1FvwmPerl(1)                      Fvwm Modules                      FvwmPerl(1)
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NAME

6       FvwmPerl - the fvwm perl manipulator and preprocessor
7

SYNOPSIS

9       FvwmPerl should be spawned by fvwm(1) for normal functionality.
10
11       To run this module, place this command somewhere in the configuration:
12
13           Module FvwmPerl [params]
14
15       or:
16
17           ModuleSynchronize FvwmPerl [params]
18
19       if you want to immediately start to send commands to FvwmPerl.
20

DESCRIPTION

22       This module is intended to extend fvwm commands with the perl scripting
23       power.  It enables to embed perl expressions in the fvwm config files
24       and construct fvwm commands.
25

INVOCATION

27       If you want to invoke the unique and persistent instanse of FvwmPerl,
28       it is suggested to do this from the StartFunction.  Calling it from the
29       top is also possible, but involves some issues not discussed here.
30
31           AddToFunc StartFunction I Module FvwmPerl
32
33       There are several command line switches:
34
35       FvwmPerl [ --eval line ] [ --load file ] [ --preprocess [ --quote char
36       ] [ --winid wid ] [ --cmd ] [ --nosend ] [ --noremove ] [ line | file ]
37       ] [ --export [names] ] [ --stay ] [ --nolock ] [ alias ]
38
39       Long switches may be abbreviated to short one-letter switches.
40
41       -e|--eval line - evaluate the given perl code
42
43       -l|--load file - evaluate perl code in the given file
44
45       -p|--preprocess [ file ] - preprocess the given fvwm config file
46
47       The following 5 options are only valid together with --preprocess
48       option.
49
50       -c|--cmd line - an fvwm command to be preprocessed instead of file
51
52       -q|--quote char - change the default '%' quote
53
54       -w|--winid wid - set explicit window context (should begin with digit,
55       may be in oct or hex form; this window id overwrites implicit window
56       context if any)
57
58       --nosend - do not send the preprocessed file to fvwm for Reading, the
59       default is send. Useful for preprocessing non fvwm config files.
60
61       --noremove - do not remove the preprocessed file after sending it to
62       fvwm for Reading, the default is remove. Useful for debugging.
63
64       -x|--export [names] - define fvwm shortcut functions (by default, two
65       functions named "Eval" and ".").  This option implies --stay.
66
67       -s|--stay - continues an execution after --eval, --load or --preprocess
68       are processed.  By default, the module is not persistent in this case,
69       i.e. --nostay is assumed.
70
71       --nolock - when one of the 3 action options is given, this option
72       causes unlocking fvwm immediately. By default the requested action is
73       executed synchronously; this only makes difference when invoked like:
74
75           ModuleSynchronous FvwmPerl --preprocess someconfig.ppp
76
77       If --nolock is added here, ModuleSynchronous returns immediately. Note
78       that Module returns immediately regardless of this option.
79

USING ALIAS

81       Aliases allow to have several module invocations and work separately
82       with all invocations, here is an example:
83
84           ModuleSynchronous FvwmPerl FvwmPerl-JustTest
85           SendToModule FvwmPerl-JustTest eval $a = 2 + 2; $b = $a
86           SendToModule FvwmPerl-JustTest eval cmd("Echo 2 + 2 = $b")
87           KillModule FvwmPerl FvwmPerl-JustTest
88

PREPROCESSING EXAMPLE

90       One of the effective proprocessing solutions is to pass the whole fvwm
91       configuration with embeded perl code to "FvwmPerl --preprocess". An
92       alternative approach is to write a perl script that produces fvwm
93       commands and sends them for execution, this script may be loaded using
94       "FvwmPerl --load". There are hovewer intermediate solutions that
95       preprocess only separate configuration lines (or alternatively, execute
96       separate perl commands that produce fvwm commands).
97
98       The following code snippet adds ability of arithmetics and string
99       scripting to certain lines that need this. To use this, you want to
100       start FvwmPerl as your first command so that other commands may be
101       asked to be preprosessed.
102
103           ModuleSynchronize FvwmPerl
104
105           AddToFunc .
106           + I SendToModule FvwmPerl preprocess -c -- $*
107
108           . Exec exec xterm -name xterm-%{++$i}%   # use unique name
109
110           . GotoDesk 0 %{ $[desk.n] + 1 }%         # go to next desk
111
112           . Exec exec %{ -x "/usr/bin/X11/aterm" ? "aterm" : "xterm" }% -sb
113
114           # center a window
115           Next (MyWindow) . Move \
116             %{($WIDTH - $[w.width]) / 2}%p %{($HEIGHT - $[w.height]) / 2}%p
117
118           . Exec exec xmessage %{2 + 2}%           # simple calculator
119
120           . %{main::show_message(2 + 2, "Yet another Calculator"); ""}%
121

