Codechange: Don't use cpp_offsetof in the save/load code.

Many of the member variables that are used in save/load are inside types
that are not standard layout types. Using pointer arithmetics to determine
addresses of members inside types that are not standard layout is generally
undefined behaviour. If we'd use C++17, it is conditionally supported, which means
each compiler may or may not support it. And even then using it for individual
array elements is syntactically not supported the the standard offsetof function.

Unfortunately, the trickery employed for saving linkgraph settings causes quite some
clutter in the settings ini files.

8 files changed, 102 insertions, 76 deletions

diff --git a/src/table/company_settings.ini b/src/table/company_settings.ini
index 8f9bee3bf..1be7ccbc2 100644
--- a/src/table/company_settings.ini
+++ b/src/table/company_settings.ini
@@ -16,8 +16,8 @@ static const SettingDesc _company_settings[] = {
 [post-amble]
 };
 [templates]
-SDT_BOOL = SDT_BOOL($base, $var,        $flags, $guiflags, $def,                        $str, $strhelp, $strval, $proc, $from, $to, $cat),
-SDT_VAR  =  SDT_VAR($base, $var, $type, $flags, $guiflags, $def, $min, $max, $interval, $str, $strhelp, $strval, $proc, $from, $to, $cat),
+SDT_BOOL = SDT_BOOL($base, $var,        $flags, $guiflags, $def,                        $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra),
+SDT_VAR  =  SDT_VAR($base, $var, $type, $flags, $guiflags, $def, $min, $max, $interval, $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra),
 SDT_END  = SDT_END()
 
 [defaults]
@@ -32,6 +32,7 @@ load     = nullptr
 from     = SL_MIN_VERSION
 to       = SL_MAX_VERSION
 cat      = SC_ADVANCED
+extra    = 0
 
 
 
diff --git a/src/table/currency_settings.ini b/src/table/currency_settings.ini
index 34199501f..f6c7c8612 100644
--- a/src/table/currency_settings.ini
+++ b/src/table/currency_settings.ini
@@ -9,9 +9,9 @@ static const SettingDesc _currency_settings[] = {
 [post-amble]
 };
 [templates]
-SDT_VAR = SDT_VAR($base, $var, $type, $flags, $guiflags, $def, $min, $max, $interval, $str, $strhelp, $strval, $proc, $from, $to, $cat),
-SDT_CHR = SDT_CHR($base, $var,        $flags, $guiflags, $def,                        $str, $strhelp, $strval, $proc, $from, $to, $cat),
-SDT_STR = SDT_STR($base, $var, $type, $flags, $guiflags, $def,                        $str, $strhelp, $strval, $proc, $from, $to, $cat),
+SDT_VAR = SDT_VAR($base, $var, $type, $flags, $guiflags, $def, $min, $max, $interval, $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra),
+SDT_CHR = SDT_CHR($base, $var,        $flags, $guiflags, $def,                        $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra),
+SDT_STR = SDT_STR($base, $var, $type, $flags, $guiflags, $def,                        $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra),
 SDT_END = SDT_END()
 
 [defaults]
@@ -26,6 +26,7 @@ load     = nullptr
 from     = SL_MIN_VERSION
 to       = SL_MAX_VERSION
 cat      = SC_ADVANCED
+extra    = 0
 
 
 
diff --git a/src/table/gameopt_settings.ini b/src/table/gameopt_settings.ini
index 08253be93..8e5da277f 100644
--- a/src/table/gameopt_settings.ini
+++ b/src/table/gameopt_settings.ini
@@ -37,13 +37,13 @@ static const SettingDesc _gameopt_settings[] = {
 [post-amble]
 };
 [templates]
-SDTG_GENERAL = SDTG_GENERAL($name, $sdt_cmd, $sle_cmd, $type, $flags, $guiflags, $var, $length, $def, $min, $max, $interval, $full, $str, $strhelp, $strval, $proc, $from, $to, $cat),
-SDTG_VAR     =     SDTG_VAR($name,                     $type, $flags, $guiflags, $var,          $def, $min, $max, $interval,        $str, $strhelp, $strval, $proc, $from, $to, $cat),
+SDTG_GENERAL = SDTG_GENERAL($name, $sdt_cmd, $sle_cmd, $type, $flags, $guiflags, $var, $length, $def, $min, $max, $interval, $full, $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra),
+SDTG_VAR     =     SDTG_VAR($name,                     $type, $flags, $guiflags, $var,          $def, $min, $max, $interval,        $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra),
 SDT_NULL     =   SDT_NULL($length, $from, $to),
-SDTC_OMANY   = SDTC_OMANY(       $var, $type, $flags, $guiflags, $def,       $max, $full,            $str, $strhelp, $strval, $proc, $from, $to,        $cat),
-SDTG_OMANY   = SDTG_OMANY($name,       $type, $flags, $guiflags, $var, $def, $max, $full,            $str, $strhelp, $strval, $proc, $from, $to,        $cat),
-SDT_OMANY    =  SDT_OMANY($base, $var, $type, $flags, $guiflags, $def,       $max, $full,            $str, $strhelp, $strval, $proc, $from, $to, $load, $cat),
-SDT_VAR      =    SDT_VAR($base, $var, $type, $flags, $guiflags, $def, $min, $max,        $interval, $str, $strhelp, $strval, $proc, $from, $to,        $cat),
+SDTC_OMANY   = SDTC_OMANY(       $var, $type, $flags, $guiflags, $def,       $max, $full,            $str, $strhelp, $strval, $proc, $from, $to,        $cat, $extra),
+SDTG_OMANY   = SDTG_OMANY($name,       $type, $flags, $guiflags, $var, $def, $max, $full,            $str, $strhelp, $strval, $proc, $from, $to,        $cat, $extra),
+SDT_OMANY    =  SDT_OMANY($base, $var, $type, $flags, $guiflags, $def,       $max, $full,            $str, $strhelp, $strval, $proc, $from, $to, $load, $cat, $extra),
+SDT_VAR      =    SDT_VAR($base, $var, $type, $flags, $guiflags, $def, $min, $max,        $interval, $str, $strhelp, $strval, $proc, $from, $to,        $cat, $extra),
 SDT_END      = SDT_END()
 
