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cc65/libsrc/c128/c128-640-480-2.s
izydorst 17a99e2709 fixed addressing problems seen on the Real Machine (tm) 
git-svn-id: svn://svn.cc65.org/cc65/trunk@1831 b7a2c559-68d2-44c3-8de9-860c34a00d81
2002-12-23 14:52:51 +00:00

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;
; Graphics driver for the 640x480x2 mode on the C128 VDC 64k
; (values for this mode based on Fred Bowen's document)
; Maciej 'YTM/Elysium' Witkowiak <ytm@elysium.pl>
; 23.12.2002
;
; NOTES:
; For any smart monkey that will try to optimize this: PLEASE do tests on real VDC,
; not only VICE.
;
; Only DONE routine contains C128-mode specific stuff, everything else will work in
; C64-mode of C128 (C64 needs full VDC init then).
;
; With special initialization and CALC we can get 320x200 double-pixel mode.
;
; Color translation values for BROWN and GRAY3 are obviously wrong, they could
; be replaced by equiv. of ORANGE and GRAY2 but this would give only 14 of 16 colors available.
;
; Register 25 ($19) is said to require different value for VDC v1, but I couldn't find what
; it should be.
.include "zeropage.inc"
.include "tgi-kernel.inc"
.include "tgi-mode.inc"
.include "tgi-error.inc"
.macpack generic
; ------------------------------------------------------------------------
; Constants
VDC_ADDR_REG = $D600 ; VDC address
VDC_DATA_REG = $D601 ; VDC data
VDC_DSP_HI = 12 ; registers used
VDC_DSP_LO = 13
VDC_DATA_HI = 18
VDC_DATA_LO = 19
VDC_VSCROLL = 24
VDC_HSCROLL = 25
VDC_COLORS = 26
VDC_CSET = 28
VDC_COUNT = 30
VDC_DATA = 31
; ------------------------------------------------------------------------
; Header. Includes jump table and constants.
.segment "JUMPTABLE"
; First part of the header is a structure that has a magic and defines the
; capabilities of the driver
.byte $74, $67, $69 ; "tgi"
.byte $00 ; TGI version number
xres: .word 640 ; X resolution
yres: .word 480 ; Y resolution
.byte 2 ; Number of drawing colors
pages: .byte 0 ; Number of screens available
.byte 8 ; System font X size
.byte 8 ; System font Y size
.res 4, $00 ; Reserved for future extensions
; Next comes the jump table. Currently all entries must be valid and may point
; to an RTS for test versions (function not implemented). A future version may
; allow for emulation: In this case the vector will be zero. Emulation means
; that the graphics kernel will emulate the function by using lower level
; primitives - for example ploting a line by using calls to SETPIXEL.
.word INSTALL
.word DEINSTALL
.word INIT
.word DONE
.word GETERROR
.word CONTROL
.word CLEAR
.word SETVIEWPAGE
.word SETDRAWPAGE
.word SETCOLOR
.word SETPALETTE
.word GETPALETTE
.word GETDEFPALETTE
.word SETPIXEL
.word GETPIXEL
.word HORLINE
.word LINE
.word BAR
.word CIRCLE
.word TEXTSTYLE
.word OUTTEXT
; ------------------------------------------------------------------------
; Data.
; Variables mapped to the zero page segment variables. Some of these are
; used for passing parameters to the driver.
