src/engine.cpp

   1 // Plastic Engine
   2 // Copyright (C) 2008  Albert Brown
   3 //
   4 // This program is free software: you can redistribute it and/or modify
   5 // it under the terms of the GNU General Public License as published by
   6 // the Free Software Foundation, either version 3 of the License, or
   7 // (at your option) any later version.
   8 //
   9 // This program is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13 //
  14 // You should have received a copy of the GNU General Public License
  15 // along with this program.  If not, see <http://www.gnu.org/licenses/>
  16
  17 // engine_core: operates subsystems when registered.  Controls timing
  18
  19 #include <stdexcept>
  20 #include <iostream>
  21 #include <string>
  22 #include "SDL.h"
  23
  24 #include "engine.hpp"
  25
  26
  27 void engine_subsystem::tick(state &s)
  28 {
  29     // To be overloaded by derived subsystems
  30 }
  31
  32
  33 engine_core *engine_core::_instance = NULL;
  34
  35 engine_core::engine_core(int argc, char *argv[])
  36 {
  37     // This is cleaner then waiting for the libraries to throw a fit
  38     if(_instance)
  39         throw std::logic_error("Only one engine_core instance "
  40                                "at a time, please.");
  41
  42     // Init SDL (nothing window/video/audio related
  43     if(SDL_Init(SDL_INIT_EVERYTHING))
  44     {
  45         // Something went wrong
  46         std::string msg = std::string("SDL failed to initialize: ")
  47             + SDL_GetError();
  48         throw std::runtime_error(msg.c_str());
  49     }
  50
  51     std::cout << "engine_core initialized." << std::endl;
  52     _instance = this;
  53 }
  54
  55 engine_core::~engine_core()
  56 {
  57     // bring down SDL
  58     SDL_Quit();
  59
  60     _instance = NULL;
  61     std::cout << "engine_core shut down." << std::endl;
  62 }
  63
  64 static bool subsystem_order_sort(std::pair<int, engine_subsystem *> a,
  65                                  std::pair<int, engine_subsystem *> b)
  66 {
  67     return (a.first < b.first);
  68 }
  69
  70 void engine_core::register_subsystem(engine_subsystem *sys, int order)
  71 {
  72     _subsystems.push_back(std::pair<int, engine_subsystem *>(order, sys));
  73     _subsystems.sort(subsystem_order_sort);
  74 }
  75
  76 void engine_core::release_subsystem(engine_subsystem *sys)
  77 {
  78     std::list<std::pair<int, engine_subsystem *> >::iterator it;
  79
  80     for(it = _subsystems.begin(); it != _subsystems.end(); ++it)
  81     {
  82         if(sys == (*it).second)
  83         {
  84             _subsystems.erase(it);
  85             break;
  86         }
  87     }
  88 }
  89
  90
  91 void engine_core::run()
  92 {
  93     // TODO: when we have a conf system, we can un-hardcode these values
  94     _state.running = true;
  95     _state.tickrate = 15;
  96     _state.speed = 100;
  97
  98     while(_state.running)
  99     {
 100         //std::cout << _subsystems.size() << std::endl;
 101         // we'll never get a signal to stop if there are no active subsystems
 102         if(_subsystems.empty())
 103         {
 104             std::cerr << "Run engine with no subsystems??" << std::endl;
 105             break;
 106         }
 107
 108         _state.time = SDL_GetTicks();
 109
 110         // Run each subsystem's 'tick' function
 111         std::list<std::pair<int, engine_subsystem *> >::iterator it;
 112         for(it = _subsystems.begin(); it != _subsystems.end(); ++it)
 113             (*it).second->tick(_state);
 114
 115         SDL_Delay(1000 / _state.tickrate);
 116     }
 117 }