 [defaults]
@@ -58,6 +58,7 @@ load     = nullptr
 from     = SL_MIN_VERSION
 to       = SL_MAX_VERSION
 cat      = SC_ADVANCED
+extra    = 0
 
 
 
diff --git a/src/table/misc_settings.ini b/src/table/misc_settings.ini
index 167f8441c..d46ebe9bb 100644
--- a/src/table/misc_settings.ini
+++ b/src/table/misc_settings.ini
@@ -13,13 +13,13 @@ static const SettingDescGlobVarList _misc_settings[] = {
 [post-amble]
 };
 [templates]
-SDTG_LIST  =  SDTG_LIST($name, $type, $length, $flags, $guiflags, $var, $def,                               $str, $strhelp, $strval, $proc, $from, $to, $cat),
-SDTG_MMANY = SDTG_MMANY($name, $type,          $flags, $guiflags, $var, $def,                        $full, $str, $strhelp, $strval, $proc, $from, $to, $cat),
-SDTG_OMANY = SDTG_OMANY($name, $type,          $flags, $guiflags, $var, $def,       $max,            $full, $str, $strhelp, $strval, $proc, $from, $to, $cat),
-SDTG_STR   =   SDTG_STR($name, $type,          $flags, $guiflags, $var, $def,                               $str, $strhelp, $strval, $proc, $from, $to, $cat),
-SDTG_SSTR  =  SDTG_SSTR($name, $type,          $flags, $guiflags, $var, $def,                               $str, $strhelp, $strval, $proc, $from, $to, $cat),
-SDTG_BOOL  =  SDTG_BOOL($name,                 $flags, $guiflags, $var, $def,                               $str, $strhelp, $strval, $proc, $from, $to, $cat),
-SDTG_VAR   =   SDTG_VAR($name, $type,          $flags, $guiflags, $var, $def, $min, $max, $interval,        $str, $strhelp, $strval, $proc, $from, $to, $cat),
+SDTG_LIST  =  SDTG_LIST($name, $type, $length, $flags, $guiflags, $var, $def,                               $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra),
+SDTG_MMANY = SDTG_MMANY($name, $type,          $flags, $guiflags, $var, $def,                        $full, $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra),
+SDTG_OMANY = SDTG_OMANY($name, $type,          $flags, $guiflags, $var, $def,       $max,            $full, $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra),
+SDTG_STR   =   SDTG_STR($name, $type,          $flags, $guiflags, $var, $def,                               $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra),
+SDTG_SSTR  =  SDTG_SSTR($name, $type,          $flags, $guiflags, $var, $def,                               $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra),
+SDTG_BOOL  =  SDTG_BOOL($name,                 $flags, $guiflags, $var, $def,                               $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra),
+SDTG_VAR   =   SDTG_VAR($name, $type,          $flags, $guiflags, $var, $def, $min, $max, $interval,        $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra),
 SDTG_END   = SDTG_END()
 
 [defaults]
@@ -34,6 +34,7 @@ load     = nullptr
 from     = SL_MIN_VERSION
 to       = SL_MAX_VERSION
 cat      = SC_ADVANCED
+extra    = 0
 
 
 
diff --git a/src/table/settings.h.preamble b/src/table/settings.h.preamble
index 3d372c245..f1facaaf0 100644
--- a/src/table/settings.h.preamble
+++ b/src/table/settings.h.preamble
@@ -61,29 +61,29 @@ static size_t ConvertLandscape(const char *value);
 
