;
; Graphics driver for the 320x200x2 and 640x200x2 modes on GEOS 64/128
; 2010-08-17, Maciej 'YTM/Elysium' Witkowiak <ytm@elysium.pl>
; 2010-08-18, Greg King

	.include 	"zeropage.inc"

      	.include 	"tgi-kernel.inc"
        .include        "tgi-error.inc"

	.include	"const.inc"
	.include	"jumptab.inc"
	.include	"geossym.inc"
	.include	"geossym2.inc"

        .macpack        generic

; ------------------------------------------------------------------------
; Constants

VDC_ADDR_REG	  := $D600		  ; VDC address
VDC_DATA_REG	  := $D601		  ; VDC data

VDC_DSP_HI	  = 12			  ; registers used
VDC_DSP_LO	  = 13
VDC_DATA_HI	  = 18
VDC_DATA_LO	  = 19
VDC_VSCROLL	  = 24
VDC_HSCROLL	  = 25
VDC_COLORS	  = 26
VDC_CSET	  = 28
VDC_COUNT	  = 30
VDC_DATA	  = 31

; ------------------------------------------------------------------------
; Header. Includes jump table and constants.

.segment        "JUMPTABLE"

; First part of the header is a structure that has a magic signature,
; and defines the capabilities of the driver.

        .byte   $74, $67, $69           ; "tgi"
        .byte   TGI_API_VERSION         ; TGI API version number
xres:   .word   320                     ; X resolution
yres:   .word   200                     ; Y resolution
        .byte   2                       ; Number of drawing colors
pages:	.byte   1                       ; Number of screens available
        .byte   8                       ; System font X size
        .byte   8                       ; System font Y size
aspect: .word   $00D4                   ; Aspect ratio (based on 4/3 display)
        .byte   0                       ; TGI driver flags

; Next comes the jump table. With the exception of IRQ, all entries must be
; valid, and may point to an RTS for test versions (function not implemented).

	.addr	INSTALL
	.addr	UNINSTALL
	.addr	INIT
	.addr	DONE
	.addr	GETERROR
	.addr	CONTROL
	.addr	CLEAR
	.addr	SETVIEWPAGE
	.addr	SETDRAWPAGE
	.addr	SETCOLOR
	.addr	SETPALETTE
	.addr	GETPALETTE
	.addr	GETDEFPALETTE
	.addr	SETPIXEL
	.addr	GETPIXEL
	.addr	LINE
	.addr	BAR
	.addr	TEXTSTYLE
	.addr	OUTTEXT
	.addr	0			; IRQ entry is unused

; ------------------------------------------------------------------------
; Data.

; Variables mapped to the zero-page segment variables. Some of these are
; used for passing parameters to the driver.

X1              = ptr1
Y1              = ptr2
X2              = ptr3
Y2              = ptr4

; Absolute variables used in the code

.bss

SCRBASE:	.res	1	; High byte of screen base (64k VDC only)

ERROR:  	.res	1     	; Error code
PALETTE:        .res    2       ; The current palette

BITMASK:        .res    1       ; $00 = clear, $01 = set pixels

OLDCOLOR:	.res	1	; colors before entering gfx mode

; Text output stuff
TEXTMAGX:       .res    1
TEXTMAGY:       .res    1
TEXTDIR:        .res    1

; Constants and tables

.rodata

DEFPALETTE:     .byte   $00, $0f        ; White on black
PALETTESIZE     = * - DEFPALETTE

; color translation table (indexed by VIC color)
COLTRANS:	.byte $00, $0f, $08, $06, $0a, $04, $02, $0c
		.byte $0d, $0b, $09, $01, $0e, $05, $03, $07
		; colors BROWN and GRAY3 are wrong

.code

; ------------------------------------------------------------------------
; INSTALL routine. Is called after the driver is loaded into memory. May
; initialize anything that has to be done just once. Is probably empty
; most of the time.
;
; Must set an error code: NO
;

INSTALL:
	lda version		; if GEOS 1.0...
	and #$f0
	cmp #$10
	beq @L40
	lda c128Flag		; at least GEOS 2.0, but we're on C128?
	bpl @L40
        lda graphMode		; GEOS 2.0, C128, but is 80 column screen enabled?
        bmi @L80
@L40:	rts			; leave default values for 40 column screen

