Add: make modal windows update more smooth

Basically, modal windows had their own thread-locking for what
drawing was possible. This is a bit nonsense now we have a
game-thread. And it makes much more sense to do things like
NewGRFScan and GenerateWorld in the game-thread, and not in a
thread next to the game-thread.

This commit changes that: it removes the threads for NewGRFScan
and GenerateWorld, and just runs the code in the game-thread.
On regular intervals it allows the draw-thread to do a tick,
which gives a much smoother look and feel.

It does slow down NewGRFScan and GenerateWorld ever so slightly
as it spends more time on drawing. But the slowdown is not
measureable on my machines (with 700+ NewGRFs / 4kx4k map and
a Debug build).

Running without a game-thread means NewGRFScan and GenerateWorld
are now blocking.

1 files changed, 17 insertions, 63 deletions

diff --git a/src/genworld.cpp b/src/genworld.cpp
index c76fe309d..03fa08819 100644
--- a/src/genworld.cpp
+++ b/src/genworld.cpp
@@ -59,18 +59,10 @@ GenWorldInfo _gw;
 /** Whether we are generating the map or not. */
 bool _generating_world;
 
-/**
- * Tells if the world generation is done in a thread or not.
- * @return the 'threaded' status
- */
-bool IsGenerateWorldThreaded()
-{
-	return _gw.threaded && !_gw.quit_thread;
-}
+class AbortGenerateWorldSignal { };
 
 /**
- * Clean up the 'mess' of generation. That is, show windows again, reset
- * thread variables, and delete the progress window.
+ * Generation is done; show windows again and delete the progress window.
  */
 static void CleanupGeneration()
 {
@@ -78,11 +70,10 @@ static void CleanupGeneration()
 
 	SetMouseCursorBusy(false);
 	/* Show all vital windows again, because we have hidden them */
-	if (_gw.threaded && _game_mode != GM_MENU) ShowVitalWindows();
+	if (_game_mode != GM_MENU) ShowVitalWindows();
 	SetModalProgress(false);
 	_gw.proc     = nullptr;
 	_gw.abortp   = nullptr;
-	_gw.threaded = false;
 
 	DeleteWindowByClass(WC_MODAL_PROGRESS);
 	ShowFirstError();
@@ -97,10 +88,8 @@ static void _GenerateWorld()
 	/* Make sure everything is done via OWNER_NONE. */
 	Backup<CompanyID> _cur_company(_current_company, OWNER_NONE, FILE_LINE);
 
-	std::unique_lock<std::mutex> lock(_modal_progress_work_mutex, std::defer_lock);
 	try {
 		_generating_world = true;
-		lock.lock();
 		if (_network_dedicated) DEBUG(net, 1, "Generating map, please wait...");
 		/* Set the Random() seed to generation_seed so we produce the same map with the same seed */
 		if (_settings_game.game_creation.generation_seed == GENERATE_NEW_SEED) _settings_game.game_creation.generation_seed = _settings_newgame.game_creation.generation_seed = InteractiveRandom();
@@ -136,14 +125,7 @@ static void _GenerateWorld()
 			/* Only generate towns, tree and industries in newgame mode. */
 			if (_game_mode != GM_EDITOR) {
 				if (!GenerateTowns(_settings_game.economy.town_layout)) {
-					_cur_company.Restore();
 					HandleGeneratingWorldAbortion();
-					BasePersistentStorageArray::SwitchMode(PSM_LEAVE_GAMELOOP);
-					if (_network_dedicated) {
-						/* Exit the game to prevent a return to main menu.  */
-						DEBUG(net, 0, "Generating map failed, aborting");
-						_exit_game = true;
-					}
 					return;
 				}
 				GenerateIndustries();
@@ -200,7 +182,6 @@ static void _GenerateWorld()
 		IncreaseGeneratingWorldProgress(GWP_GAME_START);
 
 		CleanupGeneration();
-		lock.unlock();
 
 		ShowNewGRFError();
 
