add support for scryer-prolog #114

Skgland · 2025-09-04T22:42:25Z

This add the option of running plwm with scryer-prolog instead of swi.

Caution

This is still work in progress.
Not everything works yet. See TODO section below
Use with caution

This splits the plwm binary into plwm-swi and plwm-scryer (the later is actually being a script).

Installation on debian based system

Prerequisites

rust toolchain https://www.rust-lang.org/tools/install
cargo-deb cargo install cargo-deb
debian packages run0 apt install libxft-dev libx11-dev libxrandr-dev
things that I am forgetting

Build & Install scryer-prolog

git clone https://github.com/mthom/scryer-prolog.git
cd scryer-prolog
cargo deb
run0 apt install ./target/debian/*.deb

Build & Install plwm-{core,swi,scryer}

git clone https://github.com/Skgland/plwm.git --branch scryer
cd plwm
make install-debs

TODO

- Note: jobs/1 is no longer explicitly declared as shared, but based on swipl documentation this is the default anyways

… usages of format compatible

Bool = i32 and most functions have an unused i32 return value

as suggested by triska

also fix format usage

Seeker04 · 2025-09-14T12:48:48Z

symlinks/plwm-scryer

I don't understand what purpose this link serves. I see that Cargo.toml uses it. Instead of storing in git, could we only generate this if the user specifically runs a Debian install (i.e. from tools/extra/ in tandem with my previous comment)?

I think you might be referring to https://github.com/Seeker04/plwm/pull/114/files#r2347309900, I will respond to that over there.

Usually when creating a debian package there is a links file which defines which symlinks should be created during package install, but cargo-deb the tool I am using to generate the debian package currently does not support the links file or a replacement for it¹.
And the workaround currently is to have an existing symlink which is included as if it were a regular file and for that the symlink needs to already exist.

Footnotes

https://github.com/kornelski/cargo-deb/issues/92 ↩

For now I have moved the symlink into tools/extra, but kept it in git.
An option would be to add a Makefile target for creating the symlink and have the deb-scryer target depend on it. Ideally the cargo-deb issue liked above would be fixed and we could just get rid of the workaround.

Seeker04 · 2025-09-14T12:49:41Z

src/scryer/x11plwm.c

I think, it would be less confusing if we used the same naming for this and the SWI C file, i.e.:

plx-swi.c plx-scryer.c

but I dig this new name too (more descriptive), so they could be:

x11plwm-swi.c x11plwm-scryer.c

Sounds reasonable.
Would it make sense to just have scryer/x11plwm.c and swi/x11plwm.c instead of scryer/x11plwm-scryer.c and swi/x11plwm-swi.c while having them still compile to x11plwm-scryer.so and x11plwm-swi.so,
to not have a duplicate swi/scryer in the path or would it be better to have matching filenames between the .c and .so file?

Ah, a problem with this is that this would change the module name from plx to plx-swi/x11plwm-swi unless I am missing a way to define under what module name use_foreign_library loads the predicates exposed by the dynamic library.

Seeker04 · 2025-09-14T12:50:26Z

config/config.pl

-  super + d                 ->  change_nmaster(-1)              ,
-  super + h                 ->  change_mfact(-0.05)             ,
-  super + l                 ->  change_mfact(+0.05)             ,
+  (super +         j         ->  shift_focus(down))               ,


Does scryer need the parentheses for the keymaps, hooks, etc.? Is it an error or warning that warrants these? (It's fine if its needed, just curious).

Yes, these parentheses are needed for all strictly conforming Prolog systems, adding them is good for portability also with future systems that are candidates for a plwm port. Scryer correctly rejects invalid syntax and helps to quickly detect such portability issues.

GNU Prolog is also an excellent free reference system that reliably tells us what is Prolog syntax and what is not:

| ?- T = [a -> b, c]. uncaught exception: error(syntax_error('user_input:1 (char:44) , | ] or operator expected in list'),read_term/3) | ?- T = [(a -> b), c]. T = [(a->b),c]

Please also see mthom/scryer-prolog#3030 for more information.

Seeker04 · 2025-09-14T12:51:06Z

plwm-scryer.desktop

Thank you for adding the .desktop files! It will solve #70. I think, we could put these under config/ and make tools/install.sh install them.

