Screen Scrolling Commands

[SMcNeill]

A simple set of two commands which can scroll the screen up or down for us, regardless of what screen mode we decide to use it in. Use the "U" and "D" keys in the demo to see how it works. 

Code: (Select All)

SCREEN _NEWIMAGE(640, 480, 32)
PRINT "This is a test of the Steve Scrolling System"
PRINT "This is only a test."
FOR i = 1 TO 15: PRINT i: NEXT
DO
    _LIMIT 30
    a$ = UCASE$(INKEY$)
    IF a$ = "U" THEN ScrollUp
    IF a$ = "D" THEN ScrollDown
LOOP UNTIL a$ = CHR$(27)


SUB ScrollUp
$CHECKING:OFF
DIM m AS _MEM
m = _MEMIMAGE(0)
p = _PIXELSIZE
IF p = 0 THEN w = _WIDTH * 2 ELSE w = _FONTHEIGHT * _WIDTH * p
t$ = SPACE$(m.SIZE - w)
_MEMGET m, m.OFFSET + w, t$
CLS
_MEMPUT m, m.OFFSET, t$
_MEMFREE m
$CHECKING:ON
END SUB

SUB ScrollDown
$CHECKING:OFF
DIM m AS _MEM
m = _MEMIMAGE(0)
p = _PIXELSIZE
IF p = 0 THEN w = _WIDTH * 2 ELSE w = _FONTHEIGHT * _WIDTH * p
t$ = SPACE$(m.SIZE - w)
_MEMGET m, m.OFFSET, t$
CLS
_MEMPUT m, m.OFFSET + w, t$
_MEMFREE m
$CHECKING:ON
END SUB