gig-line/Tools/ue_create_input_assets.py

# Creates the Enhanced Input assets the first-person character loads:
#   /Game/Input/IA_Move     Axis2D, WASD + left stick
#   /Game/Input/IA_Look     Axis2D, mouse XY + right stick
#   /Game/Input/IA_Jump     axis1d, Space / gamepad face button
#   /Game/Input/IMC_Default InputMappingContext holding the three mappings
#
# Run headless (imports/dirty packages are saved before exit):
#   <engine>/Engine/Binaries/Linux/UnrealEditor-Cmd <uproject> -run=pythonscript \
#     -script=<repo>/Tools/ue_create_input_assets.py -nullrhi -unattended -nopause \
#     -stdout -FullStdOutLogOutput
#
# The result goes to /tmp/gigline/input-assets.txt because 5.8's pythonscript
# commandlet swallows print() output with -stdout.
#
# Mapping choices:
#   - Look stays unit-free (no scalar modifier): the character applies its own
#     degrees-per-second, and a modifier here would double-scale.
#   - Move is a 2D axis: W = +Y, S = -Y, D = +X, A = -X via Negate on the Y axis.
#     For keyboard keys the Negate modifier's Y axis maps to the axis's Y.

import unreal

ASSET_DIR = "/Game/Input"
_KEEP_ALIVE = []


def negate_y_modifier():
    """A negate-by-Y modifier, built with its Y flag set and X/Z cleared.

    Returns the object plus its falsy reference; constructing the default
    modifier gives all axes true, so each flag is set explicitly. The caller owns
    keep-alive.
    """
    neg = unreal.InputModifierNegate()
    neg.set_editor_property("x", False)
    neg.set_editor_property("y", True)
    neg.set_editor_property("z", False)
    return neg
RESULT = "/tmp/gigline/input-assets.txt"
lines = []


def log(msg):
    lines.append(str(msg))
    unreal.log(str(msg))


def fresh(name, cls, factory):
    """Load the asset if it exists, otherwise create it.

    Deleting then recreating in the same commandlet run fails: create_asset
    returns None for a path deleted earlier in the process. Overwriting in place
    is also what keeps the assets' identities stable across reruns.
    """
    path = f"{ASSET_DIR}/{name}"
    existing = unreal.EditorAssetLibrary.load_asset(path)
    if existing is not None:
        return existing
    return unreal.AssetToolsHelpers.get_asset_tools().create_asset(
        name, ASSET_DIR, cls, factory())


def save(asset):
    unreal.EditorAssetLibrary.save_loaded_asset(asset, only_if_is_dirty=False)


def make_key(name):
    """Build an FKey by name.

    `unreal.InputCoreTypes` is not exposed to Python in 5.8 and `unreal.Key` does
    not accept a constructor argument, but the struct's `import_text` parses the
    key's export text, which is just its name.
    """
    key = unreal.Key()
    key.import_text(name)
    return key


def build():
    if not unreal.EditorAssetLibrary.does_directory_exist(ASSET_DIR):
        unreal.EditorAssetLibrary.make_directory(ASSET_DIR)

    # --- actions ---------------------------------------------------------
    # Move keys are one-dimensional: W/S carry forward/back on the value's single
    # component and D/A carry strafe, combined by the character. A 2D value would
    # need per-key axis modifiers, and modifiers do not survive the save path here.
    ia_move = fresh("IA_Move", unreal.InputAction, unreal.InputAction_Factory)
    ia_move.set_editor_property("value_type", unreal.InputActionValueType.AXIS1D)
    save(ia_move)

    ia_look = fresh("IA_Look", unreal.InputAction, unreal.InputAction_Factory)
    ia_look.set_editor_property("value_type", unreal.InputActionValueType.AXIS2D)
    save(ia_look)

    ia_jump = fresh("IA_Jump", unreal.InputAction, unreal.InputAction_Factory)
    ia_jump.set_editor_property("value_type", unreal.InputActionValueType.BOOLEAN)
    save(ia_jump)

    # --- mapping context -------------------------------------------------
    imc = fresh("IMC_Default", unreal.InputMappingContext, unreal.InputMappingContext_Factory)

    # Nine entries, one per key. No modifiers: the character negates S and A in
    # C++ instead, because a modifier object attached to a mapping struct
    # serialises as None on save in this build (the struct's object array does not
    # keep the modifier alive across the save path). One less moving part, and the
    # negation is visible where it is used.
    # Two actions feed the one-dimensional move: IA_Move for forward/back, and a
    # second action for strafe, both reporting on the value's single component.
    ia_strafe = fresh("IA_Strafe", unreal.InputAction, unreal.InputAction_Factory)
    ia_strafe.set_editor_property("value_type", unreal.InputActionValueType.AXIS1D)
    save(ia_strafe)

    ia_back = fresh("IA_MoveBack", unreal.InputAction, unreal.InputAction_Factory)
    ia_back.set_editor_property("value_type", unreal.InputActionValueType.AXIS1D)
    save(ia_back)

    ia_left = fresh("IA_StrafeLeft", unreal.InputAction, unreal.InputAction_Factory)
    ia_left.set_editor_property("value_type", unreal.InputActionValueType.AXIS1D)
    save(ia_left)

    mapping_table = [
        (ia_move, "W"), (ia_back, "S"), (ia_strafe, "D"), (ia_left, "A"),
        (ia_move, "Gamepad_LeftY"), (ia_strafe, "Gamepad_LeftX"),
        (ia_look, "MouseX"), (ia_look, "MouseY"), (ia_look, "Gamepad_Right2D"),
        (ia_jump, "SpaceBar"), (ia_jump, "Gamepad_FaceButton_Bottom"),
    ]

    mappings = []
    for action, key_name in mapping_table:
        try:
            entry = unreal.EnhancedActionKeyMapping()
            entry.set_editor_property("action", action)
            entry.set_editor_property("key", make_key(key_name))
            mappings.append(entry)
        except Exception as exc:  # noqa: BLE001
            log(f"skip {action.get_name()}/{key_name}: {exc}")

    # Array property: rebuild it rather than mutating in place.
    imc.set_editor_property("mappings", mappings)
    save(imc)

    log(f"IA_Move={ia_move.get_path_name()} IA_Look={ia_look.get_path_name()} "
        f"IA_Jump={ia_jump.get_path_name()}")
    log(f"IMC_Default={imc.get_path_name()} mappings={len(mappings)}")
    log("assets=" + ",".join(unreal.EditorAssetLibrary.list_assets(ASSET_DIR)))


try:
    build()
except Exception as exc:  # noqa: BLE001 - surface the failure in the result file
    import traceback
    log(f"FAILED: {type(exc).__name__}: {exc}")
    log(traceback.format_exc())

with open(RESULT, "w") as handle:
    handle.write("\n".join(lines))