Seeker04 · 2025-09-14T12:52:27Z

src/menu.pl

 %  @arg Prompt string appended as final argument to menucmd/1
 %  @arg Entries list of single-line strings passed as input to menucmd/1
 %  @arg Callback predicate that is called on lines selected from Entries
 spawn_menu(_, [], _) :- !.
 spawn_menu(Prompt, Entries, Callback) :-
-	(menucmd([MenuCmd|MenuArgs]) ->
+	(user:menucmd([MenuCmd|MenuArgs]) ->


Is user: mandatory to write out explicitly in Scryer? I see it was added in many places. Its SWI doc is a quite confusing too...

I think this is necessary due to a difference in the module system¹.
In short, in swi predicates from the import modules (i.e. user) are in scope in the imported module. This is not the case in scryer.

This is also why I can't just define missing predicates and import all modules in <system>/init.pl to get them into scope.

So I think there are two solutions to this:

explicitly qualify the predicate with user: (which is what I chose for now)

define the predicates in an explicit module that can be imported (user cannot be imported with use_module)

Footnotes

https://www.swi-prolog.org/pldoc/man?section=modulecompat ↩

Seeker04 · 2025-09-14T12:53:09Z

src/plwm.pl

 	(keymap_internal(Keycode, State, Action) ->
-		catch(ignore(Action), Ex, (writeln(Ex), true))
+		catch(ignore($Action), Ex, (writeln(Ex), true))


What does this dollar sign do?

This is from Scryer's library(debug), it emits a trace of the executed goal:

https://github.com/mthom/scryer-prolog/blob/dc05526c71169a88f90ba91bbbb72cad450782b0/src/lib/debug.pl#L47

Note that swi-prolog has a built-in $/1¹ which does something different.
Which likely explains the errors you are seeing when using swi (mentioned in #114 (comment)).

Footnotes

https://www.swi-prolog.org/pldoc/doc_for?object=($)/1 ↩

Seeker04 · 2025-09-14T12:53:55Z

src/plwm.pl

@@ -1649,8 +1635,7 @@
 			global_key_value(monitor_geom, Output, PrevGeom),
 			(PrevGeom \= Geom ->
 				global_key_newvalue(monitor_geom, Output, Geom),
-				format(string(Msg), "Monitor \"~s\" geometry reconfigured", [Output]),
-				writeln(Msg)
+			compat_format("Monitor \"~s\" geometry reconfigured~n", [Output])


I think, here we still need the string(Msg) and writeln(Msg) parts

Regarding compat_format/2: If a system provides format(chars(...), ...), then it is easy to describe format_//2 in terms of that:

format_(Fs, Args) --> call(format__(Fs, Args)). format__(Fs, Args, Cs0, Cs) :- format(chars(Cs0, Cs), Fs, Args).

With this compatibility definition, the Scryer code (using format_//2) can work in multiple systems.

I think I just missed this when I was reverting a bunch of changes to minimize the diff.

Seeker04 · 2025-09-14T12:56:49Z

src/utils.pl

@@ -296,3 +299,22 @@
 %  @arg NewStr output string, i.e. Str without its last character
 str_withoutlastch(Str, NewStr) :- string_length(Str, Len), Lenm1 is Len - 1, sub_string(Str, 0, Lenm1, _, NewStr).

+
+%! reassert(++Callable:callable) is det


Previously, when I put this under the utils module, it didn't work, because then swi asserted everything with the utils: prefix. Was this resolved somehow?

No, I don't think this is resolved, I think I just didn't yet run into problems due to this.

Seeker04 · 2025-09-14T12:59:59Z

I did a quick check. Most basic functionality of plwm-swi seems to work, but some things broke:

Unit tests (make test) throw many errors
menu:list_cmds/0 doesn't work, we get error(type_error(callable,(member(_28324,[...
set/2 and add/2 don't work (tried running them with the command fifo). Might be because reassert was moved to utils (see my previous comment)
All operations print this kind of error to the log:

error(determinism_error(switch_workspace(3),det,nondet,goal),context(system: <meta-call> / 1,_4890))
error(determinism_error(switch_workspace(next),det,nondet,goal),context(system: <meta-call> / 1,_7852))
error(determinism_error(shift_focus(up),det,nondet,goal),context(system: <meta-call> / 1,_30370))
error(determinism_error(shift_focus(up),det,nondet,goal),context(system: <meta-call> / 1,_5488))

There might be other issues. SWI version will need thorough manual testing before merging.

