;
; Graphics driver for the 320x200x2 mode on the C64.
;
; Based on Stephen L. Judds GRLIB code
;
.include "zeropage.inc"
.include "tgi-kernel.inc"
.include "tgi-mode.inc"
.include "tgi-error.inc"
.macpack generic
; ------------------------------------------------------------------------
; 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
.word 320 ; X resolution
.word 200 ; Y resolution
.byte 2 ; Number of drawing colors
.byte 1 ; 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 0 ; 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
ROW = tmp2 ; Bitmap row...
COL = tmp3 ; ...and column, both set by PLOT
TEMP = tmp4
TEMP2 = sreg
POINT = regsave
CHUNK = X2 ; Used in the line routine
OLDCHUNK = X2+1 ; Dito
; 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
; INIT/DONE
OLDD018: .res 1 ; Old register value
; PLOT variables
INRANGE: .res 1 ; $00 = coordinates in range
; Line routine stuff
DX: .res 2
DY: .res 2
; Circle routine stuff
CURX: .res 1
CURY: .res 1
BROW: .res 1 ; Bottom row
TROW: .res 1 ; Top row
LCOL: .res 1 ; Left column
RCOL: .res 1 ; Right column
CHUNK1: .res 1
OLDCH1: .res 1
CHUNK2: .res 1
OLDCH2: .res 1
; Text output stuff
TEXTMAGX: .res 1
TEXTMAGY: .res 1
TEXTDIR: .res 1
; Constants and tables
.rodata
DEFPALETTE: .byte $00, $01 ; White on black
PALETTESIZE = * - DEFPALETTE
BITTAB: .byte $80,$40,$20,$10,$08,$04,$02,$01
BITCHUNK: .byte $FF,$7F,$3F,$1F,$0F,$07,$03,$01
VBASE = $E000 ; Video memory base address
CBASE = $D000 ; Color memory base address
.code
; ------------------------------------------------------------------------
; INSTALL routine. Is called after the driver is loaded into memory. May
; initialize anything that has to be done just once. Is probably empty
; most of the time.
;
; Must set an error code: NO
;
INSTALL:
rts
; ------------------------------------------------------------------------
; DEINSTALL routine. Is called before the driver is removed from memory. May
; clean up anything done by INSTALL but is probably empty most of the time.
;
; Must set an error code: NO
;
DEINSTALL:
rts
; ------------------------------------------------------------------------
; INIT: Changes an already installed device from text mode to graphics
; mode. The number of the graphics mode is passed to the function in A.
; Note that INIT/DONE may be called multiple times while the driver
; is loaded, while INSTALL is only called once, so any code that is needed
; to initializes variables and so on must go here. Setting palette and
; clearing the screen is not needed because this is called by the graphics
; kernel later.
; The graphics kernel will never call INIT when a graphics mode is already
; active, so there is no need to protect against that.
;
; Must set an error code: YES
;
INIT: cmp #TGI_MODE_320_200_2 ; Correct mode?
beq @L1 ; Jump if yes
lda #TGI_ERR_INV_MODE ; ## Error
bne @L9
; Initialize variables
@L1: ldx #$FF
stx BITMASK
; Switch into graphics mode
lda $DD02 ; Set the data direction regs
ora #3
sta $DD02
lda $DD00
and #$FC ; Switch to bank 3
sta $DD00
lda $D018
sta OLDD018
lda #$48 ; Set color map to $D000, screen to $E000
sta $D018
lda $D011 ; And turn on bitmap
ora #$20
sta $D011
; 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: lda $DD02 ; Set the data direction regs
ora #3
sta $DD02
lda $DD00
ora #$03 ; Bank 0
sta $DD00
lda OLDD018 ; Screen mem --> $0400
sta $D018
lda $D011
and #<~$20
sta $D011
rts
; ------------------------------------------------------------------------
; 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: ldy #$00
tya
@L1: sta VBASE+$0000,y
sta VBASE+$0100,y
sta VBASE+$0200,y
sta VBASE+$0300,y
sta VBASE+$0400,y
sta VBASE+$0500,y
sta VBASE+$0600,y
sta VBASE+$0700,y
sta VBASE+$0800,y
sta VBASE+$0900,y
sta VBASE+$0A00,y
sta VBASE+$0B00,y
sta VBASE+$0C00,y
sta VBASE+$0D00,y
sta VBASE+$0E00,y
sta VBASE+$0F00,y
sta VBASE+$1000,y
sta VBASE+$1100,y
sta VBASE+$1200,y
sta VBASE+$1300,y
sta VBASE+$1400,y
sta VBASE+$1500,y
sta VBASE+$1600,y
sta VBASE+$1700,y
sta VBASE+$1800,y
sta VBASE+$1900,y
sta VBASE+$1A00,y
sta VBASE+$1B00,y
sta VBASE+$1C00,y
sta VBASE+$1D00,y
sta VBASE+$1E00,y
sta VBASE+$1F00,y
iny
bne @L1
rts
; ------------------------------------------------------------------------
; SETVIEWPAGE: Set the visible page. Called with the new page in A (0..n).
