; color.as - change screen colors from MSX-DOS(2)
; Copyright (C) 2001 ag0ny@ag0ny.com

BDOS		equ	00005h
DEFDTA		equ	00080h

_STROUT		equ	009h

LF		equ	00ah		; Line feed
CR		equ	00dh		; Carriage return

; RAM copy of VDP registers
; vdpregs0 -> R#0..R#7
; vdpregs1 -> R#8..R#23
;
vdpregs0	equ	0f3dfh
vdpregs1	equ	0ffe7h-8

; VDP ports
;
vdpport0	equ	098h		; VRAM read/write
vdpport1	equ	099h		; VDP registers read/write
vdpport2	equ	09ah		; Palette registers write
vdpport3	equ	09bh		; Indirect register write

; vdp - send value in A to VDP register
; syntax:	vdp	reg#
; modifies:	A
; note:		**** INTERRUPTS MUST BE DISABLED ****
;
vdp		macro	reg
		out	(vdpport1),a
		ld	a,reg or 080h
		out	(vdpport1),a
		endm

; system - execute MSX-DOS(2) function
;
system		macro	function
		ld	c,function
		call	BDOS
		endm

; ******************
; ** Main program **
; ******************

main:		ld	(STACK),sp

		; print intro message
		ld	de,MSG.INTRO
		system	_STROUT

		call	getopts

		ld	a,(COLOR.FG)
		rlca
		rlca
		rlca
		rlca
		ld	e,a
		ld	a,(COLOR.BG)
		or	e
		ld	(vdpregs0+7),a
		vdp	7

		ret

error:		system	_STROUT
		ld	sp,(STACK)
		ret

getopts:	ld	hl,DEFDTA

		ld	a,(hl)
		or	a
		ret	z		; default color change if no params

		inc	hl
		ld	a,(hl)		; because first character is the
					; length of the commandline pointer

go.1:		cp	' '
		jr	nz,go.2
		inc	hl		; skip spaces at the beginning
		ld	a,(hl)
		jr	go.1

go.2:		; get first parameter

		or	a
		ret	z

		and	000001111b
		ld	(COLOR.FG),a

		inc	hl
		ld	a,(hl)

		or	a
		ret	z
		cp	' '
		jr	z,go.3

		and	000001111b
		ld	e,a
		ld	a,(COLOR.FG)
		ld	d,a
		rlca			; x2
		rlca			; x2
		add	a,d		; x5
		rlca			; x10

		add	a,e
		ld	(COLOR.FG),a

go.3:		inc	hl
		ld	a,(hl)

		cp	' '
		jr	nz,go.4
		jr	go.3

go.4:		; get second parameter

		and	000001111b
		ld	(COLOR.BG),a

		inc	hl
		ld	a,(hl)
		or	a
		ret	z
		cp	' '
		ret	z		; more parameters ignored

		and	000001111b
		ld	e,a
		ld	a,(COLOR.BG)
		ld	d,a
		rlca			; x2
		rlca			; x2
		add	a,d		; x5
		rlca			; x10

		add	a,e
		ld	(COLOR.BG),a

		ret

; **********
; ** Data **
; **********

STACK:		defs	2
COLOR.FG:	defb	15
COLOR.BG:	defb	4

MSG.INTRO:	defb	'color.as - change screen colors from MSX-DOS(2)',CR,LF
		defb	'Copyright (C) 2001 ag0ny@ag0ny.com$'
1 ag0ny@ag0ny.com',CR,LF
		defb	CR,LF,'$'
MSG.USAGE:	defb	'Usage:    color <foreground> <background>',CR,LF
		defb	CR,LF
		defb	'          Both <foreground> and <background> must be'
		defb	' a decimal',CR,LF
		defb	'          number in the range 0..15',CR,LF,'$'