;ACME 0.94
;!sl "ddrv.l"
; Name		DuoDriver
; Purpose	Input driver for mouse and joystick
; Author	(c) Marco Baye, 1999
; Licence	Free software
; Changes:
; 23 Apr 1999	Release 2.20. Internal info:
;		DuoDriver v2.20 by Mac Bacon 23 Apr 1999. Freeware!
; Somewhen	Added self-calibration, forming release 3.00. Internal info:
;		Mac Bacon:DuoDrv3,PD
; 21 Jul 1999	Used reverse subtraction, forming release 3.01. Internal info:
;		Mac Bacon:DuoDrv3,PD
;  1 Aug 1999	Release 4.00.
;		Both 128 and 64 versions
;		Now supports overlay-sprite mouse pointer
;		Binary includes sprites
;		Released in GO64 8/1999 (without release number).
;  3 Aug 1999	Same source file for both 128 and 64 versions. Release 4.01.
;		Apart from that, virtually identical to release 4.00.
; 04 Feb 2003	Beautified
; 05 Feb 2003	Added "SpriteLine" macro and made sprites inline
; 26 May 2005	Release 4.02. All changes since release 4.00 are source-only!
;		The resulting binaries are identical to those of release 4.00
;		(which were included in GO64 magazine 8/1999)
; 26 Mar 2006	Release 4.03. Adjusted source to ACME 0.91 capabilities.
; 25 Nov 2007	Release 4.04. Adjusted source to ACME 0.94 capabilities.

; This source code file uses conditional assembly
; to decide which version to produce (C64 or C128).

; Select type of binary to assemble (64 => c64, anything else => c128)
!ifndef SYSTEM {
	!warn "Label SYSTEM not defined. Use -DSYSTEM=64 to build C64 version, -DSYSTEM=128 to build C128 version. Will now default to C64 version."
	SYSTEM = 64
}
!if SYSTEM != 64 & SYSTEM != 128 {
	!serious "Please use either -DSYSTEM=64 or -DSYSTEM=128 when assembling this project."
}


; --- Configurable values

; Start address, output file name and VIC location

!if SYSTEM = 64 {
	*=$c000
	!to "ddrv64.prg", cbm
	VIC_Base	= $d000
}
!if SYSTEM = 128 {
	*=$0c00
	!to "ddrv128.prg", cbm
	VIC_Base	= $11d6;	Location of mirror registers
}

; Pointer's maximum coordinates
	MaximumCoordinateX	= 319;	VIC value
;	MaximumCoordinateX	= 639;	VDC value
	MaximumCoordinateY	= 199

; Maximum pixel step size ("speed") for joystick acceleration routine.
	MaxStep	= $10;	(max. $7f)

; Distance before acceleration starts, in pixels.
	MaxTime	= $04;	(max. $7f)

; Sprites to use for overlay pointer
	Sprite_A	= 0
	Sprite_B	= 1

; Coordinates of "pointer pixel" within pointer sprites; adjust these
; if you use different sprites. (0,0) is sprite's upper left pixel.
	Sprite_HotspotX	= 1
	Sprite_HotspotY	= 1

; Locations to store button states, $ff = pressed, $00 = not pressed.
; Mouse uses both buttons, joystick only uses "LeftButton".
; Location to store pointer's current character coordinates.
!if SYSTEM = 64 {
	LeftButton	= $a4
	RightButton	= $a5
	CharX		= $b3
	CharY		= $b4
}
!if SYSTEM = 128 {
	LeftButton	= $fa
	RightButton	= $ff
	CharX		= $9b
	CharY		= $9c
}

; Location to store pointer's current pixel coordinates. The driver
; code relies on having *four consecutive* bytes:
; x low, x high, y low, y high
	Coordinates	= $fb;	$fb-$fe


; --- System constants

; Interrupt vector
	sys_iirq	= $0314

; I/O registers
	sid_pot		= $d419
	cia1_pra	= $dc00
	cia1_prb	= $dc01
	cia1_ddrb	= $dc03
	mmu_cr		= $ff00;	c128 only


; --- Label definitions

; New names for some precalculated values, only to improve
; readability. Don't change these.
	PointerXnow	= Coordinates
	PointerYnow	= Coordinates + 2
	SpriteA_X	= VIC_Base + 2*Sprite_A
	SpriteA_Y	= VIC_Base + 2*Sprite_A + 1
	SpriteB_X	= VIC_Base + 2*Sprite_B
	SpriteB_Y	= VIC_Base + 2*Sprite_B + 1
	Sprites_OF	= VIC_Base + 16;	X Overflow
; The character "^" in the following calculation means "to the power
; of". It is ACME syntax - if your assembler cannot do this, you may
; want to use hardcoded values here instead of calculations.
	Sprites_Bitmask	= 2^Sprite_A + 2^Sprite_B
;alternative:
;	Sprites_Bitmask	= 1<<Sprite_A | 1<<Sprite_B
	SpriteOffset_X	= $18 - Sprite_HotspotX
	SpriteOffset_Y	= $32 - Sprite_HotspotY
; In the sprite coordinate system, the graphics pixel (0,0) has the
; coordinates ($18,$32), so these are needed for converting. Blame the
; VIC.