X1 = ptr1
Y1 = ptr2
X2 = ptr3
Y2 = ptr4
RADIUS = tmp1
ADDR = tmp1 ; (2) CALC
TEMP = tmp3 ; CALC icmp
TEMP2 = tmp4 ; icmp
TEMP3 = sreg ; LINE
TEMP4 = sreg+1 ; LINE
; Line routine stuff (must be on zpage)
PB = ptr3 ; (2) LINE
UB = ptr4 ; (2) LINE
ERR = regsave ; (2) LINE
NX = regsave+2 ; (2) LINE
; Circle stuff
XX = ptr3 ; (2) CIRCLE
YY = ptr4 ; (2) CIRCLE
MaxO = sreg ; (overwritten by TEMP3+TEMP4, but restored from OG/OU anyway)
XS = regsave ; (2) CIRCLE
YS = regsave+2 ; (2) CIRCLE
; Absolute variables used in the code
.bss
ERROR: .res 1 ; Error code
PALETTE: .res 2 ; The current palette
BITMASK: .res 1 ; $00 = clear, $FF = set pixels
OLDCOLOR: .res 1 ; colors before entering gfx mode
; Line routine stuff (combined with CIRCLE to save space)
OGora:
COUNT: .res 2
OUkos:
NY: .res 2
Y3:
DX: .res 1
DY: .res 1
AY: .res 1
; Text output stuff
TEXTMAGX: .res 1
TEXTMAGY: .res 1
TEXTDIR: .res 1
; Constants and tables
.rodata
DEFPALETTE: .byte $00, $0f ; White on black
PALETTESIZE = * - DEFPALETTE
BITTAB: .byte $80,$40,$20,$10,$08,$04,$02,$01
BITMASKL: .byte %11111111, %01111111, %00111111, %00011111
.byte %00001111, %00000111, %00000011, %00000001
BITMASKR: .byte %10000000, %11000000, %11100000, %11110000
.byte %11111000, %11111100, %11111110, %11111111
; color translation table (indexed by VIC color)
COLTRANS: .byte $00, $0f, $08, $06, $0a, $04, $02, $0c
.byte $0d, $0b, $09, $01, $0e, $05, $03, $07
; colors BROWN and GRAY3 are wrong
; VDC initialization table (reg),(val),...,$ff
InitVDCTab:
.byte VDC_DSP_HI, 0 ; viewpage 0 as default
.byte VDC_DSP_LO, 0
.byte VDC_HSCROLL, $87
.byte 2, $66
.byte 4, $4c
.byte 5, $06
.byte 6, $4c
.byte 7, $47
.byte 8, $03
.byte 9, $06
.byte 27, $00
.byte $ff
SCN80CLR: .byte 27,88,147,27,88,0
.code
; ------------------------------------------------------------------------
; INSTALL routine. Is called after the driver is loaded into memory. May
; initialize anything that has to be done just once. Is probably empty
; most of the time.
;
; Must set an error code: NO
;
INSTALL:
; check for VDC version and update register $19 value
; check for VDC ram size and update number of available screens
ldx #VDC_CSET ; determine size of RAM...
jsr VDCReadReg
sta tmp1
ora #%00010000
jsr VDCWriteReg ; turn on 64k
jsr settestadr1 ; save original value of test byte
jsr VDCReadByte
sta tmp2
lda #$55 ; write $55 here
ldy #ptr1
jsr test64k ; read it here and there
lda #$aa ; write $aa here
ldy #ptr2
jsr test64k ; read it here and there
jsr settestadr1
lda tmp2
jsr VDCWriteByte ; restore original value of test byte
lda ptr1 ; do bytes match?
cmp ptr1+1
bne @have64k
lda ptr2
cmp ptr2+1
bne @have64k
ldx #VDC_CSET
lda tmp1
jsr VDCWriteReg ; restore 16/64k flag
jmp @endok ; and leave default values for 16k
@have64k:
lda #1
sta pages
@endok:
rts
test64k:
sta tmp1
sty ptr3
lda #0
sta ptr3+1
jsr settestadr1
lda tmp1
jsr VDCWriteByte ; write $55
jsr settestadr1
jsr VDCReadByte ; read here
pha
jsr settestadr2
jsr VDCReadByte ; and there
ldy #1
sta (ptr3),y
pla
dey
sta (ptr3),y
rts
settestadr1:
ldy #$02 ; test page 2 (here)
.byte $2c
settestadr2:
ldy #$42 ; or page 64+2 (there)
lda #0
jmp VDCSetSourceAddr
; ------------------------------------------------------------------------
; DEINSTALL routine. Is called before the driver is removed from memory. May
; clean up anything done by INSTALL but is probably empty most of the time.
;
; Must set an error code: NO
;
DEINSTALL:
rts
; ------------------------------------------------------------------------
; INIT: Changes an already installed device from text mode to graphics
; mode. The number of the graphics mode is passed to the function in A.
; Note that INIT/DONE may be called multiple times while the driver
; is loaded, while INSTALL is only called once, so any code that is needed
; to initializes variables and so on must go here. Setting palette and
; clearing the screen is not needed because this is called by the graphics
; kernel later.
; The graphics kernel will never call INIT when a graphics mode is already
; active, so there is no need to protect against that.
