From 9be057762227abc353f0047fdc22f532ed6cf806 Mon Sep 17 00:00:00 2001
From: Vince Weaver <vincent.weaver@maine.edu>
Date: Mon, 3 May 2021 16:48:21 -0400
Subject: [PATCH] Update xdraw

---
 graphics/hgr/xdraw/NOTES        |  15 ++++
 graphics/hgr/xdraw/xdraw_test.s | 131 ++++++++++++++++++++++++++++++++
 2 files changed, 146 insertions(+)
 create mode 100644 graphics/hgr/xdraw/NOTES
 create mode 100644 graphics/hgr/xdraw/xdraw_test.s

diff --git a/graphics/hgr/xdraw/NOTES b/graphics/hgr/xdraw/NOTES
new file mode 100644
index 00000000..d784f17c
--- /dev/null
+++ b/graphics/hgr/xdraw/NOTES
@@ -0,0 +1,15 @@
+Xdraw testing:
+
+	Size $20
+		D02A
+		D07D-D083 interesting
+		D23C
+		D251-D25D (D256 highlight)
+
+
+
+To try:
+	Cycle colors (clear background, offset X by 1)
+	Ring around dSr logo
+	"Xdraw Xtravaganza"
+	
diff --git a/graphics/hgr/xdraw/xdraw_test.s b/graphics/hgr/xdraw/xdraw_test.s
new file mode 100644
index 00000000..6a019660
--- /dev/null
+++ b/graphics/hgr/xdraw/xdraw_test.s
@@ -0,0 +1,131 @@
+; Tiny Xdraw
+
+; repeatedly draws an image from an Apple II shape table
+
+; can arbitrarily point to any memory location as a source of these
+;	some look amazing but depend on random machine state
+;	to be deterministic you should probably stick to
+;		$E7-$F0 (the program itself)
+;		$D000-$FFFF (the ROMs)
+;	shapetables are a bit complicated to explain here, but they are a
+;		series of bytes ending with a $00
+;		(note if you point to a zero, it will be interpreted as an
+;		action not an end)
+;	each byte specifies up to 3 actions, DRAW + UP DOWN LEFT RIGHT or
+;					NODRAW + UP DOWN LEFT RIGHT
+;	It is vector scaling with SCALE we hardcode to $20 and rotation
+;		which gets set to 0 after the first iteration, (which is
+;		why the first shape has arbitrary rotation and gets left)
+
+;	we are xdrawing so it will XOR with the current pixels on the screen
+
+		; NUP=0 UP=4	zz yyy xxx  , does xxx yyy zz 
+		; NRT=1 RT=5
+		; NDN=2 DN=6
+		; NLT=3 LT=7
+
+; zero page locations
+HGR_SHAPE	=	$1A
+HGR_SHAPE2	=	$1B
+HGR_BITS	=	$1C
+GBASL		=	$26
+GBASH		=	$27
+A5H		=	$45
+XREG		=	$46
+YREG		=	$47
+			; C0-CF should be clear
+			; D0-DF?? D0-D5 = HGR scratch?
+HGR_DX		=	$D0	; HGLIN
+HGR_DX2		=	$D1	; HGLIN
+HGR_DY		=	$D2	; HGLIN
+HGR_QUADRANT	=	$D3
+HGR_E		=	$D4
+HGR_E2		=	$D5
+HGR_X		=	$E0
+HGR_X2		=	$E1
+HGR_Y		=	$E2
+HGR_COLOR	=	$E4
+HGR_HORIZ	=	$E5
+HGR_SCALE	=	$E7
+HGR_SHAPE_TABLE	=	$E8
+HGR_SHAPE_TABLE2=	$E9
+HGR_COLLISIONS	=	$EA
+HGR_ROTATION	=	$F9
+FRAME		=	$FC
+XPOS		=	$FD
+YPOS		=	$FF
+
+KEYPRESS	=	$C000
+KEYRESET	=	$C010
+
+; ROM calls
+HGR2		=	$F3D8
+HGR		=	$F3E2
+HPOSN		=	$F411
+XDRAW0		=	$F65D
+XDRAW1		=	$F661
+RESTORE		=	$FF3F
+
+.zeropage
+.globalzp	rot_smc
+
+tiny_xdraw:
+
+	jsr	HGR2		; Hi-res, full screen		; 3
+				; Y=0, A=0 after this call
+
+	; we load at $E7 which is HGR_SCALE, so HGR_SCALE gets
+	;	the value of the above JSR instruction ($20)
+
+
+	; A and Y are 0 here.
+	; X is left behind by the boot process?
+
+	txa
+	jsr	HPOSN		; set screen position to X= (y,x) Y=(a)
+				; saves X,Y,A to zero page
+				; after Y= orig X/7
+				; A and X are ??
+tiny_loop:
+
+	; values for shape table
+	;	Y	X
+	;	00	E7 = neat
+	;	00	EB = OK
+	;	00	EF = good
+	;	F0	01 = cool, let's go with it
+
+smc2:
+	ldy	#$d0	; point to top byte of shape address
+
+smc1:
+	ldx	#$00	; point to bottom byte of shape address
+
+
+	; ROT in A
+
+	; this will be 0 2nd time through loop, arbitrary otherwise
+;	lda	#0		; ROT=0
+	jsr	XDRAW0		; XDRAW 1 AT X,Y
+				; Both A and X are 0 at exit
+				; Z flag set on exit
+				; Y varies
+
+
+	lda	KEYPRESS
+	bpl	tiny_loop
+
+	; key pressed
+	bit	KEYRESET
+
+	jsr	HGR2
+
+	inc	smc1+1
+	bne	tiny_loop
+	inc	smc2+1
+
+	jmp	tiny_loop	; bra
+
+
+
+