[S4t3K]

@Fokus :

pawn Code:

#define PRESSED(%0) \
    (((newkeys & (%0)) == (%0)) && ((oldkeys & (%0)) != (%0)))

Use :

pawn Code:

public OnPlayerKeyStateChange(playerid, newkeys, oldkeys)
{
      if(PRESSED(KEY_FIRE)) // The player presses "KEY_FIRE"
}

@Dubya : I think there's a way of doing it using a variable for "newkeys" and a "oldkeys" but in your player class. And then, when you must call the callback, for example in ProcessTick, (supposing you store your connected players in a std::list<Player*>, where Player is your player class and you store your AMXs in a std::list<AMX*>), do like this :

pawn Code:

// In your callback to detect keys
// player is a pointer to the player class

if(playerReleaseKey) // Do this condition by yourself, I don't know how your code is done exactly
      player->oldkeys = player->newkeys;
      player->newkeys &= KEY_PRESSED; // KEY_PRESSED is the bit value of the key the player presses
if(playerPressKey)
      player->oldkeys = player->newkeys;
      player->newkeys |= KEY_PRESSED; // same as above

// Somewhere else

PLUGIN_EXPORT void PLUGIN_CALL ProcessTick()
{
      int idx;
      for(std::list<Player*>::iterator it = players.begin(); it != players.end(); ++it)
      {
            if((*it)->newkeys != 0)
            {
                  for(std::list<AMX*>::iterator amx = amx_list.begin(); amx != amx_list.end(); ++amx_list)
                  {
                        if(amx_FindPublic(*amx, "OnVirtualKeyStateChange", &idx) != AMX_ERR_NONE) continue;
                        amx_Push(*amx, player->oldkeys);
                        amx_Push(*amx, player->newkeys);
                        amx_Push(*amx, player->playerid);
                        amx_Exec(*amx, NULL, idx);
                  }
            }
      }
}

And it will search for the forwarded callback "OnVirtualKeyStateChange(playerid, newkeys, oldkeys)", and then call it.
This way, you can have a per-player callback.

If it's not that, then sorry I haven't understood.