adjust Zapper tolerance; make Zapper input tolerance circular rather than rectangular by default

src/drivers/libretro/libretro.c

@@ -60,6 +60,8 @@ void linearFree(void* mem);
 RETRO_HW_RENDER_INTEFACE_GSKIT_PS2 *ps2 = NULL;
 #endif
 
+extern void FCEU_ZapperSetTolerance(int t);
+
 static retro_video_refresh_t video_cb = NULL;
 static retro_input_poll_t poll_cb = NULL;
 static retro_input_state_t input_cb = NULL;
@@ -1300,6 +1302,16 @@ static void check_variables(bool startup)
       else zappermode = RetroLightgun; /*default setting*/
    }
 
+   var.key = "fceumm_zapper_tolerance";
+
+   if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) && var.value)
+   {
+      FCEU_ZapperSetTolerance(atoi(var.value));
+   }
+
+   var.key = "fceumm_region";
+   if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) && var.value)
+
    var.key = "fceumm_show_crosshair";
 
    if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) && var.value)

src/drivers/libretro/libretro_core_options.h

@@ -232,6 +232,48 @@ struct retro_core_option_definition option_defs_common[] = {
       },
       "enabled",
    },
+   {
+      "fceumm_zapper_tolerance",
+      "Zapper Tolerance",
+      "Sets how many pixels from target area is on target.",
+      {
+         { "0",  NULL },
+         { "1",  NULL },
+         { "2",  NULL },
+         { "3",  NULL },
+         { "4",  NULL },
+         { "5",  NULL },
+         { "6",  NULL },
+         { "7",  NULL },
+         { "8",  NULL },
+         { "9",  NULL },
+         { "10", NULL },
+         { "11", NULL },
+         { "12", NULL },
+         { "13", NULL },
+         { "14", NULL },
+         { "15", NULL },
+         { "16", NULL },
+         { "17", NULL },
+         { "18", NULL },
+         { "19", NULL },
+         { "20", NULL },
+         { "21", NULL },
+         { "22", NULL },
+         { "23", NULL },
+         { "24", NULL },
+         { "25", NULL },
+         { "26", NULL },
+         { "27", NULL },
+         { "28", NULL },
+         { "29", NULL },
+         { "30", NULL },
+         { "31", NULL },
+         { "32", NULL },
+         { NULL, NULL },
+      },
+      "6",
+   },
    {
       "fceumm_sndquality",
       "Sound Quality",