[3.3.x] Wayland driver requires newer libxkbcommon than is available in Steam Runtime 2 'soldier'

[smcv]

In Steam Runtime 2 'soldier' SDK, building with -DSDL_WAYLAND_SHARED=OFF:

../src/video/wayland/SDL_waylandsym.h: In function ‘SDL_WAYLAND_LoadSymbols’:
../src/video/wayland/SDL_waylandsym.h:160:25: error: ‘xkb_keymap_key_get_mods_for_level’ undeclared (first use in this function); did you mean ‘xkb_keymap_key_get_syms_by_level’?
 SDL_WAYLAND_SYM(size_t, xkb_keymap_key_get_mods_for_level, (struct xkb_keymap *,
                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../src/video/wayland/SDL_waylanddyn.c:204:60: note: in definition of macro ‘SDL_WAYLAND_SYM’
 #define SDL_WAYLAND_SYM(rc, fn, params)     WAYLAND_##fn = fn;
                                                            ^~
../src/video/wayland/SDL_waylandsym.h:160:25: note: each undeclared identifier is reported only once for each function it appears in
 SDL_WAYLAND_SYM(size_t, xkb_keymap_key_get_mods_for_level, (struct xkb_keymap *,
                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../src/video/wayland/SDL_waylanddyn.c:204:60: note: in definition of macro ‘SDL_WAYLAND_SYM’
 #define SDL_WAYLAND_SYM(rc, fn, params)     WAYLAND_##fn = fn;
                                                            ^~

xkb_keymap_key_get_mods_for_level() was new in libxkbcommon 1.0, but soldier only has 0.8.2 available.

(For the builds of SDL in Debian and the Steam Runtime container runtimes, we build most dependencies with -DSDL_DEPS_SHARED=OFF to try to make missing functionality be a compile-time failure, rather than a runtime crash - it's easier to detect that sort of thing this way.)

[smcv]

Simplified reproducer (the original reproducer was an update to the Steam Runtime's own packaging based on this git snapshot):

$ podman pull registry.gitlab.steamos.cloud/steamrt/soldier/sdk:beta
$ podman run --rm -it registry.gitlab.steamos.cloud/steamrt/soldier/sdk:beta
# git clone https://github.com/libsdl-org/SDL
# cd SDL
# cmake -DSDL_DEPS_SHARED=OFF -S . -B build -GNinja -DSDL_KMSDRM=OFF -DSDL_WAYLAND=ON
# ninja -C build clean
# ninja -C build

It's OK to see some -Wincompatible-pointer-types warnings from the PulseAudio driver - soldier's libpulse is less const-correct than modern versions.

A successful workaround is to use -DSDL_WAYLAND=OFF.

[Kontrabant]

I think this can be worked around with a fallback function that uses xkb_state_key_get_level().

[smcv]

Sorry, but this doesn't seem fixed: a newer snapshot after #14106 doesn't compile for me either.

[smcv]

../src/video/wayland/SDL_waylandevents.c: In function 'xkb_legacy_get_mods_for_level':
../src/video/wayland/SDL_waylandevents.c:1465:12: error: 'mask_idx' undeclared (first use in this function); did you mean 'masks_size'?
     return mask_idx;

Did you mean?

diff --git a/src/video/wayland/SDL_waylandevents.c b/src/video/wayland/SDL_waylandevents.c
index 50810284d..8b4c2920b 100644
--- a/src/video/wayland/SDL_waylandevents.c
+++ b/src/video/wayland/SDL_waylandevents.c
@@ -1428,6 +1428,7 @@ static size_t xkb_legacy_get_mods_for_level(SDL_WaylandSeat *seat, xkb_keycode_t
         return 1;
     }
 
+    size_t mask_idx = 0;
     struct xkb_state *state = WAYLAND_xkb_state_new(seat->keyboard.xkb.keymap);
     if (state) {
         const xkb_mod_mask_t keymod_masks[] = {
@@ -1447,8 +1448,6 @@ static size_t xkb_legacy_get_mods_for_level(SDL_WaylandSeat *seat, xkb_keycode_t
         const xkb_mod_mask_t pressed_mod_mask = seat->keyboard.xkb.shift_mask | seat->keyboard.xkb.level3_mask | seat->keyboard.xkb.level5_mask;
         const xkb_mod_mask_t locked_mod_mask = seat->keyboard.xkb.caps_mask;
 
-        size_t mask_idx = 0;
-
         for (size_t i = 0; i < SDL_arraysize(keymod_masks); ++i) {
             WAYLAND_xkb_state_update_mask(state, keymod_masks[i] & pressed_mod_mask, 0, keymod_masks[i] & locked_mod_mask, 0, 0, layout);
             if (WAYLAND_xkb_state_key_get_level(state, key, layout) == level) {

(Compiles successfully, not otherwise tested - I don't know the finer details of the Wayland video driver well enough to know how to exercise this code.)

[Kontrabant]

Whoops, that was a last-second refactoring error. It seems that the buildbots don't have a version of libxkbcommon old enough to actually hit this path, so it still checked out.

It's been fixed.

[smcv]

If I've got it right (not sure), #14119 should help to detect this sort of thing - except we might need to tell it to compile with -DSDL_DEPS_SHARED=OFF to actually reproduce the original problem, I'm not sure.