Strict 60 Hz update rate without busyloops.

code/classes.h

@@ -185,6 +185,8 @@ class Math {
 
 
 class Graphics {
+		unsigned long frameLimit;
+		int thirds;
 
 	public:
 
@@ -446,8 +448,28 @@ class Graphics {
 	void updateScreen()
 	{
 		SDL_Flip(screen);
-		// Give the audio (and possibly the X server) time to work...
+	}
-		SDL_Delay(1);
+
+	/*
+	 * Delay until the next 60 Hz frame
+	 */
+	void delayFrame()
+	{
+		unsigned long now = SDL_GetTicks();
+
+		// Add 16 2/3 to frameLimit
+		frameLimit += 16;
+		if(thirds >= 2) {
+			thirds = 0;
+		} else {
+			thirds++;
+			frameLimit++;
+		}
+
+		if(now < frameLimit)
+			SDL_Delay(frameLimit - now);
+		else
+			frameLimit = now;
 	}
 
 	/*

code/game.cpp

@@ -108,7 +108,6 @@ int mainGameLoop()
 	engine.musicVolume = 100;
 
 	int rtn = 0;
-	unsigned long frameLimit = SDL_GetTicks();
 
 	int allowableAliens = 999999999;
 
@@ -276,13 +275,7 @@ int mainGameLoop()
 			break;
 		}
 
-		// (Attempt to) Limit us to 60 frame a second
+		graphics.delayFrame();
-		while (SDL_GetTicks() < (frameLimit + 16))
-		{
-			// Do nothing. If we were to insert an SDL_Delay(1) in here
-			// then we would actually lose around 10 frames per second!!
-		}
-		frameLimit = SDL_GetTicks();
 	}
 
 	graphics.flushBuffer();

code/intermission.cpp

@@ -596,8 +596,6 @@ int galaxyMap()
 	else
 		player.shield = player.maxShield;
 
-	unsigned long frameLimit = SDL_GetTicks();
-
 	flushInput();
 	engine.keyState[SDLK_LCTRL] = engine.keyState[SDLK_RCTRL] = engine.keyState[SDLK_SPACE] = 0;
 	engine.done = 0;
@@ -832,9 +830,7 @@ int galaxyMap()
 		engine.keyState[SDLK_LCTRL] = engine.keyState[SDLK_RCTRL] = engine.keyState[SDLK_SPACE] = 0;
 		doCursor();
 
-		// Limit us to 60 frame a second
+		graphics.delayFrame();
-		while (SDL_GetTicks() < (frameLimit + 16)){}
-		frameLimit = SDL_GetTicks();
 	}
 
 	Mix_HaltMusic();

code/script.cpp

@@ -237,7 +237,6 @@ void doCutscene(int scene)
 		enemy[i].engineY = (enemy[i].image[0]->h / 2);
 	}
 
-	unsigned long frameLimit = SDL_GetTicks();
 	signed char showMessage = 0;
 	signed char currentMessage = -1;
 	int timer = 60 * 4;
@@ -298,8 +297,7 @@ void doCutscene(int scene)
 		if ((showMessage) && (graphics.messageBox != NULL))
 			graphics.blit(graphics.messageBox, (800 - graphics.messageBox->w) / 2, 500);
 
-		while (SDL_GetTicks() < (frameLimit + 16)){}
+		graphics.delayFrame();
-		frameLimit = SDL_GetTicks();
 
 		if (engine.keyState[SDLK_ESCAPE])
 			break;

code/title.cpp

@@ -234,7 +234,6 @@ int doTitle()
 	signed char menuType = 0;
 
 	graphics.drawBackGround();
-	unsigned long frameLimit = SDL_GetTicks();
 
 	engine.done = 0;
 	flushInput();
@@ -453,8 +452,7 @@ int doTitle()
 			engine.keyState[SDLK_LCTRL] = engine.keyState[SDLK_RCTRL] = engine.keyState[SDLK_SPACE] = 0;
 		}
 
-		while (SDL_GetTicks() < (frameLimit + 16)){}
+		graphics.delayFrame();
-		frameLimit = SDL_GetTicks();
 	}
 
 	Mix_HaltMusic();
@@ -529,8 +527,6 @@ void showStory()
 	graphics.blit(graphics.background, 0, 0);
 	graphics.flushBuffer();
 
-	unsigned long frameLimit = SDL_GetTicks();
-
 	flushInput();
 	engine.keyState[SDLK_LCTRL] = engine.keyState[SDLK_RCTRL] = engine.keyState[SDLK_SPACE] = 0;
 
@@ -558,8 +554,7 @@ void showStory()
 			break;
 		}
 
-		while (SDL_GetTicks() < (frameLimit + 16)){}
+		graphics.delayFrame();
-		frameLimit = SDL_GetTicks();
 	}
 }
 
@@ -593,7 +588,6 @@ void gameover()
 	int x = (800 - gameover->w) / 2;
 	int y = (600 - gameover->h) / 2;
 
-	unsigned long frameLimit = SDL_GetTicks();
 	graphics.updateScreen();
 
 	flushInput();
@@ -613,9 +607,7 @@ void gameover()
 		y = ((600 - gameover->h) / 2)  - Math::rrand(-2, 2);
 		graphics.blit(gameover, x,  y);
 
-		// Limit us to 60 frame a second
+		graphics.delayFrame();
-		while (SDL_GetTicks() < (frameLimit + 16)){}
-		frameLimit = SDL_GetTicks();
 	}
 
 	SDL_FreeSurface(gameover);
@@ -693,7 +685,6 @@ void doCredits()
  	SDL_Delay(10000);
 	graphics.drawBackGround();
 
-	unsigned long frameLimit = SDL_GetTicks();
 	engine.done = 0;
 
 	lastCredit = numberOfCredits - 1;
@@ -724,8 +715,7 @@ void doCredits()
 		SDL_FillRect(graphics.screen, &r1, graphics.black);
 		SDL_FillRect(graphics.screen, &r2, graphics.black);
 
-		while (SDL_GetTicks() < (frameLimit + 16)){}
+		graphics.delayFrame();
-		frameLimit = SDL_GetTicks();
 	}
 
 	for (int i = 0 ; i < numberOfCredits ; i++)