From e50368114dc9a687cf3d15156cc006b5ac223c91 Mon Sep 17 00:00:00 2001
From: Cyp <cyp@wz2100.net>
Date: Sun, 11 Dec 2011 15:52:39 +0100
Subject: [PATCH] Allow multiple logical updates per rendered frame.

Allows maintaining game speed when the GPU can't keep up.
---
 lib/gamelib/gtime.cpp | 19 ++++++++++++++-----
 src/keybind.cpp       |  7 +++++--
 src/loop.cpp          | 31 ++++++++++++++++++++-----------
 3 files changed, 39 insertions(+), 18 deletions(-)

diff --git a/lib/gamelib/gtime.cpp b/lib/gamelib/gtime.cpp
index 08fc75c02..c09405ad9 100644
--- a/lib/gamelib/gtime.cpp
+++ b/lib/gamelib/gtime.cpp
@@ -32,6 +32,10 @@
 
 #include <time.h>
 
+// Maximum seconds per frame.
+// If not reaching the goal, force graphics updates, even if we aren't doing enough game state updates to maintain game speed.
+#define MAXIMUM_SPF 1/4
+
 /* See header file for documentation */
 UDWORD gameTime = 0, deltaGameTime = 0, graphicsTime = 0, deltaGraphicsTime = 0, realTime = 0, deltaRealTime = 0;
 float graphicsTimeFraction = 0.0, realTimeFraction = 0.0;
@@ -188,10 +192,10 @@ void gameTimeUpdate()
 		{
 			unsigned player;
 
-			// Pause time, since we are waiting GAME_GAME_TIME from other players.
-			scaledCurrTime = graphicsTime;
+			// Pause time at current game time, since we are waiting GAME_GAME_TIME from other players.
+			scaledCurrTime = gameTime;
 			baseTime = currTime;
-			timeOffset = graphicsTime;
+			timeOffset = gameTime;
 
 			debug(LOG_SYNC, "Waiting for other players. gameTime = %u, player times are {%s}", gameTime, listToString("%u", ", ", gameQueueTime, gameQueueTime + game.maxPlayers).c_str());
 			mayUpdate = false;
@@ -212,10 +216,10 @@ void gameTimeUpdate()
 		// Adjust deltas.
 		if (scaledCurrTime >= gameTime && mayUpdate)
 		{
-			if (scaledCurrTime > gameTime + GAME_TICKS_PER_UPDATE)
+			if (scaledCurrTime > gameTime + GAME_TICKS_PER_SEC*MAXIMUM_SPF)
 			{
 				// Game isn't updating fast enough...
-				uint32_t slideBack = deltaGraphicsTime - GAME_TICKS_PER_UPDATE;
+				uint32_t slideBack = deltaGraphicsTime - GAME_TICKS_PER_SEC*MAXIMUM_SPF;
 				baseTime += slideBack / modifier;  // adjust the addition to base time
 				deltaGraphicsTime -= slideBack;
 			}
@@ -235,6 +239,11 @@ void gameTimeUpdate()
 			deltaGameTime = 0;
 		}
 
+		if (deltaGameTime != 0)
+		{
+			deltaGraphicsTime = 0;  // Don't update graphics until game state is updated.
+		}
+
 		// Store the game and graphics times
 		gameTime     += deltaGameTime;
 		graphicsTime += deltaGraphicsTime;
diff --git a/src/keybind.cpp b/src/keybind.cpp
index 334572295..ba41ee133 100644
--- a/src/keybind.cpp
+++ b/src/keybind.cpp
@@ -2575,9 +2575,12 @@ float available_speed[] = {
 	5.f / 2.f,	// n
 	3.f / 1.f,	// n
 	10.f / 1.f,	// n
-	20.f / 1.f	// n
+	20.f / 1.f,     // n
+	30.f / 1.f,     // n
+	60.f / 1.f,     // n
+	100.f / 1.f,    // n
 };
-unsigned int nb_available_speeds = 12;
+unsigned int nb_available_speeds = ARRAY_SIZE(available_speed);
 
 void kf_SpeedUp( void )
 {
diff --git a/src/loop.cpp b/src/loop.cpp
index f35cd6658..51455874d 100644
--- a/src/loop.cpp
+++ b/src/loop.cpp
@@ -671,25 +671,34 @@ static void gameStateUpdate()
 /* The main game loop */
 GAMECODE gameLoop(void)
 {
-	bool            gameTicked;                     // true iff we are doing a logical update.
 	static uint32_t lastFlushTime = 0;
 
-	// Receive NET_BLAH messages.
-	// Receive GAME_BLAH messages, and if it's time, process exactly as many GAME_BLAH messages as required to be able to tick the gameTime.
-	recvMessage();
-
-	// Update gameTime and graphicsTime, and corresponding deltas. Note that gameTime and graphicsTime pause, if we aren't getting our GAME_GAME_TIME messages.
-	gameTimeUpdate();
-	gameTicked = deltaGameTime != 0;
-
-	if (gameTicked)
+	bool didTick = false;
+	while (true)
 	{
+		// Receive NET_BLAH messages.
+		// Receive GAME_BLAH messages, and if it's time, process exactly as many GAME_BLAH messages as required to be able to tick the gameTime.
+		recvMessage();
+
+		// Update gameTime and graphicsTime, and corresponding deltas. Note that gameTime and graphicsTime pause, if we aren't getting our GAME_GAME_TIME messages.
+		gameTimeUpdate();
+
+		if (deltaGameTime == 0)
+		{
+			break;  // Not doing a game state update.
+		}
+		didTick = true;
+
 		ASSERT(!paused && !gameUpdatePaused() && !editPaused(), "Nonsensical pause values.");
 
+		syncDebug("Begin game state update, gameTime = %d", gameTime);
 		gameStateUpdate();
+		syncDebug("End game state update, gameTime = %d", gameTime);
+
+		ASSERT(deltaGraphicsTime == 0, "Shouldn't update graphics and game state at once.");
 	}
 
-	if (gameTicked || realTime - lastFlushTime < 400u)
+	if (didTick || realTime - lastFlushTime < 400u)
 	{
 		lastFlushTime = realTime;
 		NETflush();  // Make sure the game time tick message is really sent over the network, and that we aren't waiting too long to send data.