;
; Must set an error code: YES
;
INIT: cmp #TGI_MODE_640_480_2 ; Correct mode?
beq @L1 ; Jump if yes
lda #TGI_ERR_INV_MODE ; ## Error
bne @L9
@L1: lda pages ; is there enough memory?
bne @L11 ; Jump if there is one screen
lda #TGI_ERR_INV_MODE ; ## Error
bne @L9
; Initialize variables
@L11: ldx #$FF
stx BITMASK
; Remeber current color value
ldx #VDC_COLORS
jsr VDCReadReg
sta OLDCOLOR
; Switch into graphics mode (set view page 0)
ldy #0
@L2: ldx InitVDCTab,y
bmi @L3
iny
lda InitVDCTab,y
jsr VDCWriteReg
iny
bne @L2
@L3:
; Done, reset the error code
lda #TGI_ERR_OK
@L9: sta ERROR
rts
; ------------------------------------------------------------------------
; DONE: Will be called to switch the graphics device back into text mode.
; The graphics kernel will never call DONE when no graphics mode is active,
; so there is no need to protect against that.
;
; Must set an error code: YES
;
DONE:
; This part is C128-mode specific
jsr $e179 ; reload character set and setup VDC
jsr $ff62
lda $d7 ; in 80-columns?
bne @L01
@L0: lda SCN80CLR,y
beq @L1
jsr $ffd2 ; print \xe,clr,\xe
iny
bne @L0
@L01: lda #147
jsr $ffd2 ; print clr
@L1: lda #0 ; restore view page
ldx #VDC_DSP_HI
jsr VDCWriteReg
lda OLDCOLOR
ldx #VDC_COLORS
jsr VDCWriteReg ; restore color (background)
lda #$47
ldx #VDC_HSCROLL
jmp VDCWriteReg ; switch to text screen
; ------------------------------------------------------------------------
; GETERROR: Return the error code in A and clear it.
GETERROR:
ldx #TGI_ERR_OK
lda ERROR
stx ERROR
rts
; ------------------------------------------------------------------------
; CONTROL: Platform/driver specific entry point.
;
; Must set an error code: YES
;
CONTROL:
lda #TGI_ERR_INV_FUNC
sta ERROR
rts
; ------------------------------------------------------------------------
; CLEAR: Clears the screen.
;
; Must set an error code: NO
;
CLEAR:
lda #0
tay
jsr VDCSetSourceAddr
lda #0
ldx #VDC_VSCROLL
jsr VDCWriteReg ; set fill mode
lda #0
jsr VDCWriteByte ; put 1rst byte (fill value)
ldy #159 ; 159 times
lda #0 ; 256 bytes
ldx #VDC_COUNT
@L1: jsr VDCWriteReg
dey
bne @L1
rts
; ------------------------------------------------------------------------
; SETVIEWPAGE: Set the visible page. Called with the new page in A (0..n).
; The page number is already checked to be valid by the graphics kernel.
;
; Must set an error code: NO (will only be called if page ok)
;
SETVIEWPAGE:
rts
; ------------------------------------------------------------------------
; SETDRAWPAGE: Set the drawable page. Called with the new page in A (0..n).
; The page number is already checked to be valid by the graphics kernel.
;
; Must set an error code: NO (will only be called if page ok)
;
SETDRAWPAGE:
rts
; ------------------------------------------------------------------------
; SETCOLOR: Set the drawing color (in A). The new color is already checked
; to be in a valid range (0..maxcolor-1).
;
; Must set an error code: NO (will only be called if color ok)
;
SETCOLOR:
tax
beq @L1
lda #$FF
@L1: sta BITMASK
rts
; ------------------------------------------------------------------------
; SETPALETTE: Set the palette (not available with all drivers/hardware).
; A pointer to the palette is passed in ptr1. Must set an error if palettes
; are not supported
;
; Must set an error code: YES
;
SETPALETTE:
ldy #PALETTESIZE - 1
@L1: lda (ptr1),y ; Copy the palette
and #$0F ; Make a valid color
sta PALETTE,y
dey
bpl @L1
; Get the color entries from the palette
ldy PALETTE+1 ; Foreground color
lda COLTRANS,y
asl a
asl a
asl a
asl a
ldy PALETTE ; Background color
ora COLTRANS,y
ldx #VDC_COLORS
jmp VDCWriteReg
; ------------------------------------------------------------------------
; GETPALETTE: Return the current palette in A/X. Must return NULL and set an
; error if palettes are not supported.
