From 61114cd8b4c44f606e6030d44142534884fca35b Mon Sep 17 00:00:00 2001
From: kub <derkub@gmail.com>
Date: Fri, 27 Mar 2020 19:25:20 +0100
Subject: [PATCH] vdp rendering fixes

---
 pico/draw.c     | 12 +++++++++---
 pico/draw_arm.S | 11 ++++++++---
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/pico/draw.c b/pico/draw.c
index dff5e075..68af73e2 100644
--- a/pico/draw.c
+++ b/pico/draw.c
@@ -486,7 +486,10 @@ static void DrawLayer(int plane_sh, int *hcache, int cellskip, int maxcells,
     // shit, we have 2-cell column based vscroll
     // luckily this doesn't happen too often
     ts.line=ymask|(shift[width]<<24); // save some stuff instead of line
-    plane_sh |= PicoMem.vsram[0x26+(~plane_sh&1)] << 16;
+    // vscroll value for leftmost cells in case of hscroll not on 16px boundary
+    // XXX it's unclear what exactly the hw is doing. Continue reading where it
+    // stopped last seems to work best (H40: 0x50 (wrap->0x00), H32 0x40).
+    plane_sh |= PicoMem.vsram[(pvid->reg[12]&1?0x00:0x20) + (plane_sh&1)] << 16;
     DrawStripVSRam(&ts, plane_sh, cellskip);
   } else {
     vscroll = PicoMem.vsram[plane_sh & 1]; // Get vertical scroll value
@@ -1173,7 +1176,10 @@ static void DrawLayerForced(int plane_sh, int cellskip, int maxcells,
     // shit, we have 2-cell column based vscroll
     // luckily this doesn't happen too often
     ts.line=ymask|(shift[width]<<24); // save some stuff instead of line
-    plane_sh |= PicoMem.vsram[0x26+(~plane_sh&1)] << 16;
+    // vscroll value for leftmost cells in case of hscroll not on 16px boundary
+    // XXX it's unclear what exactly the hw is doing. Continue reading where it
+    // stopped last seems to work best (H40: 0x50 (wrap->0x00), H32 0x40).
+    plane_sh |= PicoMem.vsram[(pvid->reg[12]&1?0x00:0x20) + (plane_sh&1)] << 16;
     DrawStripVSRamForced(&ts, plane_sh, cellskip);
   } else {
     vscroll = PicoMem.vsram[plane_sh & 1]; // Get vertical scroll value
@@ -1191,7 +1197,7 @@ static void DrawSpritesForced(unsigned char *sprited)
 {
   unsigned (*fTileFunc)(unsigned char *pd, unsigned m, unsigned int pack, int pal);
   unsigned char *pd = Pico.est.HighCol;
-  unsigned char mb[1+320+1];
+  unsigned char mb[1+320/8+1];
   unsigned char *p, *mp;
   unsigned m;
   int entry, cnt;
diff --git a/pico/draw_arm.S b/pico/draw_arm.S
index 1a0f3513..2ae6dba6 100644
--- a/pico/draw_arm.S
+++ b/pico/draw_arm.S
@@ -523,6 +523,9 @@ DrawLayer:
 @ @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
 
 .DrawStrip_vsscroll:
+    tst     r8, #1                @ if h40: lflags |= 0x10000
+    orrne   r0, r0, #0x10000
+
     rsb     r8, r3, #0
     mov     r8, r8, lsr #3        @ r8=tilex=(-ts->hscroll)>>3
     bic     r8, r8, #0x3fc00000
@@ -545,11 +548,13 @@ DrawLayer:
     eor     r3, r3, r7
     sub     r10,r10, #1<<24       @ cell--  // start from negative for hscroll
     tst     r3, #0x08
-    add_c24 r1, lr, (OFS_PMEM_vsram-OFS_PMEM_vram)
-    ldr     r3, [r1, #0x4c]       @ r3=vsram[0x26..0x27]
     subne   r10,r10, #1<<16       @ cells--
     subne   r10,r10, #1<<24       @ cell--  // even more negative
-    ror     r3, r3, #16
+
+    add_c24 r1, lr, (OFS_PMEM_vsram-OFS_PMEM_vram)
+    tst     r0, #0x10000          @ h40?
+    ldrne   r3, [r1, #0x00]       @ r3=vsram[0x00..0x01]
+    ldreq   r3, [r1, #0x40]       @ r3=vsram[0x20..0x21]
     str     r3, [r1, #0x7c]       @ vsram[0x3e..0x3f]=r3
 0:
     tst     r9, #1<<31
-- 
2.39.2