mirror of https://github.com/fadden/fdraw.git
753 lines
18 KiB
ArmAsm
753 lines
18 KiB
ArmAsm
********************************
|
|
* *
|
|
* Fast Apple II Graphics *
|
|
* By Andy McFadden *
|
|
* Version 0.3, Aug 2015 *
|
|
* *
|
|
* Circle rendering *
|
|
* (Included by FDRAW.S) *
|
|
* *
|
|
* Developed with Merlin-16 *
|
|
* *
|
|
********************************
|
|
|
|
* TODO: if USE_FAST is 0, replace the outline circle
|
|
* plot code with calls to DrawPoint (or maybe a
|
|
* common sub-function so we don't trash the input
|
|
* parameters). Saves a little space.
|
|
|
|
|
|
********************************
|
|
*
|
|
* Draw a circle. The radius is in in_rad, and
|
|
* the center is at in_x0l+in_x0h,in_y0.
|
|
*
|
|
********************************
|
|
DrawCircle
|
|
lda #$20 ;JSR
|
|
cmp _cp08 ;configured for outline?
|
|
beq :okay
|
|
jsr fixcplot
|
|
:okay
|
|
jmp calc_circle
|
|
|
|
|
|
********************************
|
|
*
|
|
* Draw filled circle.
|
|
*
|
|
********************************
|
|
FillCircle
|
|
lda #$2c ;BIT
|
|
cmp _cp08 ;configured for fill?
|
|
beq :okay
|
|
jsr fixcplot
|
|
:okay
|
|
jsr calc_circle
|
|
jmp FillRaster
|
|
|
|
|
|
* Calculate a circle, using Bresenham's algorithm. The
|
|
* results are placed into the rasterization buffers.
|
|
*
|
|
* in_rad must be from 0 to 255. The x/y center
|
|
* coordinates must be on the screen, but the circle
|
|
* can extend off the edge.
|
|
*
|
|
* The computed values are stored in the rasterization
|
|
* tables. For an outline circle, we also plot the
|
|
* points immediately.
|
|
|
|
do USE_FAST ;*****
|
|
* local storage -- not used often enough to merit DP
|
|
circ_8bit ds 1
|
|
circ_clip ds 1
|
|
fin ;*****
|
|
|
|
calc_circle
|
|
max_fast_rad equ 41
|
|
]cxl equ zloc0
|
|
]cxh equ zloc1
|
|
]cy equ zloc2
|
|
]dlo equ zloc3
|
|
]dhi equ zloc4
|
|
]xsav equ zloc5
|
|
]ysav equ zloc6
|
|
]min_x equ zloc7 ;min/max offsets from center
|
|
]max_x equ zloc8 ;(min is above center, max
|
|
]min_y equ zloc9 ; is below)
|
|
]max_y equ zloc10
|
|
]hitmp equ zloc11
|
|
* only used by hplot for outline circles
|
|
]hbasl equ zptr0
|
|
]andmask equ zloc11 ;overlaps with ]hitmp
|
|
]savxreg equ zloc12
|
|
]savyreg equ zloc13
|
|
|
|
* Special-case radius=0. It removes an annoying
|
|
* edge case (first y-- becomes 0xff, but 6502 cmp
|
|
* is unsigned).
|
|
lda in_rad
|
|
bne :notzero
|
|
ldy in_y0
|
|
sty rast_top
|
|
sty rast_bottom
|
|
lda in_x0l
|
|
sta rastx0l,y
|
|
sta rastx1l,y
|
|
lda in_x0h
|
|
sta rastx0h,y
|
|
sta rastx1h,y
|
|
rts
|
|
|
|
* Use different version of function for small
|
|
* circles, because we can do it all in 8 bits.
|
|
:notzero
|
|
do USE_FAST ;*****
|
|
ldy #$01
|
|
cmp #max_fast_rad ;in_rad in Acc
|
|
blt :use_fast
|
|
dey
|
|
:use_fast sty circ_8bit
|
|
fin ;*****
|
|
|
|
lda in_x0l ;copy center to DP for speed
|
|
sta ]cxl
|
|
lda in_x0h
|
|
sta ]cxh
|
|
lda in_y0
|
|
sta ]cy
|
|
|
|
* Compute min/max values, based on offset from center.