	; check for VDC version and update register $19 value

@L80:
	; double the x resolution and halve the aspect ratio

	asl	xres
	rol	xres+1

	lsr	aspect+1
	ror	aspect

	; update number of available screens

	ldx	#VDC_CSET	; determine size of RAM...
	jsr	VDCReadReg
	sta	tmp1
	ora	#%00010000
	jsr	VDCWriteReg	; turn on 64k

	jsr	settestadr1	; save original value of test byte
	jsr	VDCReadByte
	sta	tmp2

	lda	#$55		; write $55 here
	ldy	#ptr1
	jsr	test64k		; read it here and there
	lda	#$aa		; write $aa here
	ldy	#ptr2
	jsr	test64k		; read it here and there

	jsr	settestadr1
	lda	tmp2
	jsr	VDCWriteByte	; restore original value of test byte

	lda	ptr1		; do bytes match?
	cmp	ptr1+1
	bne	@have64k
	lda	ptr2
	cmp	ptr2+1
	bne	@have64k

	ldx	#VDC_CSET
	lda	tmp1
	jsr	VDCWriteReg	; restore 16/64k flag
	jmp	@endok		; and leave default values for 16k

@have64k:
	lda	#4
	sta	pages
@endok:
	lda     #0
	sta	SCRBASE		; draw page 0 as default
        rts

test64k:
	sta	tmp1
	sty	ptr3
	lda	#0
	sta	ptr3+1
	jsr	settestadr1
	lda	tmp1
	jsr	VDCWriteByte		; write $55
	jsr	settestadr1
	jsr	VDCReadByte		; read here
	pha
	jsr	settestadr2
	jsr	VDCReadByte		; and there
	ldy	#1
	sta	(ptr3),y
	pla
	dey
	sta	(ptr3),y
	rts

settestadr1:
	ldy	#$02			; test page 2 (here)
	.byte	$2c
settestadr2:
	ldy	#$42			; or page 64+2 (there)
	lda	#0
	jmp	VDCSetSourceAddr

; ------------------------------------------------------------------------
; UNINSTALL routine. Is called before the driver is removed from memory. May
; clean up anything done by INSTALL but is probably empty most of the time.
;
; Must set an error code: NO
;

UNINSTALL:
        rts


; ------------------------------------------------------------------------
; INIT: Changes an already installed device from text mode to graphics
; mode.
; Note that INIT/DONE may be called multiple times while the driver
; is loaded, while INSTALL is only called once, so any code that is needed
; to initializes variables and so on must go here. Setting palette and
; clearing the screen is not needed because this is called by the graphics
; kernel later.
; The graphics kernel will never call INIT when a graphics mode is already
; active, so there is no need to protect against that.
;
; Must set an error code: YES
;

INIT:
	ldx #$01
	stx BITMASK		; solid black as pattern
	lda #1
	jsr SetPattern
	lda #ST_WR_FORE		; write only on foreground
	sta dispBufferOn

        lda graphMode
        bmi @L80

; Remember current color value (40 columns)
	lda screencolors
	sta OLDCOLOR
	jmp @L99

; Remember current color value (80 columns)
@L80:	lda scr80colors
	sta OLDCOLOR
@L99:	lda #0
	jsr SETVIEWPAGE		; switch into viewpage 0

; Done, reset the error code

	lda     #TGI_ERR_OK
	sta     ERROR
        rts

; ------------------------------------------------------------------------
; DONE: Will be called to switch the graphics device back into text mode.
; The graphics kernel will never call DONE when no graphics mode is active,
; so there is no need to protect against that.
;
; Must set an error code: NO
;

DONE:
	lda #0
	jsr SETVIEWPAGE		; switch into viewpage 0

	lda graphMode
	bmi @L80

	lda OLDCOLOR
	sta screencolors	; restore color for 40 columns
	ldx #0
@L1:	sta COLOR_MATRIX,x
	sta COLOR_MATRIX+$0100,x
	sta COLOR_MATRIX+$0200,x
	sta COLOR_MATRIX+1000-256,x
	inx
	bne @L1
	rts

@L80:	lda OLDCOLOR		; restore color for 80 columns
	ldx #VDC_COLORS
	jmp VDCWriteReg

; ------------------------------------------------------------------------
; GETERROR: Return the error code in A and clear it.