;
; Must set an error code: YES
;
GETPALETTE:
lda #<PALETTE
ldx #>PALETTE
rts
; ------------------------------------------------------------------------
; GETDEFPALETTE: Return the default palette for the driver in A/X. Must
; return NULL and set an error of palettes are not supported.
;
; Must set an error code: YES
;
GETDEFPALETTE:
lda #<DEFPALETTE
ldx #>DEFPALETTE
rts
; ------------------------------------------------------------------------
; SETPIXEL: Draw one pixel at X1/Y1 = ptr1/ptr2 with the current drawing
; color. The coordinates passed to this function are never outside the
; visible screen area, so there is no need for clipping inside this function.
;
; Must set an error code: NO
;
SETPIXELCLIP:
lda Y1+1
bmi @finito ; y<0
lda X1+1
bmi @finito ; x<0
lda xres
ldx xres+1
sta ADDR
stx ADDR+1
ldx #ADDR
lda X1
ldy X1+1
jsr icmp ; if (xres<x1)
bcs @cont ; !(xres<x1)
@finito:rts
@cont: lda yres
ldx yres+1
sta ADDR
stx ADDR+1
ldx #ADDR
lda Y1
ldy Y1+1
jsr icmp ; if (yres<y1)
bcc @finito
SETPIXEL:
jsr CALC ; Calculate coordinates
stx TEMP
lda ADDR
ldy ADDR+1
jsr VDCSetSourceAddr
jsr VDCReadByte
ldx TEMP
sta TEMP
eor BITMASK
and BITTAB,X
eor TEMP
pha
lda ADDR
ldy ADDR+1
jsr VDCSetSourceAddr
pla
jsr VDCWriteByte
@L9: rts
; ------------------------------------------------------------------------
; GETPIXEL: Read the color value of a pixel and return it in A/X. The
; coordinates passed to this function are never outside the visible screen
; area, so there is no need for clipping inside this function.
GETPIXEL:
jsr CALC ; Calculate coordinates
stx TEMP ; preserve X
lda ADDR
ldy ADDR+1
jsr VDCSetSourceAddr
jsr VDCReadByte
ldx TEMP
ldy #$00
and BITTAB,X
beq @L1
iny
@L1: tya ; Get color value into A
ldx #$00 ; Clear high byte
rts
; ------------------------------------------------------------------------
; HORLINE: Draw a horizontal line from X1/Y to X2/Y, where X1 = ptr1,
; Y = ptr2 and X2 = ptr3, using the current drawing color.
;
; This is a special line drawing entry used when the line is know to be
; horizontal, for example by the BAR emulation routine. If the driver does
; not have special code for horizontal lines, it may just copy Y to Y2 and
; proceed with the generic line drawing code.
;
; Note: Line coordinates will always be sorted (Y1 <= X2) and clipped.
;
; Must set an error code: NO
;
HORLINE:
lda X1
pha
lda X1+1
pha
jsr CALC ; get data for LEFT
lda BITMASKL,x ; remember left address and bitmask
pha
lda ADDR
pha
lda ADDR+1
pha
lda X2
sta X1
lda X2+1
sta X1+1
jsr CALC ; get data for RIGHT
lda BITMASKR,x
sta TEMP3
pla ; recall data for LEFT
sta X1+1
pla
sta X1 ; put left address into X1
pla
cmp #%11111111 ; if left bit <> 0
beq @L1
sta TEMP2 ; do left byte only...
lda X1
ldy X1+1
jsr VDCSetSourceAddr
jsr VDCReadByte
sta TEMP
eor BITMASK
and TEMP2
eor TEMP
pha
lda X1
ldy X1+1
jsr VDCSetSourceAddr
pla
jsr VDCWriteByte
inc X1 ; ... and proceed
bne @L1
inc X1+1
; do right byte (if Y2=0 ++ADDR and skip)
@L1: lda TEMP3
cmp #%11111111 ; if right bit <> 7
bne @L11
inc ADDR ; right bit = 7 - the next one is the last
bne @L10
inc ADDR+1
@L10: bne @L2
@L11: lda ADDR ; do right byte only...
