Key modifier maps with multiple modifiers do not allow parse/serialize roundtrip

[Twey]

If I remap a shift key:

# symbols/remappedshift
default partial alphanumeric_keys
xkb_symbols "basic" {
    include "us(basic)"
    name[Group1]= "Remapped shift keys";
    key <LFSH> {	[ Alt_L ] };
    modifier_map Mod1 { <LFSH> };
};

then if I run

xkbcli compile-keymap \
    --include . \
    --include-defaults \
    --layout remappedshift \
| xkbcli interactive-wayland

and press <LFSH> with e.g. a then xkbcli interactive-wayland says:

Hyprland: key down [ LFSH ] keysyms [ Alt_L                           ] unicode [   ] layout [ #0 Remapped shift keys ] level [ 0 ] mods [ ] leds [  ] 
Hyprland: state    [ depressed-mods: 0x00000008; effective-mods: 0x00000008; ]
Hyprland: key down [ AC01 ] keysyms [ a                               ] unicode [ a ] layout [ #0 Remapped shift keys ] level [ 0 ] mods [ Mod1 Alt Meta ] leds [  ] 
Hyprland: key up   [ AC01 ] 
Hyprland: key up   [ LFSH ] 
Hyprland: state    [ depressed-mods: 0x00000000; effective-mods: 0x00000000; ]

Now if I copy it to $XDG_CONFIG_HOME and load it as a Wayland layout (I'm using Hyprland) and try the same thing without the pipe, the resulting keystroke is the shifted variant, though it includes the -Shift modifier:

Hyprland: key down [ LFSH ] keysyms [ Alt_L                           ] unicode [   ] layout [ #1 Remapped shift keys ] level [ 0 ] mods [ ] leds [ Group 2 ] 
Hyprland: state    [ depressed-mods: 0x00000009; effective-mods: 0x00000009; ]
Hyprland: key down [ AC01 ] keysyms [ A                               ] unicode [ A ] layout [ #1 Remapped shift keys ] level [ 1 ] mods [ -Shift Mod1 Alt Meta ] leds [ Group 2 ] 
Hyprland: key up   [ AC01 ] 
Hyprland: key up   [ LFSH ] 
Hyprland: state    [ depressed-mods: 0x00000000; effective-mods: 0x00000000; ]

(Applications seem to ignore the -Shift and treat this the same as Alt+Shift+s.)

I don't know whether there is a correct way to remap modifiers like this, but I would expect the behaviours here to be the same.

[wismill]

Please dump the Wayland keymap xkbcli dump-keymap-wayland --raw > /tmp/keymap.xkb and upload it here.

[Twey]

Thanks for the tip! Attached.

It looks like it might be to do with the fact that I'm using multiple layouts to test (gb,hdpm,remappedshift). The modifier_map sections seem to have been merged in a strange way. If I just use remappedshift without any additional layouts things work as I expect.

[wismill]

The issue is that <LFSH> has a modifier map with multiple modifiers and the parsing/serializing libxkbcommon does not roundtrip (nor with xkbcomp). I filed #1054 to fix it.

However in your case you probably do not want this though. Could you try adding modifier_map None { Shift_L };?

[Twey]

Thank you, that does seem to work, but I'm not really sure how!

I tried with modifier_map None { <LFSH> } previously and that didn't fix it, but modifier_map None { Shift_L } seems to.

My dumped map now says

	modifier_map Shift { <RTSH> };
	modifier_map Control { <LCTL>, <RCTL> };
	modifier_map Mod1 { <LALT>, <ALT>, <META> };
	modifier_map Mod2 { <NMLK> };
	modifier_map Mod3 { <LVL5>, <HYPR> };
	modifier_map Mod4 { <LWIN>, <RWIN>, <SUPR> };
	modifier_map Mod5 { <LVL3> };

which seems like it should interfere with shift functionality in my other layouts, but somehow doesn't?

I guess I'm a bit confused as to how modifier_map does/should interact with multiple layouts. In general using multiple layouts seems to merge them with one group per layout, e.g.

        key <AC04>               {
                symbols[Group1]= [               f,               F,         dstroke,     ordf
eminine ],
                symbols[Group2]= [               h,               H,         dstroke,     ordf
eminine ],
                symbols[Group3]= [               f,               F ]
        };

But there's no equivalent structure for modifier_maps.

[wismill]

modifier_map is a key property thus cannot be defined per group.

modifier_map only overrides other entries with the exact same target: e.g. if you used a keysym, you must use the same keysym and not the corresponding keycode. Same if you used a keycode.

See the corresponding doc.