; This is file VIDEO7.ASM
;
; Copyright (C) 1991 DJ Delorie, 24 Kirsten Ave, Rochester NH 03867-2954
;
; This file is distributed under the terms listed in the document
; "copying.dj", available from DJ Delorie at the address above.
; A copy of "copying.dj" should accompany this file; if not, a copy
; should be available from where this file was obtained.  This file
; may not be distributed without a verbatim copy of "copying.dj".
;
; This file is distributed WITHOUT ANY WARRANTY; without even the implied
; warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
;

cseg	segment	byte public 'code'
	assume	cs:cseg, ds:cseg, es:cseg, ss:nothing

	dw	offset init_routine
	dw	offset paging_routine
	dw	0	; set to 1 if separate read & write windows or
			; only 64K of video RAM (ie: no paging)

def_tw	dw	80	; filled in by go32 if GO32 env. var. is set
def_th	dw	25
def_gw	dw	640
def_gh	dw	480

;--------------------------------------------------------------------------
; Entry: AX=mode selection
;		0=80x25 text
;		1=default text
;		2=text CX cols by DX rows
;		3=biggest text
;		4=320x200 graphics
;		5=default graphics
;		6=graphics CX width by DX height
;		7=biggest non-interlaced graphics
;		8=biggest graphics
;
; NOTE: This runs in real mode, but don't mess with the segment registers.
;
; Exit:  CX=width (in pixels or characters)
;        DX=height

init_table	label	word
	dw	offset init_0
	dw	offset init_1
	dw	offset init_2
	dw	offset init_3
	dw	offset init_4
	dw	offset init_5
	dw	offset init_6
	dw	offset init_7
	dw	offset init_8

init_routine	proc	far
	cmp	ax,8
	jbe	valid_req
	ret
valid_req:
	shl	ax,1
	mov	bx,ax
	jmp	init_table[bx]

init_0: ; 80x25 text
	mov	ax,3
	int	10h
	mov	cx,80
	mov	dx,25
	ret

init_1: ; default text
	mov	cx,def_tw
	mov	dx,def_th
	jmp	init_2

init_2_table	label	word
	dw	01h, 40, 25
	dw	03h, 80, 25
init_2_tend	label	word

init_2: ; CX*DX text
	mov	si,offset init_2_table
init_2a:
	cmp	[si+2],cx
	jb	init_2b
	cmp	[si+4],dx
	jb	init_2b
	; got a big enough one!
	jmp	init_2c
init_2b:
	cmp	si,offset init_2_tend - 6
	je	init_2c
	add	si,6
	jmp	init_2a
init_2c:
	mov	ax,[si]
	push	si
	int	10h
	pop	si
	mov	cx,[si+2]
	mov	dx,[si+4]
	ret

init_3: ; biggest text
	mov	ax,[init_2_tend-6]
	int	10h
	mov	cx,[init_2_tend-4]
	mov	dx,[init_2_tend-2]
	ret

init_4: ; 320x200 graphics
	mov	ax,13h
	int	10h
	mov	cx,320
	mov	dx,200
	ret

init_5: ; default graphics - should be 640x480 if supported
	mov	cx,def_gw
	mov	dx,def_gh
	jmp	init_6

init_6_table	label	word
	dw	13h, 320, 200
	dw	66h, 640, 400
	dw	67h, 640, 480
	dw	68h, 720, 540
	dw	69h, 800, 600
init_6_tend	label	word

init_6: ; CX*DX graphics
	mov	si,offset init_6_table
init_6a:
	cmp	[si+2],cx
	jb	init_6b
	cmp	[si+4],dx
	jb	init_6b
	; got a big enough one!
	jmp	init_6c
init_6b:
	cmp	si,offset init_6_tend - 6
	je	init_6c
	add	si,6
	jmp	init_6a
init_6c:
	mov	ax,[si]
	push	si
	cmp	ax,13h
	je	usual_way
	mov	bx,ax
	mov	ax,6f05h
usual_way:
	int	10h
	pop	si
	mov	cx,[si+2]
	mov	dx,[si+4]
	ret

init_7: ; biggest non-interlaced graphics
	mov	ax,6f05h
	mov	bl,69h
	int	10h
	mov	cx,800
	mov	dx,600
	ret

init_8: ; biggest graphics
	mov	ax,6f05h
	mov	bl,69h
	int	10h
	mov	cx,800
	mov	dx,600
	ret

init_routine	endp

;--------------------------------------------------------------------------
; Entry: AH=read page
;        AL=write page
;
; NOTE: This runs in protected mode!  Don't mess with the segment registers!
; This code must be relocatable and may not reference any data!
;
; Exit: VGA configured.
;       AX,BX,CX,DX,SI,DI may be trashed
;
; Code derived from VGAKIT Version 3.4
;	Copyright 1988,89,90 John Bridges

	assume	ds:nothing, es:nothing

paging_routine	proc	far
	and	ax,15
	mov	ch,al
	mov	dx,3c4h
	mov	ax,0ea06h
	out	dx,ax
	mov	ah,ch
	and	ah,1
	mov	al,0f9h
	out	dx,ax
	mov	al,ch
	and	al,1100b
	mov	ah,al
	shr	ah,1
	shr	ah,1
	or	ah,al
	mov	al,0f6h
	out	dx,al
	inc	dx
	in	al,dx
	dec	dx
	and	al,not 1111b
	or	ah,al
	mov	al,0f6h
	out	dx,ax
	mov	ah,ch
	mov	cl,4
	shl	ah,cl
	and	ah,100000b
	mov	dl,0cch
	in	al,dx
	mov	dl,0c2h
	and	al,not 100000b
	or	al,ah
	out	dx,al

	ret
paging_routine	endp

;--------------------------------------------------------------------------

cseg	ends
	end