<*PRAGMA LL*>

INTERFACE JoinParent;

IMPORT ETAgent, JoinedVBT, VBT, Rect, ScrnCursor;

TYPE Join = JoinedVBT.Public OBJECT parents: T := NIL END;

TYPE
  T <: Public;
  Public =
    ETAgent.T OBJECT             <* LL >= {JoinedVBT.T child of T, VBT.mu} *>
      link: T
    METHODS
      <* LL.sup <= VBT.mu *>
      init (join: JoinedVBT.T): T;
    END;

The northwest corner of the parent's domain is positioned at point (north, west) in Joined's domain; this will be maintained as the parent is reshaped or rescreened.

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

New(...) is equivalent to NEW(ParentT).init(...).

PROCEDURE Rem (prnt: T);
<* LL = VBT.mu *>

Cause the child of prnt to lose parent prnt, and mark it for redisplay.

PROCEDURE Child (prnt: T): JoinedVBT.T;
<* LL = VBT.mu *>

Return the JoinedVBT for which prnt is a parent.

PROCEDURE Succ (v: JoinedVBT.T; prnt: T): T;
<* LL.sup = VBT.mu OR LL.sup = v *>

Return the successor to parent prnt of v. It is a checked runtime error if prnt is not a parent of v. As with Split.Succ, the successor of NIL is the first parent; the successor the last parent is NIL; and the successor of NIL is NIL if v has no parents.

PROCEDURE Current(v: JoinedVBT.T): T;
<* LL.sup = v OR LL.sup = VBT.mu *>

PROCEDURE SetInput(v: JoinedVBT.T; prnt: T);
<* LL.sup = VBT.mu *>

PROCEDURE NeedsRescreen(v: JoinedVBT.T): BOOLEAN;
<* LL.sup = VBT.mu *>

PROCEDURE ST(v: JoinedVBT.T): VBT.ScreenType;
<* LL.sup = VBT.mu *>

PROCEDURE Domain(v: JoinedVBT.T): Rect.T;
<* LL.sup = VBT.mu *>

PROCEDURE SetCursor(v: T; cs: ScrnCursor.T);
<* LL.sup = JoinedVBT child of v *>

END JoinParent.