Re: A83: Re: Clearing & xoring rectangles
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Re: A83: Re: Clearing & xoring rectangles
HLine: (not tested)
; IN: d = x1, e = x2, l = y
lh h,0 ; clear high byte
sla l ; * 2
sla l ; * 4
ld b,l ; save y * 4
sla l ; * 8
rl h ; handle overflow
ld a,l ; get low byte
add a,b ; add saved value (*4 + *8 = *12)
ld l,a ; save low byte
ld bc,VRAM ; VRAM = start of video ram (graph buffer)
adc hl,bc ; compute pointer, including overflow from *4 + *8
ld a,d ; get x1
sub e ; compute x2-x1
jr nc,HLineP ; if it's positive, continue
neg ; make it positive
HLineP:
ld a,d ; get x1
and %11111000 ; clear lower 3 bits
-----Original Message-----
From: Henry Davidowich <rdaneelolivaw@hotmail.com>
To: assembly-83@lists.ticalc.org <assembly-83@lists.ticalc.org>
Date: Sunday, October 25, 1998 6:25 PM
Subject: Re: A83: Re: Clearing & xoring rectangles
>
>Thanks to Dave Phillips, JKhum98, and James Matthews. The _ILine idea
>should work, but I was hoping for something faster. Like working with
>the bits of the graph screen. Any ideas? BTW, I do want to fill the
>rect. Thanks!
>
>______________________________________________________
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