Add start parameter to FindArg()

Before this change, the FindArg() function was well suited for finding
command-line options that only appear once. It’s very resonable for
FindArg() to only support arguments that appear one time because Descent
3 doesn’t have any command-line options that should be specified
multiple times. For example, it would be pretty pointless to do
something like this:

  Descent3 -useexedir -useexedir

or something like this:

  Descent3 -aspect 1.0 -aspect 1.6

It does, however, sometimes makes sense to repeat command-line options for
other applications. For example, you can specify -e multiple times when
running grep [1]:

  grep -e pattern1 -e pattern2 file.txt

The main motivation behind this change is to make it easier to create a
future commit. That future commit will add a command-line option named
“-additionaldir”. -additionaldir will be similar to grep’s -e flag. In
other words, it will make sense to do this:

  Descent3 -additionaldir /home/user/dir1 -additionaldir /home/user/dir2

Adding a start parameter to FindArg() now will make it easier for that
future commit parse the multiple occurrences of -additionaldir.

Unfortunately, there is one drawback to this change. In Descent3/args.h,
I gave the start parameter a default value of 1. Giving the start
parameter a default value allowed me to add the start parameter without
having to change most of the calls to the FindArg() function. There was
one situation where I had to change how FindArg was called, though.
DLLFindArg is a pointer to the FindArg() function. You cannot give
function pointers default arguments [2]. As a result,
FindArg("-someargument") works, but DLLFindArg("-someargument") does
not. Instead, you have to write DLLFindArg("-someargument", 1) which is
a little bit annoying.

[1]: <https://www.gnu.org/software/grep/manual/html_node/Matching-Control.html>
[2]: <https://stackoverflow.com/a/9760710/7593853>

Descent3/args.cpp

@@ -103,22 +103,26 @@ const char *SkipArgPrefix(const char *arg) {
   return arg;
 }
 
-int FindArg(const char *which) {
+int FindArg(const char *which, int start) {
   if (which == nullptr)
     return 0;
 
   auto which_matches = [which = SkipArgPrefix(which)](char *arg) -> bool {
     return strcasecmp(which, SkipArgPrefix(arg)) == 0;
   };
 
-  for (int i = 1; i <= TotalArgs; i++) {
+  for (int i = start; i <= TotalArgs; i++) {
     if (which_matches(GameArgs[i])) {
       mprintf(0, "FindArg: Found [%s] at argument index (%d).", which, i);
       return i;
     }
   }
 
-  mprintf(0, "FindArg: Did not find [%s] on command line.", which);
+  if (start == 1) {
+    mprintf(0, "FindArg: Did not find [%s] on command line.", which);
+  } else {
+    mprintf(0, "FindArg: Did not find [%s] on command line at index %i or after index %i.", which, start, start);
+  }
   return 0;
 }
 

Descent3/args.h

@@ -28,7 +28,7 @@ void GatherArgs(const char *str);
 void GatherArgs(char **argv);
 
 // Returns index of argument sought, or 0 if not found
-int FindArg(const char *which);
+int FindArg(const char *which, int start = 1);
 int FindArgChar(const char *which, char singleCharArg);
 
 const char *GetArg(int index);

netgames/dmfc/dmfcbase.cpp

@@ -1207,7 +1207,7 @@ void DMFCBase::GameInit(int teams) {
   Remote_Initialize();
 
   // see if we should display Outrage logo at all
-  if (DLLFindArg("-nooutragelogo"))
+  if (DLLFindArg("-nooutragelogo", 1))
     m_bDisplayOutrageLogo = false;
   else
     m_bDisplayOutrageLogo = true;
@@ -4916,7 +4916,7 @@ void DMFCBase::ParseStartupScript(void) {
 
   int autoexec_arg = -1;
 
-  if ((autoexec_arg = DLLFindArg("-autoexec")) != 0) {
+  if ((autoexec_arg = DLLFindArg("-autoexec", 1)) != 0) {
     // a specific autoexec.dmfc file was specified, use that
     strcpy(path, GetGameArg(autoexec_arg + 1));
     mprintf(0, "Override AUTOEXEC.DMFC to %s\n", path);

netgames/dmfc/dmfcfunctions.cpp

@@ -483,7 +483,7 @@ void (*DLLg3_DrawSpecialLine)(g3Point *p0, g3Point *p1);
 void (*DLLg3_DrawPlanarRotatedBitmap)(vector *pos, vector *norm, angle rot_angle, float width,
                                                    float height, int bm);
 void (*DLLPlayerStopSounds)(int slot);
-int (*DLLFindArg)(const char *which);
+int (*DLLFindArg)(const char *which, int start);
 int (*DLLFireWeaponFromObject)(object *obj, int weapon_num, int gun_num, bool f_force_forward,
                                             bool f_force_target);
 int (*DLLCreateAndFireWeapon)(vector *pos, vector *dir, object *parent, int weapon_num);

netgames/includes/gamedll_header.h

@@ -1591,7 +1591,7 @@ typedef void (*PlayerStopSounds_fp)(int slot);
 DMFCDLLOUT(PlayerStopSounds_fp DLLPlayerStopSounds;)
 
 // Returns index of argument sought, or 0 if not found
-typedef int (*FindArg_fp)(const char *which);
+typedef decltype(&FindArg) FindArg_fp;
 DMFCDLLOUT(FindArg_fp DLLFindArg;)
 
 // Given an object and a weapon, fires a shot from that object