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Applecorn
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Fixes to SHRLINELO. (SHRLINEHI still doesn't work)

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Bobbi Webber-Manners 2023-01-03 19:53:12 -05:00
parent e585fabd8b
commit 78245db5fc
2 changed files with 67 additions and 14 deletions
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applecorn.po
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mainmem.shr.s
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@ -422,14 +422,9 @@ SHRLINE LDA A2L ; y1
:X1 JSR SHRLINESWAP ; Swap parms
JMP SHRLINELO
:YDOM SEP #$30 ; 8 bit M & X
MX %11 ; Tell Merlin
LDA SHRYPIXEL ; y0
:YDOM LDA SHRYPIXEL ; y0
CMP A2L ; y1
BCS :Y1 ; y0 >= y1
REP #$30 ; 16 bit M & X
MX %00 ; Tell Merlin
JMP SHRLINEHI ; y0 < y1
:Y1 JSR SHRLINESWAP ; Swap parms
JMP SHRLINEHI
@ -459,15 +454,10 @@ SHRLINELO LDA A1L ; x1
SEC
SBC SHRXPIXEL ; Subtract x0
STA :DX
SEP #$30 ; 8 bit M & X
MX %11 ; Tell Merlin
LDA A2L ; y1
SEC
SBC SHRYPIXEL ; Subtract y0
STA :DY+0
STZ :DY+1
REP #$30 ; 16 bit M & X
MX %00 ; Tell Merlin
STA :DY
LDA #$0001
STA :YI ; yi = 1
LDA :DY
@ -532,13 +522,76 @@ SHRLINELO LDA A1L ; x1
* Plot y-dominant line (steep gradient)
* Called in 16 bit 65816 native mode. Returns in emulation mode.
SHRLINEHI
* TODO: Write me!
SHRLINEHI LDA A1L ; x1
SEC
SBC SHRXPIXEL ; Subtract x0
STA :DX
LDA A2L ; y1
STA :LIM+0 ; We re-use A1L/H later
SEC
SBC SHRYPIXEL ; Subtract y0
STA :DY
LDA #$0001
STA :XI ; xi = 1
LDA :DX
BPL :S1 ; Skip if dx = 0
EOR #$FFFF ; Negate dx
INC A
STA :DX ; dx = -dx
LDA #$FFFF
STA :XI ; xi = -1
:S1 LDA :DX ; dx
ASL ; 2 * dx
SEC
SBC :DY ; (2 * dx) - dy
STA :D ; D = (2 * dx) - dy
LDA SHRXPIXEL ; x0
STA A1L ; x = x0 (re-using A1L/H)
LDA :DX
SEC
SBC :DY
ASL
STA :DY ; DY now (2 * (dx - dy)
LDA :DX
ASL
STA :DX ; DX now (2 * dx)
LDX SHRYPIXEL ; y = y0
:L1 STX A2L ; Store y-coord for SHRPOINT
PHX
SEP #$30 ; 8 bit M & X
MX %11 ; Tell Merlin
JSR SHRPOINT ; x in A1L/H, y in A2L
REP #$30 ; 16 bit M & X
MX %00 ; Tell Merlin
PLX
LDA :D
BMI :S2 ; D < 0
CLC
ADC :DY
STA :D ; D = D + (2 * (dx - dy))
LDA A1L ; x
CLC
ADC :XI
STA A1L ; x = x + xi
BRA :S3
:S2 CLC
ADC :DX
STA :D ; D = D + 2 * dx
:S3 INX
CPX :LIM ; Compare with y1
BNE :L1
SEC ; 65816 emulation mode
XCE
MX %11 ; Tell Merlin
PLP ; Resume normal service
RTS
:DX DW $0000 ; dx initially, then (2 * dx)
:DY DW $0000 ; dy initially, then (2 * (dy - dx)))
:XI DW $0000 ; +1 or -1
:D DW $0000 ; D
:LIM DW $0000 ; x1 gets stashed here
* Convert high-resolution screen coordinates