From b7a8bf2a23a759743ab376296ffa3f4d0fe8a766 Mon Sep 17 00:00:00 2001
From: Steven Hugg <hugg@fasterlight.com>
Date: Tue, 28 May 2019 20:50:06 -0400
Subject: [PATCH] astrocade: new stack layout for bios calls

---
 presets/astrocade/acbios.h | 23 +++--------------------
 presets/astrocade/acbios.s | 33 ++++++++++++++++++++++++---------
 presets/astrocade/vsync.c  | 20 ++++++++++++--------
 3 files changed, 39 insertions(+), 37 deletions(-)

diff --git a/presets/astrocade/acbios.h b/presets/astrocade/acbios.h
index 744f6b6a..b042fe4e 100644
--- a/presets/astrocade/acbios.h
+++ b/presets/astrocade/acbios.h
@@ -16,12 +16,6 @@ typedef struct {
 const FontDescriptor __at(0x206) FNTSYS;
 const FontDescriptor __at(0x20d) FNTSML;
 
-// STACK MANIPULATION
-
-#define DECSP1 __asm__("dec sp")
-#define DECSP2 __asm__("dec sp"); __asm__("dec sp")
-#define DECSP3 __asm__("dec sp"); __asm__("dec sp"); __asm__("dec sp")
-
 // BIOS COMMANDS
 
 #define STRDIS	0x34
@@ -40,20 +34,9 @@ const FontDescriptor __at(0x20d) FNTSML;
 void activate_interrupts(void);
 void wait_for_vsync(void);
 
-void _display_string(byte x, byte y, byte options, const char* str);
-#define display_string(x,y,opts,str) \
-	DECSP1; \
-        _display_string(x,y,opts,str);
-
-void _paint_rectangle(byte x, byte y, byte w, byte h, byte colormask);
-#define paint_rectangle(x,y,w,h,colormask) \
-	DECSP1; \
-        _paint_rectangle(x,y,w,h,colormask);
-
-void _write_relative(byte x, byte y, byte magic, const char* pattern);
-#define write_relative(x,y,magic,pattern) \
-	DECSP1; \
-        _write_relative(x,y,magic,pattern);
+void display_string(byte x, byte y, byte options, const char* str);
+void paint_rectangle(byte x, byte y, byte w, byte h, byte colormask);
+void write_relative(byte x, byte y, byte magic, const char* pattern);
 
 // QUICK MACROS
 
diff --git a/presets/astrocade/acbios.s b/presets/astrocade/acbios.s
index fe1c3a2d..f189f763 100644
--- a/presets/astrocade/acbios.s
+++ b/presets/astrocade/acbios.s
@@ -421,10 +421,10 @@ _wait_for_vsync:
 ;        .db	1
 
 ; build a SYSSUK block on the stack
-; the caller needs to dec SP before calling
-; so we have room for a RET opcode
-	.globl	__display_string
-__display_string:
+;                <return addr> <5 bytes>
+; <endsuk5> <oldret> rst <cmd> <5 bytes> ret
+	.globl	_display_string
+_display_string:
         ld	h,#(STRDIS+1)
 syssuk5:
 	pop	de		; return address
@@ -432,21 +432,36 @@ syssuk5:
         push	hl		; SYSSUK <command>
         ld	iy,#0
         add	iy,sp		; SP -> IY
+        ld	ix,#7
+        add	ix,sp		; SP+7 -> IX
         push	de		; push return addr
+        ld	e,(ix)		; load what's there
+        push	de		; push it
         ld	d,#0xc9		; ret opcode
-        ld	7(iy),d		; store after params
+        ld	(ix),d		; store after params
+        ld	hl,#endsuk5
+        push	hl
         ld	ix,#0x20d	; alternate font desc.
         jp	(iy)		; jump to RST
 
+endsuk5:
+        pop	de		; old ret value
+	pop	hl		; return address
+        ld	ix,#7
+        add	ix,sp		; SP+7 -> IX
+        ld	(ix),e		; restore old ret value
+	pop	de		; get rid of SYSSUK cmd
+	jp	(hl)		; caller takes care of rest
+
 ; RECTAN x y w h colormask
-	.globl	__paint_rectangle
-__paint_rectangle:
+	.globl	_paint_rectangle
+_paint_rectangle:
         ld	h,#(RECTAN+1)
         jp	syssuk5
 
 ; WRITP x y magic pattern
-	.globl	__write_relative
-__write_relative:
+	.globl	_write_relative
+_write_relative:
         ld	h,#(WRITR+1)
         jp	syssuk5
 
diff --git a/presets/astrocade/vsync.c b/presets/astrocade/vsync.c
index a00a36e7..ef9f565b 100644
--- a/presets/astrocade/vsync.c
+++ b/presets/astrocade/vsync.c
@@ -8,12 +8,15 @@
 //#link "acbios.s"
 
 const byte player_bitmap[] =
-{3,14,/*{w:12,h:16,bpp:2,brev:1}*/0x00,0x3C,0x00,0x00,0x18,0x00,0x00,0x3C,0x00,0x00,0x18,0x00,0x04,0x18,0x20,0x0C,0x3C,0x30,0x3C,0x3C,0x3C,0x1F,0xE7,0xF4,0x1F,0x66,0xF4,0x17,0xE7,0xE4,0x17,0xE7,0xE4,0x1C,0x7E,0x34,0x1C,0xFF,0x34,0x3C,0x18,0x3C,0x0C,0x18,0x30,0x04,0x18,0x20};
+{0,0,	// X, Y offset
+ 3,14,	// width (bytes) and height (lines)
+ /*{w:12,h:16,bpp:2,brev:1}*/
+ 0x00,0x3C,0x00,0x00,0x18,0x00,0x00,0x3C,0x00,0x00,0x18,0x00,0x04,0x18,0x20,0x0C,0x3C,0x30,0x3C,0x3C,0x3C,0x1F,0xE7,0xF4,0x1F,0x66,0xF4,0x17,0xE7,0xE4,0x17,0xE7,0xE4,0x1C,0x7E,0x34,0x1C,0xFF,0x34,0x3C,0x18,0x3C,0x0C,0x18,0x30,0x04,0x18,0x20};
 
 /*{pal:"astrocade",layout:"astrocade"}*/
 const byte palette[8] = {
-  0x06, 0x62, 0xF1, 0x04,
-  0x07, 0xD4, 0x35, 0x01,
+  0x07, 0xD4, 0x33, 0x01,
+  0x07, 0xD4, 0x33, 0x01,
 };
 
 void setup_registers() {
@@ -24,16 +27,17 @@ void setup_registers() {
 
 void main() {
   byte x,y;
-  x=10;
-  y=10;
+  x=20;
+  y=20;
   setup_registers();
   clrscr();
   activate_interrupts();
   while (1) {
-    render_sprite(player_bitmap, x, y, M_MOVE);
+    write_relative(x, y, M_MOVE, player_bitmap);
     wait_for_vsync();
-    erase_sprite(player_bitmap, x, y);
     x++;
-    y++;
+//    erase_sprite(player_bitmap, x, y);
+//    x++;
+//    y++;
   }
 }