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|
; Atari Taipan routines for rendering enemy lorchas.
; Lorcha (boat), a type of sailing vessel having a Chinese
; junk rig on a Portuguese or European style hull.
.include "atari.inc"
.import _jsleep
.export _draw_lorcha, _sink_lorcha, _damage_lorcha, _clear_lorcha, _flash_lorcha
; TODO: maybe replace position tables with mul40? see
; libsrc/atari/mul40.s, which is getting linked anyway
; because conio uses it.
.rodata
; offset from start of screen for each ship position (0-9)
lorcha_pos_lo:
.byte <320, <328, <336, <344, <352
.byte <640, <648, <656, <664, <672
lorcha_pos_hi:
.byte >320, >328, >336, >344, >352
.byte >640, >648, >656, >664, >672
; ZP working variables start at $d4, aka FR0 (floating point reg 0).
temp = $d4
andmask = temp
flashing = temp+1
destptr = $d6
lcount = $d8
which = $d9
sinkdelay = $da
; clrtobot.s needs these:
.exportzp destptr
.export bump_destptr
; Our lorcha is a 7x7 block of ATASCII characters. We're storing
; directly to screen RAM, so we use 'internal' codes.
; To edit the graphics, see shipshape[] in convfont.c.
lorcha_data:
.incbin "LORCHA.DAT"
; fully-damaged version of the lorcha, damaged_shipshape[] in convfont.c
damaged_data:
.incbin "DAMAGED.DAT"
.ifdef CART_TARGET
.segment "HIGHCODE"
.else
.code
.endif
; void __fastcall__ flash_lorcha(int which);
_flash_lorcha:
ldx #$80
stx flashing
bne drawit
; void __fastcall__ clear_lorcha(int which);
_clear_lorcha:
ldx #0
stx andmask
stx flashing
beq drawit
; void __fastcall__ draw_lorcha(int which);
_draw_lorcha:
ldx #$ff
stx andmask
ldx #0
stx flashing
; the above 3 entry points set up flashing and/or andmask,
; then branch to the common routine here.
; flashing = 1: invert all the character codes (ignore andmask). turns
; ship inverse, or back to normal, using the data that's
; already in screen RAM (meaning, damage is preserved).
; flashing = 0: copy lorcha_data to destptr, ANDing with andmask:
; andmask = 0: clear lorcha
; andmask = $ff: draw lorcha
drawit:
tax
jsr setup_destptr
ldx #0
line:
ldy #0
char:
bit flashing
bpl noflash
lda (destptr),y
eor #$80
clc
bcc storeit
noflash:
lda lorcha_data,x
and andmask
storeit:
sta (destptr),y
inx
iny
cpy #7
bne char
jsr bump_destptr
cpx #49
bne line
rts
; sinking the lorcha means copying each line of screen RAM
; from the one above it. has to be done in reverse order.
_sink_lorcha:
sta which
lda #6
sta lcount
; set sinkdelay to 3, 5, or 7 jiffies
@rnd:
lda RANDOM
eor RTCLOK+2
and #$06
beq @rnd
ora #1
sta sinkdelay
sinkloop:
ldx which
jsr setup_destptr
clc
lda destptr
adc #200 ; 40 bytes/line * 5 lines
sta destptr
lda destptr+1
adc #0
sta destptr+1
; delay for sinkdelay jiffies
ldx #0
lda sinkdelay
jsr _jsleep
ldx #6 ; line loop counter
; at start of loop, destptr points to last line, and temp
; is unitialized.
slineloop:
; temp=destptr; destptr-=40;
lda destptr
sta temp
sec
sbc #40
sta destptr
lda destptr+1
sta temp+1
sbc #0
sta destptr+1
; now loop over 7 bytes
ldy #6
sbyteloop:
lda (destptr),y
sta (temp),y
dey
bpl sbyteloop
dex
bpl slineloop
dec lcount
bpl sinkloop
rts ; end of _sink_lorcha
;;;;;;;;;;;;;;;;;;;;;;;;;;;;
_damage_lorcha:
tax
jsr setup_destptr
xrand:
; get random number 0-48 in X:
lda 53770 ; RANDOM
lsr
lsr
cmp #49
bcs xrand
tax
getpiece:
lda damaged_data,x
cmp lorcha_data,x
beq xrand ; if it's a piece that can't show damage,
; ditch it and start over
sta temp ; stash the piece
; which row/col? call bump_destptr (x/7)-1 times.
txa
calcrow:
sec
sta temp+1 ; this holds the modulus (x%7)
sbc #7
bcc rowdone
pha
jsr bump_destptr
pla
clc
bcc calcrow
rowdone:
lda temp ; the piece
ldy temp+1
sta (destptr),y
rts ; end of _damage_lorcha
; a couple of utility functions for dealing with destptr:
; add 40 to destptr. trashes A, preserves X/Y.
bump_destptr:
lda destptr
clc
adc #40
sta destptr
lda destptr+1
adc #0
sta destptr+1
rts
; sets up destptr to point to correct position for the given
; ship number (0-9) in X reg. trashes A, preserves X/Y.
setup_destptr:
lda lorcha_pos_lo,x
clc
adc SAVMSC
sta destptr
lda lorcha_pos_hi,x
clc
adc SAVMSC+1
sta destptr+1
rts
|
