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.include "atari.inc"
.export _clrtobot, _clrtoeol, _clrtoline, _cspaces
.import mul40 ; from cc65's runtime
.importzp tmp3 ; ditto
.import bump_destptr ; these two are
.importzp destptr ; from draw_lorcha.s
.import _cspace
; void clrtobot(void);
; void clrtoeol(void);
; void clrtoline(unsigned char line);
; this stuff doesn't disturb conio's (and the OS's) idea of the
; current cursor position. It's *way* faster than writing them in
; C in terms of cclear() (which uses one cputc() call per blank).
_clrtobot: ; same as clrtoline(24);
lda #24
bne _clrtoline
_clrtoeol:
lda ROWCRS
; fall through to _clrtoline
_clrtoline:
sta tmp3 ; stash our arg
lda #0
sta OLDCHR ; stop conio from redrawing stuff after we clear it
; setup destptr to start of current line, NOT
; current cursor position.
lda ROWCRS
jsr mul40 ; AX = A*40 (addr of start-of-row)
clc
adc SAVMSC ; add to screen pointer
sta destptr
txa
adc SAVMSC+1
sta destptr+1
; X = current row, Y = current column. Stop clearing a line when Y == 40,
; we're done when X == 24. Apologies, the names X and Y are backwards
; compared to proper Cartesian coordinates.
ldx ROWCRS
ldy COLCRS
lda #0
clrloop:
sta (destptr),y ; blank a character (A == 0, screen code for a space)
iny
cpy #40
bne clrloop
ldy #0
inx
cpx tmp3
bcs done
jsr bump_destptr
lda #0
tay
beq clrloop
done:
rts
_cspaces:
sta tmp3
@lp:
jsr _cspace
dec tmp3
bne @lp
rts
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