gameboy-putln.asm

gameboy-putln.asm

strlen:
  	;; string address is in hl, output is in bc
		ld bc, 0
.loop:
		ld a, (hli)
		cp 0
		ret z
		inc bc
		jr .loop

putln:
		;; string address is in hl, y coordinate is in a
		push hl
		push af
		call strlen
		;; string length is now in bc
		ld hl, SCRN0 				; hl will store our destination, for now
		;; center the string (on X)
		ld a, 21
		sub c
		srl a
		add a, l
		ld l, a
		pop af					; we need the y coordinate now
.multloop:
		cp 0
		jr z, .multexit
		dec a
		ld de, SCRN_VY_B
		add hl, de
		jr .multloop
.multexit:
		;; move hl into de, our final dest storage
		ld d, h
		ld e, l
		pop hl
		;; string address is in hl, destination is in de, length is in bc
		;; we're set (tail-call!)
		jp mem_CopyVRAM