|
|
* These are compared against offset-from-center x/y.
|
|
* We need tight bounds on Y because we use it to
|
|
* compute the rast_render top/bottom. Getting tight
|
|
* bounds on X is not so important, but we still need
|
|
* it for the no-clip optimization.
|
|
ldx #$04 ;count edges needing clip
|
|
|
|
lda #NUM_ROWS-1 ;191
|
|
sec
|
|
sbc ]cy ;maxY = 191-cy
|
|
cmp in_rad
|
|
blt :ylimok
|
|
lda in_rad ;clamp to radius
|
|
dex
|
|
:ylimok sta ]max_y ;maxY = 191-cy
|
|
|
|
lda ]cy ;minY = cy
|
|
cmp in_rad
|
|
blt :ylimok2
|
|
lda in_rad ;clamp to radius
|
|
dex
|
|
:ylimok2 sta ]min_y
|
|
|
|
lda ]cxh
|
|
beq :xlimlo
|
|
* Examples (note #<NUM_COLS-1 is 279-256 = 23):
|
|
* cx=265 (cxh=1 cxl=11), 23-11=14, chk rad
|
|
lda #<NUM_COLS-1 ;maxX = 279-cx
|
|
sec
|
|
sbc ]cxl
|
|
cmp in_rad
|
|
blt :xlimhok
|
|
lda in_rad ;clamp to radius
|
|
dex
|
|
:xlimhok sta ]max_x
|
|
|
|
lda in_rad ;min X always out of range
|
|
dex ; so just clamp to radius
|
|
sta ]min_x
|
|
jmp :xlimdone
|
|
|
|
* Examples:
|
|
* For cx=0 to 24, we can never pass right edge (our
|
|
* maximum radius is 255).
|
|
* cx=3, 23-3=20 + carry set --> bad, must use rad
|
|
* cx=24, 23-24=255 + carry clear --> ok, chk rad
|
|
* cx=255, 23-255=24 + carry clear --> ok, chk rad
|
|
:xlimlo
|
|
lda #<NUM_COLS-1 ;maxX = 279-cx
|
|
sec
|
|
sbc ]cxl
|
|
bcs :xuserad
|
|
cmp in_rad
|
|
blt :xlimok
|
|
:xuserad lda in_rad ;clamp to radius
|
|
dex
|
|
:xlimok sta ]max_x
|
|
|
|
lda ]cxl ;minX = (cx > 255) ?
|
|
cmp in_rad
|
|
blt :xlimok2
|
|
lda in_rad ;clamp to radius
|
|
dex
|
|
:xlimok2 sta ]min_x
|
|
|
|
:xlimdone
|
|
|
|
do USE_FAST ;*****
|
|
stx circ_clip
|
|
fin ;*****
|
|
|
|
* set top/bottom rows for rasterizer
|
|
lda ]cy
|
|
clc
|
|
adc ]max_y
|
|
sta rast_bottom
|
|
lda ]cy
|
|
sec
|
|
sbc ]min_y
|
|
sta rast_top
|
|
|
|
DO 0 ;debug debug debug
|
|
LDA ]min_x ;save a copy where the
|
|
STA $0380 ; monitor won't trash it
|
|
LDA ]max_x
|
|
STA $0381
|
|
LDA ]min_y
|
|
STA $0382
|
|
LDA ]max_y
|
|
STA $0383
|
|
FIN
|
|
|
|
* Set initial conditions for Bresenham.
|
|
ldx #0 ;:x = 0
|
|
stx ]xsav
|
|
ldy in_rad ;:y = rad
|
|
sty ]ysav
|
|
lda #1 ;:d = 1 - rad
|
|
sec
|
|
sbc ]ysav ;in_rad
|
|
sta ]dlo
|
|
bcs :hizero ;C==1 if in_rad<=1
|
|
ldx #$ff ;C was 0, make neg
|
|
:hizero stx ]dhi
|
|
|
|
*
|
|
* Outer loop -- plot 8 points, then update values.
