Program:   Superbase
Version:   2.0
Topic:     Mouse event in Superbase
Date:      January 8, 1993


Summary:   An event procedure is a SUB procedure that is
triggered by an event, such as a mouse click or a keystroke,
and responds by executing the code for the event.  Superbase
supports seven event classes.  This technote concentrates on
a mouse event and its use during data entry in a multi-file
form.  This technote uses the example files from the STOCK
directory to illustrate the example.

Consider the following DML program. ( The lines starting
with REM: are remarks for user readability and can be
ignored)

REM: Switch to the stock directory.
DIRECTORY "c:\sb4w\samples\stock"

REM: Open the following files.
OPEN FILE "Customer"
OPEN FILE "Items"
OPEN FILE "Order"
OPEN FILE "Video"

REM: Load the multi-file form ORDER.
LOAD FORM "Order"

REM: Make the Customer file the current file and CustomerNo
field the current index.
FILE "Customer"
INDEX customerno.Customer

REM: Select the record for which customerno.Customer=00178
and view it.
SELECT FORM KEY "00178"
FORM

REM: Place the cursor on the first field and the form is
ready for data entry.
ENTER 1,0
END

When you run the above program, the order form comes up on
the screen with the 00178 record details.  The cursor is
blinking on the first field.  Note that the detail block has
its own vertical scroll bars attached.  If you try to use
the scroll bars on the detail block, the mouse does not
respond.

To activate  the mouse, you need to use the mouse event
class which traps mouse clicks.  Note that the middle mouse
button is not supported.

To set up and use the mouse event is a two step procedure:
* Defining an event class
* Switching it on and off

It is best you define all your events on the SUB main or at
the very beginning of your application. You can define the
mouse event by issuing the following command:

ON EVENTCLASS MOUSE CALL mouseproc()
When this command is executed, it checks for the syntax of
mouseproc procedure, but does not actually call the
procedure.  The mouseproc procedure is called only when a
mouse is clicked.  The mouseproc procedure takes four
parameters: Queue time, Button identifier and action, X
coordinate, and Y coordinate.  For more information, refer
to Chapter 7 on Event Driven Programming in the "Developing
Applications" manual.

To turn on the mouse event issue the following command:
EVENTCLASS MOUSE ON

With these commands the above program can be rewritten as
follows:

SUB main()
REM: Switch to the stock directory.
DIRECTORY "c:\sb4w\samples\stock"

REM: Define the mouse event class.
ON EVENTCLASS MOUSE CALL mouseproc()

REM: Open the following files.
OPEN FILE "Customer"
OPEN FILE "Items"
OPEN FILE "Order"
OPEN FILE "Video"

REM: Load the multi-file form ORDER.
LOAD FORM "Order"

REM: Make the Customer file the current file and CustomerNo
field the current index.
FILE "Customer"
INDEX customerno.Customer

REM: Select the record for which customerno.Customer=00178
and view it.
SELECT FORM KEY "00178"
FORM

REM:  Turn on the mouse event.
EVENTCLASS MOUSE ON

REM: Place the cursor on the first field and the form is
ready for data entry.
ENTER 1,0
END SUB

REM: mouseproc.
SUB mouseproc(t%,c%%,x%%,y%%)
     REM: Return to Superbase for default processing as if
mouse had never been trapped.
     EVENTDEFAULT
END SUB

When you run the above program notice that the user has
complete control over the position of the cursor as well as
the scroll bars on the detail block.