; --- Entry point

; Because this routine is the first, the file can be BOOTed on a c128.
; Initialisation code, installs driver on IRQ vector.
; Fetch IRQ vector and write to end
Init		lda sys_iirq
		ldx sys_iirq+1
		sta mod16
		stx mod16+1
; Let IRQ vector point to driver code
		lda #<Entry
		ldx #>Entry
		php
		sei
		sta sys_iirq
		stx sys_iirq+1
		plp
!if SYSTEM=128 {
		lda mmu_cr
		tay
		and #$fe;	activate I/O chips
		sta mmu_cr
}

; Init mouse buttons
		lda #$11
		sta cia1_prb
!if SYSTEM=128 {sty mmu_cr	}

!if SYSTEM = 64 {
; Copy sprites to tape buffer
		ldx #127
-			lda Sprites,x
			sta $0340,x
			dex
			bpl -
		lda #Sprites_Bitmask
; Set sprite block pointers
		ldx #$0d
		stx 2040+Sprite_A
		inx
		stx 2040+Sprite_B
; Activate pointer sprites
		ora VIC_Base+21
		sta VIC_Base+21
}
		rts


; --- Variables

; Pixel counter before accelerating
JoyWaittime	!byte 0


; --- Main code

Entry
; The driver consists of several distinct parts. To minimise
; performance wastage, you should remove all parts you don't need for
; the specific application.


; --- Part 0, initialisations

; Make sure decimal mode is off
		cld
; Set button states to "not pressed", so the other parts only have to
; deal with setting them to "pressed".
		lda #$00
		sta LeftButton
		sta RightButton


; --- Part 1, handling mouse movements

; mouse x
		ldx #$00; 0 means "x stuff"
		jsr PotDelta
; Now signed x movement is in A/Y. Add to current x value.
		clc
		adc PointerXnow
		sta PointerXnow
		tya
		adc PointerXnow+1
		sta PointerXnow+1
; mouse y
		ldx #$01; 1 means "y stuff"
		jsr PotDelta
; Now signed y movement is in A/Y. Mouse and computer use different y
; directions, so don't add to, but subtract from current y value.
; This is a reverse subtraction - it might be harder to understand,
; but it is both faster and smaller than the usual way.
		clc
		sbc PointerYnow
		eor #$ff
		sta PointerYnow
		tya
		sbc PointerYnow+1
		eor #$ff
		sta PointerYnow+1


; --- Part 2, handling mouse buttons

; Prepare CIA by setting bits to input
		ldy #$11
		sty cia1_ddrb
		ldx #$ff; $ff means "pressed"
		lda #$10; check left button
		bit cia1_prb
		bne +
			stx LeftButton; store state
+		lda #$01; check right button
		bit cia1_prb
		bne +
			stx RightButton; store state
; Reset CIA to normal state
+		ldy #$00
		sty cia1_ddrb


; --- Part 3, handling the joystick

; Fetch byte holding direction flags
		lda cia1_pra
		tax; ...and remember it
		; Check 'up' direction
		ror
		bcs ++
		; Subtract current step size from y value if needed.
		tay
		sec
		lda PointerYnow
		sbc JoyStepsize
		sta PointerYnow
		bcs +
		dec PointerYnow+1
+		tya
		; Check 'down' direction
++		ror
		bcs ++
		; Add current step size to y value if needed.
		tay
		;clc;	C is always clear here
		lda PointerYnow
		adc JoyStepsize
		sta PointerYnow
		bcc +
		inc PointerYnow+1
+		tya
		; Check 'left' direction
++		ror
		bcs ++
		; Subtract current step size from x value if needed.
		tay
		sec
		lda PointerXnow
		sbc JoyStepsize
		sta PointerXnow
		bcs +
		dec PointerXnow+1
+		tya
		; Check 'right' direction
++		ror
		bcs ++
		; Add current step size to x value if needed.
		tay
		;clc;	C is always clear here
		lda PointerXnow
		adc JoyStepsize
		sta PointerXnow
		bcc +
			inc PointerXnow+1
+		tya
++

