PROCESS EVENTS statement

PROCESS EVENTS

r-proevs.p
DEFINE VARIABLE ix AS INTEGER NO-UNDO. DEFINE VARIABLE stop-sel AS LOGICAL NO-UNDO. DEFINE BUTTON stop-it LABEL "STOP". DISPLAY stop-it. ON CHOOSE OF stop-it stop-sel = TRUE. ENABLE stop-it. DO ix = 1 TO 1000: DISPLAY ix VIEW-AS TEXT. PROCESS EVENTS. IF stop-sel THEN LEAVE. END.

r-proevs.p

DEFINE VARIABLE ix       AS INTEGER NO-UNDO. 
DEFINE VARIABLE stop-sel AS LOGICAL NO-UNDO. 
DEFINE BUTTON stop-it LABEL "STOP". 
DISPLAY stop-it. 
ON CHOOSE OF stop-it 
  stop-sel = TRUE. 
ENABLE stop-it. 
DO ix = 1 TO 1000:   
  DISPLAY ix VIEW-AS TEXT. 
  PROCESS EVENTS. 
  IF stop-sel THEN LEAVE.  
END.

On each pass through the loop, the procedure displays the new value of ix and then checks whether any events are waiting to be processed. If no events have occurred, execution continues and the loop iterates. If the STOP button has been chosen, that event is processed changing the value of stop-sel. When execution continues, the program exits the loop.

If the loop does not contain the PROCESS EVENTS statement, the choose event never processes and the loop iterates until ix equals 1,000.

The WAIT-FOR statement processes all pending events and blocks all other execution until a specified event occurs. The PROCESS EVENTS statement processes all pending events and immediately continues execution with the next statement.

If there are any asynchronous requests for which PROCEDURE-COMPLETE events have been received but not yet processed, this statement processes these events as described for the WAIT-FOR statement.

You cannot call the .NET method system.Windows.Forms.Application:DoEvent( ) in ABL. The PROCESS EVENTS statement performs the function of this method.

.NET can raise exceptions in the context of an ABL session when this statement executes.