programs/sub-suite/print_char.s


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print_char:
;	sta a		; Save the typed character for now.
	pha		; Preserve the character.
;	ldb #2		; Make sure that set_ptr sets the third pointer.
	lda.d #buffer	; Set the third pointer to the start of the screen buffer.
	pha.q		; Push the pointer onto the stack.
	lda sp+9	; Get the character back.
;	jsr set_ptr	;
;	ldb #0		; Set B to zero.
;	tba		; Set the Accumulator to zero.
;	lda a		; Get back the character.
	cmp #$1B	; Did the user type an escape character?
	beq esc		; Yes, so go check the escape code.
	cmp #'\n'	; No, but did the user type a newline?
	beq nl		; Yes, so handle the newline.
	cmp #$C		; No, but did the user type Ctrl+L?
	beq clr_scr	; Yes, so clear the screen.
	cmp #19		; No, but did the user type Ctrl+S?
	beq en_step	; Yes, so enable clock/instruction stepping.
	cmp #18		; No, but did the user type Ctrl+R?
	beq dis_step	; Yes, so disable clock/instruction stepping.
	cmp #'\b'	; No, but did the user type a backspace?
	beq bs		; Yes, so handle the backspace.
	cmp #$7F	; No, but did they type Delete?
	beq bs		; Yes, so treat it as a backspace.
printc:
	lda #0		; No, so start trying to print a character.
	sta d		;
	lda (sp+1), y	; Are we at the end of the string?
	beq @save	; Yes, so just print the character.
	lda b		; No, but was the flag set?
	bne @save	; Yes, so don't shift the line.
	sty.w scr_ptr	; No, so save the cursor index for later.
	jsr fndend	; Find the end of the line.
	bra @shift	; Start shifting the line right.
@update:
	lda scr_col	; Save the current column position for later.
	sta scr_tcol	;
@update1:
	jsr findend	; Find the end of the line.
	sta e		; Use it for redrawing the line.
	sta scr_row	; Set the row position to to the end of the line.
	jsr findst	; Find the start of the line.
	lda scr_row	; Get the start of the line.
@update2:
	sta f		; Set the starting line, to the start of the line.
	jsr rdrw_ln	; Redraw the line.
	lda scr_trow	; Get the real row position back.
	sta scr_row	;
	lda scr_tcol	; Get the real column position back.
	sta scr_col	;
	jsr update_pos	; Update the cursor's position.
	dec d		;
	bra @save1	;
@shift:
	ldy.w scr_ptr3	;
	inc scr_ptr3	;
	tyx		;
	dey		;
	ldb #1		;
	stb d		;
	jsr shftln	;
	ldb #1		;
	stb d		;
;	lda a		;
	lda sp+9	;
	sta (sp+1), y	; store typed character into the input buffer.
	lda scr_row	;
	sta scr_trow	;
	bra @update	;
@save:
	ldb d		;
	bne @update	;
@save1:
;	lda a		;
	lda sp+9	;
	sta (sp+1), y	; store typed character into the input buffer.
@incr:
	inc scr_col	; Increment the cursor's x coordinate.
	iny		;
@wrapped:
	ldb #1		;
	stb f		;
	ldb scr_col	;
	cpb #maxcol+1	;
	bcs @scrolled	;
@print:
	sta scr		; Echo typed character.
	ldb f		;
	beq @wrap	;
	bra printc_end	;
@scrolled:
	ldb scr_row	;
	cpb #maxrow	;
	bcs @scroll	;
@wrapped2:
	ldb #0		;
	stb f		;
	bra @print	;
@scroll:
	sta scr		; Echo typed character.
	clc		;
	lda #1		;
	sta wrapped	;
	jsr scrl_down	;
@wrap:
	ldb #0
	stb scr_col	;
	ldb scr_row	;
	cpb #maxrow	;
	bcs @wrap2	;
@wrap1:
	inc scr_row	;
@wrap2:
	phx.w		;
	clc		;
	lda scr_row	;
	adc scr_str	;
	tax		;
	jsr setbit	;
	plx.w		;
	jsr update_pos	;
printc_end:
	pla.q		; Pull the pointer off the stack.
	pla		; Pull the character off the stack.
	and #0		; Reset A.
	rts		;

nl:
	lda #0		; Reset A.
	ldb (sp+1), y	; Is this character not a null terminator?
	bne @scroll	; Yes, so don't overwrite it.
	sta (sp+1), y	; No, so overwrite it.
@scroll:
	sta scr_col	; Move the cursor to the start of the next line.
	lda scr_row	; Get the row position.
	cmp #maxrow	; Are we at the bottom of the screen?
	bcc @incr	; No, so move down one line.
	jsr scrl_down	; Yes, so scroll down one line.
	bra @end	; We are done.
@incr:
	inc scr_row	; Move the cursor down by one line.
	jsr update_pos	; Update the cursor's position.
@end:
	lda #'\n'	; Print the newline.
	sta a		;
	rts		;