ACTIONS

123       There are several actions that FvwmPerl may perform:
124
125       eval perl-code
126           Evaluate a line of perl code.
127
128           A special function cmd("command") may be used in perl code to send
129           commands back to fvwm.
130
131           If perl code contains an error, it is printed to the standard error
132           stream with the [FvwmPerl][eval]: header prepended.
133
134       load file-name
135           Load a file of perl code. If the file is not fully qualified, it is
136           searched in the user directory $FVWM_USERDIR (usually ~/.fvwm) and
137           the system wide data directory $FVWM_DATADIR.
138
139           A special function cmd("command") may be used in perl code to send
140           commands back to fvwm.
141
142           If perl code contains an error, it is printed to the standard error
143           stream with the [FvwmPerl][load]: header prepended.
144
145       preprocess [-q|--quote char] [-c|--cmd] [line | file]
146           Preprocess fvwm config file or (if --cmd is given) line. This file
147           contains lines that are not touched (usually fvwm commands) and
148           specially preformatted perl code that is processed and replaced.
149           Text enclosed in %{ ... }% delimiters, that may start anywhere on
150           the line and end anywhere on the same or an other line, is perl
151           code.
152
153           The quote parameter changes perl code delimiters.  If a single char
154           is given, like '@', the delimiters are @{ ... }@. If the given
155           quote is 2 chars, like <>, the quotes are <{ ... }>
156
157           The perl code is substituted for the result of its evaluation. I.e.
158           %{$a = "c"; ++$a}% is replaced with "d".
159
160           The evaluation is unlike eval and load is done under the package
161           PreprocessNamespace and without use strict, so you are free to use
162           any variable names without fear of conflicts. Just don't use
163           uninitialized variables to mean undef or empty list (they may be in
164           fact initialized by the previous preprocess action), and do a
165           clean-up if needed. The variables and function in the main package
166           are still available, like ::cmd() or ::skip(), but it is just not a
167           good idea to access them while preprocessing.
168
169           There is a special function include(file) that loads a file,
170           preprocesses it and returns the preprocessed result. Avoid
171           recursion.
172
173           If any embedded perl code contains an error, it is printed to the
174           standard error stream and prepended with the
175           [FvwmPerl][preprocess]: header. The result of substitution is empty
176           in this case.
177
178           The following variables may be used in the perl code:
179
180           $USER, $DISPLAY, $WIDTH, $HEIGHT, $FVWM_VERSION, $FVWM_MODULEDIR,
181           $FVWM_DATADIR, $FVWM_USERDIR
182
183           The following line based directives are recognized when
184           preprocessing. They are processed after the perl code (if any) is
185           substituted.
186
187           %Repeat count
188               Causes the following lines to be repeated count times.
189
190           %ModuleConfig module-name [ destroy ]
191               Causes the following lines to be interpreted as the given
192               module configuration. If "destroy" is specified the previous
193               module configuration is destroyed first.
194
195           %Prefix prefix
196               Prefixes the following lines with the quoted prefix.
197
198           %End any-optional-comment
199               Ends any of the directives described above, may be nested.
200
201           Examples:
202
203               %Prefix "AddToFunc SwitchToWindow I"
204                   Iconify off
205                   WindowShade off
206                   Raise
207                   WarpToWindow 50 50
208               %End
209
210               %ModuleConfig FvwmPager destroy
211                   Colorset 0
212                   Font lucidasans-10
213                   DeskTopScale 28
214                   MiniIcons
215               %End ModuleConfig FvwmPager
216
217               %Prefix "All (MyWindowToAnimate) ResizeMove "
218               100 100 %{($WIDTH - 100) / 2}% %{($HEIGHT - 100) / 2}%
219               %Repeat %{$count}%
220               br w+2c w+2c w-1c w-1c
221               %End
222               %Repeat %{$count}%
223               br w-2c w-2c w+1c w+1c
224               %End
225               %End Prefix
226
227           Additional preprocess parameters --nosend and --noremove may be
228           given too. See their description at the top.
229
230       export [func-names]
231           Send to fvwm the definition of shortcut functions that help to
232           activate different actions of the module (i.e. eval, load and
233           preprocess).
234
235           Function names (func-names) may be separated by commas or/and
236           whitespace. By default, two functions "Eval" and "." are assumed.
237
238           The actual action defined in a function is guessed from the
239           function name if possible, where function name "." is reserved for
240           preprocess action.
241
242           For example, any of these two fvwm commands
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244              SendToModule MyPerl export PerlEval,PP
245              FvwmPerl --export PerlEval,PP MyPerl
246
247           define the following two shortcut functions:
248
249             DestroyFunc PerlEval
250             AddToFunc I SendToModule MyPerl eval $*
251             DestroyFunc PP
252             AddToFunc I SendToModule MyPerl preprocess -c -- $*
253
254       These 4 actions may be requested in one of 3 ways: 1) in the command
255       line when FvwmPerl is invoked (in this case FvwmPerl is short-lived
256       unless --stay or --export is also given), 2) by sending the
257       corresponding message in fvwm config using SendToModule, 3) by calling
258       the corresponding perl function in perl code.
259

