Hello,

I believe currently there is no possibility to change the modifier keys used
for the default keybindings. This means that if you want to use the Mod4 key
instead of Meta, you must unbind all the respective keys and remap them. With
this new option you can achieve it in a simple way. Use case for this arrives
when you want to use the Alt key for your applications, and move the default
Meta modifier to Mod4 for example.

Example of configuration:
# Swap Meta with Mod4 and Control with Shift
swap-mods MC 4S

Here is the patch:

Index: cwmrc.5
===================================================================
RCS file: /cvs/xenocara/app/cwm/cwmrc.5,v
retrieving revision 1.78
diff -u -p -r1.78 cwmrc.5
--- cwmrc.5	20 Jul 2023 14:39:34 -0000	1.78
+++ cwmrc.5	10 Apr 2024 19:02:53 -0000
@@ -207,6 +207,16 @@ The default behavior for new windows is 
 By enabling sticky group mode,
 .Xr cwm 1
 will assign new windows to the currently selected group.
+.It Ic swap-mods Ar mods1 mods2
+Swap modifiers for mouse and keyboard. Modifiers in
+.Ar mods1
+are swapped with
+.Ar mods2
+in order. The same modifiers are recognised as for
+.Ar key 
+in
+.Nm bind-key .
+.Pp
 .It Ic unbind-key Ar key
 Unbind function bound to
 .Ar key .
@@ -498,6 +508,9 @@ unbind-key CMS-equal
 # Mouse bindings
 bind-mouse M-2		window-lower
 bind-mouse M-3		window-resize
+
+# Swap Meta with Mod4 and Shift with Control
+swap-mods MS 4C
 .Ed
 .Sh SEE ALSO
 .Xr cwm 1
Index: conf.c
===================================================================
RCS file: /cvs/xenocara/app/cwm/conf.c,v
retrieving revision 1.256
diff -u -p -r1.256 conf.c
--- conf.c	20 Jul 2023 14:39:34 -0000	1.256
+++ conf.c	10 Apr 2024 19:02:53 -0000
@@ -665,6 +665,46 @@ conf_unbind_mouse(struct conf *c, struct
 	}
 }
 
+int
+conf_swap_mods(struct conf *c, const char *mods1, const char *mods2)
+{
+	struct bind_ctx *bind = NULL;
+	unsigned int i;
+	unsigned int mask1, mask2;
+
+	if (strlen(mods1) != strlen(mods2))
+		return 0;
+
+	for (;*mods1; ++mods1, ++mods2) {
+		mask1 = mask2= 0;
+		for (i = 0; i < nitems(bind_mods); ++i) {
+			if (bind_mods[i].ch == *mods1)
+				mask1 = bind_mods[i].mask;
+			if (bind_mods[i].ch == *mods2)
+				mask2 = bind_mods[i].mask;
+		}
+
+		if (!mask1 || !mask2)
+			return 0;
+
+		TAILQ_FOREACH(bind, &c->keybindq, entry) {
+			bind->modmask =
+			    (bind->modmask & ~(mask1 | mask2)) |
+			    ((bind->modmask & mask1) ? mask2 : 0) |
+			    ((bind->modmask & mask2) ? mask1 : 0);
+		}
+
+		TAILQ_FOREACH(bind, &c->mousebindq, entry) {
+			bind->modmask =
+			    (bind->modmask & ~(mask1 | mask2)) |
+			    ((bind->modmask & mask1) ? mask2 : 0) |
+			    ((bind->modmask & mask2) ? mask1 : 0);
+		}
+	}
+
+	return 1;
+}
+
 void
 conf_grab_kbd(Window win)
 {
Index: calmwm.h
===================================================================
RCS file: /cvs/xenocara/app/cwm/calmwm.h,v
retrieving revision 1.379
diff -u -p -r1.379 calmwm.h
--- calmwm.h	20 Jul 2023 14:39:34 -0000	1.379
+++ calmwm.h	10 Apr 2024 19:02:53 -0000
@@ -543,6 +543,8 @@ int			 conf_bind_key(struct conf *, cons
     			     const char *);
 int			 conf_bind_mouse(struct conf *, const char *,
     			     const char *);
+int			 conf_swap_mods(struct conf *, const char*,
+			     const char *);
 void			 conf_clear(struct conf *);
 void			 conf_client(struct client_ctx *);
 void			 conf_cmd_add(struct conf *, const char *,
Index: parse.y
===================================================================
RCS file: /cvs/xenocara/app/cwm/parse.y,v
retrieving revision 1.75
diff -u -p -r1.75 parse.y
--- parse.y	24 Dec 2021 16:00:47 -0000	1.75
+++ parse.y	10 Apr 2024 19:02:53 -0000
@@ -68,7 +68,7 @@ typedef struct {
 
 %}
 
-%token	BINDKEY UNBINDKEY BINDMOUSE UNBINDMOUSE
+%token	BINDKEY UNBINDKEY BINDMOUSE UNBINDMOUSE SWAPMODS
 %token	FONTNAME STICKY GAP
 %token	AUTOGROUP COMMAND IGNORE WM
 %token	YES NO BORDERWIDTH MOVEAMOUNT HTILE VTILE
@@ -256,6 +256,16 @@ main		: FONTNAME STRING		{
 			}
 			free($2);
 		}
+		| SWAPMODS numberstring numberstring {
+			if (!conf_swap_mods(conf, $2, $3)) {
+				yyerror("invalid swap-mods: %s %s", $2, $3);
+				free($2);
+				free($3);
+				YYERROR;
+			}
+			free($2);
+			free($3);
+		}
 		;
 
 color		: COLOR colors
@@ -351,6 +361,7 @@ lookup(char *s)
 		{ "selfont", 		FONTSELCOLOR},
 		{ "snapdist",		SNAPDIST},
 		{ "sticky",		STICKY},
+		{ "swap-mods",		SWAPMODS},
 		{ "unbind-key",		UNBINDKEY},
 		{ "unbind-mouse",	UNBINDMOUSE},
 		{ "ungroupborder",	UNGROUPBORDER},