fix cell scroll drawing

pico/draw.c

@@ -261,7 +261,11 @@ static void DrawStripVSRam(struct TileStrip *ts, int plane_sh, int cellskip)
   // Draw tiles across screen:
   tilex=(-ts->hscroll)>>3;
   dx=((ts->hscroll-1)&7)+1;
-  if(dx != 8) cell--; // have hscroll, start with negative cell
+  if (ts->hscroll & 0x0f) {
+    int adj = ((ts->hscroll ^ dx) >> 3) & 1;
+    cell -= adj + 1;
+    ts->cells -= adj;
+  }
   cell+=cellskip;
   tilex+=cellskip;
   dx+=cellskip<<3;

pico/draw2_arm.S

@@ -73,8 +73,17 @@ BackFillFull:
 
 @ -------- some macros --------
 
+@ helpers
+.macro add_c24 d s c
+    add     \d, \s, #(\c & 0x00ff00)
+.if \c & 0x0000ff
+    add     \d, \d, #(\c & 0x0000ff)
+.endif
+.if \c & 0xff0000
+    add     \d, \d, #(\c & 0xff0000)
+.endif
+.endm
 
-@ helper
 @ TileLineSinglecol (r1=pdest, r2=pixels8, r3=pal) r4: scratch, r0: pixels8_old
 .macro TileLineSinglecol notsinglecol=0
     and     r2, r2, #0xf        @ #0x0000000f
@@ -411,8 +420,7 @@ DrawLayerFull:
     mla     r11, r4, r7, r11      @ scrpos+=8*328*(planestart-START_ROW);
 
     @ Get vertical scroll value:
-    add     r7, r10, #0x012000
+    add_c24 r7, r10, (OFS_PMEM_vsram-OFS_PMEM_vram)
-    add     r7, r7,  #0x000180    @ r7=Pico.vsram (Pico+0x22180)
     ldr     r7, [r7]
     tst     r0, r0
     moveq   r7, r7, lsl #22

pico/draw_arm.S

@@ -19,7 +19,17 @@
 .equ PDRAW_PLANE_HI_PRIO, (1<<6)
 .equ PDRAW_SHHI_DONE,     (1<<7)
 
-@ helper
+@ helpers
+.macro add_c24 d s c
+    add     \d, \s, #(\c & 0x00ff00)
+.if \c & 0x0000ff
+    add     \d, \d, #(\c & 0x0000ff)
+.endif
+.if \c & 0xff0000
+    add     \d, \d, #(\c & 0xff0000)
+.endif
+.endm
+
 .macro TilePixel pat lsrr offs
 .if !\lsrr
     ands    r4, \pat, r2
@@ -344,8 +354,7 @@ DrawLayer:
     bne     .DrawStrip_vsscroll
 
     @ Get vertical scroll value:
-    add     r7, lr,  #0x012000
+    add_c24 r7, lr, (OFS_PMEM_vsram-OFS_PMEM_vram)
-    add     r7, r7,  #0x000180    @ r7=PicoMem.vsram (PicoMem+0x22180)
     ldr     r7, [r7]
 
     tst     r8, #2
@@ -522,17 +531,22 @@ DrawLayer:
     add     r7, r1, #1            @ r7=dx=((ts->hscroll-1)&7)+1
 
     mov     r10,r9, lsl #16
+    orr     r10,r10, #0xff000000  @ will be adjusted on entering loop
     tst     r0, #1
     orrne   r10,r10, #0x8000
+    tst     r3, #0x0f             @ hscroll & 0x0f?
+    beq     0f
+    eor     r3, r3, r7
+    sub     r10,r10, #1<<24       @ cell--  // start from negative for hscroll
+    tst     r3, #0x08
+    subne   r10,r10, #1<<16       @ cells--
+    subne   r10,r10, #1<<24       @ cell--  // even more negative
+0:
     tst     r9, #1<<31
     mov     r3, #0
-    orr     r10,r10, #0xff000000 @ will be adjusted on entering loop
     orrne   r10,r10, #1<<23 @ r10=(cell[31:24]|sh[23]|hi_not_empty[22]|cells_max[21:16]|plane[15]|ty[14:0])
     movne   r3, #0x40       @ default to shadowed pal on sh mode
 
-    cmp     r7, #8
-    subne   r10,r10, #0x01000000 @ have hscroll, start with negative cell
-
     and     r9, r9, #0xff00
     add     r8, r8, r9, lsr #8   @ tilex+=cellskip
     add     r7, r7, r9, lsr #5   @ dx+=cellskip<<3;
@@ -556,8 +570,7 @@ DrawLayer:
     ble     .dsloop_vs_exit
 
     @ calc offset and read tileline code to r7, also calc ty
-    add     r7, lr, #0x012000
+    add_c24 r7, lr, (OFS_PMEM_vsram-OFS_PMEM_vram)
-    add     r7, r7, #0x000180     @ r7=PicoMem.vsram (PicoMem+0x22180)
     add     r7, r7, r10,asr #23   @ vsram + ((cell&~1)<<1)
     bic     r7, r7, #3
     tst     r10,#0x8000           @ plane1?

pico/pico_int.h

@@ -356,7 +356,6 @@ struct PicoEState
   unsigned short HighPal[0x100];
 };
 
-// some assembly stuff still depends on these, do not touch!
 struct PicoMem
 {
   unsigned char ram[0x10000];  // 0x00000 scratch ram
@@ -366,9 +365,9 @@ struct PicoMem
   };
   unsigned char zram[0x2000];  // 0x20000 Z80 ram
   unsigned char ioports[0x10]; // XXX: fix asm and mv
-  unsigned char pad[0xf0];     // unused
+  unsigned short cram[0x40];   // 0x22010
-  unsigned short cram[0x40];   // 0x22100
+  unsigned char pad[0x70];     // 0x22050 DrawStripVSRam reads 0 from here
-  unsigned short vsram[0x40];  // 0x22180
+  unsigned short vsram[0x40];  // 0x22100
 };
 
 // sram

pico/pico_int_o32.h

@@ -24,3 +24,5 @@
 #define OFS_EST_PicoOpt      0x20
 #define OFS_EST_Draw2FB      0x24
 #define OFS_EST_HighPal      0x28
+#define OFS_PMEM_vram        0x10000
+#define OFS_PMEM_vsram       0x22100

tools/mkoffsets.c

@@ -18,6 +18,9 @@
 #define DUMP_EST(f, field) \
 	DUMP(f, "OFS_EST_", struct PicoEState, field)
 
+#define DUMP_PMEM(f, field) \
+	DUMP(f, "OFS_PMEM_", struct PicoMem, field)
+
 extern struct Pico p;
 
 int main(int argc, char *argv[])
@@ -58,6 +61,8 @@ int main(int argc, char *argv[])
   DUMP_EST(f, PicoOpt);
   DUMP_EST(f, Draw2FB);
   DUMP_EST(f, HighPal);
+  DUMP_PMEM(f, vram);
+  DUMP_PMEM(f, vsram);
   fclose(f);
 
   return 0;