Seeker04 · 2025-09-14T13:02:29Z

@Skgland First and foremost, sorry for taking so long to react. Thank you very much for this amazing work! It looks very promising. I never thought progress towards scryer could be made this fast!

I quickly glanced over the changes and made some comments above. I understand, this is still heavily in a draft stage, but early feedback might be useful.

I'm still yet to fire up the scryer version, because I'm not on a Debian-based system, but I'll tackle it.

Cheers

src/setting.pl

- a few tests have a false added to force them to fail as the otherwise they currently break plunit and cause all later tests to not run

Skgland added 30 commits August 13, 2025 21:53

declare 0-arg predicates as atom :- ... . instead of atom() :- ... .

f140b4e

adjust dynamic declarations

5e5a8c8

- Note: jobs/1 is no longer explicitly declared as shared, but based on swipl documentation this is the default anyways

replace ceil with ceiling

def2330

fix invalid arguments 6.3.3.1

32658f3

stub some things for now and import lists and iso_ext modules

b15fa67

adjust obt_arguments stub

f845a05

move reassert definition to utils

003730c

define dynamic predicates also in settings

3236714

fix condig.pl

7a27bf1

fix config loading

6782061

stub more things

7a61970

start implementing ffi

51e1dbc

implement more ffi

45e6f23

import lib assoc in utils

caf6b0a

add two more C macro wrappers

1e80729

adjust stubs

0b5845d

make running this easier make run, implement more ffi and make some…

b3f4796

… usages of format compatible

assert that the Length of ArrayValues matches NElements

d00eeb0

fix ffi function declarations

b1e10d5

Bool = i32 and most functions have an unused i32 return value

implement x_create_simple_window

f93bbab

add script for running

0a7ab23

ignore return value

725d2a6

use chars_si

78845c5

as suggested by triska

implement x_ungrab_key/4

f582a8d

use chars_utf8bytes

ecd57b3

stub atom_string/2

ea18449

replace string/1 with chars_si/1

12f0c74

fix mixup of ModAtoms and Mods

b8a5137

also fix format usage

replace string/1 with chars_si/1

d9453fe

fix format usages

1a93d06

Seeker04 reviewed Sep 14, 2025

View reviewed changes

Skgland added 5 commits September 14, 2025 17:18

move desktop file into config folder

95d0417

load init.pl for tests

f493c5a

address some review comments

fde6c38

adjust install/uninstall script

2c07b97

fix path to debian packages

be13f74

triska mentioned this pull request Sep 14, 2025

Portability to different Prolog systems with stubs-file #113

Open

Skgland added 6 commits September 14, 2025 22:47

revert change from format/3 and writeln/1 to format/2

9bb7e0a

fix logo path in README.md

e2a7520

move reassert back into plwm.pl

6b19667

inclue usr/local/lib in LD_LIBRARY_PATH

eb4b25c

try to fix add

a321326

remove unused Makefile

3c29206

triska reviewed Sep 14, 2025

View reviewed changes

src/setting.pl Show resolved Hide resolved

Skgland added 7 commits September 20, 2025 01:03

fix some tests

32c7d9f

- a few tests have a false added to force them to fail as the otherwise they currently break plunit and cause all later tests to not run

fix list_cmds

9e0b283

fix string_concat

4baa831

hanlde path aliases in process_create in scryer

2e30f7d

fix unknown predicate (:)/2 in scryer

13e8d07

handle read_string/3 in scryer

4bf9954

handle split_string/4 in scryer

19ff19e

add support for scryer-prolog #114

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add support for scryer-prolog #114

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Skgland commented Sep 4, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Installation on debian based system

Prerequisites

Build & Install scryer-prolog

Build & Install plwm-{core,swi,scryer}

TODO

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Skgland Sep 14, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Seeker04 commented Sep 14, 2025

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Skgland commented Sep 4, 2025 •

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Skgland Sep 14, 2025 •

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