GETERROR:
       	ldx	#TGI_ERR_OK
	lda	ERROR
	stx	ERROR
        rts

; ------------------------------------------------------------------------
; CONTROL: Platform/driver specific entry point.
;
; Must set an error code: YES
;

CONTROL:
	lda	#TGI_ERR_INV_FUNC
	sta	ERROR
        rts

; ------------------------------------------------------------------------
; CLEAR: Clears the screen.
;
; Must set an error code: NO
;

CLEAR:
	    lda curPattern
	    pha
	    lda #0
	    jsr SetPattern
	    ldx #0
	    stx r3L
	    stx r3H
	    stx r2L
	    lda #199
	    sta r2H
	    lda graphMode
	    bpl @L40
	    lda #>639			; 80 columns
	    ldx #<639
	    bne @L99
@L40:	    lda #>319			; 40 columns
	    ldx #<319
@L99:	    sta r4H
	    stx r4L
	    jsr Rectangle
	    pla
	    sta curPattern
	    rts

; ------------------------------------------------------------------------
; SETVIEWPAGE: Set the visible page. Called with the new page in A (0..n).
; The page number is already checked to be valid by the graphics kernel.
;
; Must set an error code: NO (will only be called if page ok)
;

SETVIEWPAGE:
	ldx graphMode
	bmi @L80
	rts
@L80:	clc
	ror
	ror
	ror
	ldx	#VDC_DSP_HI
	jmp	VDCWriteReg

; ------------------------------------------------------------------------
; SETDRAWPAGE: Set the drawable page. Called with the new page in A (0..n).
; The page number is already checked to be valid by the graphics kernel.
;
; Must set an error code: NO (will only be called if page ok)
;

SETDRAWPAGE:
	ldx graphMode
	bmi @L80
	rts
@L80:	clc
	ror
	ror
	ror
	sta	SCRBASE
	rts

; ------------------------------------------------------------------------
; SETCOLOR: Set the drawing color (in A). The new color is already checked
; to be in a valid range (0..maxcolor-1).
;
; Must set an error code: NO (will only be called if color ok)
;

SETCOLOR:
        tax
        beq     @L1
        lda	#1
@L1:    sta     BITMASK
	jmp	SetPattern	; need to have either 0 or 1

; ------------------------------------------------------------------------
; SETPALETTE: Set the palette (not available with all drivers/hardware).
; A pointer to the palette is passed in ptr1. Must set an error if palettes
; are not supported
;
; Must set an error code: YES
;

SETPALETTE:
	jsr	GETERROR	; clear error (if any)

        ldy     #PALETTESIZE - 1
@L1:    lda     (ptr1),y        ; Copy the palette
        and     #$0F            ; Make a valid color
        sta     PALETTE,y
        dey
        bpl     @L1

; Put colors from palette into screen

	lda	graphMode
	bmi	@L80

	lda	PALETTE+1	; foreground
	asl	a
	asl	a
	asl	a
	asl	a
	ora	PALETTE		; background
	ldx	#0
@L2:	sta	COLOR_MATRIX,x
	sta	COLOR_MATRIX+$0100,x
	sta	COLOR_MATRIX+$0200,x
	sta	COLOR_MATRIX+1000-256,x
	inx
	bne	@L2
	rts

@L80:   ldy     PALETTE+1       ; Foreground color
	lda	COLTRANS,y
        asl     a
        asl     a
        asl     a
        asl     a
        ldy     PALETTE         ; Background color
	ora	COLTRANS,y

	ldx	#VDC_COLORS
	jmp	VDCWriteReg

; ------------------------------------------------------------------------
; GETPALETTE: Return the current palette in A/X. Even drivers that cannot
; set the palette should return the default palette here, so there's no
; way for this function to fail.
;
; Must set an error code: NO
;

GETPALETTE:
        lda     #<PALETTE
        ldx     #>PALETTE
        rts

; ------------------------------------------------------------------------
; GETDEFPALETTE: Return the default palette for the driver in A/X. All
; drivers should return something reasonable here, even drivers that don't
; support palettes, otherwise the caller has no way to determine the colors
; of the (not changeable) palette.
;
; Must set an error code: NO (all drivers must have a default palette)
;

GETDEFPALETTE:
        lda     #<DEFPALETTE
        ldx     #>DEFPALETTE
        rts

; ------------------------------------------------------------------------
; SETPIXEL: Draw one pixel at X1/Y1 = ptr1/ptr2 with the current drawing
; color. The coordinates passed to this function are never outside the
; visible screen area, so there is no need for clipping inside this function.
;
; Must set an error code: NO
;

SETPIXEL:
	lda	X1
	ldx	X1+1
	ldy	Y1
	sta	r3L
	stx	r3H
	sty	r11L
	sec
	lda	BITMASK		; set or clear C flag
	bne	@L1
	clc
@L1:	lda	#0
	jmp	DrawPoint

; ------------------------------------------------------------------------
; GETPIXEL: Read the color value of a pixel and return it in A/X. The
; coordinates passed to this function are never outside the visible screen
; area, so there is no need for clipping inside this function.