; The page number is already checked to be valid by the graphics kernel.
;
; Must set an error code: NO (will only be called if page ok)
;
SETVIEWPAGE:
rts
; ------------------------------------------------------------------------
; SETDRAWPAGE: Set the drawable page. Called with the new page in A (0..n).
; The page number is already checked to be valid by the graphics kernel.
;
; Must set an error code: NO (will only be called if page ok)
;
SETDRAWPAGE:
rts
; ------------------------------------------------------------------------
; SETCOLOR: Set the drawing color (in A). The new color is already checked
; to be in a valid range (0..maxcolor-1).
;
; Must set an error code: NO (will only be called if color ok)
;
SETCOLOR:
tax
beq @L1
lda #$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
lda PALETTE+1 ; Foreground color
asl a
asl a
asl a
asl a
ora PALETTE ; Background color
tax
; Initialize the color map with the new color settings (it is below the
; I/O area)
ldy #$00
sei
lda $01 ; Get ROM config
pha ; Save it
and #%11111100 ; Clear bit 0 and 1
sta $01
txa ; Load color code
@L2: sta CBASE+$0000,y
sta CBASE+$0100,y
sta CBASE+$0200,y
sta CBASE+$0300,y
iny
bne @L2
pla
sta $01
cli
; Done
rts
; ------------------------------------------------------------------------
; 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
;
SETPIXEL:
jsr CALC ; Calculate coordinates
sei ; Get underneath ROM
lda $01
pha
lda #$34
sta $01
lda (POINT),Y
eor BITMASK
and BITTAB,X
eor (POINT),Y
sta (POINT),Y
pla
sta $01
cli
@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
sei ; Get underneath ROM
lda $01
pha
lda #$34
sta $01
lda (POINT),Y
ldy #$00
and BITTAB,X
beq @L1
iny
@L1: pla
sta $01
cli
tya ; Get color value into A
ldx #$00 ; Clear high byte
rts
; ------------------------------------------------------------------------
; HORLINE: Draw a horizontal line from X1/Y to X2/Y, where X1 = ptr1,
; Y = ptr2 and X2 = ptr3, using the current drawing color.
;
; This is a special line drawing entry used when the line is know to be
; horizontal, for example by the BAR emulation routine. If the driver does
; not have special code for horizontal lines, it may just copy Y to Y2 and
; proceed with the generic line drawing code.
;
; Note: Line coordinates will always be sorted (Y1 <= X2) and clipped.
;
; Must set an error code: NO
;
HORLINE:
lda ptr2
sta ptr4
lda ptr2+1
sta ptr4+1
; jmp LINE
; ------------------------------------------------------------------------
; LINE: Draw a line from X1/Y1 to X2/Y2, where X1/Y1 = ptr1/ptr2 and
; X2/Y2 = ptr3/ptr4 using the current drawing color.
;
; To deal with off-screen coordinates, the current row
; and column (40x25) is kept track of. These are set
; negative when the point is off the screen, and made
; positive when the point is within the visible screen.
;
; X1,X2 etc. are set up above (x2=LINNUM in particular)
; Format is LINE x2,y2,x1,y1
;
; Must set an error code: NO
;
LINE:
@CHECK: lda X2 ;Make sure x1<x2
sec
sbc X1
tax
lda X2+1
sbc X1+1
bpl @CONT
lda Y2 ;If not, swap P1 and P2
ldy Y1
sta Y1
sty Y2
lda Y2+1
ldy Y1+1
sta Y1+1
sty Y2+1
lda X1
ldy X2
sty X1
sta X2
lda X2+1
ldy X1+1
sta X1+1
sty X2+1
bcc @CHECK
@CONT: sta DX+1
stx DX
ldx #$C8 ;INY
lda Y2 ;Calculate dy
sec
sbc Y1
tay
lda Y2+1
sbc Y1+1
bpl @DYPOS ;Is y2>=y1?
lda Y1 ;Otherwise dy=y1-y2
sec
sbc Y2
tay
ldx #$88 ;DEY
@DYPOS: sty DY ; 8-bit DY -- FIX ME?
stx YINCDEC
stx XINCDEC
jsr CALC ; Set up .X,.Y,POINT, and INRANGE
lda BITCHUNK,X
sta OLDCHUNK
sta CHUNK
sei ; Get underneath ROM
lda #$34
sta $01
ldx DY
cpx DX ;Who's bigger: dy or dx?
bcc STEPINX ;If dx, then...
lda DX+1
bne STEPINX
;
; Big steps in Y
;
; To simplify my life, just use PLOT to plot points.