ldy ADDR+1
jsr VDCSetSourceAddr
jsr VDCReadByte
sta TEMP
eor BITMASK
and TEMP3
eor TEMP
pha
lda ADDR
ldy ADDR+1
jsr VDCSetSourceAddr
pla
jsr VDCWriteByte
@L2: ; do the fill in the middle
lda ADDR ; calculate offset in full bytes
sec
sbc X1
beq @L3 ; if equal - there are no more bytes
sta ADDR
lda X1 ; setup for the left side
ldy X1+1
jsr VDCSetSourceAddr
lda BITMASK ; get color
jsr VDCWriteByte ; put 1st value
ldx ADDR
dex
beq @L3 ; 1 byte already written
stx ADDR ; if there are more bytes - fill them...
ldx #VDC_VSCROLL
lda #0
jsr VDCWriteReg ; setup for fill
ldx #VDC_COUNT
lda ADDR
jsr VDCWriteReg ; ... fill them NOW!
@L3: pla
sta X1+1
pla
sta X1
rts
; ------------------------------------------------------------------------
; LINE: Draw a line from X1/Y1 to X2/Y2, where X1/Y1 = ptr1/ptr2 and
; X2/Y2 = ptr3/ptr4 using the current drawing color.
;
; Must set an error code: NO
;
LINE:
; if (x2>x1) {
ldx #X1
lda X2
ldy X2+1
jsr icmp
bcc @L0137
beq @L0137
; x2<->x1 }
lda X1
ldx X2
sta X2
stx X1
lda X1+1
ldx X2+1
sta X2+1
stx X1+1
@L0137: ; if (y2>y1) {
ldx #Y1
lda Y2
ldy Y2+1
jsr icmp
bcc @L013F
bne @nequal
jmp HORLINE ; x1/x2 are sorted, y1==y2 - do faster horizontal line draw
@nequal:
; y2<->y1 }
lda Y1
ldx Y2
sta Y2
stx Y1
lda Y1+1
ldx Y2+1
sta Y2+1
stx Y1+1
@L013F:
; nx = x2 - x1
lda X2
sec
sbc X1
sta NX
lda X2+1
sbc X1+1
sta NX+1
; ny = y2 - y1
lda Y2
sec
sbc Y1
sta NY
lda Y2+1
sbc Y1+1
sta NY+1
; if (nx<ny) {
ldx #NX
lda NY
ldy NY+1
jsr icmp
bcs @L041B
; nx <-> ny
lda NX
ldx NY
sta NY
stx NX
lda NX+1
ldx NY+1
sta NY+1
stx NX+1
; dx = dy = 0; ax = ay = 1 }
ldy #1
sty AY
dey
beq @L025A
; else { dx = dy = 1; ax = ay = 0 }
@L041B: ldy #0
sty AY
iny
@L025A: sty DX
sty DY
; err = 0
lda #0
sta ERR
sta ERR+1
; for (count=nx;count>0;--count) {
lda NX
ldx NX+1
sta COUNT
stx COUNT+1
@L0166: lda COUNT ; count>0
ora COUNT+1
bne @L0167
rts
; setpixel(X1,Y1)
@L0167: jsr SETPIXELCLIP
; pb = err - ny
lda ERR
sec
sbc NY
sta PB
lda ERR+1
sbc NY+1
sta PB+1
tax
; ub = pb + nx
lda PB
clc
adc NX
sta UB
txa
adc NX+1
sta UB+1
; x1 = x1 + dx
lda X1
clc
adc DX
sta X1
bcc @L0254
inc X1+1
; y1 = y1 + ay
@L0254:
lda Y1
clc
adc AY
sta Y1
bcc @L0255
inc Y1+1
@L0255:
; if (abs(pb)<abs(ub)) {
lda PB
ldy PB+1
jsr abs
sta TEMP3
sty TEMP4
lda UB
ldy UB+1
jsr abs
ldx #TEMP3
jsr icmp
bpl @L017B
; err = pb
lda PB
ldx PB+1
jmp @L025B
; } else { x1 = x1 + ay
@L017B:
lda X1
clc
adc AY
sta X1
bcc @L0256
inc X1+1
; y1 = y1 + dy
@L0256:
lda Y1
clc
adc DY
sta Y1
bcc @L0257
inc Y1+1
; err = ub }
@L0257:
lda UB
ldx UB+1
@L025B:
sta ERR
stx ERR+1
; } (--count)
sec
lda COUNT
sbc #1
sta COUNT
bcc @L0260
jmp @L0166
@L0260: dec COUNT+1
jmp @L0166
; ------------------------------------------------------------------------
; BAR: Draw a filled rectangle with the corners X1/Y1, X2/Y2, where
; X1/Y1 = ptr1/ptr2 and X2/Y2 = ptr3/ptr4 using the current drawing color.
