xenial (1) FvwmPerl.1.gz

Provided by: fvwm_2.6.5.ds-4.1_amd64 bug

NAME

       FvwmPerl - the fvwm perl manipulator and preprocessor

SYNOPSIS

       FvwmPerl should be spawned by fvwm(1) for normal functionality.

       To run this module, place this command somewhere in the configuration:

           Module FvwmPerl [params]

       or:

           ModuleSynchronize FvwmPerl [params]

       if you want to immediately start to send commands to FvwmPerl.

DESCRIPTION

       This module is intended to extend fvwm commands with the perl scripting power.  It enables to embed perl
       expressions in the fvwm config files and construct fvwm commands.

INVOCATION

       If you want to invoke the unique and persistent instanse of FvwmPerl, it is suggested to do this from the
       StartFunction.  Calling it from the top is also possible, but involves some issues not discussed here.

           AddToFunc StartFunction I Module FvwmPerl

       There are several command line switches:

       FvwmPerl [ --eval line ] [ --load file ] [ --preprocess [ --quote char ] [ --winid wid ] [ --cmd ] [
       --nosend ] [ --noremove ] [ line | file ] ] [ --export [names] ] [ --stay ] [ --nolock ] [ alias ]

       Long switches may be abbreviated to short one-letter switches.

       -e|--eval line - evaluate the given perl code

       -l|--load file - evaluate perl code in the given file

       -p|--preprocess [ file ] - preprocess the given fvwm config file

       The following 5 options are only valid together with --preprocess option.

       -c|--cmd line - an fvwm command to be preprocessed instead of file

       -q|--quote char - change the default '%' quote

       -w|--winid wid - set explicit window context (should begin with digit, may be in oct or hex form; this
       window id overwrites implicit window context if any)

       --nosend - do not send the preprocessed file to fvwm for Reading, the default is send. Useful for
       preprocessing non fvwm config files.

       --noremove - do not remove the preprocessed file after sending it to fvwm for Reading, the default is
       remove. Useful for debugging.

       -x|--export [names] - define fvwm shortcut functions (by default, two functions named "Eval" and ".").
       This option implies --stay.

       -s|--stay - continues an execution after --eval, --load or --preprocess are processed.  By default, the
       module is not persistent in this case, i.e. --nostay is assumed.

       --nolock - when one of the 3 action options is given, this option causes unlocking fvwm immediately. By
       default the requested action is executed synchronously; this only makes difference when invoked like:

           ModuleSynchronous FvwmPerl --preprocess someconfig.ppp

       If --nolock is added here, ModuleSynchronous returns immediately. Note that Module returns immediately
       regardless of this option.

USING ALIAS

       Aliases allow to have several module invocations and work separately with all invocations, here is an
       example:

           ModuleSynchronous FvwmPerl FvwmPerl-JustTest
           SendToModule FvwmPerl-JustTest eval $a = 2 + 2; $b = $a
           SendToModule FvwmPerl-JustTest eval cmd("Echo 2 + 2 = $b")
           KillModule FvwmPerl FvwmPerl-JustTest

PREPROCESSING EXAMPLE

       One of the effective proprocessing solutions is to pass the whole fvwm configuration with embeded perl
       code to "FvwmPerl --preprocess". An alternative approach is to write a perl script that produces fvwm
       commands and sends them for execution, this script may be loaded using "FvwmPerl --load". There are
       hovewer intermediate solutions that preprocess only separate configuration lines (or alternatively,
       execute separate perl commands that produce fvwm commands).

       The following code snippet adds ability of arithmetics and string scripting to certain lines that need
       this. To use this, you want to start FvwmPerl as your first command so that other commands may be asked
       to be preprosessed.

