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Q31936: Example of Using SetUEvent, ON UEVENT to Detect Mouse Presence

Article: Q31936
Product(s): See article
Version(s): 6.00 6.00b 7.00 7.10
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_QuickBas | mspl13_basic
Last Modified: 17-JAN-1991

The following example uses the SetUEvent routine and the ON UEVENT
statement to trap a user-defined event. An event occurs in the sample
program below if the Microsoft Mouse is not installed. The program
traps the event if and when it occurs, and then prints a message.

The user-defined event-trapping feature is found in QuickBASIC version
4.00b, Microsoft BASIC Compiler versions 6.00 and 6.00b for MS-DOS,
and Microsoft BASIC Professional Development System (PDS) versions
7.00 and 7.10 for MS-DOS. The SetUEvent routine and the ON UEVENT
statement are not found in QuickBASIC version 4.00 or earlier.

For more information on the CALL INTERRUPT statement used in the code
example below to call the Microsoft Mouse, query on the following
words in this database:

   mouse and CALL and INTERRUPT

INTERRUPT is an external routine located in QB.LIB on the QuickBASIC
release disk.

Code Example
------------

DECLARE SUB mouse (m0, m1, m2, m3)
' change following line to include QBX.BI if in BASIC PDS 7.00/7.10
REM $INCLUDE: 'QB.BI'

ON UEVENT GOSUB handler
UEVENT ON

m0 = 0: CALL mouse(m0, m1, m2, m3)                 'Initialize the MOUSE
   IF NOT m0 THEN CALL SetUEvent    'If no Mouse installed print message
'-------------- Other program code can be written here -----------------
END
handler:
   PRINT "No Mouse installed"
END

SUB mouse (m0, m1, m2, m3) STATIC         'Talks to the MOUSE.COM driver
DIM inregs AS RegType: DIM outregs AS RegType
   inregs.ax = m0                                    'Load the registers
   inregs.bx = m1
   inregs.cx = m2
   inregs.dx = m3
   CALL INTERRUPT(51, inregs, outregs)   'Call the mouse driver interrupt
   m0 = outregs.ax
   m1 = outregs.bx                             'Return values from driver
   m2 = outregs.cx
   m3 = outregs.dx
END SUB

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