input-method-exit-on-invalid-key

input-method-exit-on-invalid-key is a variable defined in `mule-cmds.el'.
Its value is

nil

Documentation:
This flag controls the behavior of an input method on invalid key input.
Usually, when a user types a key which doesn't start any character
handled by the input method, the key is handled by turning off the
input method temporarily. After that key, the input method is re-enabled.
But, if this flag is non-nil, the input method is never back on.