip on error", "don't hide"

2. add your function selectAlawindows in install2.pm

sub selectAlawindows  { $o->selectAlawindows }

3. add your function selectAlawindows in install/steps_interactive.pm

sub selectAlawindows {
    my ($o) = @_;
    $o->{alawindows} = $o->ask_yesorno('', _("Throw everything away as windobe does?"), 1);
}

4. add your function selectAlawindows in install/steps.pm (not needed in that
case, except for auto_install)

sub selectAlawindows  {}