; Contrary to most other functions, the graphics kernel will sort and clip
; the coordinates before calling the driver, so on entry the following
; conditions are valid:
; X1 <= X2
; Y1 <= Y2
; (X1 >= 0) && (X1 < XRES)
; (X2 >= 0) && (X2 < XRES)
; (Y1 >= 0) && (Y1 < YRES)
; (Y2 >= 0) && (Y2 < YRES)
;
; Must set an error code: NO
;
BAR:
inc Y2
bne @L0
inc Y2+1
@L0: jsr HORLINE
inc Y1
bne @L1
inc Y1+1
@L1: lda Y1
cmp Y2
bne @L0
lda Y1+1
cmp Y2+1
bne @L0
rts
; ------------------------------------------------------------------------
; CIRCLE: Draw a circle around the center X1/Y1 (= ptr1/ptr2) with the
; radius in tmp1 and the current drawing color.
;
; Must set an error code: NO
;
CIRCLE:
lda RADIUS
bne @L1
jmp SETPIXELCLIP ; Plot as a point
@L1: sta XX
; x = r;
lda #0
sta XX+1
sta YY
sta YY+1
sta MaxO
sta MaxO+1
; y =0; mo=0;
lda X1
ldx X1+1
sta XS
stx XS+1
lda Y1
ldx Y1+1
sta YS
stx YS+1 ; XS/YS to remember the center
; while (y<x) {
@L013B: ldx #YY
lda XX
ldy XX+1
jsr icmp
bcc @L12
rts
@L12: ; plot points in 8 slices...
lda XS
clc
adc XX
sta X1
lda XS+1
adc XX+1
sta X1+1 ; x1 = xs+x
lda YS
clc
adc YY
sta Y1
pha
lda YS+1
adc YY+1
sta Y1+1 ; (stack)=ys+y, y1=(stack)
pha
jsr SETPIXELCLIP ; plot(xs+x,ys+y)
lda YS
sec
sbc YY
sta Y1
sta Y3
lda YS+1
sbc YY+1
sta Y1+1 ; y3 = y1 = ys-y
sta Y3+1
jsr SETPIXELCLIP ; plot(xs+x,ys-y)
pla
sta Y1+1
pla
sta Y1 ; y1 = ys+y
lda XS
sec
sbc XX
sta X1
lda XS+1
sbc XX+1
sta X1+1
jsr SETPIXELCLIP ; plot (xs-x,ys+y)
lda Y3
sta Y1
lda Y3+1
sta Y1+1
jsr SETPIXELCLIP ; plot (xs-x,ys-y)
lda XS
clc
adc YY
sta X1
lda XS+1
adc YY+1
sta X1+1 ; x1 = xs+y
lda YS
clc
adc XX
sta Y1
pha
lda YS+1
adc XX+1
sta Y1+1 ; (stack)=ys+x, y1=(stack)
pha
jsr SETPIXELCLIP ; plot(xs+y,ys+x)
lda YS
sec
sbc XX
sta Y1
sta Y3
lda YS+1
sbc XX+1
sta Y1+1 ; y3 = y1 = ys-x
sta Y3+1
jsr SETPIXELCLIP ; plot(xs+y,ys-x)
pla
sta Y1+1
pla
sta Y1 ; y1 = ys+x(stack)
lda XS
sec
sbc YY
sta X1
lda XS+1
sbc YY+1
sta X1+1
jsr SETPIXELCLIP ; plot (xs-y,ys+x)
lda Y3
sta Y1
lda Y3+1
sta Y1+1
jsr SETPIXELCLIP ; plot (xs-y,ys-x)
; og = mo+y+y+1
lda MaxO
ldx MaxO+1
clc
adc YY
tay
txa
adc YY+1
tax
tya
clc
adc YY
tay
txa
adc YY+1
tax
tya
clc
adc #1
bcc @L0143
inx
@L0143: sta OGora
stx OGora+1
; ou = og-x-x+1
sec
sbc XX
tay
txa
sbc XX+1
tax
tya
sec
sbc XX
tay
txa
sbc XX+1
tax
tya
clc
adc #1
bcc @L0146
inx
@L0146: sta OUkos
stx OUkos+1
; ++y
inc YY
bne @L0148
inc YY+1
@L0148: ; if (abs(ou)<abs(og))
lda OUkos
ldy OUkos+1
jsr abs
sta TEMP3
sty TEMP4
lda OGora
ldy OGora+1
jsr abs
ldx #TEMP3
jsr icmp
bpl @L0149
; { --x;
sec
lda XX
sbc #1
sta XX
bcs @L014E
dec XX+1
@L014E: ; mo = ou; }
lda OUkos
ldx OUkos+1
jmp @L014G
; else { mo = og }
@L0149: lda OGora
ldx OGora+1
@L014G: sta MaxO
stx MaxO+1
; }
jmp @L013B
; ------------------------------------------------------------------------
; TEXTSTYLE: Set the style used when calling OUTTEXT. Text scaling in X and Y
; direction is passend in X/Y, the text direction is passed in A.