           ModuleSynchronize FvwmPerl

           AddToFunc .
           + I SendToModule FvwmPerl preprocess -c -- $*

           . Exec exec xterm -name xterm-%{++$i}%   # use unique name

           . GotoDesk 0 %{ $[desk.n] + 1 }%         # go to next desk

           . Exec exec %{ -x "/usr/bin/X11/aterm" ? "aterm" : "xterm" }% -sb

           # center a window
           Next (MyWindow) . Move \
             %{($WIDTH - $[w.width]) / 2}%p %{($HEIGHT - $[w.height]) / 2}%p

           . Exec exec xmessage %{2 + 2}%           # simple calculator

           . %{main::show_message(2 + 2, "Yet another Calculator"); ""}%

ACTIONS

       There are several actions that FvwmPerl may perform:

       eval perl-code
           Evaluate a line of perl code.

           A special function cmd("command") may be used in perl code to send commands back to fvwm.

           If perl code contains an error, it is printed to the standard error stream with the [FvwmPerl][eval]:
           header prepended.

       load file-name
           Load a file of perl code. If the file is not fully qualified, it is searched in the user directory
           $FVWM_USERDIR (usually ~/.fvwm) and the system wide data directory $FVWM_DATADIR.

           A special function cmd("command") may be used in perl code to send commands back to fvwm.

           If perl code contains an error, it is printed to the standard error stream with the [FvwmPerl][load]:
           header prepended.

       preprocess [-q|--quote char] [-c|--cmd] [line | file]
           Preprocess fvwm config file or (if --cmd is given) line. This file contains lines that are not
           touched (usually fvwm commands) and specially preformatted perl code that is processed and replaced.
           Text enclosed in %{ ... }% delimiters, that may start anywhere on the line and end anywhere on the
           same or another line, is perl code.

           The quote parameter changes perl code delimiters.  If a single char is given, like '@', the
           delimiters are @{ ... }@. If the given quote is 2 chars, like <>, the quotes are <{ ... }>

           The perl code is substituted for the result of its evaluation. I.e. %{$a = "c"; ++$a}% is replaced
           with "d".

           The evaluation is unlike eval and load is done under the package PreprocessNamespace and without use
           strict, so you are free to use any variable names without fear of conflicts. Just don't use
           uninitialized variables to mean undef or empty list (they may be in fact initialized by the previous
           preprocess action), and do a clean-up if needed. The variables and function in the main package are
           still available, like ::cmd() or ::skip(), but it is just not a good idea to access them while
           preprocessing.

           There is a special function include(file) that loads a file, preprocesses it and returns the
           preprocessed result. Avoid recursion.

           If any embedded perl code contains an error, it is printed to the standard error stream and prepended
           with the [FvwmPerl][preprocess]: header. The result of substitution is empty in this case.

           The following variables may be used in the perl code:

           $USER, $DISPLAY, $WIDTH, $HEIGHT, $FVWM_VERSION, $FVWM_MODULEDIR, $FVWM_DATADIR, $FVWM_USERDIR

           The following line based directives are recognized when preprocessing. They are processed after the
           perl code (if any) is substituted.

           %Repeat count
               Causes the following lines to be repeated count times.

           %ModuleConfig module-name [ destroy ]
               Causes the following lines to be interpreted as the given module configuration. If "destroy" is
               specified the previous module configuration is destroyed first.

           %Prefix prefix
               Prefixes the following lines with the quoted prefix.

           %End any-optional-comment
               Ends any of the directives described above, may be nested.

           Examples:

               %Prefix "AddToFunc SwitchToWindow I"
                   Iconify off
                   WindowShade off
                   Raise
                   WarpToWindow 50 50
               %End

               %ModuleConfig FvwmPager destroy
                   Colorset 0
                   Font lucidasans-10
                   DeskTopScale 28
                   MiniIcons
               %End ModuleConfig FvwmPager

               %Prefix "All (MyWindowToAnimate) ResizeMove "
               100 100 %{($WIDTH - 100) / 2}% %{($HEIGHT - 100) / 2}%
               %Repeat %{$count}%
               br w+2c w+2c w-1c w-1c
               %End
               %Repeat %{$count}%
               br w-2c w-2c w+1c w+1c
               %End
               %End Prefix

           Additional preprocess parameters --nosend and --noremove may be given too. See their description at
           the top.

       export [func-names]
           Send to fvwm the definition of shortcut functions that help to activate different actions of the
           module (i.e. eval, load and preprocess).

