genesis: make the vram memory domain properly invalidate the tile cache and the vdp viewer properly regenerate the tile cache. may or may not fix issue 265.

BizHawk.Emulation.Cores/Consoles/Sega/gpgx/GPGX.cs

@@ -591,8 +591,27 @@ namespace BizHawk.Emulation.Cores.Consoles.Sega.gpgx
 				if (area == IntPtr.Zero || pname == IntPtr.Zero || size == 0)
 					continue;
 				string name = Marshal.PtrToStringAnsi(pname);
-
-				mm.Add(MemoryDomain.FromIntPtrSwap16(name, size, MemoryDomain.Endian.Big, area));
+				if (name == "VRAM")
+				{
+					byte* p = (byte*)area;
+					mm.Add(new MemoryDomain(name, size, MemoryDomain.Endian.Unknown,
+						delegate(int addr)
+						{
+							if (addr < 0 || addr >= 65536)
+								throw new ArgumentOutOfRangeException();
+							return p[addr];
+						},
+						delegate(int addr, byte val)
+						{
+							if (addr < 0 || addr >= 65536)
+								throw new ArgumentOutOfRangeException();
+							LibGPGX.gpgx_poke_vram(addr, val);
+						}));
+				}
+				else
+				{
+					mm.Add(MemoryDomain.FromIntPtrSwap16(name, size, MemoryDomain.Endian.Big, area));
+				}
 			}
 			MemoryDomains = new MemoryDomainList(mm, 0);
 		}
@@ -619,6 +638,7 @@ namespace BizHawk.Emulation.Cores.Consoles.Sega.gpgx
 		public void UpdateVDPViewContext(LibGPGX.VDPView view)
 		{
 			LibGPGX.gpgx_get_vdp_view(view);
+			LibGPGX.gpgx_flush_vram(); // fully regenerate internal caches as needed
 		}
 
 		LibGPGX.mem_cb ExecCallback;

BizHawk.Emulation.Cores/Consoles/Sega/gpgx/LibGPGX.cs

@@ -265,6 +265,12 @@ namespace BizHawk.Emulation.Cores.Consoles.Sega.gpgx
 		[DllImport("libgenplusgx.dll", CallingConvention = CallingConvention.Cdecl)]
 		public static extern void gpgx_get_vdp_view([Out] VDPView view);
 
+		[DllImport("libgenplusgx.dll", CallingConvention = CallingConvention.Cdecl)]
+		public static extern void gpgx_poke_vram(int addr, byte value);
+
+		[DllImport("libgenplusgx.dll", CallingConvention = CallingConvention.Cdecl)]
+		public static extern void gpgx_flush_vram();
+
 		[StructLayout(LayoutKind.Sequential)]
 		public struct RegisterInfo
 		{

genplus-gx/cinterface/cinterface.c

@@ -307,6 +307,16 @@ GPGX_EX void gpgx_sram_commitwrite(void)
 	}
 }
 
+GPGX_EX void gpgx_poke_vram(int addr, uint8 val)
+{
+	write_vram_byte(addr, val);
+}
+
+GPGX_EX void gpgx_flush_vram(void)
+{
+	flush_vram_cache();
+}
+
 GPGX_EX const char* gpgx_get_memdom(int which, void **area, int *size)
 {
 	if (!area || !size)

genplus-gx/core/vdp_ctrl.c

@@ -180,6 +180,28 @@ static void (*const dma_func[16])(unsigned int length) =
 };
 
 
+void write_vram_byte(int addr, uint8 val)
+{
+	uint8 *p;
+	addr &= 0xffff;
+	p = &vram[addr];
+	if (*p != val)
+	{
+		int name;
+		*p = val;
+		MARK_BG_DIRTY(addr);
+	}
+}
+
+void flush_vram_cache(void)
+{
+    if (bg_list_index)
+    {
+		update_bg_pattern_cache(bg_list_index);
+		bg_list_index = 0;
+    }
+}
+
 /*--------------------------------------------------------------------------*/
 /* Init, reset, context functions                                           */
 /*--------------------------------------------------------------------------*/

genplus-gx/core/vdp_ctrl.h

@@ -102,4 +102,7 @@ extern unsigned int vdp_hvc_r(unsigned int cycles);
 extern void vdp_test_w(unsigned int data);
 extern int vdp_68k_irq_ack(int int_level);
 
+void write_vram_byte(int addr, uint8 val);
+void flush_vram_cache(void);
+
 #endif /* _VDP_H_ */