;
; No more!
; Added special plotting routine -- cool!
;
; X is now counter, Y is y-coordinate
;
; On entry, X=DY=number of loop iterations, and Y=
; Y1 AND #$07
STEPINY:
lda #00
sta OLDCHUNK ;So plotting routine will work right
lda CHUNK
lsr ;Strip the bit
eor CHUNK
sta CHUNK
txa
bne @CONT ;If dy=0 it's just a point
inx
@CONT: lsr ;Init counter to dy/2
;
; Main loop
;
YLOOP: sta TEMP
lda INRANGE ;Range check
bne @SKIP
lda (POINT),y ;Otherwise plot
eor BITMASK
and CHUNK
eor (POINT),y
sta (POINT),y
@SKIP:
YINCDEC:
iny ;Advance Y coordinate
cpy #8
bcc @CONT ;No prob if Y=0..7
jsr FIXY
@CONT: lda TEMP ;Restore A
sec
sbc DX
bcc YFIXX
YCONT: dex ;X is counter
bne YLOOP
YCONT2: lda (POINT),y ;Plot endpoint
eor BITMASK
and CHUNK
eor (POINT),y
sta (POINT),y
YDONE: lda #$37
sta $01
cli
rts
YFIXX: ;x=x+1
adc DY
lsr CHUNK
bne YCONT ;If we pass a column boundary...
ror CHUNK ;then reset CHUNK to $80
sta TEMP2
lda COL
bmi @C1 ;Skip if column is negative
cmp #39 ;End if move past end of screen
bcs YDONE
@C1: lda POINT ;And add 8 to POINT
adc #8
sta POINT
bcc @CONT
inc POINT+1
@CONT: inc COL ;Increment column
bne @C2
lda ROW ;Range check
cmp #25
bcs @C2
lda #00 ;Passed into col 0
sta INRANGE
@C2: lda TEMP2
dex
bne YLOOP
beq YCONT2
;
; Big steps in X direction
;
; On entry, X=DY=number of loop iterations, and Y=
; Y1 AND #$07
.bss
COUNTHI:
.byte $00 ;Temporary counter
;only used once
.code
STEPINX:
ldx DX
lda DX+1
sta COUNTHI
cmp #$80
ror ;Need bit for initialization
sta Y1 ;High byte of counter
txa
bne @CONT ;Could be $100
dec COUNTHI
@CONT: ror
;
; Main loop
;
XLOOP: lsr CHUNK
beq XFIXC ;If we pass a column boundary...
XCONT1: sbc DY
bcc XFIXY ;Time to step in Y?
XCONT2: dex
bne XLOOP
dec COUNTHI ;High bits set?
bpl XLOOP
XDONE: lsr CHUNK ;Advance to last point
jsr LINEPLOT ;Plot the last chunk
EXIT: lda #$37
sta $01
cli
rts
;
; CHUNK has passed a column, so plot and increment pointer
; and fix up CHUNK, OLDCHUNK.
;
XFIXC: sta TEMP
jsr LINEPLOT
lda #$FF
sta CHUNK
sta OLDCHUNK
lda COL
bmi @C1 ;Skip if column is negative
cmp #39 ;End if move past end of screen
bcs EXIT
@C1: lda POINT
adc #8
sta POINT
bcc @CONT
inc POINT+1
@CONT: inc COL
bne @C2
lda ROW
cmp #25
bcs @C2
lda #00
sta INRANGE
@C2: lda TEMP
sec
bcs XCONT1
;
; Check to make sure there isn't a high bit, plot chunk,
; and update Y-coordinate.
;
XFIXY: dec Y1 ;Maybe high bit set
bpl XCONT2
adc DX
sta TEMP
lda DX+1
adc #$FF ;Hi byte
sta Y1
jsr LINEPLOT ;Plot chunk
lda CHUNK
sta OLDCHUNK
lda TEMP
XINCDEC:
iny ;Y-coord
cpy #8 ;0..7 is ok
bcc XCONT2
sta TEMP
jsr FIXY
lda TEMP
jmp XCONT2
;
; Subroutine to plot chunks/points (to save a little
; room, gray hair, etc.)
