dos33fsprogs/graphics/hgr/xdraw/xdraw_test.s
2021-05-10 01:49:01 -04:00

133 lines
2.6 KiB
ArmAsm

; Tiny Xdraw
; repeatedly draws an image from an Apple II shape table
; can arbitrarily point to any memory location as a source of these
; some look amazing but depend on random machine state
; to be deterministic you should probably stick to
; $E7-$F0 (the program itself)
; $D000-$FFFF (the ROMs)
; shapetables are a bit complicated to explain here, but they are a
; series of bytes ending with a $00
; (note if you point to a zero, it will be interpreted as an
; action not an end)
; each byte specifies up to 3 actions, DRAW + UP DOWN LEFT RIGHT or
; NODRAW + UP DOWN LEFT RIGHT
; It is vector scaling with SCALE we hardcode to $20 and rotation
; which gets set to 0 after the first iteration, (which is
; why the first shape has arbitrary rotation and gets left)
; we are xdrawing so it will XOR with the current pixels on the screen
; NUP=0 UP=4 zz yyy xxx , does xxx yyy zz
; NRT=1 RT=5
; NDN=2 DN=6
; NLT=3 LT=7
; zero page locations
HGR_SHAPE = $1A
HGR_SHAPE2 = $1B
HGR_BITS = $1C
GBASL = $26
GBASH = $27
A5H = $45
XREG = $46
YREG = $47
; C0-CF should be clear
; D0-DF?? D0-D5 = HGR scratch?
HGR_DX = $D0 ; HGLIN
HGR_DX2 = $D1 ; HGLIN
HGR_DY = $D2 ; HGLIN
HGR_QUADRANT = $D3
HGR_E = $D4
HGR_E2 = $D5
HGR_X = $E0
HGR_X2 = $E1
HGR_Y = $E2
HGR_COLOR = $E4
HGR_HORIZ = $E5
HGR_SCALE = $E7
HGR_SHAPE_TABLE = $E8
HGR_SHAPE_TABLE2= $E9
HGR_COLLISIONS = $EA
HGR_ROTATION = $F9
FRAME = $FC
XPOS = $FD
YPOS = $FF
KEYPRESS = $C000
KEYRESET = $C010
; ROM calls
HGR2 = $F3D8
HGR = $F3E2
HPOSN = $F411
XDRAW0 = $F65D
XDRAW1 = $F661
RESTORE = $FF3F
.zeropage
.globalzp rot_smc
tiny_xdraw:
jsr HGR2 ; Hi-res, full screen ; 3
; Y=0, A=0 after this call
; we load at $E7 which is HGR_SCALE, so HGR_SCALE gets
; the value of the above JSR instruction ($20)
; A and Y are 0 here.
; X is left behind by the boot process?
txa
jsr HPOSN ; set screen position to X= (y,x) Y=(a)
; saves X,Y,A to zero page
; after Y= orig X/7
; A and X are ??
tiny_loop:
; values for shape table
; Y X
; 00 E7 = neat
; 00 EB = OK
; 00 EF = good
; F0 01 = cool, let's go with it
smc2:
; ldy #$d0 ; point to top byte of shape address
ldy #$d3 ; point to top byte of shape address
smc1:
ldx #$00 ; point to bottom byte of shape address
; ROT in A
; this will be 0 2nd time through loop, arbitrary otherwise
lda #0 ; ROT=0
jsr XDRAW0 ; XDRAW 1 AT X,Y
; Both A and X are 0 at exit
; Z flag set on exit
; Y varies
lda KEYPRESS
bpl tiny_loop
; key pressed
bit KEYRESET
jsr HGR2
inc smc1+1
bne tiny_loop
inc smc2+1
jmp tiny_loop ; bra