; Based on Stephen L. Judd's GRLIB code.
;
; 2017-01-13, Greg King
+; 2018-03-13, Sven Klose
;
.include "zeropage.inc"
.addr BAR
.addr TEXTSTYLE
.addr OUTTEXT
- .addr 0 ; IRQ entry is unused
; ------------------------------------------------------------------------
; Data.
Y2 := ptr4
TEXT := ptr3
-ROW := tmp2 ; Bitmap row...
-COL := tmp3 ; ...and column, both set by PLOT
TEMP := tmp4
TEMP2 := sreg
POINT := regsave
-INRANGE := regsave+2 ; PLOT variable, $00 = coordinates in range
CHUNK := X2 ; Used in the line routine
OLDCHUNK := X2+1 ; Dito
;
INSTALL:
- rts
+; rts ; fall through
; ------------------------------------------------------------------------
sta VBASE+$1C00,y
sta VBASE+$1D00,y
sta VBASE+$1E00,y
- sta VBASE+$1F00,y
+ sta VBASE+$1E40,y ; preserve vectors
iny
bne @L1
rts
;
SETVIEWPAGE:
- rts
+; rts ; fall through
; ------------------------------------------------------------------------
; SETDRAWPAGE: Set the drawable page. Called with the new page in A (0..n).
; 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
;
stx YINCDEC
stx XINCDEC
- jsr CALC ; Set up .X,.Y,POINT, and INRANGE
+ jsr CALC ; Set up .X, .Y, and POINT
lda BITCHUNK,X
sta OLDCHUNK
sta CHUNK
;
YLOOP: sta TEMP
- lda INRANGE ;Range check
- bne @SKIP
-
- lda (POINT),y ;Otherwise plot
+ lda (POINT),y
eor BITMASK
and CHUNK
eor (POINT),y
sta (POINT),y
-@SKIP:
YINCDEC:
iny ;Advance Y coordinate
cpy #8
and CHUNK
eor (POINT),y
sta (POINT),y
-YDONE: lda #$36
+ lda #$36
sta $01
cli
rts
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
+ 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
+@CONT: lda TEMP2
dex
bne YLOOP
beq YCONT2
dec COUNTHI ;High bits set?
bpl XLOOP
-XDONE: lsr CHUNK ;Advance to last point
+ lsr CHUNK ;Advance to last point
jsr LINEPLOT ;Plot the last chunk
EXIT: lda #$36
sta $01
lda #$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
+ lda POINT
+ clc
adc #8
sta POINT
- bcc @CONT
+ lda TEMP
+ bcc XCONT1
inc POINT+1
-@CONT: inc COL
- bne @C2
- lda ROW
- cmp #25
- bcs @C2
- lda #00
- sta INRANGE
-@C2: lda TEMP
- sec
- bcs XCONT1
+ jmp XCONT1
;
; Check to make sure there isn't a high bit, plot chunk,
; and update Y-coordinate.
; room, gray hair, etc.)
;
LINEPLOT: ; Plot the line chunk
- lda INRANGE
- bne @SKIP
-
- lda (POINT),Y ; Otherwise plot
+ lda (POINT),Y
eor BITMASK
ora CHUNK
and OLDCHUNK
eor CHUNK
eor (POINT),Y
sta (POINT),Y
-@SKIP: rts
+ rts
;
; Subroutine to fix up pointer when Y decreases through
;
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
+ lda POINT
adc #<320
sta POINT
lda POINT+1
adc #>320
sta POINT+1
-@CONT1: inc ROW
- bne @DONE
- lda COL
- bpl @CLEAR
-@DONE: rts
+ rts
@DECPTR: ;Okay, subtract 320 then
ldy #7 ;Y decreased through 0
lda POINT+1
sbc #>320
sta POINT+1
-@CONT2: dec ROW
- bmi @TOAST
- lda ROW
- cmp #24
- bne @DONE
- lda COL
- bmi @DONE
-@CLEAR: 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.
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.
+; Calculate all variables to plot the pixel at X1/Y1.
CALC: lda Y1
- sta ROW
+ sta TEMP2
and #7
tay
lda Y1+1
lsr ; Neg is possible
- ror ROW
+ ror TEMP2
lsr
- ror ROW
+ ror TEMP2
lsr
- ror ROW
+ ror TEMP2
lda #00
sta POINT
- lda ROW
+ lda TEMP2
cmp #$80
ror
ror POINT
cmp #$80
ror
ror POINT ; row*64
- adc ROW ; +row*256
+ adc TEMP2 ; +row*256
clc
adc #>VBASE ; +bitmap base
sta POINT+1
lda X1
tax
- sta COL
- lda X1+1
- lsr
- ror COL
- lsr
- ror COL
- lsr
- ror COL
-
- txa
and #$F8
clc
adc POINT ; +(X AND #$F8)
txa
and #7
tax
-
- lda ROW
- cmp #25
- bcs @L9
- lda COL
- cmp #40
- bcs @L9
- lda #00
-@L9: sta INRANGE
rts
projects / cc65 / blobdiff