Copyright (C) 1994, Digital Equipment Corp.
<*PRAGMA LL*>An
AnchorBtnVBT.T is a button that activates a pull-down menu when
you click on it or roll into it from another anchor button.
Associated with each anchor button b is
\medskip\bulletitem b.menu, the menu to be activated,
\medskip\bulletitem b.hfudge and b.vfudge, dimensions in millimeters
that control where the menu is popped up,
\medskip\bulletitem b.n, a count of the number of ZSplit ancestors
of b to skip when looking for the ZSplit to insert the
menu into.
\medskip\noindent A down click on an anchor button b {\it activates}
it by:
\medskip\bulletitem calling the method b.pre(), and then
\medskip\bulletitem inserting the window b.menu so that its
northwest corner is b.hfudge millimeters to the right and
b.vfudge millimeters below the southwest corner of b.
The menu will be inserted into the (b.n)th ZSplit ancestor of
b (counting the first ZSplit ancestor as zero), or as an
undecorated top-level window if b has at most b.n ZSplit
ancestors.
\medskip\noindent The anchor button will be deactivated when it gets
another mouse transition or when the user rolls the mouse over a
sibling anchor button, in which case the sibling will be activated.
Two anchor buttons are siblings if they have the same ``anchor parent''.
The anchor parent is specified when the anchor button is created;
if it is NIL, then the normal parent is used as the anchor parent.
When an anchor button is deactivated, its cancel method is called
and its menu is deleted from its ZSplit.
The default pre method highlights the anchor button; the default
cancel method unhighlights it.
In the common case in which the user down-clicks on the anchor, rolls over the menu, and up-clicks on one of the items, the upclick will be delivered to the item first, which will invoke the appropriate action, and then will be delivered to the anchor button (since the anchor button has the mouse focus), which will delete the menu.
A HighlightVBT is automatically inserted over the menu when it is
inserted, and discarded when the menu is deleted. This allows the
menu items to highlight themselves without interfering with the
highlighting of the anchor button.
The action procedure and post method of an anchor button are never
called. The pre and cancel methods can be overridden; for
example, the pre method could prepare the menu before it is
inserted. This is the reason the menu field is revealed in the type
declaration.
The same menu can be associated with several anchor buttons, provided that only one of them is active at a time.
INTERFACEThe callAnchorBtnVBT ; IMPORT ButtonVBT, VBT; TYPE T <: Public; Public = ButtonVBT.T OBJECT menu: VBT.T METHODS <* LL.sup <= VBT.mu *> init(ch: VBT.T; menu: VBT.T; n: CARDINAL := 0; anchorParent: VBT.T := NIL; hfudge, vfudge := 0.0; ref: REFANY := NIL): T END;
v.init(...) initializes the button with the given
attributes, and adds ref to v's property set if it is not NIL.
This includes a call to ButtonVBT.T.init(v, ch).
You must not change the menu while the AnchorBtnVBT is active.
PROCEDURE New( ch: VBT.T; menu: VBT.T; n: CARDINAL := 0; anchorParent: VBT.T := NIL; hfudge, vfudge := 0.0; ref: REFANY := NIL): T; <* LL.sup <= VBT.mu *>
New(...)is equivalent toNEW(T).init(...).
PROCEDURE SetParent(v: T; p: VBT.T); <* LL.sup = VBT.mu *>
Set the anchor parent ofvto bep. Ifvis active, this is a checked runtime error.
PROCEDURE GetParent(v: T): VBT.T; <* LL.sup = VBT.mu *>
Return the anchor parent of v. PROCEDURE Set(v: T; n: CARDINAL; hfudge, vfudge: REAL); <* LL.sup = VBT.mu *>
Set the attributes ofv. Ifvis active, this is a checked runtime error.
PROCEDURE Get(v: T; VAR n: CARDINAL; VAR hfudge, vfudge: REAL); <* LL.sup = VBT.mu *>
Fetch the attributes of v. PROCEDURE IsActive(v: T): BOOLEAN; <* LL.sup = VBT.mu *>
ReturnTRUEif and only ifvis active.
END AnchorBtnVBT.