(Mednafen PSX) Reimplement dithering core option

libretro.cpp

@@ -543,6 +543,25 @@ static void check_variables(void)
          log_cb(RETRO_LOG_INFO, "PCE CD Audio settings changed.\n");
    }
 #elif defined(WANT_PSX_EMU)
+   extern void PSXDitherApply(bool);
+
+   var.key = "psx_dithering";
+
+   if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var))
+   {
+      static bool old_apply_dither = false;
+      bool apply_dither = true;
+      if (strcmp(var.value, "enabled") == 0)
+         apply_dither = true;
+      else if (strcmp(var.value, "disabled") == 0)
+         apply_dither = false;
+      if (apply_dither != old_apply_dither)
+      {
+         PSXDitherApply(apply_dither);
+         old_apply_dither = apply_dither;
+      }
+   }
+   
    var.key = "psx_enable_analog_toggle";
 
    if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var))

mednafen/psx-09333/gpu.cpp

@@ -87,11 +87,6 @@
   Vertical start and end can be changed during active display, with effect(though it needs to be vs0->ve0->vs1->ve1->..., vs0->vs1->ve0 doesn't apparently do anything 
   different from vs0->ve0.
 */
-
-namespace MDFN_IEN_PSX
-{
-//FILE *fp;
-
 static const int32 dither_table[4][4] =
 {
  { -4,  0, -3,  1 },
@@ -100,6 +95,37 @@ static const int32 dither_table[4][4] =
  {  3, -1,  2, -2 },
 };
 
+uint8 DitherLUT[4][4][512];	// Y, X, 8-bit source value(256 extra for saturation)
+
+void PSXDitherApply(bool enable)
+{
+   for(int y = 0; y < 4; y++)
+      for(int x = 0; x < 4; x++)
+         for(int v = 0; v < 512; v++)
+         {
+            int value = v;
+            if (enable)
+               value += dither_table[y][x];
+
+            value >>= 3;
+
+            if(value < 0)
+               value = 0;
+
+            if(value > 0x1F)
+               value = 0x1F;
+
+            DitherLUT[y][x][v] = value;
+         }
+}
+
+namespace MDFN_IEN_PSX
+{
+//FILE *fp;
+
+
+
+
 PS_GPU::PS_GPU(bool pal_clock_and_tv, int sls, int sle) : BlitterFIFO(0x20) // 0x10 on actual PS1 GPU, 0x20 here(see comment at top of gpu.h)	// 0x10)
 {
  HardwarePALType = pal_clock_and_tv;

mednafen/psx-09333/gpu.h

@@ -160,8 +160,6 @@ class PS_GPU
   uint8 RGB8SAT_Over[256];
  };
 
- uint8 DitherLUT[4][4][512];	// Y, X, 8-bit source value(256 extra for saturation)
-
  bool LineSkipTest(unsigned y);
 
  template<int BlendMode, bool MaskEval_TA, bool textured>