 /* Macros for various objects to go in the configuration file.
  * This section is for global variables */
-#define SDTG_GENERAL(name, sdt_cmd, sle_cmd, type, flags, guiflags, var, length, def, min, max, interval, full, str, strhelp, strval, proc, from, to, cat)\
-	{NSD_GENERAL(name, def, sdt_cmd, guiflags, min, max, interval, full, str, strhelp, strval, proc, nullptr, cat), SLEG_GENERAL(sle_cmd, var, type | flags, length, from, to)}
+#define SDTG_GENERAL(name, sdt_cmd, sle_cmd, type, flags, guiflags, var, length, def, min, max, interval, full, str, strhelp, strval, proc, from, to, cat, extra)\
+	{NSD_GENERAL(name, def, sdt_cmd, guiflags, min, max, interval, full, str, strhelp, strval, proc, nullptr, cat), SLEG_GENERAL(sle_cmd, var, type | flags, length, from, to, extra)}
 
-#define SDTG_VAR(name, type, flags, guiflags, var, def, min, max, interval, str, strhelp, strval, proc, from, to, cat)\
-	SDTG_GENERAL(name, SDT_NUMX, SL_VAR, type, flags, guiflags, var, 0, def, min, max, interval, nullptr, str, strhelp, strval, proc, from, to, cat)
+#define SDTG_VAR(name, type, flags, guiflags, var, def, min, max, interval, str, strhelp, strval, proc, from, to, cat, extra)\
+	SDTG_GENERAL(name, SDT_NUMX, SL_VAR, type, flags, guiflags, var, 0, def, min, max, interval, nullptr, str, strhelp, strval, proc, from, to, cat, extra)
 
-#define SDTG_BOOL(name, flags, guiflags, var, def, str, strhelp, strval, proc, from, to, cat)\
-	SDTG_GENERAL(name, SDT_BOOLX, SL_VAR, SLE_BOOL, flags, guiflags, var, 0, def, 0, 1, 0, nullptr, str, strhelp, strval, proc, from, to, cat)
+#define SDTG_BOOL(name, flags, guiflags, var, def, str, strhelp, strval, proc, from, to, cat, extra)\
+	SDTG_GENERAL(name, SDT_BOOLX, SL_VAR, SLE_BOOL, flags, guiflags, var, 0, def, 0, 1, 0, nullptr, str, strhelp, strval, proc, from, to, cat, extra)
 
-#define SDTG_LIST(name, type, length, flags, guiflags, var, def, str, strhelp, strval, proc, from, to, cat)\
-	SDTG_GENERAL(name, SDT_INTLIST, SL_ARR, type, flags, guiflags, var, length, def, 0, 0, 0, nullptr, str, strhelp, strval, proc, from, to, cat)
+#define SDTG_LIST(name, type, length, flags, guiflags, var, def, str, strhelp, strval, proc, from, to, cat, extra)\
+	SDTG_GENERAL(name, SDT_INTLIST, SL_ARR, type, flags, guiflags, var, length, def, 0, 0, 0, nullptr, str, strhelp, strval, proc, from, to, cat, extra)
 
-#define SDTG_STR(name, type, flags, guiflags, var, def, str, strhelp, strval, proc, from, to, cat)\
-	SDTG_GENERAL(name, SDT_STRING, SL_STR, type, flags, guiflags, var, sizeof(var), def, 0, 0, 0, nullptr, str, strhelp, strval, proc, from, to, cat)
+#define SDTG_STR(name, type, flags, guiflags, var, def, str, strhelp, strval, proc, from, to, cat, extra)\
+	SDTG_GENERAL(name, SDT_STRING, SL_STR, type, flags, guiflags, var, sizeof(var), def, 0, 0, 0, nullptr, str, strhelp, strval, proc, from, to, cat, extra)
 
-#define SDTG_SSTR(name, type, flags, guiflags, var, def, str, strhelp, strval, proc, from, to, cat)\
-    SDTG_GENERAL(name, SDT_STDSTRING, SL_STDSTR, type, flags, guiflags, var, sizeof(var), def, 0, 0, 0, nullptr, str, strhelp, strval, proc, from, to, cat)
+#define SDTG_SSTR(name, type, flags, guiflags, var, def, str, strhelp, strval, proc, from, to, cat, extra)\
+    SDTG_GENERAL(name, SDT_STDSTRING, SL_STDSTR, type, flags, guiflags, var, sizeof(var), def, 0, 0, 0, nullptr, str, strhelp, strval, proc, from, to, cat, extra)
 
