psx_mod_set_pad_transform(player, &PSXModPadTransform) registers stage 2b
of pad_external_input: after the physical pad and any controller source,
before the mouse policy. The transform sees the resolved pad plus the
port's host extras (gamepad present, LT/RT 0..255 from SDL, unthresholded)
and may rewrite buttons, sticks and the presented controller type, e.g. a
NeGcon whose I/II come from the triggers. Output is pre-filled as a
pass-through, validated (struct size, ranges, type within allowed_types)
and replaced by neutral when invalid; detaching or a mod/session reset
owes one neutral release frame. initial_type sets the boot/hotplug type.
The resolver stays pure: host extras arrive through a new capture hook and
the transform through another, both covered in pad_external_input_test.
Under the input guard the transform runs on zero triggers and its output
is neutralized. A NeGcon result resets the mouse policy rather than letting
it overwrite the I/II bytes. Offline only: netplay, resim, selfcheck replay
and plain debug overrides never reach it.
With no transform registered every pad is bit-identical to before.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Shokunin