|
|
*
|
|
circ_loop
|
|
|
|
do USE_FAST ;*****
|
|
lda circ_clip
|
|
beq ncypy
|
|
jmp with_clip
|
|
|
|
* Quick version, no clipping required
|
|
* row cy+y: cx-x and cx+x
|
|
ncypy
|
|
lda ]ysav
|
|
clc
|
|
adc ]cy
|
|
tay ;y-coord in Y-reg
|
|
|
|
lda ]cxl
|
|
sec
|
|
sbc ]xsav
|
|
sta rastx0l,y
|
|
lda ]cxh
|
|
sbc #$00
|
|
sta rastx0h,y
|
|
_cp00 jsr cplotl
|
|
|
|
lda ]cxl
|
|
clc
|
|
adc ]xsav
|
|
sta rastx1l,y
|
|
lda ]cxh
|
|
adc #$00
|
|
sta rastx1h,y
|
|
_cp01 jsr cplotrn
|
|
|
|
* row cy-y: cx-x and cx+x
|
|
ncymy
|
|
lda ]cy
|
|
sec
|
|
sbc ]ysav
|
|
tay ;y-coord in Y-reg
|
|
|
|
lda ]cxl
|
|
sec
|
|
sbc ]xsav
|
|
sta rastx0l,y
|
|
lda ]cxh
|
|
sbc #$00
|
|
sta rastx0h,y
|
|
_cp02 jsr cplotl
|
|
|
|
lda ]cxl
|
|
clc
|
|
adc ]xsav
|
|
sta rastx1l,y
|
|
lda ]cxh
|
|
adc #$00
|
|
sta rastx1h,y
|
|
_cp03 jsr cplotrn
|
|
|
|
* row cy+x: cx-y and cx+y
|
|
ncypx
|
|
lda ]xsav ;off bottom?
|
|
clc
|
|
adc ]cy
|
|
tay ;y-coord in Y-reg
|
|
|
|
lda ]cxl
|
|
sec
|
|
sbc ]ysav
|
|
sta rastx0l,y
|
|
lda ]cxh
|
|
sbc #$00
|
|
sta rastx0h,y
|
|
_cp04 jsr cplotl
|
|
|
|
lda ]cxl
|
|
clc
|
|
adc ]ysav
|
|
sta rastx1l,y
|
|
lda ]cxh
|
|
adc #$00
|
|
sta rastx1h,y
|
|
_cp05 jsr cplotrn
|
|
|
|
* row cy-x: cx-y and cx+y
|
|
ncymx
|
|
lda ]cy
|
|
sec
|
|
sbc ]xsav
|
|
tay ;y-coord in Y-reg
|
|
|
|
lda ]cxl
|
|
sec
|
|
sbc ]ysav
|
|
sta rastx0l,y
|
|
lda ]cxh
|
|
sbc #$00
|
|
sta rastx0h,y
|
|
_cp06 jsr cplotl
|
|
|
|
lda ]cxl
|
|
clc
|
|
adc ]ysav
|
|
sta rastx1l,y
|
|
lda ]cxh
|
|
adc #$00
|
|
sta rastx1h,y
|
|
_cp07 jsr cplotrn
|
|
|
|
* CLICK
|
|
jmp circ_plot_done
|
|
|
|
fin ;***** (USE_FAST)
|
|
|
|
*
|
|
* Same thing, but this time clipping edges.
|
|
*
|
|
with_clip
|
|
|
|
* row cy+y: cx-x and cx+x
|
|
ccypy
|
|
lda ]ysav ;off bottom?
|
|
cmp ]max_y
|
|
beq :cypy_ok
|
|
bge cypy_skip ;completely off screen
|
|
:cypy_ok clc
|
|
adc ]cy
|
|
tay ;y-coord in Y-reg
|
|
|
|
ldx ]xsav ;handle cx-x
|
|
cpx ]min_x
|
|
blt :cxmx_ok
|
|
beq :cxmx_ok
|
|
lda #0 ;clip at 0
|
|
sta rastx0l,y
|
|
sta rastx0h,y
|
|
beq cxmx_done0 ;always
|
|
BREAK
|
|
:cxmx_ok lda ]cxl
|
|
sec
|
|
sbc ]xsav
|
|
sta rastx0l,y
|
|
lda ]cxh
|
|
sbc #$00
|
|
sta rastx0h,y
|
|
_cp08 jsr cplotl
|
|
cxmx_done0
|
|
|
|
cpx ]max_x ;handle cx+x
|
|
blt :cxpx_ok
|
|
beq :cxpx_ok
|
|
lda #<NUM_COLS-1
|
|
sta rastx1l,y
|
|
lda #>NUM_COLS-1
|
|
sta rastx1h,y
|
|
bne cxpx_done0 ;always
|
|
BREAK
|
|
:cxpx_ok lda ]cxl
|
|
clc
|
|
adc ]xsav
|
|
sta rastx1l,y
|
|
lda ]cxh
|
|
adc #$00
|
|
sta rastx1h,y
|
|
_cp09 jsr cplotr
|
|
cxpx_done0
|
|
cypy_skip
|
|
|
|
* row cy-y: cx-x and cx+x
|
|
ccymy
|
|
lda ]ysav ;off top?
