mist: improved IIgs support

thanks to 4am, this turns black backgrounds on and enables the
PAGE2 workaround

mist/hardware.inc

@@ -8,7 +8,10 @@ CLR80COL	=	$C000	; PAGE0/PAGE1 normal
 SET80COL	=	$C001	; PAGE0/PAGE1 switches PAGE0 in Aux instead
 EIGHTYCOLOFF	=	$C00C
 EIGHTYCOLON	=	$C00D
+TBCOLOR		=	$C022	; IIgs text foreground / background colors
+NEWVIDEO	=	$C029	; IIgs graphics modes
 SPEAKER		=	$C030
+CLOCKCTL	=	$C034	; bits 0-3 are IIgs border color
 SET_GR		=	$C050
 SET_TEXT	=	$C051
 FULLGR		=	$C052
@@ -19,6 +22,12 @@ LORES		=	$C056	; Enable LORES graphics
 HIRES		=	$C057	; Enable HIRES graphics
 AN3		=	$C05E	; Annunciator 3
 
+
+
+
+
+
+
 PADDLE_BUTTON0	=	$C061
 PADDL0		=	$C064
 PTRIG		=	$C070
@@ -34,8 +43,10 @@ VLINE	= $F828			;; VLINE A,$2D at Y
 CLRSCR	= $F832			;; Clear low-res screen
 CLRTOP	= $F836			;; clear only top of low-res screen
 SETCOL	= $F864			;; COLOR=A
+ROM_TEXT2COPY = $F962		;; iigs
 TEXT	= $FB36
 TABV	= $FB5B			;; VTAB to A
+ROM_MACHINEID = $FBB3		;; iigs
 BELL	= $FBDD			;; ring the bell
 BASCALC	= $FBC1			;;
 VTAB	= $FC22			;; VTAB to CV
@@ -52,6 +63,7 @@ COUT1	= $FDF0			;; output A to screen
 
 
 
+
 COLOR_BLACK		=	0
 COLOR_RED		=	1
 COLOR_DARKBLUE		=	2

mist/mist_title.s

@@ -25,6 +25,41 @@ mist_start:
 	bit	HIRES
 	bit	FULLGR
 
+	;===================
+	; machine workarounds
+	;===================
+	; mostly IIgs
+	;===================
+	; thanks to 4am who provided this code from Total Replay
+
+	lda	ROM_MACHINEID
+	cmp	#$06
+	bne	not_a_iigs
+	sec
+	jsr	$FE1F			; check for IIgs
+	bcs	not_a_iigs
+
+	; gr/text page2 handling broken on early IIgs models
+	; this enables the workaround
+
+	jsr	ROM_TEXT2COPY		; set alternate display mode on IIgs
+	cli				; enable VBL interrupts
+
+	; also set background color to black instead of blue
+	lda	NEWVIDEO
+	and	#%00011111	; bit 7 = 0 -> IIgs Apple II-compat video modes
+				; bit 6 = 0 -> IIgs 128K memory map same as IIe
+				; bit 5 = 0 -> IIgs DHGR is color, not mono
+				; bits 0-4 unchanged
+	sta   NEWVIDEO
+	lda   #$F0
+	sta   TBCOLOR			; white text on black background
+	lda   #$00
+	sta   CLOCKCTL			; black border
+	sta   CLOCKCTL			; set twice for VidHD
+
+not_a_iigs:
+
 	;===================
 	; setup location
 	;===================