Example: System Widget Event Handler
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10 ! *********************************************************************
20 ! Example: SYSTEM Widget Event Handler
30 !
40 ! This program shows how to handle queued events from a SYSTEM
50 ! widget. A SYSTEM widget has an attribute named *QUEUE EVENTS,
60 ! which is normally turned off. In that state, the SYSTEM widget
70 ! will not queue up events -- you get one and all later ones are lost.
80 !
90 ! If you set *QUEUE EVENTS to 1, however, events are queued --
100 ! which leads to the problem of sorting out events from each other.
110 !
120 ! This program shows how this is done by queueing up events from
130 ! three SLIDER widgets contained in a SYSTEM widget. When you
140 ! tell the program to flush the queue, it lists the queued events
150 ! by source SLIDER and event type and gives the number of
160 ! events in each category.
170 !
180 ! This is a somewhat contrived program in that the level of
190 ! event handling demonstrated here is overkill. Under normal
200 ! circumstances, event queueing should not be a concern. In
210 ! fact, this program has to go to considerable lengths to force
220 ! the events to be queued -- by raising the SYSTEM PRIORITY
230 ! to mask out the SLIDER events, and only lowering it when
240 ! it polls a TOGGLEBUTTON and gets back a 1.
250 !
260 ! The SYSTEM MENU event that allows you to exit the program
270 ! is set to a high priority level, so you can exit the program at
280 ! any time.
290 !
300 ! **************************************************************
310 !
320 CLEAR SCREEN
330 INTEGER N ! General-purpose variable
340 INTEGER D(1:4),Dw,Dh,Iw,Ih ! Variables for display handling
350 INTEGER Px,Py,Pw,Ph ! PANEL parameters
360 INTEGER Gx,Gy ! Internal layout gaps
370 INTEGER Nc,R,Sx,Sy,Sw,Sh ! Parameters for SYSTEM widget SLIDERS
380 INTEGER Prx,Pry,Prw,Prh ! Parameters for PRINTER widget
390 INTEGER Tx,Ty,Th,Tw ! Parameters for TOGGLE BUTTON
400 DIM Ev$(1:2)[50],S$[50] ! Return event source - GP string
410 !
420 ! Set up a PANEL in the center of the printing display and put
430 ! a SYSTEM MENU on it so you can quit the program.
440 !
450 STATUS CRT,13;N
460 GESCAPE CRT,3;D(*)
470 Dw=D(3)-D(1)
480 Dh=(D(4)-D(2))*((N-7)/N)
490 !
500 Pw=Dw*.99
510 Ph=Dh*.99
520 Px=(Dw-Pw)/2
530 Py=(Dh-Ph)/2
540 !
550 ASSIGN @Main TO WIDGET "PANEL";SET ("VISIBLE":0)
560 CONTROL @Main;SET ("X":Px+100,"Y":Py+50,"WIDTH":.75*Pw,"HEIGHT":.75*Ph)
570 CONTROL @Main;SET ("SYSTEM MENU":"Quit")
580 CONTROL @Main;SET ("MAXIMIZABLE":0,"RESIZABLE":0)
590 CONTROL @Main;SET ("TITLE":" Example: SYSTEM Widget Event Handling")
600 STATUS @Main;RETURN ("INSIDE WIDTH":Iw,"INSIDE HEIGHT":Ih)
610 !
620 ! Create a SYSTEM widget as a child of the main PANEL, populate
630 ! with SLIDER widgets.
640 !
650 ASSIGN @Sys TO WIDGET "SYSTEM";PARENT @Main
660 !
670 Gx=Iw*.01
680 Gy=Gx
690 !
700 Nc=3
710 Sh=Ih*.85
720 Sw=Iw*.11
730 Sy=Gy
740 !
750 FOR C=1 TO Nc
760 Sx=(C-1)*Sw+Gy
770 S$="S"&VAL$(C)
780 CONTROL @Sys;SET ("*NAME":S$,"*CREATE":"SLIDER")
790 CONTROL @Sys;SET ("X":Sx,"Y":Sy,"WIDTH":Sw,"HEIGHT":Sh)
800 NEXT C
810 !
820 ! Set up a TOGGLEBUTTON to indicate when to trap events
830 !