-#define SDTG_OMANY(name, type, flags, guiflags, var, def, max, full, str, strhelp, strval, proc, from, to, cat)\
-	SDTG_GENERAL(name, SDT_ONEOFMANY, SL_VAR, type, flags, guiflags, var, 0, def, 0, max, 0, full, str, strhelp, strval, proc, from, to, cat)
+#define SDTG_OMANY(name, type, flags, guiflags, var, def, max, full, str, strhelp, strval, proc, from, to, cat, extra)\
+	SDTG_GENERAL(name, SDT_ONEOFMANY, SL_VAR, type, flags, guiflags, var, 0, def, 0, max, 0, full, str, strhelp, strval, proc, from, to, cat, extra)
 
-#define SDTG_MMANY(name, type, flags, guiflags, var, def, full, str, strhelp, strval, proc, from, to, cat)\
-	SDTG_GENERAL(name, SDT_MANYOFMANY, SL_VAR, type, flags, guiflags, var, 0, def, 0, 0, 0, full, str, strhelp, strval, proc, from, to, cat)
+#define SDTG_MMANY(name, type, flags, guiflags, var, def, full, str, strhelp, strval, proc, from, to, cat, extra)\
+	SDTG_GENERAL(name, SDT_MANYOFMANY, SL_VAR, type, flags, guiflags, var, 0, def, 0, 0, 0, full, str, strhelp, strval, proc, from, to, cat, extra)
 
 #define SDTG_NULL(length, from, to)\
 	{{"", nullptr, SDT_NUMX, SGF_NONE, 0, 0, 0, nullptr, STR_NULL, STR_NULL, STR_NULL, nullptr, nullptr, SC_NONE}, SLEG_NULL(length, from, to)}
@@ -92,48 +92,48 @@ static size_t ConvertLandscape(const char *value);
 
 /* Macros for various objects to go in the configuration file.
  * This section is for structures where their various members are saved */
-#define SDT_GENERAL(name, sdt_cmd, sle_cmd, type, flags, guiflags, base, var, length, def, min, max, interval, full, str, strhelp, strval, proc, load, from, to, cat)\
-	{NSD_GENERAL(name, def, sdt_cmd, guiflags, min, max, interval, full, str, strhelp, strval, proc, load, cat), SLE_GENERAL(sle_cmd, base, var, type | flags, length, from, to)}
+#define SDT_GENERAL(name, sdt_cmd, sle_cmd, type, flags, guiflags, base, var, length, def, min, max, interval, full, str, strhelp, strval, proc, load, from, to, cat, extra)\
+	{NSD_GENERAL(name, def, sdt_cmd, guiflags, min, max, interval, full, str, strhelp, strval, proc, load, cat), SLE_GENERAL(sle_cmd, base, var, type | flags, length, from, to, extra)}
 
-#define SDT_VAR(base, var, type, flags, guiflags, def, min, max, interval, str, strhelp, strval, proc, from, to, cat)\
-	SDT_GENERAL(#var, SDT_NUMX, SL_VAR, type, flags, guiflags, base, var, 1, def, min, max, interval, nullptr, str, strhelp, strval, proc, nullptr, from, to, cat)
+#define SDT_VAR(base, var, type, flags, guiflags, def, min, max, interval, str, strhelp, strval, proc, from, to, cat, extra)\
+	SDT_GENERAL(#var, SDT_NUMX, SL_VAR, type, flags, guiflags, base, var, 1, def, min, max, interval, nullptr, str, strhelp, strval, proc, nullptr, from, to, cat, extra)
 
-#define SDT_BOOL(base, var, flags, guiflags, def, str, strhelp, strval, proc, from, to, cat)\
-	SDT_GENERAL(#var, SDT_BOOLX, SL_VAR, SLE_BOOL, flags, guiflags, base, var, 1, def, 0, 1, 0, nullptr, str, strhelp, strval, proc, nullptr, from, to, cat)
+#define SDT_BOOL(base, var, flags, guiflags, def, str, strhelp, strval, proc, from, to, cat, extra)\
+	SDT_GENERAL(#var, SDT_BOOLX, SL_VAR, SLE_BOOL, flags, guiflags, base, var, 1, def, 0, 1, 0, nullptr, str, strhelp, strval, proc, nullptr, from, to, cat, extra)
 
-#define SDT_LIST(base, var, type, flags, guiflags, def, str, strhelp, strval, proc, from, to, cat)\
-	SDT_GENERAL(#var, SDT_INTLIST, SL_ARR, type, flags, guiflags, base, var, lengthof(((base*)8)->var), def, 0, 0, 0, nullptr, str, strhelp, strval, proc, nullptr, from, to, cat)
+#define SDT_LIST(base, var, type, flags, guiflags, def, str, strhelp, strval, proc, from, to, cat, extra)\
+	SDT_GENERAL(#var, SDT_INTLIST, SL_ARR, type, flags, guiflags, base, var, lengthof(((base*)8)->var), def, 0, 0, 0, nullptr, str, strhelp, strval, proc, nullptr, from, to, cat, extra)
 
