********************************
* *
* Amper-fdraw *
* By Andy McFadden *
* For fdraw version 0.3 *
* *
* Applesoft ampersand *
* interface for fdraw. *
* *
* Developed with Merlin-16 *
* *
********************************
lst off
org $1d60
* All of the handler entry points can fit on a single
* page, so it's possible to save a few bytes by
* dropping the high jump table and just hardcoding
* the first page into the jump. This requires that
* the ORG be at $xx00.
PUT FDRAW.DEFS
* Applesoft BASIC tokens.
tok_plot equ $8d
tok_hgr2 equ $90
tok_hgr equ $91
tok_hcolor equ $92
tok_hplot equ $93
tok_draw equ $94
tok_xdraw equ $95
tok_inverse equ $9e
tok_clear equ $bd
tok_new equ $bf
tok_to equ $c1
tok_at equ $c5
*tok_sgn equ $d2
tok_scrn equ $d7
tok_exp equ $dd
tok_cos equ $de
tok_sin equ $df
* System locations.
PCL equ $3a ;used by monitor
PCH equ $3b ;used by monitor
A1L equ $3c ;used by monitor
A1H equ $3d ;used by monitor
LINNUM equ $50 ;50-51
FACLO equ $a1
CHRGET equ $b1 ;advance ptr, get next tok
CHRGOT equ $b7 ;get next tok (no advance)
TXTPTR equ $b8
HPAG equ $e6 ;$20 or $40
AMPERV equ $3f5
TXTCLR equ $c050
TXTSET equ $c051
MIXCLR equ $c052
MIXSET equ $c053
LOWSCR equ $c054
HISCR equ $c055
LORES equ $c056
HIRES equ $c057
ERROR equ $d412 ;error based on X reg
FRMNUM equ $dd67
SynError equ $dec9 ;throw SYNTAX ERROR
CHKCOM equ $debe
IllQError equ $e199 ;throw ILLEGAL QUANTITY ERROR
GETADR equ $e752
GETBYT equ $e6f8 ;gets byte, in X/FACLO
HFNS equ $f6b9 ;get hi-res x/y for hplot
* Prepare the ampersand vector.
*
* Ideally we'd check to see if the existing vector is
* different from ours, and if so, jump to it when we
* get a token we don't recognize. Not convinced
* there's an actual use case for this.
init
lda #$4c ;JMP, in case it got
sta AMPERV ; trashed
lda #<dispatch
sta AMPERV+1
lda #>dispatch
sta AMPERV+2
rts
* Entry point from BASIC. The token is in A.
dispatch
ldx #:cmdend-:cmdtab-1
]loop cmp :cmdtab,x
beq :match
dex
bpl ]loop
jmp SynError
:match
lda :jmptabh,x
* lda #>h_new ;all on first page
pha
lda :jmptabl,x
pha
jmp CHRGET ;eat token, jump
:cmdtab dfb tok_new
dfb tok_hgr
dfb tok_hgr2
dfb tok_scrn
dfb tok_hcolor
dfb tok_inverse
dfb tok_clear
dfb tok_hplot
dfb tok_xdraw
dfb tok_draw
dfb tok_exp
dfb tok_cos
dfb tok_sin
dfb tok_at
dfb tok_plot
:cmdend
:jmptabl dfb <h_new-1
dfb <h_hgr-1
dfb <h_hgr2-1
dfb <h_scrn-1
dfb <h_hcolor-1
dfb <h_inverse-1
dfb <h_clear-1
dfb <h_hplot-1
dfb <h_xdraw-1
dfb <h_draw-1
dfb <h_exp-1
dfb <h_cos-1
dfb <h_sin-1
dfb <h_at-1
dfb <h_plot-1
:jmptabh dfb >h_new-1
dfb >h_hgr-1
dfb >h_hgr2-1
dfb >h_scrn-1
dfb >h_hcolor-1
dfb >h_inverse-1
dfb >h_clear-1
dfb >h_hplot-1
dfb >h_xdraw-1
dfb >h_draw-1
dfb >h_exp-1
dfb >h_cos-1
dfb >h_sin-1
dfb >h_at-1
dfb >h_plot-1
********************************
* &NEW - initialize
h_new
lda #$20 ;match Init result
sta g_cur_page
lda #$00
sta g_hcolor
tax ;init "previous hplot"
tay ; coord to zero
jsr storeprv
ldx #139 ;279/2
ldy #0
lda #95 ;191/2
jsr storeac
jmp f_Init
********************************
* &HGR - show page 1 with mixed text, and clear screen.
* Sets the color to zero.
h_hgr
ldx #$20 ;page 1
lda #$00 ;$c054
beq hgr_com
********************************
* &HGR2 - show page 2 with no text, and clear screen.