; --- Part 4, handling joystick button

		ror
		bcs +
		lda #$ff;	$ff means "pressed"
		sta LeftButton
+

; --- Part 5, joystick acceleration

; Restore joystick direction bits and check whether to set speed to
; zero.
		txa
		and #$0f;	Clear unneeded bits
		cmp #$0f;	Any direction bit ?
		bne +
; No direction was used, so reset speed and wait counter to normal.
		lda #$01
		sta JoyStepsize
		lda #MaxTime
		sta JoyWaittime
		jmp Part5End
+
; A direction bit was used, so check whether to accelerate: If speed
; is already maximum speed, don't accelerate.
JoyStepsize=*+1
		lda #$00;	(self-modifying)
; If the variable "JoyStepsize" would have been defined as a separate
; location (using "!byte"), it would have taken a byte of memory. By
; storing the value inside an LDA command's argument, we save that one
; byte. It might make a difference. :)
		cmp #MaxStep;	If speed is max.,
		bcs Part5End;	don't accelerate.
		; Speed isn't maximum yet. Check whether
		; we have to wait before accelerating.
		dec JoyWaittime
		bpl Part5End
		; Counter has underrun, so accelerate.
		inc JoyWaittime; reset counter
		inc JoyStepsize; increase speed
Part5End

; --- Part 6, restrict coordinate range

; restrict x value
		ldx #$00;	0 means "x stuff"
		jsr Restrict
; restrict y value
		ldx #$02;	2 means "y stuff"
		jsr Restrict

; --- Part 7, positioning sprites

; Set sprites' x positions
		lda PointerXnow
		clc
		adc #SpriteOffset_X
		sta SpriteA_X;	set both sprites
		sta SpriteB_X
		lda Sprites_OF;	get x overflow
		bcs SetOF
		ldx PointerXnow+1
		bne SetOF
		and #Sprites_Bitmask XOR $ff
		bcc StoreOF;	C is clear here
SetOF		ora #Sprites_Bitmask
StoreOF		sta Sprites_OF;	set x overflow

; Set sprites' y positions
		lda PointerYnow
		clc
		adc #SpriteOffset_Y
		sta SpriteA_Y
		sta SpriteB_Y
; The y value's high byte is useless in this case.

; --- Part 8, making char coordinates

; Convert x coordinate. There are different "best" routines for
; different resolutions, so I've given the VIC and VDC routines.
		lda PointerXnow
		lsr
		lsr
		lsr
		ldx PointerXnow+1
		;ora OrTable,x;	VDC only (see below for data table)
		beq +;	VIC only
		ora #$20;	VIC only
+		sta CharX

; Convert y coordinate.
		lda PointerYnow
		lsr
		lsr
		lsr
		sta CharY

; --- Add further parts here

; Here you can add further routines, for example to use the button
; states to fake keypresses etc.

; --- The end

; The initialisation routine sets the argument to the address of the
; previous IRQ routine.
mod16=*+1:	jmp $ffff;	(self-modifying)

; This table is for part 8.
;OrTable	!byte 0,32,64;	VDC only

; --- "Restrict" subroutine

PointerXmax	!word MaximumCoordinateX
PointerYmax	!word MaximumCoordinateY
; "y" word must follow directly after "x" word in memory.

Restrict
; Restrict internal coordinates to configured range. Entry conditions:
; X is direction handle (0 = x, 2 = y)
		lda PointerXnow+1,x
		bmi SetTo0
		cmp PointerXmax+1,x
		bcc Eosr
		bne +
		lda PointerXmax,x
		cmp PointerXnow,x
		bcs Eosr
+		lda PointerXmax,x
		ldy PointerXmax+1,x
		jmp DefCo
SetTo0		lda #0
		tay
DefCo		sta PointerXnow,x
		sty PointerXnow+1,x
Eosr		rts

; --- "Pot" subroutine

; This routine computes the mouse movements and therefore contains the
; self-calibration stuff and the other improvements over the standard
; 1351 driver.
PotMax		!word 0;	max. POTs yet plus 1 !
PotMin		!word $ffff;	lowest POTs yet
PotOld		!word 0;	old values
PotWidth	!word 0;	interval width
HalfPotWidth	!word 0;	half width
; (buffered for speed increase)
; The above variables are not really words: The first byte is the x
; value, the second byte is the y value respectively.


