Other Event Incorrectly Triggers CALL SETUEVENT/ON UEVENT Trap (46182)

MORE INFORMATION

The problem does not apply to QuickBasic versions 4.0 and earlier because they don't support user-defined event trapping (ON UEVENT GOSUB and CALL SETUEVENT).

Example 1

SETUEVENT improperly activates at the same frequency as the ON TIMER event. This behavior continues to occur until the TIMER OFF statement is used. The problem occurs both in a compiled .EXE program and in the QB.EXE environment. SETUEVENT can be called from another language or from the Basic program itself to reproduce the problem.

The following sample code demonstrates the problem in a compiled .EXE program or in the QB.EXE environment:

' Turn the timer and uevent on:
TIMER ON
UEVENT ON

' Set up the handler routines for events:
ON UEVENT GOSUB ueventhandler
ON TIMER(1) GOSUB timerhandler   ' Timer event occurs every 1 second.

'Invoke a user-defined event just once:
CALL setuevent
PRINT "Press any key to end."
WHILE INKEY$ = ""
WEND
END
				

ueventhandler:

  PRINT "This uevent should only occur once."
  RETURN
				

timerhandler:

  PRINT "A timer event occurred."
  ' TIMER OFF   'Add this line to work around the problem.
  RETURN
				

Example 2

A key trapping event also causes this behavior, for example:

ON UEVENT GOSUB UEtrap
ON KEY(1) GOSUB F1trap
UEVENT ON
KEY(1) ON
PRINT "F1 is trapped. Press enter to trigger Uevent"
WHILE INKEY$ <> CHR$(13): WEND    'F1 key will be trapped
CALL SetUevent             'trigger Uevent
PRINT "Pressing F1 now will cause both events to fire"
WHILE INKEY$ <> CHR$(13): WEND    'Pressing F1 now fires both events
END
UEtrap:
  PRINT "UEvent trapped"
  RETURN
F1trap:
  PRINT "F1 trapped"
  RETURN
				

Related Problem

In the QB.EXE environment, simply stopping the execution of the program and commenting out the ON TIMER statement fails to stop the activation of the SETUEVENT event during subsequent program runs. For more information on this separate QB.EXE environment problem, query on the following words: