Change: Split up Window::OnTick into OnGameTick and OnRealtimeTick. Adjust timers to work with milliseconds instead of ticks.

21 files changed, 144 insertions, 64 deletions

diff --git a/src/airport_gui.cpp b/src/airport_gui.cpp
index 6437f236c..243f91b24 100644
--- a/src/airport_gui.cpp
+++ b/src/airport_gui.cpp
@@ -543,7 +543,7 @@ public:
 		this->SelectFirstAvailableAirport(false);
 	}
 
-	virtual void OnTick()
+	virtual void OnRealtimeTick(uint delta_ms)
 	{
 		CheckRedrawStationCoverage(this);
 	}
diff --git a/src/dock_gui.cpp b/src/dock_gui.cpp
index f09720b35..e2224dfa2 100644
--- a/src/dock_gui.cpp
+++ b/src/dock_gui.cpp
@@ -451,7 +451,7 @@ public:
 		}
 	}
 
-	virtual void OnTick()
+	virtual void OnRealtimeTick(uint delta_ms)
 	{
 		CheckRedrawStationCoverage(this);
 	}
diff --git a/src/graph_gui.cpp b/src/graph_gui.cpp
index 48b8c4c84..4f8fe6870 100644
--- a/src/graph_gui.cpp
+++ b/src/graph_gui.cpp
@@ -539,7 +539,7 @@ public:
 		if (widget == WID_CV_KEY_BUTTON) ShowGraphLegend();
 	}
 
-	virtual void OnTick()
+	virtual void OnGameTick()
 	{
 		this->UpdateStatistics(false);
 	}
@@ -998,9 +998,9 @@ struct PaymentRatesGraphWindow : BaseGraphWindow {
 		}
 	}
 
-	virtual void OnTick()
+	virtual void OnGameTick()
 	{
-		/* Override default OnTick */
+		/* Override default OnGameTick */
 	}
 
 	/**
@@ -1239,7 +1239,7 @@ public:
 	}
 
 
-	virtual void OnTick()
+	virtual void OnGameTick()
 	{
 		if (this->companies.NeedResort()) {
 			this->SetDirty();
@@ -1472,7 +1472,7 @@ struct PerformanceRatingDetailWindow : Window {
 		}
 	}
 
-	virtual void OnTick()
+	virtual void OnGameTick()
 	{
 		if (_pause_mode != PM_UNPAUSED) return;
 
diff --git a/src/group_gui.cpp b/src/group_gui.cpp
index aef934ccf..dbb1baa0f 100644
--- a/src/group_gui.cpp
+++ b/src/group_gui.cpp
@@ -858,7 +858,7 @@ public:
 		this->SetDirty();
 	}
 
-	virtual void OnTick()
+	virtual void OnGameTick()
 	{
 		if (_pause_mode != PM_UNPAUSED) return;
 		if (this->groups.NeedResort() || this->vehicles.NeedResort()) {
diff --git a/src/industry_gui.cpp b/src/industry_gui.cpp
index 98c9edda2..50ef28359 100644
--- a/src/industry_gui.cpp
+++ b/src/industry_gui.cpp
@@ -647,7 +647,7 @@ public:
 		if (success && !_settings_client.gui.persistent_buildingtools) ResetObjectToPlace();
 	}
 
-	virtual void OnTick()
+	virtual void OnGameTick()
 	{
 		if (_pause_mode != PM_UNPAUSED) return;
 		if (!this->timer_enabled) return;
diff --git a/src/main_gui.cpp b/src/main_gui.cpp
index 199546d43..12ee574bb 100644
--- a/src/main_gui.cpp
+++ b/src/main_gui.cpp
@@ -235,10 +235,11 @@ enum {
 
 struct MainWindow : Window
 {
-	uint refresh;
+	int refresh;
 
