'===========================================================================
' Subject: VERTICAL SYNC DEMO                Date: 05-15-97 (10:04)       
' Author:  Davey W. Taylor                   Code: QB, QBasic, PDS        
' Origin:  audio.squad@mailbox.swipnet.se  Packet: GRAPHICS.ABC
'===========================================================================
'Demonstration of how to sync graphics to the screens vertical retrace
'Davey W Taylor

DECLARE SUB SetPal (Attr%, Red%, Green%, Blue%)
SCREEN 1
CLS
PRINT ".05 delay without sync"
DO
SetPal 0, 0, 0, 0                            'change pal
s# = TIMER: DO: LOOP UNTIL TIMER - s# >= .05 'delay
SetPal 0, 15, 15, 15                         'change pal
s# = TIMER: DO: LOOP UNTIL TIMER - s# >= .05 'delay
LOOP WHILE INKEY$ = ""
SetPal 0, 0, 0, 0
CLS
PRINT ".05 delay with sync"
DO
WAIT &H3DA, 8                                'wait for retrace
SetPal 0, 0, 0, 0                            'change pal
s# = TIMER: DO: LOOP UNTIL TIMER - s# >= .05 'delay
WAIT &H3DA, 8                                'wait for retrace
SetPal 0, 15, 15, 15                         'change pal
s# = TIMER: DO: LOOP UNTIL TIMER - s# >= .05 'delay
LOOP WHILE INKEY$ = ""

DEFINT A-Z
SUB SetPal (Attr%, Red%, Green%, Blue%) 'SUB to set a color attribute
OUT &H3C7, Attr%
OUT &H3C8, Attr%
OUT &H3C9, Red%
OUT &H3C9, Green%
OUT &H3C9, Blue%
END SUB