; Compute the signed distance of mouse movement.
; Entry conditions: X is direction handle (0 = x, 1 = y)
; Exit conditions: A/Y are signed distance (low/high)

; First, get new value and clear "recalculate signal width" flag.
PotDelta	lda sid_pot,x
		ldy #$00
		; Check whether new value is lower than lowest known.
		cmp PotMin,x
		bcs +
		; Store new "lowest" und set "recalculate signal width" flag.
		sta PotMin,x
		ldy #$ff
+		; Check whether new value is higher than highest known.
		cmp PotMax,x
		bcc +
; Set "recalculate signal width" flag and store new "highest".
		ldy #$ff
		pha;	Remember current value
		adc #$00;	Add one (C is set)
		sta PotMax,x
; Value $ff (0 after adding) means that there is no mouse connected,
; so reset min/max in that case.
		beq ResetMM;	Stack is untidy...
		pla;	Restore current value
+		; If flag is set, recalculate signal width.
		iny;	Check flag
		bne ++
		tay;	Buffer current value.
		lda PotMax,x;	Get highest+1
		sec;	Subtract lowest
		sbc PotMin,x
		bcc +
		sta PotWidth,x;	Store signal
		lsr;	width and half signal
		sta HalfPotWidth,x;	width
+		tya;	Restore current value.
++		; Calculate distance
		tay;	Buffer current value.
		sec
		sbc PotOld,x
		pha
		tya
		sta PotOld,x
		pla
		beq zero;	If not moved, exit.
		bcc minus;	Negative difference

; Positive difference:
; Check whether movement caused a value wrap-around.
		cmp HalfPotWidth,x
		bcc Decrease
		beq Decrease
; It did, so calculate "real" distance and jump to exit
		;sec;	C is always set here
		sbc PotWidth,x;	Fix distance

; We now know that the (fixed) distance is really negative, so we
; finally wipe out that annoying bit 0 noise by incrementing the
; value.
Increase	;clc;	C is always clear here
		adc #$01
		beq zero;	If increasing gives zero, jump to zero handler.
		ldy #$ff;	Set up high byte for negative values.
		rts

; Negative difference:
; Check whether movement caused a value wrap-around.
minus		eor #$ff;	Complement
; If we would do a real negation (by adding "1"), then we would need
; to branch using BCC *and* BEQ. So the above way might be harder to
; understand, but it is both shorter *and* faster - which I like. :)
		cmp HalfPotWidth,x
		eor #$ff;	Restore value
		bcc Increase
; Movement caused a value wrap-around, so calculate "real" distance and exit.
		clc
		adc PotWidth,x;	Fix distance

; We now know that the (fixed) distance is really positive, so we
; finally wipe out that annoying bit 0 noise by decrementing the value.
Decrease	sec
		sbc #$01

; No difference or positive difference; both need zero as the high byte.
zero		ldy #0
		rts

; If there is no mouse, reset "lowest" ("highest" will have been reset
; already) and return zero.
ResetMM		tay;	Set Y to zero.
		pla;	Tidy stack
		lda #$ff;	Reset "lowest"
		sta PotMin,x
		tya;	Return with A/Y = 0
		rts

; --- Include sprites

; Because the c64 version copies the sprite data into the tape buffer
; on initialisation, the data is included right here.
; In the c128 version, we skip memory until we reach $0e00 - this is
; where the sprites are stored by default.

!if SYSTEM = 128 {
	!align $ffff, $e00, $0
}

!macro SpriteLine .v {
	!by .v>>16, (.v>>8)&255, .v&255
}

Sprites		;	     765432107654321076543210
		+SpriteLine %........................
		+SpriteLine %.#......................
		+SpriteLine %.##.....................
		+SpriteLine %.###....................
		+SpriteLine %.####...................
		+SpriteLine %.#####..................
		+SpriteLine %.######.................
		+SpriteLine %.#######................
		+SpriteLine %.########...............
		+SpriteLine %.#########..............
		+SpriteLine %.########...............
		+SpriteLine %.######.................
		+SpriteLine %.######.................
		+SpriteLine %.##..##.................
		+SpriteLine %.#....##................
		+SpriteLine %......##................
		+SpriteLine %.......##...............
		+SpriteLine %.......##...............
		+SpriteLine %........##..............
		+SpriteLine %........##..............
		+SpriteLine %........................
		!byte 0;	pad to 64-byte block
		;	     765432107654321076543210
		+SpriteLine %##......................
		+SpriteLine %###.....................
		+SpriteLine %####....................
		+SpriteLine %#####...................
		+SpriteLine %######..................
		+SpriteLine %#######.................
		+SpriteLine %########................
		+SpriteLine %#########...............
		+SpriteLine %##########..............
		+SpriteLine %###########.............
		+SpriteLine %###########.............
		+SpriteLine %#########...............
		+SpriteLine %########................
		+SpriteLine %########................
		+SpriteLine %###..####...............
		+SpriteLine %##...####...............
		+SpriteLine %......####..............
		+SpriteLine %......####..............
		+SpriteLine %.......####.............
		+SpriteLine %.......####.............
		+SpriteLine %........###.............