-	static const uint LINKGRAPH_REFRESH_PERIOD = 0xff;
-	static const uint LINKGRAPH_DELAY = 0xf;
+	/* Refresh times in milliseconds */
+	static const uint LINKGRAPH_REFRESH_PERIOD = 7650;
+	static const uint LINKGRAPH_DELAY = 450;
 
 	MainWindow(WindowDesc *desc) : Window(desc)
 	{
@@ -253,9 +254,9 @@ struct MainWindow : Window
 		this->refresh = LINKGRAPH_DELAY;
 	}
 
-	virtual void OnTick()
+	virtual void OnRealtimeTick(uint delta_ms)
 	{
-		if (--this->refresh > 0) return;
+		if (!TimerElapsed(this->refresh, delta_ms)) return;
 
 		this->refresh = LINKGRAPH_REFRESH_PERIOD;
 
diff --git a/src/misc_gui.cpp b/src/misc_gui.cpp
index b122d172d..31faae2d4 100644
--- a/src/misc_gui.cpp
+++ b/src/misc_gui.cpp
@@ -454,15 +454,16 @@ static const char * const _credits[] = {
 
 struct AboutWindow : public Window {
 	int text_position;                       ///< The top of the scrolling text
-	byte counter;                            ///< Used to scroll the text every 5 ticks
 	int line_height;                         ///< The height of a single line
 	static const int num_visible_lines = 19; ///< The number of lines visible simultaneously
 
+	static const uint TIMER_INTERVAL = 150;  ///< Scrolling interval in ms
+	uint timer;
+
 	AboutWindow() : Window(&_about_desc)
 	{
 		this->InitNested(WN_GAME_OPTIONS_ABOUT);
 
-		this->counter = 5;
 		this->text_position = this->GetWidget<NWidgetBase>(WID_A_SCROLLING_TEXT)->pos_y + this->GetWidget<NWidgetBase>(WID_A_SCROLLING_TEXT)->current_y;
 	}
 
@@ -502,11 +503,11 @@ struct AboutWindow : public Window {
 		}
 	}
 
-	virtual void OnTick()
+	virtual void OnRealtimeTick(uint delta_ms)
 	{
-		if (--this->counter == 0) {
-			this->counter = 5;
-			this->text_position--;
+		uint count = CountIntervalElapsed(this->timer, delta_ms, TIMER_INTERVAL);
+		if (count > 0) {
+			this->text_position -= count;
 			/* If the last text has scrolled start a new from the start */
 			if (this->text_position < (int)(this->GetWidget<NWidgetBase>(WID_A_SCROLLING_TEXT)->pos_y - lengthof(_credits) * this->line_height)) {
 				this->text_position = this->GetWidget<NWidgetBase>(WID_A_SCROLLING_TEXT)->pos_y + this->GetWidget<NWidgetBase>(WID_A_SCROLLING_TEXT)->current_y;
diff --git a/src/newgrf_gui.cpp b/src/newgrf_gui.cpp
index d506eb026..0b0512544 100644
--- a/src/newgrf_gui.cpp
+++ b/src/newgrf_gui.cpp
@@ -403,7 +403,7 @@ struct NewGRFParametersWindow : public Window {
 						par_info->SetValue(this->grf_config, val);
 
 						this->clicked_button = num;
-						this->timeout = 5;
+						this->timeout = 150;
 					}
 				} else if (par_info->type == PTYPE_UINT_ENUM && !par_info->complete_labels && click_count >= 2) {
 					/* Display a query box so users can enter a custom value. */
@@ -483,9 +483,9 @@ struct NewGRFParametersWindow : public Window {
 		}
 	}
 
-	virtual void OnTick()
+	virtual void OnRealtimeTick(uint delta_ms)
 	{
-		if (--this->timeout == 0) {
+		if (TimerElapsed(this->timeout, delta_ms)) {
 			this->clicked_button = UINT_MAX;
 			this->SetDirty();
 		}
diff --git a/src/news_gui.cpp b/src/news_gui.cpp
index 71a39eb3a..183b27b90 100644
--- a/src/news_gui.cpp
+++ b/src/news_gui.cpp
@@ -260,11 +260,13 @@ struct NewsWindow : Window {
 	uint16 chat_height;   ///< Height of the chat window.
 	uint16 status_height; ///< Height of the status bar window
 	const NewsItem *ni;   ///< News item to display.
-	static uint duration; ///< Remaining time for showing current news message (may only be accessed while a news item is displayed).
+	static int duration;  ///< Remaining time for showing the current news message (may only be access while a news item is displayed).
+
+	uint timer;
 
 	NewsWindow(WindowDesc *desc, const NewsItem *ni) : Window(desc), ni(ni)
 	{
-		NewsWindow::duration = 555;
+		NewsWindow::duration = 16650;
 		const Window *w = FindWindowByClass(WC_SEND_NETWORK_MSG);
 		this->chat_height = (w != NULL) ? w->height : 0;
 		this->status_height = FindWindowById(WC_STATUS_BAR, 0)->height;
@@ -485,11 +487,18 @@ struct NewsWindow : Window {
 		this->SetWindowTop(newtop);
 	}
 
-	virtual void OnTick()
+	virtual void OnRealtimeTick(uint delta_ms)
 	{
-		/* Scroll up newsmessages from the bottom in steps of 4 pixels */
-		int newtop = max(this->top - 4, _screen.height - this->height - this->status_height - this->chat_height);
-		this->SetWindowTop(newtop);
+		int count = CountIntervalElapsed(this->timer, delta_ms, 15);
+		if (count > 0) {
+			/* Scroll up newsmessages from the bottom */
+			int newtop = max(this->top - 2 * count, _screen.height - this->height - this->status_height - this->chat_height);
+			this->SetWindowTop(newtop);
+		}
+
+		/* Decrement the news timer. We don't need to action an elapsed event here,
+		 * so no need to use TimerElapsed(). */
+		if (NewsWindow::duration > 0) NewsWindow::duration -= delta_ms;
 	}
 
 private:
@@ -536,7 +545,7 @@ private:
 	}
 };
 
-/* static */ uint NewsWindow::duration = 0; // Instance creation.
+/* static */ int NewsWindow::duration = 0; // Instance creation.
 
 
 /** Open up an own newspaper window for the news item */
@@ -588,11 +597,8 @@ static bool ReadyForNextItem()
 	 * Check if the status bar message is still being displayed? */
 	if (IsNewsTickerShown()) return false;
 
-	/* Newspaper message, decrement duration counter */
-	if (NewsWindow::duration != 0) NewsWindow::duration--;
-
 	/* neither newsticker nor newspaper are running */
-	return (NewsWindow::duration == 0 || FindWindowById(WC_NEWS_WINDOW, 0) == NULL);
+	return (NewsWindow::duration <= 0 || FindWindowById(WC_NEWS_WINDOW, 0) == NULL);
 }
 
 /** Move to the next news item */
diff --git a/src/openttd.cpp b/src/openttd.cpp
index 3d25f5d3d..fdde19140 100644
--- a/src/openttd.cpp
+++ b/src/openttd.cpp
@@ -76,7 +76,7 @@ void IncreaseDate();
 void DoPaletteAnimations();
 void MusicLoop();
 void ResetMusic();
-void CallWindowTickEvent();
+void CallWindowGameTickEvent();
 bool HandleBootstrap();
 
 extern Company *DoStartupNewCompany(bool is_ai, CompanyID company = INVALID_COMPANY);
@@ -1363,7 +1363,6 @@ void StateGameLoop()
 #ifndef DEBUG_DUMP_COMMANDS
 		Game::GameLoop();
 #endif
-		CallWindowTickEvent();
 		return;
 	}
 
@@ -1381,7 +1380,7 @@ void StateGameLoop()
 		BasePersistentStorageArray::SwitchMode(PSM_LEAVE_GAMELOOP);
 		UpdateLandscapingLimits();
 
-		CallWindowTickEvent();
+		CallWindowGameTickEvent();
 		NewsLoop();
 	} else {
 		if (_debug_desync_level > 2 && _date_fract == 0 && (_date & 0x1F) == 0) {
@@ -1411,7 +1410,7 @@ void StateGameLoop()
 #endif
 		UpdateLandscapingLimits();
 
-		CallWindowTickEvent();
+		CallWindowGameTickEvent();
 		NewsLoop();
 		cur_company.Restore();
 	}
diff --git a/src/rail_gui.cpp b/src/rail_gui.cpp
index 5a533e5c5..234edbf22 100644
--- a/src/rail_gui.cpp
+++ b/src/rail_gui.cpp
@@ -1368,7 +1368,7 @@ public:
 		}
 	}
 
-	virtual void OnTick()
+	virtual void OnRealtimeTick(uint delta_ms)
 	{
 		CheckRedrawStationCoverage(this);
 	}
diff --git a/src/road_gui.cpp b/src/road_gui.cpp
index 6faa42262..e3091ec8a 100644
--- a/src/road_gui.cpp
+++ b/src/road_gui.cpp
@@ -1053,7 +1053,7 @@ struct BuildRoadStationWindow : public PickerWindowBase {
 		}
 	}
 
-	virtual void OnTick()
+	virtual void OnRealtimeTick(uint delta_ms)
 	{
 		CheckRedrawStationCoverage(this);
 	}
diff --git a/src/smallmap_gui.cpp b/src/smallmap_gui.cpp
index 135d7491c..447d25e4a 100644
--- a/src/smallmap_gui.cpp
+++ b/src/smallmap_gui.cpp
@@ -1570,10 +1570,10 @@ int SmallMapWindow::GetPositionOnLegend(Point pt)
 	}
 }
 
-/* virtual */ void SmallMapWindow::OnTick()
+/* virtual */ void SmallMapWindow::OnRealtimeTick(uint delta_ms)
 {
 	/* Update the window every now and then */
-	if (--this->refresh != 0) return;
+	if (!TimerElapsed(this->refresh, delta_ms)) return;
 
 	if (this->map_type == SMT_LINKSTATS) {
 		uint32 company_mask = this->GetOverlayCompanyMask();
diff --git a/src/smallmap_gui.h b/src/smallmap_gui.h
index c3151b1a7..60b39b7a3 100644
--- a/src/smallmap_gui.h
+++ b/src/smallmap_gui.h
@@ -67,8 +67,8 @@ protected:
 
 	static const uint LEGEND_BLOB_WIDTH = 8;              ///< Width of the coloured blob in front of a line text in the #WID_SM_LEGEND widget.
 	static const uint INDUSTRY_MIN_NUMBER_OF_COLUMNS = 2; ///< Minimal number of columns in the #WID_SM_LEGEND widget for the #SMT_INDUSTRY legend.
-	static const uint FORCE_REFRESH_PERIOD = 0x1F; ///< map is redrawn after that many ticks
-	static const uint BLINK_PERIOD         = 0x0F; ///< highlight blinking interval
+	static const uint FORCE_REFRESH_PERIOD = 930; ///< map is redrawn after that many milliseconds.
+	static const uint BLINK_PERIOD         = 450; ///< highlight blinking interval in milliseconds.
 
 	uint min_number_of_columns;    ///< Minimal number of columns in legends.
 	uint min_number_of_fixed_rows; ///< Minimal number of rows in the legends for the fixed layouts only (all except #SMT_INDUSTRY).
@@ -79,7 +79,7 @@ protected:
 	int32 subscroll; ///< Number of pixels (0..3) between the right end of the base tile and the pixel at the top-left corner of the smallmap display.
 	int zoom;        ///< Zoom level. Bigger number means more zoom-out (further away).
 
-	uint8 refresh;   ///< Refresh counter, zeroed every FORCE_REFRESH_PERIOD ticks.
+	int refresh;     ///< Refresh timer, in millseconds.
 	LinkGraphOverlay *overlay;
 
 	static void BreakIndustryChainLink();
@@ -187,7 +187,7 @@ public:
 	virtual void OnInvalidateData(int data = 0, bool gui_scope = true);
 	virtual bool OnRightClick(Point pt, int widget);
 	virtual void OnMouseWheel(int wheel);
-	virtual void OnTick();
+	virtual void OnRealtimeTick(uint delta_ms);
 	virtual void OnScroll(Point delta);
 	virtual void OnMouseOver(Point pt, int widget);
 };
diff --git a/src/station_gui.cpp b/src/station_gui.cpp
index 3f64b139a..4c0bf295c 100644
--- a/src/station_gui.cpp
+++ b/src/station_gui.cpp
@@ -621,7 +621,7 @@ public:
 		}
 	}
 
-	virtual void OnTick()
+	virtual void OnGameTick()
 	{
 		if (_pause_mode != PM_UNPAUSED) return;
 		if (this->stations.NeedResort()) {
@@ -2312,7 +2312,7 @@ struct SelectStationWindow : Window {
 		DeleteWindowById(WC_SELECT_STATION, 0);
 	}
 
-	virtual void OnTick()
+	virtual void OnRealtimeTick(uint delta_ms)
 	{
 		if (_thd.dirty & 2) {
 			_thd.dirty &= ~2;
diff --git a/src/statusbar_gui.cpp b/src/statusbar_gui.cpp
index 25efa6bb1..e45697130 100644
--- a/src/statusbar_gui.cpp
+++ b/src/statusbar_gui.cpp
@@ -79,10 +79,11 @@ static bool DrawScrollingStatusText(const NewsItem *ni, int scroll_pos, int left
 struct StatusBarWindow : Window {
 	bool saving;
 	int ticker_scroll;
+	uint ticker_timer;
 	int reminder_timeout;
 
 	static const int TICKER_STOP    = 1640; ///< scrolling is finished when counter reaches this value
-	static const int REMINDER_START =   91; ///< initial value of the reminder counter (right dot on the right)
+	static const int REMINDER_START = 1350; ///< time in ms for reminder notification (red dot on the right) to stay
 	static const int REMINDER_STOP  =    0; ///< reminder disappears when counter reaches this value
 	static const int COUNTER_STEP   =    2; ///< this is subtracted from active counters every tick
 
@@ -203,6 +204,7 @@ struct StatusBarWindow : Window {
 			case SBI_SHOW_REMINDER:   this->reminder_timeout = REMINDER_START; break;
 			case SBI_NEWS_DELETED:
 				this->ticker_scroll    =   TICKER_STOP; // reset ticker ...
+				this->ticker_timer     = 0;
 				this->reminder_timeout = REMINDER_STOP; // ... and reminder
 				break;
 		}
@@ -217,19 +219,20 @@ struct StatusBarWindow : Window {
 		}
 	}
 
-	virtual void OnTick()
+	virtual void OnRealtimeTick(uint delta_ms)
 	{
 		if (_pause_mode != PM_UNPAUSED) return;
 
 		if (this->ticker_scroll < TICKER_STOP) { // Scrolling text
-			this->ticker_scroll += COUNTER_STEP;
-			this->SetWidgetDirty(WID_S_MIDDLE);
+			uint count = CountIntervalElapsed(this->ticker_timer, delta_ms, 15);
+			if (count > 0) {
+				this->ticker_scroll += count;
+				this->SetWidgetDirty(WID_S_MIDDLE);
+			}
 		}
 
-		if (this->reminder_timeout > REMINDER_STOP) { // Red blot to show there are new unread newsmessages
-			this->reminder_timeout -= COUNTER_STEP;
-		} else if (this->reminder_timeout < REMINDER_STOP) {
-			this->reminder_timeout = REMINDER_STOP;
+		// Red blot to show there are new unread newsmessages
+		if (TimerElapsed(this->reminder_timeout, delta_ms)) {
 			this->SetWidgetDirty(WID_S_MIDDLE);
 		}
 	}
diff --git a/src/toolbar_gui.cpp b/src/toolbar_gui.cpp
index 40ac3634f..4f0f14011 100644
--- a/src/toolbar_gui.cpp
+++ b/src/toolbar_gui.cpp
@@ -1978,6 +1978,8 @@ enum MainToolbarHotkeys {
 
 /** Main toolbar. */
 struct MainToolbarWindow : Window {
+	int timer;
+
 	MainToolbarWindow(WindowDesc *desc) : Window(desc)
 	{
 		this->InitNested(0);
@@ -1988,6 +1990,8 @@ struct MainToolbarWindow : Window {
 		this->SetWidgetDisabledState(WID_TN_FAST_FORWARD, _networking); // if networking, disable fast-forward button
 		PositionMainToolbar(this);
 		DoZoomInOutWindow(ZOOM_NONE, this);
+
+		this->timer = MILLISECONDS_PER_TICK;
 	}
 
 	virtual void FindWindowPlacementAndResize(int def_width, int def_height)
@@ -2092,8 +2096,11 @@ struct MainToolbarWindow : Window {
 		_last_started_action = CBF_NONE;
 	}
 
-	virtual void OnTick()
+	virtual void OnRealtimeTick(uint delta_ms)
 	{
+		if (!TimerElapsed(this->timer, delta_ms)) return;
+		this->timer = MILLISECONDS_PER_TICK;
+
 		if (this->IsWidgetLowered(WID_TN_PAUSE) != !!_pause_mode) {
 			this->ToggleWidgetLoweredState(WID_TN_PAUSE);
 			this->SetWidgetDirty(WID_TN_PAUSE);
@@ -2310,6 +2317,8 @@ enum MainToolbarEditorHotkeys {
 };
 
 struct ScenarioEditorToolbarWindow : Window {
+	int timer;
+
 	ScenarioEditorToolbarWindow(WindowDesc *desc) : Window(desc)
 	{
 		this->InitNested(0);
@@ -2318,6 +2327,8 @@ struct ScenarioEditorToolbarWindow : Window {
 		CLRBITS(this->flags, WF_WHITE_BORDER);
 		PositionMainToolbar(this);
 		DoZoomInOutWindow(ZOOM_NONE, this);
+
+		this->timer = MILLISECONDS_PER_TICK;
 	}
 
 	virtual void FindWindowPlacementAndResize(int def_width, int def_height)
@@ -2445,8 +2456,11 @@ struct ScenarioEditorToolbarWindow : Window {
 		this->SetWidgetDirty(WID_TE_DATE_FORWARD);
 	}
 
-	virtual void OnTick()
+	virtual void OnRealtimeTick(uint delta_ms)
 	{
+		if (!TimerElapsed(this->timer, delta_ms)) return;
+		this->timer = MILLISECONDS_PER_TICK;
+
 		if (this->IsWidgetLowered(WID_TE_PAUSE) != !!_pause_mode) {
 			this->ToggleWidgetLoweredState(WID_TE_PAUSE);
 			this->SetDirty();
diff --git a/src/vehicle_gui.cpp b/src/vehicle_gui.cpp
index 4926f7a4f..7e0fa14b6 100644
--- a/src/vehicle_gui.cpp
+++ b/src/vehicle_gui.cpp
@@ -1676,7 +1676,7 @@ public:
 		this->SetDirty();
 	}
 
-	virtual void OnTick()
+	virtual void OnGameTick()
 	{
 		if (_pause_mode != PM_UNPAUSED) return;
 		if (this->vehicles.NeedResort()) {
@@ -2733,7 +2733,7 @@ public:
 		}
 	}
 
-	virtual void OnTick()
+	virtual void OnGameTick()
 	{
 		const Vehicle *v = Vehicle::Get(this->window_number);
 		bool veh_stopped = v->IsStoppedInDepot();
diff --git a/src/window.cpp b/src/window.cpp
index 22084c200..7457bdcbf 100644
--- a/src/window.cpp
+++ b/src/window.cpp
@@ -3075,13 +3075,32 @@ void InputLoop()
 }
 