* Sets the color to zero.
h_hgr2
ldx #$40 ;page 2
lda #$01 ;$c055
;fall through to hgr_com
* We go slightly out of our way to clear the screen
* before tripping the softswitches. This avoids
* flashing the previous hi-res page contents when
* entering from text mode.
*
* We also want to go nomix-page2 but page1-mix
* (note reverse order) to avoid flashing text pg 2.
hgr_com stx f_in_arg
stx g_cur_page
stx HPAG ;probably useful
pha
jsr f_SetPage
lda #$00
sta f_in_arg
jsr f_SetColor
jsr f_Clear
lda g_hcolor ;restore color
sta f_in_arg
jsr f_SetColor
bit TXTCLR ;$c050
bit HIRES ;$c057
pla
beq :pg1
bit MIXCLR ;$c052
bit HISCR ;$c055
rts
:pg1 bit LOWSCR ;$c054
bit MIXSET ;$c053
rts
********************************
* &SCRN({1,2}) - set the current hi-res page
h_scrn
jsr GETBYT
cpx #1
beq :okay
cpx #2
beq :okay
jmp IllQError
:okay jsr CHRGET ;eat ')' (we assume)
txa ;X/Y unaltered
asl
asl
asl
asl
asl ;multiply x32
sta g_cur_page
sta f_in_arg
jmp f_SetPage
********************************
* &HCOLOR={0-7} - set the current color
h_hcolor
jsr GETBYT ;get color
cpx #8
blt :okay
jmp IllQError
:okay stx f_in_arg
stx g_hcolor
jmp f_SetColor
********************************
* &INVERSE - flip pages
*
* If we're currently drawing on $20, we set the page
* to $40 and hit $c054 to show $20. And vice-versa.
* The goal is to make double-buffered animation easy.
h_inverse
lda g_cur_page
eor #$60
sta g_cur_page
ldx #$00
cmp #$40 ;about to start drawing on 2?
beq :showpg1 ;yes, show page 1
inx ;no, show page 2
:showpg1 ldy LOWSCR,x
sta f_in_arg
jmp f_SetPage
********************************
* &CLEAR - clear current page to current color.
h_clear
jmp f_Clear ;well, that was easy
********************************
* &XDRAW left,top,right,bottom - draw rectangle outline
h_xdraw
jsr getltrb
jmp f_DrawRect
********************************
* &DRAW left,top,right,bottom - draw filled rectangle
h_draw
jsr getltrb
jmp f_FillRect
********************************
* &EXP {0,1} - set line draw mode
h_exp
jsr GETBYT
cpx #2
blt :okay
jmp IllQError
:okay stx f_in_arg
jmp f_SetLineMode
********************************
* &COS cx,cy,rad - draw outline circle
h_cos
jsr getcxcyr
jmp f_DrawCircle
********************************
* &SIN cx,cy,rad - draw filled circle
h_sin
jsr getcxcyr
jmp f_FillCircle
********************************
* &AT x,y - select center for array draw
h_at
jsr HFNS
jmp storeac
********************************
* &PLOT vertexAddr, indexAddr, indexCount [AT cx,cy]
* draw lines from arrays of vertices and indices
h_plot jmp array_draw
********************************
* &HPLOT x,y - draw a point
* &HPLOT TO x,y - draw a line from last point to x,y
* &HPLOT x0,y0 to x1,y1 - draw a line
lst on ;last token handler --
h_hplot equ * ; must be on first page
lst off ; to omit high byte table
jsr CHRGOT ;check next token
lst off
cmp #tok_to ;is this an "HPLOT TO"?
beq :leadingto
jsr getx1y1 ;get the first coord
jsr copy1to0
jsr CHRGOT ;see if single point
cmp #tok_to
beq :hplot_to ;nope, draw line
jsr copy0toprev ;draw point, and save x/y
jmp f_DrawPoint ; for subsequent HPLOT TO
:leadingto ;"HPLOT TO", restore the
lda g_prevxl ; previous coord to x0/y0
sta f_in_x0l ;(can't rely on f_in_zzz
lda g_prevxh ; being there -- we might
sta f_in_x0h ; have drawn a rect)
lda g_prevy
sta f_in_y0
:hplot_to
jsr CHRGET ;eat the TO
jsr getx1y1 ;get the coords
jsr f_DrawLine ;draw it
jsr copy1to0 ;shift 1->0 for next round
jsr CHRGOT
cmp #tok_to ;another TO?
beq :hplot_to ;yes, branch
jmp copy0toprev ;no, save prev and bail
* Get coordinates and store in X1/Y1.
