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.\" $Id: menu_driver.3x,v 1.47 2024/03/16 15:35:01 tom Exp $
.TH menu_driver 3X 2024-03-16 "ncurses @NCURSES_MAJOR@.@NCURSES_MINOR@" "Library calls"
.de bP
.ie n  .IP \(bu 4
.el    .IP \(bu 2
..
.SH NAME
\fBmenu_driver\fP \-
command-processing loop of the menu system
.SH SYNOPSIS
.nf
\fB#include <menu.h>
.PP
\fBint menu_driver(MENU *\fImenu\fP, int \fIc\fP);
.fi
.SH DESCRIPTION
Once a menu has been posted (displayed), you should funnel input events to it
through \fBmenu_driver\fP.  This routine has three major input cases:
.bP
The input is a form navigation request.
Navigation request codes are constants defined in \fB<form.h>\fP,
which are distinct from the key- and character codes
returned by \fBwgetch\fP(3X).
.bP
The input is a printable character.
Printable characters (which must be positive, less than 256) are
checked according to the program's locale settings.
.bP
The input is the KEY_MOUSE special key associated with an mouse event.
.PP
The menu driver requests are as follows:
.TP 5
REQ_LEFT_ITEM
Move left to an item.
.TP 5
REQ_RIGHT_ITEM
Move right to an item.
.TP 5
REQ_UP_ITEM
Move up to an item.
.TP 5
REQ_DOWN_ITEM
Move down to an item.
.TP 5
REQ_SCR_ULINE
Scroll up a line.
.TP 5
REQ_SCR_DLINE
Scroll down a line.
.TP 5
REQ_SCR_DPAGE
Scroll down a page.
.TP 5
REQ_SCR_UPAGE
Scroll up a page.
.TP 5
REQ_FIRST_ITEM
Move to the first item.
.TP 5
REQ_LAST_ITEM
Move to the last item.
.TP 5
REQ_NEXT_ITEM
Move to the next item.
.TP 5
REQ_PREV_ITEM
Move to the previous item.
.TP 5
REQ_TOGGLE_ITEM
Select/deselect an item.
.TP 5
REQ_CLEAR_PATTERN
Clear the menu pattern buffer.
.TP 5
REQ_BACK_PATTERN
Delete the previous character from the pattern buffer.
.TP 5
REQ_NEXT_MATCH
Move to the next item matching the pattern match.
.TP 5
REQ_PREV_MATCH
Move to the previous item matching the pattern match.
.PP
If the second argument is a printable character, the code appends
it to the pattern buffer and attempts to move to the next item matching
the new pattern.
If there is no such match, \fBmenu_driver\fP returns
\fBE_NO_MATCH\fP and deletes the appended character from the buffer.
.PP
If the second argument is one of the above pre-defined requests, the
corresponding action is performed.
.SS "Mouse Handling"
If the second argument is the KEY_MOUSE special key, the associated
mouse event is translated into one of the above pre-defined requests.
Currently only clicks in the user window (e.g., inside the menu display
area or the decoration window) are handled.
.PP
If you click above the display region of the menu:
.bP
a REQ_SCR_ULINE is generated for a single click,
.bP
a REQ_SCR_UPAGE is generated for a double-click and
.bP
a REQ_FIRST_ITEM is generated for a triple-click.
.PP
If you click below the display region of the menu:
.bP
a REQ_SCR_DLINE is generated for a single click,
.bP
a REQ_SCR_DPAGE is generated for a double-click and
.bP
a REQ_LAST_ITEM is generated for a triple-click.
.PP
If you click at an item inside the display area of the menu:
.bP
the menu cursor is positioned to that item.
.bP
If you double-click an item a REQ_TOGGLE_ITEM
is generated and \fBE_UNKNOWN_COMMAND\fP is returned.
This return value makes sense,
because a double click usually means that an item-specific action should
be returned.
It is exactly the purpose of this return value to signal that an
application specific command should be executed.
.bP
If a translation
into a request was done, \fBmenu_driver\fP returns the result of this request.
.PP
If you clicked outside the user window
or the mouse event could not be translated
into a menu request an \fBE_REQUEST_DENIED\fP is returned.
.SS "Application-defined Commands"
If the second argument is neither printable nor one of the above
pre-defined menu requests or KEY_MOUSE,
the drive assumes it is an application-specific
command and returns \fBE_UNKNOWN_COMMAND\fP.  Application-defined commands
should be defined relative to \fBMAX_COMMAND\fP, the maximum value of these
pre-defined requests.
.SH RETURN VALUE
\fBmenu_driver\fP return one of the following error codes:
.TP 5
.B E_OK
The routine succeeded.
.TP 5
.B E_SYSTEM_ERROR
System error occurred (see \fBerrno\fP(3)).
.TP 5
.B E_BAD_ARGUMENT
Routine detected an incorrect or out-of-range argument.
.TP 5
.B E_BAD_STATE
Routine was called from an initialization or termination function.
.TP 5
.B E_NOT_POSTED
The menu has not been posted.
.TP 5
.B E_UNKNOWN_COMMAND
The menu driver code saw an unknown request code.
.TP 5
.B E_NO_MATCH
Character failed to match.
.TP 5
.B E_REQUEST_DENIED
The menu driver could not process the request.
.SH PORTABILITY
These routines emulate the System V menu library.
They were not supported on
Version 7 or BSD versions.
The support for mouse events is \fI\%ncurses\fP specific.
.SH AUTHORS
Juergen Pfeifer.
Manual pages and adaptation for new curses by Eric S. Raymond.
.SH SEE ALSO
\fB\%curses\fP(3X),
\fB\%getch\fP(3X),
\fB\%menu\fP(3X)