Merge branch 'master' into jgrpp

# Conflicts:
#	src/company_cmd.cpp
#	src/core/geometry_func.cpp
#	src/date.cpp
#	src/genworld_gui.cpp
#	src/gfx.cpp
#	src/object_gui.cpp
#	src/openttd.cpp
#	src/settings_type.h
#	src/video/allegro_v.cpp
#	src/video/dedicated_v.cpp
#	src/video/null_v.cpp
#	src/video/sdl2_v.cpp
#	src/video/sdl_v.cpp
#	src/video/win32_v.cpp

src/video/allegro_v.cpp

@@ -23,7 +23,9 @@
 #include "../core/random_func.hpp"
 #include "../core/math_func.hpp"
 #include "../framerate_type.h"
+#include "../progress.h"
 #include "../thread.h"
+#include "../window_func.h"
 #include "allegro_v.h"
 #include <allegro.h>
 
@@ -235,7 +237,7 @@ bool VideoDriver_Allegro::ClaimMousePointer()
 	return true;
 }
 
-struct VkMapping {
+struct AllegroVkMapping {
 	uint16 vk_from;
 	byte vk_count;
 	byte map_to;
@@ -244,7 +246,7 @@ struct VkMapping {
 #define AS(x, z) {x, 0, z}
 #define AM(x, y, z, w) {x, y - x, z}
 
-static const VkMapping _vk_mapping[] = {
+static const AllegroVkMapping _vk_mapping[] = {
 	/* Pageup stuff + up/down */
 	AM(KEY_PGUP, KEY_PGDN, WKC_PAGEUP, WKC_PAGEDOWN),
 	AS(KEY_UP,     WKC_UP),
@@ -302,7 +304,7 @@ static uint32 ConvertAllegroKeyIntoMy(WChar *character)
 	int scancode;
 	int unicode = ureadkey(&scancode);
 
-	const VkMapping *map;
+	const AllegroVkMapping *map;
 	uint key = 0;
 
 	for (map = _vk_mapping; map != endof(_vk_mapping); ++map) {
@@ -445,34 +447,16 @@ void VideoDriver_Allegro::Stop()
 	if (--_allegro_instance_count == 0) allegro_exit();
 }
 
-#if defined(UNIX) || defined(__OS2__)
-# include <sys/time.h> /* gettimeofday */
-
-static uint32 GetTime()
-{
-	struct timeval tim;
-
-	gettimeofday(&tim, nullptr);
-	return tim.tv_usec / 1000 + tim.tv_sec * 1000;
-}
-#else
-static uint32 GetTime()
-{
-	return GetTickCount();
-}
-#endif
-
-
 void VideoDriver_Allegro::MainLoop()
 {
-	uint32 cur_ticks = GetTime();
-	uint32 last_cur_ticks = cur_ticks;
-	uint32 next_tick = cur_ticks + MILLISECONDS_PER_TICK;
+	auto cur_ticks = std::chrono::steady_clock::now();
+	auto last_realtime_tick = cur_ticks;
+	auto next_game_tick = cur_ticks;
+	auto next_draw_tick = cur_ticks;
 
 	CheckPaletteAnim();
 
 	for (;;) {
-		uint32 prev_cur_ticks = cur_ticks; // to check for wrapping
 		InteractiveRandom(); // randomness
 
 		PollEvent();
@@ -491,11 +475,33 @@ void VideoDriver_Allegro::MainLoop()
 			_fast_forward = 0;
 		}
 
-		cur_ticks = GetTime();
-		if (cur_ticks >= next_tick || (_fast_forward && !_pause_mode) || cur_ticks < prev_cur_ticks) {
-			_realtime_tick += cur_ticks - last_cur_ticks;
-			last_cur_ticks = cur_ticks;
-			next_tick = cur_ticks + MILLISECONDS_PER_TICK;
+		cur_ticks = std::chrono::steady_clock::now();
+
+		/* If more than a millisecond has passed, increase the _realtime_tick. */
+		if (cur_ticks - last_realtime_tick > std::chrono::milliseconds(1)) {
+			auto delta = std::chrono::duration_cast<std::chrono::milliseconds>(cur_ticks - last_realtime_tick);
+			IncreaseRealtimeTick(delta.count());
+			last_realtime_tick += delta;
+		}
+
+		if (cur_ticks >= next_game_tick || (_fast_forward && !_pause_mode)) {
+			if (_fast_forward && !_pause_mode) {
+				next_game_tick = cur_ticks + this->GetGameInterval();
+			} else {
+				next_game_tick += this->GetGameInterval();
+				/* Avoid next_game_tick getting behind more and more if it cannot keep up. */
+				if (next_game_tick < cur_ticks - ALLOWED_DRIFT * this->GetGameInterval()) next_game_tick = cur_ticks;
+			}
+
+			GameLoop();
+			GameLoopPaletteAnimations();
+		}
+
+		/* Prevent drawing when switching mode, as windows can be removed when they should still appear. */
+		if (cur_ticks >= next_draw_tick && (_switch_mode == SM_NONE || HasModalProgress())) {
+			next_draw_tick += this->GetDrawInterval();
+			/* Avoid next_draw_tick getting behind more and more if it cannot keep up. */
+			if (next_draw_tick < cur_ticks - ALLOWED_DRIFT * this->GetDrawInterval()) next_draw_tick = cur_ticks;
 
 			bool old_ctrl_pressed = _ctrl_pressed;
 			bool old_shift_pressed = _shift_pressed;
@@ -513,17 +519,22 @@ void VideoDriver_Allegro::MainLoop()
 			if (old_ctrl_pressed != _ctrl_pressed) HandleCtrlChanged();
 			if (old_shift_pressed != _shift_pressed) HandleShiftChanged();
 
-			GameLoop();
-			GameLoopPaletteAnimations();
-
+			InputLoop();
 			UpdateWindows();
 			CheckPaletteAnim();
+
 			DrawSurfaceToScreen();
-		} else {
-			CSleep(1);
-			NetworkDrawChatMessage();
-			DrawMouseCursor();
-			DrawSurfaceToScreen();
+		}
+
+		/* If we are not in fast-forward, create some time between calls to ease up CPU usage. */
+		if (!_fast_forward || _pause_mode) {
+			/* See how much time there is till we have to process the next event, and try to hit that as close as possible. */
+			auto next_tick = std::min(next_draw_tick, next_game_tick);
+			auto now = std::chrono::steady_clock::now();
+
+			if (next_tick > now) {
+				std::this_thread::sleep_for(next_tick - now);
+			}
 		}
 	}
 }