-#define SDT_STR(base, var, type, flags, guiflags, def, str, strhelp, strval, proc, from, to, cat)\
-	SDT_GENERAL(#var, SDT_STRING, SL_STR, type, flags, guiflags, base, var, sizeof(((base*)8)->var), def, 0, 0, 0, nullptr, str, strhelp, strval, proc, nullptr, from, to, cat)
+#define SDT_STR(base, var, type, flags, guiflags, def, str, strhelp, strval, proc, from, to, cat, extra)\
+	SDT_GENERAL(#var, SDT_STRING, SL_STR, type, flags, guiflags, base, var, sizeof(((base*)8)->var), def, 0, 0, 0, nullptr, str, strhelp, strval, proc, nullptr, from, to, cat, extra)
 
-#define SDT_CHR(base, var, flags, guiflags, def, str, strhelp, strval, proc, from, to, cat)\
-	SDT_GENERAL(#var, SDT_STRING, SL_VAR, SLE_CHAR, flags, guiflags, base, var, 1, def, 0, 0, 0, nullptr, str, strhelp, strval, proc, nullptr, from, to, cat)
+#define SDT_CHR(base, var, flags, guiflags, def, str, strhelp, strval, proc, from, to, cat, extra)\
+	SDT_GENERAL(#var, SDT_STRING, SL_VAR, SLE_CHAR, flags, guiflags, base, var, 1, def, 0, 0, 0, nullptr, str, strhelp, strval, proc, nullptr, from, to, cat, extra)
 
-#define SDT_OMANY(base, var, type, flags, guiflags, def, max, full, str, strhelp, strval, proc, from, to, load, cat)\
-	SDT_GENERAL(#var, SDT_ONEOFMANY, SL_VAR, type, flags, guiflags, base, var, 1, def, 0, max, 0, full, str, strhelp, strval, proc, load, from, to, cat)
+#define SDT_OMANY(base, var, type, flags, guiflags, def, max, full, str, strhelp, strval, proc, from, to, load, cat, extra)\
+	SDT_GENERAL(#var, SDT_ONEOFMANY, SL_VAR, type, flags, guiflags, base, var, 1, def, 0, max, 0, full, str, strhelp, strval, proc, load, from, to, cat, extra)
 
-#define SDT_MMANY(base, var, type, flags, guiflags, def, full, str, proc, strhelp, strval, from, to, cat)\
-	SDT_GENERAL(#var, SDT_MANYOFMANY, SL_VAR, type, flags, guiflags, base, var, 1, def, 0, 0, 0, full, str, strhelp, strval, proc, nullptr, from, to, cat)
+#define SDT_MMANY(base, var, type, flags, guiflags, def, full, str, proc, strhelp, strval, from, to, cat, extra)\
+	SDT_GENERAL(#var, SDT_MANYOFMANY, SL_VAR, type, flags, guiflags, base, var, 1, def, 0, 0, 0, full, str, strhelp, strval, proc, nullptr, from, to, cat, extra)
 
 #define SDT_NULL(length, from, to)\
 	{{"", nullptr, SDT_NUMX, SGF_NONE, 0, 0, 0, nullptr, STR_NULL, STR_NULL, STR_NULL, nullptr, nullptr, SC_NONE}, SLE_CONDNULL(length, from, to)}
 
 
-#define SDTC_VAR(var, type, flags, guiflags, def, min, max, interval, str, strhelp, strval, proc, from, to, cat)\
-	SDTG_GENERAL(#var, SDT_NUMX, SL_VAR, type, flags, guiflags, _settings_client.var, 1, def, min, max, interval, nullptr, str, strhelp, strval, proc, from, to, cat)
+#define SDTC_VAR(var, type, flags, guiflags, def, min, max, interval, str, strhelp, strval, proc, from, to, cat, extra)\
+	SDTG_GENERAL(#var, SDT_NUMX, SL_VAR, type, flags, guiflags, _settings_client.var, 1, def, min, max, interval, nullptr, str, strhelp, strval, proc, from, to, cat, extra)
 
-#define SDTC_BOOL(var, flags, guiflags, def, str, strhelp, strval, proc, from, to, cat)\
-	SDTG_GENERAL(#var, SDT_BOOLX, SL_VAR, SLE_BOOL, flags, guiflags, _settings_client.var, 1, def, 0, 1, 0, nullptr, str, strhelp, strval, proc, from, to, cat)
+#define SDTC_BOOL(var, flags, guiflags, def, str, strhelp, strval, proc, from, to, cat, extra)\
+	SDTG_GENERAL(#var, SDT_BOOLX, SL_VAR, SLE_BOOL, flags, guiflags, _settings_client.var, 1, def, 0, 1, 0, nullptr, str, strhelp, strval, proc, from, to, cat, extra)
 
-#define SDTC_LIST(var, type, flags, guiflags, def, str, strhelp, strval, proc, from, to, cat)\
-	SDTG_GENERAL(#var, SDT_INTLIST, SL_ARR, type, flags, guiflags, _settings_client.var, lengthof(_settings_client.var), def, 0, 0, 0, nullptr, str, strhelp, strval, proc, from, to, cat)
+#define SDTC_LIST(var, type, flags, guiflags, def, str, strhelp, strval, proc, from, to, cat, extra)\
+	SDTG_GENERAL(#var, SDT_INTLIST, SL_ARR, type, flags, guiflags, _settings_client.var, lengthof(_settings_client.var), def, 0, 0, 0, nullptr, str, strhelp, strval, proc, from, to, cat, extra)
 
-#define SDTC_STR(var, type, flags, guiflags, def, str, strhelp, strval, proc, from, to, cat)\
-	SDTG_GENERAL(#var, SDT_STRING, SL_STR, type, flags, guiflags, _settings_client.var, sizeof(_settings_client.var), def, 0, 0, 0, nullptr, str, strhelp, strval, proc, from, to, cat)
+#define SDTC_STR(var, type, flags, guiflags, def, str, strhelp, strval, proc, from, to, cat, extra)\
+	SDTG_GENERAL(#var, SDT_STRING, SL_STR, type, flags, guiflags, _settings_client.var, sizeof(_settings_client.var), def, 0, 0, 0, nullptr, str, strhelp, strval, proc, from, to, cat, extra)
 
-#define SDTC_OMANY(var, type, flags, guiflags, def, max, full, str, strhelp, strval, proc, from, to, cat)\
-	SDTG_GENERAL(#var, SDT_ONEOFMANY, SL_VAR, type, flags, guiflags, _settings_client.var, 1, def, 0, max, 0, full, str, strhelp, strval, proc, from, to, cat)
+#define SDTC_OMANY(var, type, flags, guiflags, def, max, full, str, strhelp, strval, proc, from, to, cat, extra)\
+	SDTG_GENERAL(#var, SDT_ONEOFMANY, SL_VAR, type, flags, guiflags, _settings_client.var, 1, def, 0, max, 0, full, str, strhelp, strval, proc, from, to, cat, extra)
 
 #define SDT_END() {{nullptr, nullptr, SDT_NUMX, SGF_NONE, 0, 0, 0, nullptr, STR_NULL, STR_NULL, STR_NULL, nullptr, nullptr, SC_NONE}, SLE_END()}
 
diff --git a/src/table/settings.ini b/src/table/settings.ini
index eebb23f7e..2e085058f 100644
--- a/src/table/settings.ini
+++ b/src/table/settings.ini
@@ -62,18 +62,18 @@ const SettingDesc _settings[] = {
 [post-amble]
 };
 [templates]
-SDTG_BOOL  =  SDTG_BOOL($name,              $flags, $guiflags, $var, $def,                        $str, $strhelp, $strval, $proc, $from, $to,        $cat),
-SDTG_VAR   =   SDTG_VAR($name,       $type, $flags, $guiflags, $var, $def, $min, $max, $interval, $str, $strhelp, $strval, $proc, $from, $to,        $cat),
-SDTG_OMANY = SDTG_OMANY($name,       $type, $flags, $guiflags, $var, $def,       $max, $full,     $str, $strhelp, $strval, $proc, $from, $to,        $cat),
-SDTC_BOOL  =  SDTC_BOOL(       $var,        $flags, $guiflags, $def,                              $str, $strhelp, $strval, $proc, $from, $to,        $cat),
-SDTC_LIST  =  SDTC_LIST(       $var, $type, $flags, $guiflags, $def,                              $str, $strhelp, $strval, $proc, $from, $to,        $cat),
-SDTC_OMANY = SDTC_OMANY(       $var, $type, $flags, $guiflags, $def,             $max, $full,     $str, $strhelp, $strval, $proc, $from, $to,        $cat),
-SDTC_STR   =   SDTC_STR(       $var, $type, $flags, $guiflags, $def,                              $str, $strhelp, $strval, $proc, $from, $to,        $cat),
-SDTC_VAR   =   SDTC_VAR(       $var, $type, $flags, $guiflags, $def,       $min, $max, $interval, $str, $strhelp, $strval, $proc, $from, $to,        $cat),
-SDT_BOOL   =   SDT_BOOL($base, $var,        $flags, $guiflags, $def,                              $str, $strhelp, $strval, $proc, $from, $to,        $cat),
-SDT_OMANY  =  SDT_OMANY($base, $var, $type, $flags, $guiflags, $def,             $max, $full,     $str, $strhelp, $strval, $proc, $from, $to, $load, $cat),
-SDT_STR    =    SDT_STR($base, $var, $type, $flags, $guiflags, $def,                              $str, $strhelp, $strval, $proc, $from, $to,        $cat),
-SDT_VAR    =    SDT_VAR($base, $var, $type, $flags, $guiflags, $def,       $min, $max, $interval, $str, $strhelp, $strval, $proc, $from, $to,        $cat),
+SDTG_BOOL  =  SDTG_BOOL($name,              $flags, $guiflags, $var, $def,                        $str, $strhelp, $strval, $proc, $from, $to,        $cat, $extra),
+SDTG_VAR   =   SDTG_VAR($name,       $type, $flags, $guiflags, $var, $def, $min, $max, $interval, $str, $strhelp, $strval, $proc, $from, $to,        $cat, $extra),
+SDTG_OMANY = SDTG_OMANY($name,       $type, $flags, $guiflags, $var, $def,       $max, $full,     $str, $strhelp, $strval, $proc, $from, $to,        $cat, $extra),
+SDTC_BOOL  =  SDTC_BOOL(       $var,        $flags, $guiflags, $def,                              $str, $strhelp, $strval, $proc, $from, $to,        $cat, $extra),
+SDTC_LIST  =  SDTC_LIST(       $var, $type, $flags, $guiflags, $def,                              $str, $strhelp, $strval, $proc, $from, $to,        $cat, $extra),
+SDTC_OMANY = SDTC_OMANY(       $var, $type, $flags, $guiflags, $def,             $max, $full,     $str, $strhelp, $strval, $proc, $from, $to,        $cat, $extra),
+SDTC_STR   =   SDTC_STR(       $var, $type, $flags, $guiflags, $def,                              $str, $strhelp, $strval, $proc, $from, $to,        $cat, $extra),
+SDTC_VAR   =   SDTC_VAR(       $var, $type, $flags, $guiflags, $def,       $min, $max, $interval, $str, $strhelp, $strval, $proc, $from, $to,        $cat, $extra),
+SDT_BOOL   =   SDT_BOOL($base, $var,        $flags, $guiflags, $def,                              $str, $strhelp, $strval, $proc, $from, $to,        $cat, $extra),
+SDT_OMANY  =  SDT_OMANY($base, $var, $type, $flags, $guiflags, $def,             $max, $full,     $str, $strhelp, $strval, $proc, $from, $to, $load, $cat, $extra),
+SDT_STR    =    SDT_STR($base, $var, $type, $flags, $guiflags, $def,                              $str, $strhelp, $strval, $proc, $from, $to,        $cat, $extra),
+SDT_VAR    =    SDT_VAR($base, $var, $type, $flags, $guiflags, $def,       $min, $max, $interval, $str, $strhelp, $strval, $proc, $from, $to,        $cat, $extra),
 SDT_NULL   =   SDT_NULL($length, $from, $to),
 SDT_END    = SDT_END()
 
