Multiple modifier keys with Mod-Tap

[JosNun]

Heyo!

I'm trying to customize my base layer keymap as described here, and I can't seem to get it to build properly. My goal is to have holding G and H press all the modifier keys (super, ctrl, alt, and shift).

Here is what my custom_config.h looks like:

#define MIRYOKU_LAYER_BASE \
&kp Q,             &kp W,             &kp E,             &kp R,             &kp T,                                      &kp Y,                                &kp U,             &kp I,             &kp O,             &kp P,             \
U_MT(LGUI, A),     U_MT(LALT, S),     U_MT(LCTRL, D),    U_MT(LSHFT, F),    &kp U_MT(LG(LA(LC(LSHFT))), G),             &kp U_MT(RG(RA(RC(RSHFT))), H),       U_MT(RSHFT, J),    U_MT(RCTRL, K),    U_MT(RALT, L),     U_MT(RGUI, SQT),   \
U_LT(U_BUTTON, Z), U_MT(RALT, X),     &kp C,             &kp V,             &kp B,                                      &kp N,                                &kp M,             &kp COMMA,         U_MT(RALT, DOT),   U_LT(U_BUTTON, SLASH),\
U_NP,              U_NP,              U_LT(U_MEDIA, ESC),U_LT(U_NAV, SPACE),U_LT(U_MOUSE, TAB),                         U_LT(U_SYM, RET),  U_LT(U_NUM, BSPC), U_LT(U_FUN, DEL),  U_NP,              U_NP

For reference, the repo is here: https://github.com/JosNun/miryoku_zmk

The failed build job (with stack trace) is here: https://github.com/JosNun/miryoku_zmk/actions/runs/12857264695

Interestingly, the firmware for the right half of the keyboard builds fine. I'm not sure if the keymap lands on that half, though, since that's the remote half, and the left one is the master?

U_MT(LG(LA(LC(LSHFT))), G) is what my keycode (not sure if that's the right term?) is for the key, but I'm not sure if that's the right syntax, or if there's something else I should be using? Maybe the U_MT behavior itself can't handle multiple modifiers?

Any pointers for a direction to look next would be greatly appreciated!

[manna-harbour]

Failing only on the left is normal as the peripheral doesn't have the keymap.

According to the ZMK docs for mod-tap and modifiers, &mt LG(LA(LC(LSHFT))) G should be correct. You might like to try it by editing a default keymap in ZMK as a test, or rewriting it without the U_MT macro (i.e. as written above). If that doesn't work, ask on the ZMK discord. According to an old comment there, even if the syntax is correct and it builds it still won't work in practice due to implementation limitations.

[JosNun]

Thanks for the response! Rewriting it without the macro seems to have worked, and mod-tap is working as I expect, so the broken behavior mentioned in the old comment must have been fixed. Thanks for the help, and I appreciate you pointing me in the right direction!

Not sure why the macro isn't working, but that's an exploration for another day

[JosNun]

Worth noting, that to use the same macro (and get the same behavior) as the rest of my home row keys, I had to use &u_mt instead of &mt. Probably obvious in hindsight, but figured I'd not it here for posterity :)