;
LINEPLOT: ; Plot the line chunk
lda INRANGE
bne @SKIP
lda (POINT),Y ; Otherwise plot
eor BITMASK
ora CHUNK
and OLDCHUNK
eor CHUNK
eor (POINT),Y
sta (POINT),Y
@SKIP: rts
;
; Subroutine to fix up pointer when Y decreases through
; zero or increases through 7.
;
FIXY: cpy #255 ;Y=255 or Y=8
beq @DECPTR
@INCPTR: ;Add 320 to pointer
ldy #0 ;Y increased through 7
lda ROW
bmi @C1 ;If negative, then don't update
cmp #24
bcs @TOAST ;If at bottom of screen then quit
@C1: lda POINT
adc #<320
sta POINT
lda POINT+1
adc #>320
sta POINT+1
@CONT1: inc ROW
bne @DONE
lda COL
bmi @DONE
lda #00
sta INRANGE
@DONE: rts
@DECPTR: ;Okay, subtract 320 then
ldy #7 ;Y decreased through 0
lda POINT
sec
sbc #<320
sta POINT
lda POINT+1
sbc #>320
sta POINT+1
@CONT2: dec ROW
bmi @TOAST
lda ROW
cmp #24
bne @DONE
lda COL
bmi @DONE
lda #00
sta INRANGE
rts
@TOAST: pla ;Remove old return address
pla
jmp EXIT ;Restore interrupts, etc.
; ------------------------------------------------------------------------
; 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: 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
sta CURY
bne @L1
jmp SETPIXEL ; Plot as a point
@L1: clc
adc Y1
sta Y1
bcc @L2
inc Y1+1
@L2: jsr CALC ; Compute XC, YC+R
lda ROW
sta BROW
lda COL
sta LCOL
sta RCOL
sty Y2 ; Y AND 07
lda BITCHUNK,X
sta CHUNK1 ; Forwards chunk
sta OLDCH1
lsr
eor #$FF
sta CHUNK2 ; Backwards chunk
sta OLDCH2
lda POINT
sta TEMP2 ; TEMP2 = forwards high pointer
sta X2 ; X2 = backwards high pointer
lda POINT+1
sta TEMP2+1
sta X2+1
; Next compute CY-R
lda Y1
sec
sbc RADIUS
bcs @C3
dec Y1+1
sec
@C3: sbc RADIUS
bcs @C4
dec Y1+1
@C4: sta Y1
jsr CALC ; Compute new coords
sty Y1
lda POINT
sta X1 ; X1 will be the backwards
lda POINT+1 ; low-pointer
sta X1+1 ; POINT will be forwards
lda ROW
sta TROW
sei ; Get underneath ROM
lda #$34
sta $01
lda RADIUS
lsr ; A=r/2
ldx #00
stx CURX ; y=0
; Main loop
@LOOP: inc CURX ; x=x+1
lsr CHUNK1 ; Right chunk
bne @CONT1
jsr UPCHUNK1 ; Update if we move past a column
@CONT1: asl CHUNK2
bne @CONT2
jsr UPCHUNK2
@CONT2: sec
sbc CURX ; a=a-x
bcs @LOOP
adc CURY ;if a<0 then a=a+y; y=y-1
tax
jsr PCHUNK1
jsr PCHUNK2
lda CHUNK1
sta OLDCH1
lda CHUNK2
sta OLDCH2
txa
dec CURY ;(y=y-1)
dec Y2 ;Decrement y-offest for upper
bpl @CONT3 ;points
jsr DECYOFF
@CONT3: ldy Y1
iny
sty Y1
cpy #8
bcc @CONT4
jsr INCYOFF
@CONT4: ldy CURX
cpy CURY ;if y<=x then punt
bcc @LOOP ;Now draw the other half
;
; Draw the other half of the circle by exactly reversing
; the above!
;
NEXTHALF:
lsr OLDCH1 ;Only plot a bit at a time
asl OLDCH2
lda RADIUS ;A=-R/2-1
lsr
eor #$FF
@LOOP:
tax
jsr PCHUNK1 ;Plot points
jsr PCHUNK2
txa
dec Y2 ;Y2=bottom
bpl @CONT1
jsr DECYOFF
@CONT1: inc Y1
ldy Y1
cpy #8
bcc @CONT2
jsr INCYOFF
@CONT2: ldx CURY
beq @DONE
clc
adc CURY ;a=a+y
dec CURY ;y=y-1
bcc @LOOP
inc CURX
sbc CURX ;if a<0 then x=x+1; a=a+x
lsr CHUNK1
bne @CONT3
tax
jsr UPCH1 ;Upchunk, but no plot
@CONT3: lsr OLDCH1 ;Only the bits...