;
; Must set an error code: NO
;
TEXTSTYLE:
stx TEXTMAGX
sty TEXTMAGY
sta TEXTDIR
rts
; ------------------------------------------------------------------------
; OUTTEXT: Output text at X/Y = ptr1/ptr2 using the current color and the
; current text style. The text to output is given as a zero terminated
; string with address in ptr3.
;
; Must set an error code: NO
;
OUTTEXT:
rts
; ------------------------------------------------------------------------
; Calculate all variables to plot the pixel at X1/Y1.
;------------------------
;< X1,Y1 - pixel
;> ADDR - address of card
;> X - bit number (X1 & 7)
CALC:
lda Y1
pha
lda Y1+1
pha
lsr
ror Y1 ; Y=Y/2
sta Y1+1
sta ADDR+1
lda Y1
asl
rol ADDR+1
asl
rol ADDR+1 ; Y*4
clc
adc Y1
sta ADDR
lda Y1+1
adc ADDR+1
sta ADDR+1 ; Y*4+Y=Y*5
lda ADDR
asl
rol ADDR+1
asl
rol ADDR+1
asl
rol ADDR+1
asl
rol ADDR+1
sta ADDR ; Y*5*16=Y*80
lda X1+1
sta TEMP
lda X1
lsr TEMP
ror
lsr TEMP
ror
lsr TEMP
ror
clc
adc ADDR
sta ADDR
lda ADDR+1 ; ADDR = Y*80+x/8
adc TEMP
sta ADDR+1
pla
sta Y1+1
pla
sta Y1
and #1
beq @even ; even line - no offset
lda ADDR
clc
adc #<21360
sta ADDR
lda ADDR+1
adc #>21360
sta ADDR+1 ; odd lines are 21360 bytes farther
@even: lda X1
and #7
tax
rts
;-------------
; copies of some runtime routines
abs:
; a/y := abs(a/y)
dey
iny
bpl @L1
; negay
clc
eor #$ff
adc #1
pha
tya
eor #$ff
adc #0
tay
pla
@L1: rts
icmp:
; compare a/y to zp,x
sta TEMP ; TEMP/TEMP2 - arg2
sty TEMP2
lda $0,x
pha
lda $1,x
tay
pla
tax
tya ; x/a - arg1 (a=high)
sec
sbc TEMP2
bne @L4
cpx TEMP
beq @L3
adc #$ff
ora #$01
@L3: rts
@L4: bvc @L3
eor #$ff
ora #$01
rts
;-------------
; VDC helpers
VDCSetSourceAddr:
pha
tya
ldx #VDC_DATA_HI
jsr VDCWriteReg
pla
ldx #VDC_DATA_LO
bne VDCWriteReg
VDCReadByte:
ldx #VDC_DATA
VDCReadReg:
stx VDC_ADDR_REG
@L0: bit VDC_ADDR_REG
bpl @L0
lda VDC_DATA_REG
rts
VDCWriteByte:
ldx #VDC_DATA
VDCWriteReg:
stx VDC_ADDR_REG
@L0: bit VDC_ADDR_REG
bpl @L0
sta VDC_DATA_REG
rts
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