GETPIXEL:
	lda	X1
	ldx	X1+1
	ldy	Y1
	sta	r3L
	stx	r3H
	sty	r11L
	jsr	TestPoint
	ldx	#0
	bcc	@L1
	inx
@L1:	txa
	ldx	#0
	rts

; ------------------------------------------------------------------------
; LINE: Draw a line from X1/Y1 to X2/Y2, where X1/Y1 = ptr1/ptr2 and
; X2/Y2 = ptr3/ptr4 using the current drawing color.
;
; Must set an error code: NO
;

LINE:
	lda	X1
	ldx	X1+1
	ldy	Y1
	sta	r3L
	stx	r3H
	sty	r11L
	lda	X2
	ldx	X2+1
	ldy	Y2
	sta	r4L
	stx	r4H
	sty	r11H
	sec
	lda	BITMASK		; set or clear C flag
	bne	@L1
	clc
@L1:	lda	#0
	jmp	DrawLine

; ------------------------------------------------------------------------
; BAR: Draw a filled rectangle with the corners X1/Y1, X2/Y2, where
; X1/Y1 = ptr1/ptr2 and X2/Y2 = ptr3/ptr4 using the current drawing color.
; Contrary to most other functions, the graphics kernel will sort and clip
; the coordinates before calling the driver, so on entry the following
; conditions are valid:
;       X1 <= X2
;       Y1 <= Y2
;       (X1 >= 0) && (X1 < XRES)
;       (X2 >= 0) && (X2 < XRES)
;       (Y1 >= 0) && (Y1 < YRES)
;       (Y2 >= 0) && (Y2 < YRES)
;
; Must set an error code: NO
;

BAR:
	lda	X1
	ldx	X1+1
	ldy	Y1
	sta	r3L
	stx	r3H
	sty	r2L
	lda	X2
	ldx	X2+1
	ldy	Y2
	sta	r4L
	stx	r4H
	sty	r2H
	jmp	Rectangle

; ------------------------------------------------------------------------
; TEXTSTYLE: Set the style used when calling OUTTEXT. Text scaling in X and Y
; direction is passend in X/Y, the text direction is passed in A.
;
; Must set an error code: NO
;

TEXTSTYLE:
        stx     TEXTMAGX
        sty     TEXTMAGY
        sta     TEXTDIR
        rts


; ------------------------------------------------------------------------
; OUTTEXT: Output text at X/Y = ptr1/ptr2 using the current color and the
; current text style. The text to output is given as a zero terminated
; string with address in ptr3.
;
; Must set an error code: NO
;

OUTTEXT:
	lda	TEXTDIR
;	cmp	#TGI_TEXT_HORIZONTAL	; this is equal 0
	bne	@vertical

	lda	X1		; horizontal text output
	ldx	X1+1
	ldy	Y1
	sta	r11L
	stx	r11H
	sty	r1H
	lda	ptr3
	ldx	ptr3+1
	sta	r0L
	stx	r0H
	jmp	PutString

@vertical:
	lda	X1		; vertical text output
	ldx	X1+1
	ldy	Y1
	sta 	r11L
	stx	r11H
	sty	r1H
	ldy	#0
	lda	(ptr3),y
	beq	@end
	jsr	PutChar
	inc	ptr3
	bne	@L1
	inc	ptr3+1
@L1:	lda	Y1
	clc
	adc	#8
	sta	Y1
	bne	@vertical
@end:	rts

;-------------
; VDC helpers

VDCSetSourceAddr:
	pha
	tya
	ldx	#VDC_DATA_HI
	jsr	VDCWriteReg
	pla
	ldx	#VDC_DATA_LO
	bne	VDCWriteReg

VDCReadByte:
	ldx	#VDC_DATA
VDCReadReg:
	stx	VDC_ADDR_REG
@L0:	bit	VDC_ADDR_REG
	bpl	@L0
	lda	VDC_DATA_REG
	rts

VDCWriteByte:
	ldx	#VDC_DATA
VDCWriteReg:
	stx	VDC_ADDR_REG
@L0:	bit	VDC_ADDR_REG
	bpl	@L0
	sta	VDC_DATA_REG
	rts