           Function names (func-names) may be separated by commas or/and whitespace. By default, two functions
           "Eval" and "." are assumed.

           The actual action defined in a function is guessed from the function name if possible, where function
           name "." is reserved for preprocess action.

           For example, any of these two fvwm commands

              SendToModule MyPerl export PerlEval,PP
              FvwmPerl --export PerlEval,PP MyPerl

           define the following two shortcut functions:

             DestroyFunc PerlEval
             AddToFunc I SendToModule MyPerl eval $*
             DestroyFunc PP
             AddToFunc I SendToModule MyPerl preprocess -c -- $*

       These 4 actions may be requested in one of 3 ways: 1) in the command line when FvwmPerl is invoked (in
       this case FvwmPerl is short-lived unless --stay or --export is also given), 2) by sending the
       corresponding message in fvwm config using SendToModule, 3) by calling the corresponding perl function in
       perl code.

FUNCTIONS

       There are several functions that perl code may call:

       cmd($fvwm_command)
           In case of eval or load - send back to fvwm a string $fvwm_command. In case of preprocess - append a
           string $fvwm_command to the output of the embedded perl code.

       do_eval($perl_code)
           This function is equivalent to the eval functionality on the string $perl_code, described above.

       load($filename)
           This function is equivalent to the load functionality on the file $filename, described above.

       preprocess(@params, ["-c $command"] [$filename])
           This function is equivalent to the preprocess functionality with the given parameters and the file
           $filename described above.

       export($func_names, [$do_unexport])
           This function is equivalent to the export functionality with the given $func_names, described above.
           May also unexport the function names if the second parameter is true.

           Function names should be separated by commas or/and whitespace. If $func_names is empty then
           functions "Eval" and "." are assumed.

       stop()
           Terminates the module.

       skip()
           Skips the rest of the event callback code, i.e. the module returns to listen to new module events.

       unlock()
           Unsynchronizes the event callback from fvwm. This may be useful to prevent deadlocks, i.e. usually
           fvwm kills the non-responding module if the event callback is not finished in ModuleTimeout seconds.
           This prevents it.

           This example causes FvwmPerl to suspend its execution for one minute:

               SendModule FvwmPerl eval unlock(); sleep(60);

           However, verify that there is no way a new message is sent by fvwm while the module is busy, and fvwm
           stays locked on this new message for too long. See also the detach solution if you need long lasting
           operations.

       detach()
           Forks and detaches the rest of the event callback code from the main process. This may be useful to
           prevent killing the module if its event callback should take a long time to complete and it may be
           done in the detached child. The detached child may still send commands to fvwm (don't rely on this),
           but not receive the events of course, it exits immediately after the callback execution is finished.

           If you use detach(), better only send commands to fvwm in one process (the main one or the detached
           one), doing otherwise may often cause conflicts.

       show_message($msg, $title[, $use_stderr_too=1])
           Shows a dialog window with the given message, using whichever X tool is found in the system.

           See FVWM::Module::Toolkit::show_message for more information.

VARIABLES

       There are several global variables in the main namespace that may be used in the perl code:

           $a, $b, ... $h
           @a, @b, ... @h
           %a, %b, ... %h

       They all are initialized to the empty value and may be used to store a state between different calls to
       FvwmPerl actions (eval and load).

       If you need more readable variable names, either write "no strict 'vars';" at the start of every perl
       code or use a hash for this, like:

           $h{id} = $h{first_name} . " " . $h{second_name}

       or use a package name, like:

           @MyMenu::terminals = qw( xterm rxvt );
           $MyMenu::item_num = @MyMenu::terminals;

       There may be a configuration option to turn strictness on and off.

MESSAGES

       FvwmPerl may receive messages using the fvwm command SendToModule. The names, meanings and parameters of
       the messages are the same as the corresponding actions, described above.

