# The TranslateVBT interface

A `TranslateVBT.T` is a filter that maintains a translation between the coordinate systems of the child and parent such that the child's coordinate system has its origin at the northwest corner of the child domain. The child can be `NIL`, in which case the `TranslateVBT` ignores all events.

    INTERFACE TranslateVBT;

    IMPORT VBT, Filter;

    TYPE T <: Filter.T;

The call `v.init(ch)` initializes `v` as a `TranslateVBT` with child `ch`.

    PROCEDURE New(ch: VBT.T): T; <* LL.sup <= VBT.mu *>

`New(...)` is equivalent to `NEW(T).init(...)`.

    END TranslateVBT.