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SHR: slight optimization of stupid line clipping

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Bobbi Webber-Manners 2023-01-08 00:05:22 -05:00
parent 8f0564f38f
commit 9ca5a702ca
2 changed files with 37 additions and 15 deletions
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applecorn.po
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52
mainmem.shr.s
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@ -256,19 +256,20 @@ SHRPLOT >>> ENTMAIN
:S1 CMP #$40 ; Plot point
BNE :BAIL ; Other? Bail out
BIT SHRCURROUT ; Point in window?
BMI :S2 ; No - skip drawing
PHP ; Disable interrupts
SEI
CLC ; 65816 native mode
XCE
SEP #$30 ; 8 bit M & X
MX %11 ; Tell Merlin
JSR SHRPOINT
JSR SHRPOINT2
SEC ; 65816 emulation mode
XCE
MX %11 ; Tell Merlin
PLP ; Resume normal service
BRA :S2
:S2 PLA ; Store prev pt in screen coords
STA SHRYPIXEL+1
PLA
@ -277,6 +278,8 @@ SHRPLOT >>> ENTMAIN
STA SHRXPIXEL+1
PLA
STA SHRXPIXEL+0
LDA SHRCURROUT ; Current 'outside window' flag
STA SHRPREVOUT ; Previous 'outside window' flag
:DONE >>> XF2AUX,GFXPLOTRET
:BAIL PLA
PLA
@ -308,7 +311,13 @@ SHRPLOTCOL LDA SHRGFXFGMASK ; Preserve FG colour
* Plot a point
* Called in 65816 native mode, 8 bit M & X
SHRPOINT REP #$30 ; 16 bit M & X
SHRPOINT BIT SHRCURROUT ; First point outside?
BMI :CHECK ; If so, check coords
BIT SHRPREVOUT ; Second point outside?
BMI :CHECK ; If so, check coords
BRA SHRPOINT2 ; Neither outside
:CHECK REP #$30 ; 16 bit M & X
MX %00 ; Tell Merlin
LDA A2L ; y coordinate
CMP SHRWINBTM
@ -719,15 +728,9 @@ SHRCOORD MAC
ADC #0 ; Add in carry (9th bit)
XBA ; Clever trick: fewer shifts
STA A2L ; Into A2L/H
SEC ; Back to emulation mode
XCE
MX %11 ; Tell Merlin
PLP ; Normal service resumed
BRA SHRCOORDEND
BRA SHRCOORDCHK
SHRCOORDNEG MX %00 ; Tell Merlin we are 16 bit
EOR #$FFFF ; Negate
SHRCOORDNEG EOR #$FFFF ; Negate
INC A
ASL ; *2
ADC SHRVDUQ+7 ; *3
@ -751,12 +754,31 @@ SHRCOORDNEG MX %00 ; Tell Merlin we are 16 bit
EOR #$FFFF ; Negate
INC A
STA A2L ; Into A2L/H
SEC ; Back to emulation mode
XCE
SHRCOORDCHK CMP SHRWINBTM ; y coordinate
BMI SHRCOORDOUT
CMP SHRWINTOP
BEQ SHRCOORDCHK2
BPL SHRCOORDOUT
SHRCOORDCHK2 LDA A1L ; x coordinate
CMP SHRWINLFT
BMI SHRCOORDOUT
CMP SHRWINRGT
BPL SHRCOORDOUT
BRA SHRCOORDIN
SHRCOORDOUT SEP #$30 ; 8 bit M & X
MX %11 ; Tell Merlin
SEC
ROR SHRCURROUT ; Set SHRCURROUT to $80
BRA SHRCOORDEND
SHRCOORDIN SEP #$30 ; 8 bit M & X
MX %11 ; Tell Merlin
STZ SHRCURROUT ; Reset SHRCURROUT
SHRCOORDEND SEC ; Back to emulation mode
XCE
PLP ; Normal service resumed
SHRCOORDEND EOM
EOM
* Another coordinate transform, used by VDU25