getx1y1
jsr HFNS
store1 stx f_in_x1l ;store X/Y/A in coord1
sty f_in_x1h
sta f_in_y1
rts
* Save x0/y0 as our "previous" coordinate.
copy0toprev
ldx f_in_x0l
ldy f_in_x0h
lda f_in_y0
storeprv stx g_prevxl ;store X/Y/A in g_prev
sty g_prevxh
sta g_prevy
rts
* Copy X1/Y1 into X0/Y0.
copy1to0
ldx f_in_x1l
ldy f_in_x1h
lda f_in_y1
store0 stx f_in_x0l ;store X/Y/A in coord 0
sty f_in_x0h
sta f_in_y0
rts
* Store X/Y/A into array-center.
storeac stx g_ac_xl
sty g_ac_xh
sta g_ac_y
rts
* Get left/top/right/bottom coordinates.
getltrb
jsr HFNS
jsr store0 ;save as X0/Y0
jsr CHKCOM ;eat a comma
jsr HFNS
jsr store1 ;save as X1/Y1
rts
* Get center coordinates and radius.
getcxcyr
jsr HFNS ;get CX and CY
jsr store0 ;save as X0/Y0
jsr CHKCOM ;eat a comma
jsr GETBYT ;convert to 0-255
stx f_in_rad
rts
* Array-draw handler.
*
* We know that fdraw doesn't use LINNUM or A1L/A1H,
* so it's safe to use them here.
array_draw
]vertices equ A1L ;2b
]indices equ LINNUM ;2b
]count equ PCL
]cur equ PCH
jsr FRMNUM ;get vertex buffer address
jsr GETADR
lda LINNUM ;copy to A1L
sta ]vertices
lda LINNUM+1
sta ]vertices+1
jsr CHKCOM ;eat the comma
jsr FRMNUM ;get index buffer address
jsr GETADR ;leave it in LINNUM
jsr CHKCOM
jsr GETBYT ;get the count
cpx #128 ;range check (0-127)
blt :countok
jmp IllQError
:countok txa
beq :done ;nothing to do
asl ;double it
sta ]count ;stash it
lda #$00
sta ]cur
* Check for optional AT cx,cy.
jsr CHRGOT
cmp #tok_at
bne :noat
JSR CHRGET ;eat the AT
lda LINNUM ;the code that reads the
pha ; hi-res coordinates will
lda LINNUM+1 ; overwrite LINNUM, so
pha ; we have to save & restore
jsr h_at
pla
sta LINNUM+1
pla
sta LINNUM
:noat
]loop jsr getvertex
bcs :skip2
jsr store0
jsr getvertex
bcs :skip
jsr store1
jsr f_DrawLine
dfb $2c ;BIT addr
:skip2 inc ]cur
:skip lda ]cur
cmp ]count
blt ]loop
:done rts
* Get the Nth vertex, specified by ]cur, and load it
* into X/Y/A (xlo/xhi/y). Returns with carry set if
* the vertex is invalid.
*
* Increments ]cur by 1.
getvertex
ldy ]cur
inc ]cur
lda (]indices),y
bmi :badv ;must be 0-127
jsr :calcvertex
ldx g_out_x
ldy g_out_x+1
beq :xok ;0-255, ok
cpy #1
bne :badv ;512+
cpx #280-256
bge :badv ;280-511
:xok
lda g_out_y+1
bne :badv ;Y is neg or > 255
lda g_out_y
cmp #192
bcc :goodv
:badv
sec
:goodv rts
* Get VX and VY, merging with AC, and store in
* 16-bit g_out_x and g_out_y. Range not checked
* here. On entry, A has vertex index.
:calcvertex
asl
tay
ldx #$00 ;hi byte of vertex
lda (]vertices),y ;x-coord
bpl :xpos
dex ;sign-extend hi byte
:xpos clc
adc g_ac_xl
sta g_out_x
txa
adc g_ac_xh
sta g_out_x+1
iny
ldx #$00
lda (]vertices),y ;y-coord
bpl :ypos
dex ;sign-extend hi byte
:ypos clc
adc g_ac_y
sta g_out_y
bcc :nocarry
inx
:nocarry stx g_out_y+1
rts
********************************
* Global variables
g_cur_page ds 1 ;$20 or $40
g_hcolor ds 1
g_prevxl ds 1
g_prevxh ds 1
g_prevy ds 1
g_ac_xl ds 1 ;Center-point coordinates
g_ac_xh ds 1 ; for array-based line
g_ac_y ds 1 ; draw (&AT, &PLOT).
g_out_x ds 2 ;16-bit coordinates for
g_out_y ds 2 ; array-based line draw
lst on
end equ *
sav amperfdraw
lst off