@@ -89,6 +89,7 @@ load     = nullptr
 from     = SL_MIN_VERSION
 to       = SL_MAX_VERSION
 cat      = SC_ADVANCED
+extra    = 0
 
 
 
@@ -644,6 +645,7 @@ interval = 2
 str      = STR_CONFIG_SETTING_LINKGRAPH_INTERVAL
 strval   = STR_JUST_COMMA
 strhelp  = STR_CONFIG_SETTING_LINKGRAPH_INTERVAL_HELPTEXT
+extra    = offsetof(LinkGraphSettings, recalc_interval)
 
 [SDT_VAR]
 base     = GameSettings
@@ -657,6 +659,8 @@ interval = 1
 str      = STR_CONFIG_SETTING_LINKGRAPH_TIME
 strval   = STR_JUST_COMMA
 strhelp  = STR_CONFIG_SETTING_LINKGRAPH_TIME_HELPTEXT
+extra    = offsetof(LinkGraphSettings, recalc_time)
+
 
 [SDT_VAR]
 base     = GameSettings
@@ -671,6 +675,8 @@ interval = 1
 str      = STR_CONFIG_SETTING_DISTRIBUTION_PAX
 strval   = STR_CONFIG_SETTING_DISTRIBUTION_MANUAL
 strhelp  = STR_CONFIG_SETTING_DISTRIBUTION_PAX_HELPTEXT
+extra    = offsetof(LinkGraphSettings, distribution_pax)
+
 
 [SDT_VAR]
 base     = GameSettings
@@ -685,6 +691,8 @@ interval = 1
 str      = STR_CONFIG_SETTING_DISTRIBUTION_MAIL
 strval   = STR_CONFIG_SETTING_DISTRIBUTION_MANUAL
 strhelp  = STR_CONFIG_SETTING_DISTRIBUTION_MAIL_HELPTEXT
+extra    = offsetof(LinkGraphSettings, distribution_mail)
+
 
 [SDT_VAR]
 base     = GameSettings
@@ -699,6 +707,8 @@ interval = 1
 str      = STR_CONFIG_SETTING_DISTRIBUTION_ARMOURED
 strval   = STR_CONFIG_SETTING_DISTRIBUTION_MANUAL
 strhelp  = STR_CONFIG_SETTING_DISTRIBUTION_ARMOURED_HELPTEXT
+extra    = offsetof(LinkGraphSettings, distribution_armoured)
+
 
