From d87d43ce228e9b2e795fa85c5dee3708c2812625 Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Mon, 14 Mar 2022 10:12:49 +0100
Subject: [PATCH] Update the screen auto-byte to bring it up to spec

---
 src/main.c | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/src/main.c b/src/main.c
index 8894133..fcd42a4 100644
--- a/src/main.c
+++ b/src/main.c
@@ -364,27 +364,33 @@ screen_deo(Device *d, u8 port) {
             if(d->dat[0x6] & 0x02) DEVPOKE16(0xa, y + 1); /* auto y+1 */
         } break;
         case 0xf: {
-            u16 x, y, addr;
+            u16 x, y, dx, dy, addr;
             u8 twobpp = !!(d->dat[0xf] & 0x80);
             DEVPEEK16(x, 0x8);
             DEVPEEK16(y, 0xa);
             DEVPEEK16(addr, 0xc);
-            if(addr > 0xfff8 - twobpp * 8) {
+            u8 n = d->dat[0x6] >> 4;
+            dx = (d->dat[0x6] & 0x01) << 3;
+            dy = (d->dat[0x6] & 0x02) << 2;
+            if(addr > 0x10000 - ((n + 1) << (3 + twobpp))) {
                 return;
             }
             u8 *layer = (d->dat[0xf] & 0x40) ? pixels_fg : pixels_bg;
             u8 color = d->dat[0xf] & 0xf;
             u8 flipx = d->dat[0xf] & 0x10;
             u8 flipy = d->dat[0xf] & 0x20;
-            u8 *sprite = &d->u->ram[addr];
-            if (twobpp) {
-                ppu_2bpp(layer, x, y, sprite, color, flipx, flipy);
-            } else {
-                ppu_1bpp(layer, x, y, sprite, color, flipx, flipy);
+            for(size_t i = 0; i <= n; i++) {
+                u8 *sprite = &d->u->ram[addr];
+                if (twobpp) {
+                    ppu_2bpp(layer, x + dy * i, y + dx * i, sprite, color, flipx, flipy);
+                } else {
+                    ppu_1bpp(layer, x + dy * i, y + dx * i, sprite, color, flipx, flipy);
+                }
+                addr += (d->dat[0x6] & 0x04) << (1 + twobpp);
             }
-            if(d->dat[0x6] & 0x04) DEVPOKE16(0xc, addr + 8 + twobpp * 8); /* auto addr+length */
-            if(d->dat[0x6] & 0x01) DEVPOKE16(0x8, x + 8);                 /* auto x+8 */
-            if(d->dat[0x6] & 0x02) DEVPOKE16(0xa, y + 8);                 /* auto y+8 */
+            DEVPOKE16(0xc, addr);   /* auto addr+length */
+            DEVPOKE16(0x8, x + dx); /* auto x+8 */
+            DEVPOKE16(0xa, y + dy); /* auto y+8 */
         } break;
 	}
     reqdraw = 1;