 /**
+ * Dispatch OnRealtimeTick event over all windows
+ */
+void CallWindowRealtimeTickEvent(uint delta_ms)
+{
+	Window *w;
+	FOR_ALL_WINDOWS_FROM_FRONT(w) {
+		w->OnRealtimeTick(delta_ms);
+	}
+}
+
+/**
  * Update the continuously changing contents of the windows, such as the viewports
  */
 void UpdateWindows()
 {
+	static uint32 last_realtime_tick = _realtime_tick;
+	uint delta_ms = _realtime_tick - last_realtime_tick;
+	last_realtime_tick = _realtime_tick;
+
+	if (delta_ms == 0) return;
+
 	PerformanceMeasurer framerate(PFE_DRAWING);
 	PerformanceAccumulator::Reset(PFE_DRAWWORLD);
 
+	CallWindowRealtimeTickEvent(delta_ms);
+
 	Window *w;
 
 	static int highlight_timer = 1;
@@ -3263,13 +3282,13 @@ void InvalidateWindowClassesData(WindowClass cls, int data, bool gui_scope)
 }
 
 /**
- * Dispatch WE_TICK event over all windows
+ * Dispatch OnTick event over all windows
  */
-void CallWindowTickEvent()
+void CallWindowGameTickEvent()
 {
 	Window *w;
 	FOR_ALL_WINDOWS_FROM_FRONT(w) {
-		w->OnTick();
+		w->OnGameTick();
 	}
 }
 
diff --git a/src/window_func.h b/src/window_func.h
index 453b88978..f2ae638fe 100644
--- a/src/window_func.h
+++ b/src/window_func.h
@@ -56,4 +56,36 @@ void DeleteWindowByClass(WindowClass cls);
 bool EditBoxInGlobalFocus();
 Point GetCaretPosition();
 
+/**
+ * Count how many times the interval has elapsed, and update the timer.
+ * Use to ensure a specific amount of events happen within a timeframe, e.g. for animation.
+ * The timer value does not need to be initialised.
+ * @param timer Timer to test. Value will be increased.
+ * @param delta Time since last test.
+ * @param interval Timing interval.
+ * @return Number of times the interval has elapsed.
+ */
+static inline uint CountIntervalElapsed(uint &timer, uint delta, uint interval)
+{
+	uint count = delta / interval;
+	if (timer + (delta % interval) >= interval) count++;
+	timer = (timer + delta) % interval;
+	return count;
+}
+
+/**
+ * Test if a timer has elapsed, and update the timer.
+ * Use to ensure an event happens only once within a timeframe, e.g. for window updates.
+ * The timer value must be initialised in order for the timer to elapsed.
+ * @param timer Timer to test. Value will be decreased.
+ * @param delta Time since last test.
+ * @return True iff the timer has elapsed.
+ */
+static inline bool TimerElapsed(int &timer, uint delta)
+{
+	if (timer <= 0) return false;
+	timer -= delta;
+	return timer <= 0;
+}
+
 #endif /* WINDOW_FUNC_H */
diff --git a/src/window_gui.h b/src/window_gui.h
index b81b06e39..f5f9734c3 100644
--- a/src/window_gui.h
+++ b/src/window_gui.h
@@ -678,7 +678,7 @@ public:
 	/**
 	 * Called once per (game) tick.
 	 */
-	virtual void OnTick() {}
+	virtual void OnGameTick() {}
 
 	/**
 	 * Called once every 100 (game) ticks.
@@ -686,6 +686,11 @@ public:
 	virtual void OnHundredthTick() {}
 
 	/**
+	 * Called periodically.
+	 */
+	virtual void OnRealtimeTick(uint delta_ms) {}
+
+	/**
 	 * Called when this window's timeout has been reached.
 	 */
 	virtual void OnTimeout() {}