asl CHUNK2 ;Fix chunks
bne @CONT4
tax
jsr UPCH2
@CONT4: asl OLDCH2
bcs @LOOP
@DONE:
CIRCEXIT: ;Restore interrupts
lda #$37
sta $01
cli
rts
;
; Decrement lower pointers
;
DECYOFF:
tay
lda #7
sta Y2
lda X2 ;If we pass through zero, then
sec
sbc #<320 ;subtract 320
sta X2
lda X2+1
sbc #>320
sta X2+1
lda TEMP2
sec
sbc #<320
sta TEMP2
lda TEMP2+1
sbc #>320
sta TEMP2+1
tya
dec BROW
bmi EXIT2
rts
EXIT2: pla ;Grab return address
pla
jmp CIRCEXIT ;Restore interrupts, etc.
; Increment upper pointers
INCYOFF:
tay
lda #00
sta Y1
lda X1
clc
adc #<320
sta X1
lda X1+1
adc #>320
sta X1+1
lda POINT
clc
adc #<320
sta POINT
lda POINT+1
adc #>320
sta POINT+1
@ISKIP: inc TROW
bmi @DONE
lda TROW
cmp #25
bcs EXIT2
@DONE: tya
rts
;
; UPCHUNK1 -- Update right-moving chunk pointers
; Due to passing through a column
;
UPCHUNK1:
tax
jsr PCHUNK1
UPCH1: lda #$FF ;Alternative entry point
sta CHUNK1
sta OLDCH1
lda TEMP2
clc
adc #8
sta TEMP2
bcc @CONT
inc TEMP2+1
clc
@CONT: lda POINT
adc #8
sta POINT
bcc @DONE
inc POINT+1
@DONE: txa
inc RCOL
rts
;
; UPCHUNK2 -- Update left-moving chunk pointers
;
UPCHUNK2:
tax
jsr PCHUNK2
UPCH2: lda #$FF
sta CHUNK2
sta OLDCH2
lda X2
sec
sbc #8
sta X2
bcs @CONT
dec X2+1
sec
@CONT: lda X1
sbc #8
sta X1
bcs @DONE
dec X1+1
@DONE: txa
dec LCOL
rts
;
; Plot right-moving chunk pairs for circle routine
;
PCHUNK1:
lda RCOL ;Make sure we're in range
cmp #40
bcs @SKIP2
lda CHUNK1 ;Otherwise plot
eor OLDCH1
sta TEMP
lda TROW ;Check for underflow
bmi @SKIP
ldy Y1
lda (POINT),y
eor BITMASK
and TEMP
eor (POINT),y
sta (POINT),y
@SKIP: lda BROW ;If CY+Y >= 200...
cmp #25
bcs @SKIP2
ldy Y2
lda (TEMP2),y
eor BITMASK
and TEMP
eor (TEMP2),y
sta (TEMP2),y
@SKIP2: rts
;
; Plot left-moving chunk pairs for circle routine
;
PCHUNK2:
lda LCOL ;Range check in X
cmp #40
bcs EXIT3
lda CHUNK2 ;Otherwise plot
eor OLDCH2
sta TEMP
lda TROW ;Check for underflow
bmi @SKIP
ldy Y1
lda (X1),y
eor BITMASK
and TEMP
eor (X1),y
sta (X1),y
@SKIP: lda BROW ;If CY+Y >= 200...
cmp #25
bcs EXIT3
ldy Y2
lda (X2),y
eor BITMASK
and TEMP
eor (X2),y
sta (X2),y
EXIT3: rts
; ------------------------------------------------------------------------
; 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. If the point is out
; of range, a carry is returned and INRANGE is set to a value !0 zero. If
; the coordinates are valid, INRANGE is zero and the carry clear.
CALC: lda Y1
sta ROW
and #7
tay
lda Y1+1
lsr ; Neg is possible
ror ROW
lsr
ror ROW
lsr
ror ROW
lda #00
sta POINT
lda ROW
cmp #$80
ror
ror POINT
cmp #$80
ror
ror POINT ; row*64
adc ROW ; +row*256
clc
adc #>VBASE ; +bitmap base
sta POINT+1
lda X1
tax
sta COL
lda X1+1
lsr
ror COL
lsr
ror COL
lsr
ror COL
txa
and #$F8
clc
adc POINT ; +(X AND #$F8)
sta POINT
lda X1+1
adc POINT+1
sta POINT+1
txa
and #7
tax
lda ROW
cmp #25
bcs @L9
lda COL
cmp #40
bcs @L9
lda #00
@L9: sta INRANGE
rts