|
|
cmp ]min_y
|
|
beq :cymy_ok
|
|
bge cymy_skip
|
|
:cymy_ok lda ]cy
|
|
sec
|
|
sbc ]ysav
|
|
tay ;y-coord in Y-reg
|
|
|
|
ldx ]xsav ;handle cx-x
|
|
cpx ]min_x
|
|
blt :cxmx_ok
|
|
beq :cxmx_ok
|
|
lda #0 ;clip at 0
|
|
sta rastx0l,y
|
|
sta rastx0h,y
|
|
beq cxmx_done1 ;always
|
|
BREAK
|
|
:cxmx_ok lda ]cxl
|
|
sec
|
|
sbc ]xsav
|
|
sta rastx0l,y
|
|
lda ]cxh
|
|
sbc #$00
|
|
sta rastx0h,y
|
|
_cp10 jsr cplotl
|
|
cxmx_done1
|
|
|
|
cpx ]max_x ;handle cx+x
|
|
blt :cxpx_ok
|
|
beq :cxpx_ok
|
|
lda #<NUM_COLS-1
|
|
sta rastx1l,y
|
|
lda #>NUM_COLS-1
|
|
sta rastx1h,y
|
|
bne cxpx_done1 ;always
|
|
BREAK
|
|
:cxpx_ok lda ]cxl
|
|
clc
|
|
adc ]xsav
|
|
sta rastx1l,y
|
|
lda ]cxh
|
|
adc #$00
|
|
sta rastx1h,y
|
|
_cp11 jsr cplotr
|
|
cxpx_done1
|
|
cymy_skip
|
|
|
|
* row cy+x: cx-y and cx+y
|
|
ccypx
|
|
lda ]xsav ;off bottom?
|
|
cmp ]max_y
|
|
beq :cypx_ok
|
|
bge cypx_skip
|
|
:cypx_ok clc
|
|
adc ]cy
|
|
tay ;y-coord in Y-reg
|
|
|
|
ldx ]ysav ;handle cx-y
|
|
cpx ]min_x
|
|
blt :cxmy_ok
|
|
beq :cxmy_ok
|
|
lda #0 ;clip at 0
|
|
sta rastx0l,y
|
|
sta rastx0h,y
|
|
beq cxmy_done2 ;always
|
|
BREAK
|
|
:cxmy_ok lda ]cxl
|
|
sec
|
|
sbc ]ysav
|
|
sta rastx0l,y
|
|
lda ]cxh
|
|
sbc #$00
|
|
sta rastx0h,y
|
|
_cp12 jsr cplotl
|
|
cxmy_done2
|
|
|
|
cpx ]max_x ;handle cx+y
|
|
blt :cxpy_ok
|
|
beq :cxpy_ok
|
|
lda #<NUM_COLS-1
|
|
sta rastx1l,y
|
|
lda #>NUM_COLS-1
|
|
sta rastx1h,y
|
|
bne cxpy_done2 ;always
|
|
BREAK
|
|
:cxpy_ok lda ]cxl
|
|
clc
|
|
adc ]ysav
|
|
sta rastx1l,y
|
|
lda ]cxh
|
|
adc #$00
|
|
sta rastx1h,y
|
|
_cp13 jsr cplotr
|
|
cxpy_done2
|
|
cypx_skip
|
|
|
|
* row cy-x: cx-y and cx+y
|
|
ccymx
|
|
lda ]xsav ;off top?