       Additionally, a message stop causes a module to quit.

       A message unexport [func-names] undoes the effect of export, described in the ACTIONS section.

       A message dump dumps the contents of the changed variables (not yet).

EXAMPLES

       A simple test:

           SendToModule FvwmPerl eval $h{dir} = $ENV{HOME}
           SendToModule FvwmPerl eval load($h{dir} . "/test.fpl")
           SendToModule FvwmPerl load $[HOME]/test.fpl
           SendToModule FvwmPerl preprocess config.ppp
           SendToModule FvwmPerl export Eval,PerlEval,PerlLoad,PerlPP
           SendToModule FvwmPerl unexport PerlEval,PerlLoad,PerlPP
           SendToModule FvwmPerl stop

       The following example handles root backgrounds in fvwmrc. All these commands may be added to
       StartFunction.

           Module FvwmPerl --export PerlEval

           # find all background pixmaps for a later use
           PerlEval $a = $ENV{HOME} . "/bg"; \
             opendir DIR, $a; @b = grep { /xpm$/ } readdir(DIR); closedir DIR

           # build a menu of background pixmaps
           AddToMenu MyBackgrounds "My Backgrounds" Title
           PerlEval foreach $b (@b) \
             { cmd("AddToMenu MyBackgrounds '$b' Exec fvwm-root $a/$b") }

           # choose a random background to load on start-up
           PerlEval cmd("AddToFunc \
             InitFunction + I Exec exec fvwm-root $a/" . $b[int(random(@b))])

ESCAPING

       SendToModule just like any other fvwm commands expands several dollar prefixed variables.  This may clash
       with the dollars perl uses. You may avoid this by prefixing SendToModule with a leading dash. The
       following 2 lines in each pair are equivalent:

           SendToModule FvwmPerl eval $$d = "$[DISPLAY]"
           -SendToModule FvwmPerl eval $d = "$ENV{DISPLAY}"

           SendToModule FvwmPerl eval \
               cmd("Echo desk=$d, display=$$d")
           SendToModule FvwmPerl preprocess -c \
               Echo desk=%("$d")%, display=%{$$d}%

       Another solution to avoid escaping of special symbols like dollars and backslashes is to create a perl
       file in ~/.fvwm and then load it:

           SendToModule FvwmPerl load build-menus.fpl

       If you need to preprocess one command starting with a dash, you should precede it using "--".

           # this prints the current desk, i.e. "0"
           SendToModule FvwmPerl preprocess -c Echo "$%{$a = "c"; ++$a}%"
           # this prints "$d"
           SendToModule FvwmPerl preprocess -c -- -Echo "$%{"d"}%"
           # this prints "$d" (SendToModule expands $$ to $)
           SendToModule FvwmPerl preprocess -c -- -Echo "$$%{"d"}%"
           # this prints "$$d"
           -SendToModule FvwmPerl preprocess -c -- -Echo "$$%{"d"}%"

       Again, it is suggested to put your command(s) into file and preprocess the file instead.

CAVEATS

       FvwmPerl being written in perl and dealing with perl, follows the famous perl motto: "There's more than
       one way to do it", so the choice is yours.

       Here are more pairs of equivalent lines:

           Module FvwmPerl --load "my.fpl" --stay
           Module FvwmPerl -e 'load("my.fpl")' -s

           SendToModule FvwmPerl preprocess --quote '@' my.ppp
           SendToModule FvwmPerl eval preprocess({quote => '@'}, "my.ppp");

       Warning, you may affect the way FvwmPerl works by evaluating appropriate perl code, this is considered a
       feature not a bug.  But please don't do this, write your own fvwm module in perl instead.

SEE ALSO

       The fvwm(1) man page describes all available commands.

       Basically, in your perl code you may use any function or class method from the perl library installed
       with fvwm, see the man pages of perl packages General::FileSystem, General::Parse and FVWM::Module.

AUTHOR

       Mikhael Goikhman <migo@homemail.com>.