840 Th=Ih-(Sh+3*Gy)
850 Tw=Iw/2
860 Tx=Gx+(3*Sw-Tw)/2
870 Ty=Ih-(Th+Gy)
880 ASSIGN @Toggle TO WIDGET "TOGGLEBUTTON";PARENT @Main
890 CONTROL @Toggle;SET ("X":Tx+50,"Y":Ty,"WIDTH":Tw,"HEIGHT":Th)
900 CONTROL @Toggle;SET ("LABEL":"Flush Queue")
910 !
920 ! Set up a PRINTER widget on the main PANEL (not as part of
930 ! the SYSTEM widget) to log event handling
940 !
950 Prw=Iw-(3*Sw+3*Gy)
960 Prh=Ih-2*Gy
970 Prx=Iw-(Prw+Gy)
980 Pry=Gy
990 !
1000 ASSIGN @Prn TO WIDGET "PRINTER";PARENT @Main
1010 CONTROL @Prn;SET ("X":Prx,"Y":Pry,"WIDTH":Prw,"HEIGHT":Prh)
1020 !
1030 ! Set up events to trap the SLIDERs in the SYSTEM widget, and
1040 ! set up a high priority trap on the "Quit" button in the SYSTEM
1050 ! MENU
1060 !
1070 CONTROL @Sys;SET ("*QUEUE EVENTS":1)
1080 ON EVENT @Sys,"CHANGED" GOSUB Handler
1090 ON EVENT @Sys,"DONE" GOSUB Handler
1100 ON EVENT @Main,"SYSTEM MENU",15 GOTO Finis
1110 !
1120 ! Set event to quit on SYSTEM MENU, make whole thing visible, loop
1130 ! -- mask out normal events until user toggles the TOGGLEBUTTON
1140 !
1150 CONTROL @Main;SET ("VISIBLE":1)
1160 LOOP
1170 SYSTEM PRIORITY 1
1180 REPEAT
1190 STATUS @Toggle;RETURN ("VALUE":N)
1200 UNTIL (N<>0)
1210 CONTROL @Toggle;SET ("VALUE":0)
1220 CONTROL @Prn;SET ("TEXT":"")
1230 SYSTEM PRIORITY 0
1240 END LOOP
1250 !
1260 ! This event handler confirms SLIDER events by printing out the
1270 ! event and its source. It performs a loop, checking to see
1280 ! if there are events in the queue. If there are, it reads the
1290 ! first event in the queue and flushes all the same events.
1300 ! (You could also read them out if you like.) It continues
1310 ! doing this until it cleans out the queue.
1320 !
1330 Handler: !
1340 LOOP
1350 !
1360 ! Determine total number of events in queue
1370 !
1380 CONTROL @Sys;SET ("*EVENT WIDGET FILTER":"")
1390 CONTROL @Sys;SET ("*EVENT NAME FILTER":"")
1400 STATUS @Sys;RETURN ("*QUEUED EVENTS":N)
1410 !
1420 EXIT IF N=0
1430 !
1440 S$="> Total events in queue: "&VAL$(N)
1450 CONTROL @Prn;SET ("APPEND TEXT":S$)
1460 !
1470 ! Get ID of first source in queue.
1480 !
1490 STATUS @Sys;RETURN ("*QUEUED EVENT":Ev$(*))
1500 !
1510 ! Determine how many of the same events are in the
1520 ! queue and then flush them
1530 !
1540 CONTROL @Sys;SET ("*EVENT WIDGET FILTER":Ev$(1))
1550 CONTROL @Sys;SET ("*EVENT NAME FILTER":Ev$(2))
1560 STATUS @Sys;RETURN ("*FLUSH QUEUED EVENTS":N)
1570 !
1580 S$=" Widget / Event / Total: "
1590 S$=S$&Ev$(1)&" / "&Ev$(2)&" / "&VAL$(N+1)
1600 CONTROL @Prn;SET ("APPEND TEXT":S$)
1610 !
1620 CONTROL @Prn;SET ("APPEND TEXT":"")
1630 !
1640 END LOOP
1650 RETURN
1660 !
1670 Finis: !
1680 ASSIGN @Main TO * ! Delete PANEL widget
1690 CLEAR SCREEN
1700 END