|
|
cmp ]min_y
|
|
beq :cymx_ok
|
|
bge cymx_skip
|
|
:cymx_ok lda ]cy
|
|
sec
|
|
sbc ]xsav
|
|
tay ;y-coord in Y-reg
|
|
|
|
ldx ]ysav ;handle cx-y
|
|
cpx ]min_x
|
|
blt :cxmy_ok
|
|
beq :cxmy_ok
|
|
lda #0 ;clip at 0
|
|
sta rastx0l,y
|
|
sta rastx0h,y
|
|
beq cxmy_done3 ;always
|
|
BREAK
|
|
:cxmy_ok lda ]cxl
|
|
sec
|
|
sbc ]ysav
|
|
sta rastx0l,y
|
|
lda ]cxh
|
|
sbc #$00
|
|
sta rastx0h,y
|
|
_cp14 jsr cplotl
|
|
cxmy_done3
|
|
|
|
cpx ]max_x ;handle cx+y
|
|
blt :cxpy_ok
|
|
beq :cxpy_ok
|
|
lda #<NUM_COLS-1
|
|
sta rastx1l,y
|
|
lda #>NUM_COLS-1
|
|
sta rastx1h,y
|
|
bne cxpy_done3 ;always
|
|
BREAK
|
|
:cxpy_ok lda ]cxl
|
|
clc
|
|
adc ]ysav
|
|
sta rastx1l,y
|
|
lda ]cxh
|
|
adc #$00
|
|
sta rastx1h,y
|
|
_cp15 jsr cplotr
|
|
cxpy_done3
|
|
cymx_skip
|
|
|
|
circ_plot_done
|
|
* Update X/Y/D. Up to about radius=41 we can maintain
|
|
* 'd' in an 8-bit register.
|
|
do USE_FAST ;*****
|
|
lda circ_8bit
|
|
beq circ_slow
|
|
|
|
*
|
|
* Bresenham update, with 8-bit 'd'.
|
|
*
|
|
ldx ]xsav
|
|
lda ]dlo
|
|
bmi :dneg
|
|
txa ;:d = d + ((x-y)*4) +5
|
|
sec
|
|
sbc ]ysav ;x <= y, may be neg or 0
|
|
asl
|
|
asl
|
|
clc ;can't know carry
|
|
adc #5
|
|
clc ;still don't want carry
|
|
adc ]dlo
|
|
sta ]dlo
|
|
dec ]ysav ;:y--
|
|
jmp :loopbot
|
|
:dneg txa ;:d = d + (x*4) +3
|
|
asl
|
|
asl ;x always pos, C=0
|
|
DO 0
|
|
BCC :TEST ;debug
|
|
BREAK ;debug
|
|
:TEST ;debug
|
|
FIN
|
|
adc #3
|
|
adc ]dlo
|
|
sta ]dlo
|
|
:loopbot
|
|
inx ;:x++
|
|
stx ]xsav
|
|
cpx ]ysav
|
|
beq :again
|
|
bge circ_done
|
|
:again jmp circ_loop
|
|
|
|
fin ;*****
|
|
|
|
*
|
|
* Bresenham update, with 16-bit 'd'
|
|
*
|
|
circ_slow
|
|
CLICK
|
|
ldx ]xsav
|
|
lda ]dhi
|
|
bmi :dneg
|
|
lda ]dlo
|
|
clc
|
|
adc #5
|
|
sta ]dlo
|
|
bcc :noinc
|
|
inc ]dhi
|
|
:noinc
|
|
txa ;:d = d + ((x-y)*4) +5
|
|
ldy #$00
|
|
sty ]hitmp
|
|
sec
|
|
sbc ]ysav ;x <= y, may be neg or 0
|
|
beq :xeqy ;if x==y, nothing to add
|
|
ldy #$ff
|
|
sty ]hitmp
|
|
asl
|
|
rol ]hitmp
|
|
asl
|
|
rol ]hitmp
|
|
clc
|
|
adc ]dlo
|
|
sta ]dlo
|
|
lda ]dhi
|
|
adc ]hitmp
|
|
sta ]dhi
|
|
:xeqy
|
|
dec ]ysav ;:y--
|
|
jmp :loopbot
|
|
|
|
:dneg lda ]dlo ;:d = d + (x*4) + 3
|
|
clc
|
|
adc #3
|
|
sta ]dlo
|
|
bcc :noinc2
|
|
inc ]dhi
|
|
:noinc2 txa
|
|
ldy #0 ;x always positive
|
|
sty ]hitmp
|
|
asl
|
|
rol ]hitmp
|
|
asl
|
|
rol ]hitmp
|
|
clc ;not needed?