FUNCTIONS

261       There are several functions that perl code may call:
262
263       cmd($fvwm_command)
264           In case of eval or load - send back to fvwm a string $fvwm_command.
265           In case of preprocess - append a string $fvwm_command to the output
266           of the embedded perl code.
267
268       do_eval($perl_code)
269           This function is equivalent to the eval functionality on the string
270           $perl_code, described above.
271
272       load($filename)
273           This function is equivalent to the load functionality on the file
274           $filename, described above.
275
276       preprocess(@params, ["-c $command"] [$filename])
277           This function is equivalent to the preprocess functionality with
278           the given parameters and the file $filename described above.
279
280       export($func_names, [$do_unexport])
281           This function is equivalent to the export functionality with the
282           given $func_names, described above. May also unexport the function
283           names if the second parameter is true.
284
285           Function names should be separated by commas or/and whitespace. If
286           $func_names is empty then functions "Eval" and "." are assumed.
287
288       stop()
289           Terminates the module.
290
291       skip()
292           Skips the rest of the event callback code, i.e. the module returns
293           to listen to new module events.
294
295       unlock()
296           Unsynchronizes the event callback from fvwm. This may be useful to
297           prevent deadlocks, i.e. usually fvwm kills the non-responding
298           module if the event callback is not finished in ModuleTimeout
299           seconds. This prevents it.
300
301           This example causes FvwmPerl to suspend its execution for one
302           minute:
303
304               SendModule FvwmPerl eval unlock(); sleep(60);
305
306           However, verify that there is no way a new message is sent by fvwm
307           while the module is busy, and fvwm stays locked on this new message
308           for too long. See also the detach solution if you need long lasting
309           operations.
310
311       detach()
312           Forks and detaches the rest of the event callback code from the
313           main process. This may be useful to prevent killing the module if
314           its event callback should take a long time to complete and it may
315           be done in the detached child. The detached child may still send
316           commands to fvwm (don't rely on this), but not receive the events
317           of course, it exits immediately after the callback execution is
318           finished.
319
320           If you use detach(), better only send commands to fvwm in one
321           process (the main one or the detached one), doing otherwise may
322           often cause conflicts.
323
324       show_message($msg, $title[, $use_stderr_too=1])
325           Shows a dialog window with the given message, using whichever X
326           tool is found in the system.
327
328           See FVWM::Module::Toolkit::show_message for more information.
329

VARIABLES

331       There are several global variables in the main namespace that may be
332       used in the perl code:
333
334           $a, $b, ... $h
335           @a, @b, ... @h
336           %a, %b, ... %h
337
338       They all are initialized to the empty value and may be used to store a
339       state between different calls to FvwmPerl actions (eval and load).
340
341       If you need more readable variable names, either write "no strict
342       'vars';" at the start of every perl code or use a hash for this, like:
343
344           $h{id} = $h{first_name} . " " . $h{second_name}
345
346       or use a package name, like:
347
348           @MyMenu::terminals = qw( xterm rxvt );
349           $MyMenu::item_num = @MyMenu::terminals;
350
351       There may be a configuration option to turn strictness on and off.
352

