cc65/libsrc/atari7800/cputc.s

;
; Mark Keates, Christian Groessler, Piotr Fusik, Karri Kaksonen
;
; void cputcxy (unsigned char x, unsigned char y, char c);
; void cputc (char c);
;

        .export         _cputc
	.export		_textcolor
        .import         _gotoxy, _gotox, _gotoy, pusha0
	.import		pushax
	.import		_screen
	.import		CURS_X, CURS_Y

        .include        "atari7800.inc"
        .include        "extzp.inc"

	.data
;-----------------------------------------------------------------------------
; Holder of the text colour offset
; 0 = red, 42 = green, 84 = white
;
txtcolor:
	.byte	0

	.code

;---------------------------------------------------------------------------
; 8x16 routine

umula0:
        ldy     #8                 ; Number of bits
	lda	#0
        lsr     ptr7800            ; Get first bit into carry
@L0:    bcc     @L1

        clc
        adc     ptrtmp
        tax
        lda     ptrtmp+1           ; hi byte of left op
        adc     ptr7800+1
        sta     ptr7800+1
        txa

@L1:    ror     ptr7800+1
        ror     a
        ror     ptr7800
        dey
        bne     @L0
        tax
        lda     ptr7800            ; Load the result
        rts

;-----------------------------------------------------------------------------
; Change the text colour
;
; Logical colour names are
; 0 = red
; 1 = green
; 2 = white
;
; The routine will also return the previous textcolor
;
        .proc   _textcolor

	beq	@L2
	sec
	sbc	#1
	beq	@L1
	lda	#84
	jmp	@L2
@L1:	lda	#42
@L2:	ldy	txtcolor
	sta	txtcolor	; Store new textcolor
	tya
	bne	@L3
	rts			; Old colour was 0
@L3:	sec
	sbc	#42
	bne	@L4
	lda	#1
	rts			; Old colour was 1
@L4:	lda #2
	rts			; Old colour was 2
        .endproc

;-----------------------------------------------------------------------------
; Put a character on screen
;
; The code will handle newlines that wrap to start of screen
;
        .proc   _cputc

	cmp     #$0A            ; LF
        bne     @L4
@L1:	lda	#0		; newline
	jsr	_gotox
        lda	CURS_Y
	cmp	#(screenrows-1)
        bne     @L2
	lda	#0
	beq	@L3
@L2:	clc
	adc	#1
@L3:	jmp	_gotoy

@L4:
	cmp	#$20		; ' '
	bne	@L5
	lda	#$00
	jmp	@L10
@L5:
	cmp	#$3F		; '?'
	bne	@L6
	lda	#$02
	jmp	@L9
@L6:
	cmp	#$7C		; '|'
	bne	@L7
	lda	#$06
	jmp	@L9
@L7:
	cmp	#$41		; >= 'A'
	bcc	@L8
	and	#$5F		; make upper case
	sec
	sbc	#($41 - 17)
	jmp	@L9
@L8:
	sec			; >= '*'
	sbc	#($2A - 1)
@L9:
	clc
	adc	txtcolor
@L10:
	asl
	pha

	lda	#0
	sta	ptr7800+1
	sta	ptrtmp+1
	lda	CURS_Y		; Find position on screen buffer
	sta	ptr7800
	lda	#charsperline
	sta	ptrtmp
	jsr	umula0
	clc
	adc	CURS_X
	bcc	@L11
	inx
@L11:	adc	#<(_screen)
	sta	ptr7800
	bcc	@L12
	inx
@L12:	clc
	txa
	adc	#>(_screen)
	sta	ptr7800+1

	pla			; Print character on screen
	ldy	#0
	sta	(ptr7800),y

        lda	CURS_X		; Increment cursor
	cmp	#(charsperline-1)
        beq	@L1
	clc
	adc	#1
	jmp	_gotox

        .endproc