 [SDT_VAR]
 base     = GameSettings
@@ -713,6 +723,8 @@ interval = 1
 str      = STR_CONFIG_SETTING_DISTRIBUTION_DEFAULT
 strval   = STR_CONFIG_SETTING_DISTRIBUTION_MANUAL
 strhelp  = STR_CONFIG_SETTING_DISTRIBUTION_DEFAULT_HELPTEXT
+extra    = offsetof(LinkGraphSettings, distribution_default)
+
 
 [SDT_VAR]
 base     = GameSettings
@@ -726,6 +738,8 @@ interval = 1
 str      = STR_CONFIG_SETTING_LINKGRAPH_ACCURACY
 strval   = STR_JUST_COMMA
 strhelp  = STR_CONFIG_SETTING_LINKGRAPH_ACCURACY_HELPTEXT
+extra    = offsetof(LinkGraphSettings, accuracy)
+
 
 [SDT_VAR]
 base     = GameSettings
@@ -739,6 +753,8 @@ interval = 5
 str      = STR_CONFIG_SETTING_DEMAND_DISTANCE
 strval   = STR_CONFIG_SETTING_PERCENTAGE
 strhelp  = STR_CONFIG_SETTING_DEMAND_DISTANCE_HELPTEXT
+extra    = offsetof(LinkGraphSettings, demand_distance)
+
 
 [SDT_VAR]
 base     = GameSettings
@@ -752,6 +768,8 @@ interval = 5
 str      = STR_CONFIG_SETTING_DEMAND_SIZE
 strval   = STR_CONFIG_SETTING_PERCENTAGE
 strhelp  = STR_CONFIG_SETTING_DEMAND_SIZE_HELPTEXT
+extra    = offsetof(LinkGraphSettings, demand_size)
+
 
 [SDT_VAR]
 base     = GameSettings
@@ -765,6 +783,8 @@ interval = 5
 str      = STR_CONFIG_SETTING_SHORT_PATH_SATURATION
 strval   = STR_CONFIG_SETTING_PERCENTAGE
 strhelp  = STR_CONFIG_SETTING_SHORT_PATH_SATURATION_HELPTEXT
+extra    = offsetof(LinkGraphSettings, short_path_saturation)
+
 
 ; Vehicles
 
diff --git a/src/table/win32_settings.ini b/src/table/win32_settings.ini
index c7915e32b..d1cc72dd7 100644
--- a/src/table/win32_settings.ini
+++ b/src/table/win32_settings.ini
@@ -15,8 +15,8 @@ static const SettingDescGlobVarList _win32_settings[] = {
 };
 #endif /* _WIN32 */
 [templates]
-SDTG_BOOL = SDTG_BOOL($name,        $flags, $guiflags, $var, $def,                        $str, $strhelp, $strval, $proc, $from, $to, $cat),
-SDTG_VAR  =  SDTG_VAR($name, $type, $flags, $guiflags, $var, $def, $min, $max, $interval, $str, $strhelp, $strval, $proc, $from, $to, $cat),
+SDTG_BOOL = SDTG_BOOL($name,        $flags, $guiflags, $var, $def,                        $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra),
+SDTG_VAR  =  SDTG_VAR($name, $type, $flags, $guiflags, $var, $def, $min, $max, $interval, $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra),
 SDTG_END  = SDTG_END()
 
 [defaults]
@@ -31,6 +31,7 @@ load     = nullptr
 from     = SL_MIN_VERSION
 to       = SL_MAX_VERSION
 cat      = SC_ADVANCED
+extra    = 0
 
 
 
diff --git a/src/table/window_settings.ini b/src/table/window_settings.ini
index fc0c57b39..524e02fdf 100644
--- a/src/table/window_settings.ini
+++ b/src/table/window_settings.ini
@@ -10,8 +10,8 @@ static const SettingDesc _window_settings[] = {
 [post-amble]
 };
 [templates]
-SDT_BOOL = SDT_BOOL($base, $var,        $flags, $guiflags, $def,                        $str, $strhelp, $strval, $proc, $from, $to, $cat),
-SDT_VAR  =  SDT_VAR($base, $var, $type, $flags, $guiflags, $def, $min, $max, $interval, $str, $strhelp, $strval, $proc, $from, $to, $cat),
+SDT_BOOL = SDT_BOOL($base, $var,        $flags, $guiflags, $def,                        $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra),
+SDT_VAR  =  SDT_VAR($base, $var, $type, $flags, $guiflags, $def, $min, $max, $interval, $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra),
 SDT_END  = SDT_END()
 
 [defaults]
@@ -27,6 +27,7 @@ load     = nullptr
 from     = SL_MIN_VERSION
 to       = SL_MAX_VERSION
 cat      = SC_ADVANCED
+extra    = 0