@@ -212,11 +193,19 @@ static void _GenerateWorld()
 			seprintf(name, lastof(name), "dmp_cmds_%08x_%08x.sav", _settings_game.game_creation.generation_seed, _date);
 			SaveOrLoad(name, SLO_SAVE, DFT_GAME_FILE, AUTOSAVE_DIR, false);
 		}
-	} catch (...) {
+	} catch (AbortGenerateWorldSignal&) {
+		CleanupGeneration();
+
 		BasePersistentStorageArray::SwitchMode(PSM_LEAVE_GAMELOOP, true);
 		if (_cur_company.IsValid()) _cur_company.Restore();
-		_generating_world = false;
-		throw;
+
+		if (_network_dedicated) {
+			/* Exit the game to prevent a return to main menu.  */
+			DEBUG(net, 0, "Generating map failed, aborting");
+			_exit_game = true;
+		} else {
+			SwitchToMode(_switch_mode);
+		}
 	}
 }
 
@@ -241,23 +230,6 @@ void GenerateWorldSetAbortCallback(GWAbortProc *proc)
 }
 
 /**
- * This will wait for the thread to finish up his work. It will not continue
- * till the work is done.
- */
-void WaitTillGeneratedWorld()
-{
-	if (!_gw.thread.joinable()) return;
-
-	_modal_progress_work_mutex.unlock();
-	_modal_progress_paint_mutex.unlock();
-	_gw.quit_thread = true;
-	_gw.thread.join();
-	_gw.threaded = false;
-	_modal_progress_work_mutex.lock();
-	_modal_progress_paint_mutex.lock();
-}
-
-/**
  * Initializes the abortion process
  */
 void AbortGeneratingWorld()
@@ -284,11 +256,7 @@ void HandleGeneratingWorldAbortion()
 
 	if (_gw.abortp != nullptr) _gw.abortp();
 
-	CleanupGeneration();
-
-	if (_gw.thread.joinable() && _gw.thread.get_id() == std::this_thread::get_id()) throw OTTDThreadExitSignal();
-
-	SwitchToMode(_switch_mode);
+	throw AbortGenerateWorldSignal();
 }
 
 /**
@@ -308,8 +276,6 @@ void GenerateWorld(GenWorldMode mode, uint size_x, uint size_y, bool reset_setti
 	_gw.abort  = false;
 	_gw.abortp = nullptr;
 	_gw.lc     = _local_company;
-	_gw.quit_thread   = false;
-	_gw.threaded      = true;
 
 	/* This disables some commands and stuff */
 	SetLocalCompany(COMPANY_SPECTATOR);
@@ -328,28 +294,16 @@ void GenerateWorld(GenWorldMode mode, uint size_x, uint size_y, bool reset_setti
 	SetupColoursAndInitialWindow();
 	SetObjectToPlace(SPR_CURSOR_ZZZ, PAL_NONE, HT_NONE, WC_MAIN_WINDOW, 0);
 
-	if (_gw.thread.joinable()) _gw.thread.join();
-
-	if (!UseThreadedModelProgress() || !VideoDriver::GetInstance()->HasGUI() || !StartNewThread(&_gw.thread, "ottd:genworld", &_GenerateWorld)) {
-		DEBUG(misc, 1, "Cannot create genworld thread, reverting to single-threaded mode");
-		_gw.threaded = false;
-		_modal_progress_work_mutex.unlock();
-		_GenerateWorld();
-		_modal_progress_work_mutex.lock();
-		return;
-	}
-
 	UnshowCriticalError();
-	/* Remove any open window */
 	DeleteAllNonVitalWindows();
-	/* Hide vital windows, because we don't allow to use them */
 	HideVitalWindows();
 
-	/* Don't show the dialog if we don't have a thread */
 	ShowGenerateWorldProgress();
 
 	/* Centre the view on the map */
 	if (FindWindowById(WC_MAIN_WINDOW, 0) != nullptr) {
 		ScrollMainWindowToTile(TileXY(MapSizeX() / 2, MapSizeY() / 2), true);
 	}
+
+	_GenerateWorld();
 }