|
|
adc ]dlo
|
|
sta ]dlo
|
|
lda ]dhi
|
|
adc ]hitmp
|
|
sta ]dhi
|
|
:loopbot
|
|
inx ;:x++
|
|
stx ]xsav
|
|
cpx ]ysav
|
|
beq :again
|
|
bge circ_done
|
|
:again jmp circ_loop
|
|
|
|
|
|
circ_done rts
|
|
|
|
|
|
* Plot a point for outline circle rendering.
|
|
*
|
|
* X and Y must be preserved. Y holds the current line
|
|
* number.
|
|
*
|
|
* Most DP locations are in use -- see the variable
|
|
* declarations at the start of the circle function.
|
|
|
|
* cplotl is the entry point for the leftmost point.
|
|
cplotl
|
|
stx ]savxreg
|
|
sty ]savyreg
|
|
|
|
lda ylooklo,y
|
|
sta ]hbasl
|
|
lda ylookhi,y
|
|
_pg_or2 ora #$20
|
|
sta ]hbasl+1
|
|
|
|
* Convert the X coordinate into byte/bit.
|
|
ldx rastx0l,y ;x coord, lo
|
|
lda rastx0h,y ;>= 256?
|
|
beq :lotabl ;no, use the low table
|
|
ldy div7hi,x
|
|
lda mod7hi,x
|
|
bpl cplotcom ;always
|
|
BREAK ;debug
|
|
:lotabl ldy div7lo,x
|
|
lda mod7lo,x
|
|
jmp cplotcom
|
|
|
|
* cplotr is the entry point for the rightmost point.
|
|
* We use rastx1 instead of rastx0.
|
|
cplotr
|
|
lda ylooklo,y
|
|
sta ]hbasl
|
|
lda ylookhi,y
|
|
_pg_or3 ora #$20
|
|
sta ]hbasl+1
|
|
|
|
* If we just plotted the left point on the same line,
|
|
* we can skip the Y-lookup by jumping here.
|
|
cplotrn
|
|
stx ]savxreg
|
|
sty ]savyreg
|
|
|
|
ldx rastx1l,y ;x coord, lo
|
|
lda rastx1h,y ;>= 256?
|
|
beq :lotabl ;no, use the low table
|
|
ldy div7hi,x
|
|
lda mod7hi,x
|
|
bpl cplotcom ;always
|
|
BREAK ;debug
|
|
:lotabl ldy div7lo,x
|
|
lda mod7lo,x
|
|
|
|
* Plot the point. The byte offset (0-39) is in Y,
|
|
* the bit offset (0-6) is in A.
|
|
cplotcom
|
|
tax
|
|
lda colorline,y ;start with color pattern
|
|
eor (]hbasl),y ;flip all bits
|
|
and andmask,x ;clear other bits
|
|
eor (]hbasl),y ;restore ours, set theirs
|
|
sta (]hbasl),y
|
|
|
|
ldx ]savxreg
|
|
ldy ]savyreg
|
|
rts
|
|
|
|
* Reconfigure calc_circle to either JSR to cplotl/r,
|
|
* or just BIT the address (a 4-cycle no-op). The
|
|
* desired instruction is in A.
|
|
fixcplot
|
|
do USE_FAST ;*****
|
|
sta _cp00
|
|
sta _cp01
|
|
sta _cp02
|
|
sta _cp03
|
|
sta _cp04
|
|
sta _cp05
|
|
sta _cp06
|
|
sta _cp07
|
|
fin ;*****
|
|
sta _cp08
|
|
sta _cp09
|
|
sta _cp10
|
|
sta _cp11
|
|
sta _cp12
|
|
sta _cp13
|
|
sta _cp14
|
|
sta _cp15
|
|
rts
|