MESSAGES

354       FvwmPerl may receive messages using the fvwm command SendToModule. The
355       names, meanings and parameters of the messages are the same as the
356       corresponding actions, described above.
357
358       Additionally, a message stop causes a module to quit.
359
360       A message unexport [func-names] undoes the effect of export, described
361       in the ACTIONS section.
362
363       A message dump dumps the contents of the changed variables (not yet).
364

EXAMPLES

366       A simple test:
367
368           SendToModule FvwmPerl eval $h{dir} = $ENV{HOME}
369           SendToModule FvwmPerl eval load($h{dir} . "/test.fpl")
370           SendToModule FvwmPerl load $[HOME]/test.fpl
371           SendToModule FvwmPerl preprocess config.ppp
372           SendToModule FvwmPerl export Eval,PerlEval,PerlLoad,PerlPP
373           SendToModule FvwmPerl unexport PerlEval,PerlLoad,PerlPP
374           SendToModule FvwmPerl stop
375
376       The following example handles root backgrounds in fvwmrc. All these
377       commands may be added to StartFunction.
378
379           Module FvwmPerl --export PerlEval
380
381           # find all background pixmaps for a later use
382           PerlEval $a = $ENV{HOME} . "/bg"; \
383             opendir DIR, $a; @b = grep { /xpm$/ } readdir(DIR); closedir DIR
384
385           # build a menu of background pixmaps
386           AddToMenu MyBackgrounds "My Backgrounds" Title
387           PerlEval foreach $b (@b) \
388             { cmd("AddToMenu MyBackgrounds '$b' Exec fvwm-root $a/$b") }
389
390           # choose a random background to load on start-up
391           PerlEval cmd("AddToFunc \
392             InitFunction + I Exec exec fvwm-root $a/" . $b[int(random(@b))])
393

ESCAPING

395       SendToModule just like any other fvwm commands expands several dollar
396       prefixed variables.  This may clash with the dollars perl uses. You may
397       avoid this by prefixing SendToModule with a leading dash. The following
398       2 lines in each pair are equivalent:
399
400           SendToModule FvwmPerl eval $$d = "$[DISPLAY]"
401           -SendToModule FvwmPerl eval $d = "$ENV{DISPLAY}"
402
403           SendToModule FvwmPerl eval \
404               cmd("Echo desk=$d, display=$$d")
405           SendToModule FvwmPerl preprocess -c \
406               Echo desk=%("$d")%, display=%{$$d}%
407
408       Another solution to avoid escaping of special symbols like dollars and
409       backslashes is to create a perl file in ~/.fvwm and then load it:
410
411           SendToModule FvwmPerl load build-menus.fpl
412
413       If you need to preprocess one command starting with a dash, you should
414       precede it using "--".
415
416           # this prints the current desk, i.e. "0"
417           SendToModule FvwmPerl preprocess -c Echo "$%{$a = "c"; ++$a}%"
418           # this prints "$d"
419           SendToModule FvwmPerl preprocess -c -- -Echo "$%{"d"}%"
420           # this prints "$d" (SendToModule expands $$ to $)
421           SendToModule FvwmPerl preprocess -c -- -Echo "$$%{"d"}%"
422           # this prints "$$d"
423           -SendToModule FvwmPerl preprocess -c -- -Echo "$$%{"d"}%"
424
425       Again, it is suggested to put your command(s) into file and preprocess
426       the file instead.
427

CAVEATS

429       FvwmPerl being written in perl and dealing with perl, follows the
430       famous perl motto: "There's more than one way to do it", so the choice
431       is yours.
432
433       Here are more pairs of equivalent lines:
434
435           Module FvwmPerl --load "my.fpl" --stay
436           Module FvwmPerl -e 'load("my.fpl")' -s
437
438           SendToModule FvwmPerl preprocess --quote '@' my.ppp
439           SendToModule FvwmPerl eval preprocess({quote => '@'}, "my.ppp");
440
441       Warning, you may affect the way FvwmPerl works by evaluating
442       appropriate perl code, this is considered a feature not a bug.  But
443       please don't do this, write your own fvwm module in perl instead.
444

SEE ALSO

446       The fvwm(1) man page describes all available commands.
447
448       Basically, in your perl code you may use any function or class method
449       from the perl library installed with fvwm, see the man pages of perl
450       packages General::FileSystem, General::Parse and FVWM::Module.
451

AUTHOR

453       Mikhael Goikhman <migo@homemail.com>.
454
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4572.5.28 (from cvs)                 2009-03-22                       FvwmPerl(1)
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