Events: split off rate counting from pump_info::ticks

This interface was extremely confusing. pum_info is designed to set `ticks_` only once. This can lead to a situation (exemplified by the music code) where if ticks() is called multiple times in a row, the subsequent times with a counter, that counter would never be incremented since the condition that tests them short circuits on the is-ticks-not-set check.

Also, giving ticks() multiple side effects was very confusing.

src/countdown_clock.cpp

@@ -17,11 +17,11 @@
 #include "team.hpp"
 #include "preferences/preferences.hpp"
 #include "sound.hpp"
+#include "utils/rate_counter.hpp"
 
 namespace {
 	const int WARNTIME = 20000; //start beeping when 20 seconds are left (20,000ms)
-	unsigned timer_refresh = 0;
-	const unsigned timer_refresh_rate = 50; // prevents calling SDL_GetTicks() too frequently
+	utils::rate_counter timer_refresh_rate{50}; // prevents calling SDL_GetTicks() too frequently
 }
 
 
@@ -57,7 +57,7 @@ void countdown_clock::update_team(int new_timestamp)
 //make sure we think about countdown even while dialogs are open
 void countdown_clock::process(events::pump_info &info)
 {
-	if(info.ticks(&timer_refresh, timer_refresh_rate)) {
+	if(timer_refresh_rate.poll()) {
 		update(info.ticks());
 	}
 }

src/events.cpp

@@ -778,9 +778,9 @@ void process_tooltip_strings(int mousex, int mousey)
 	}
 }
 
-int pump_info::ticks(unsigned* refresh_counter, unsigned refresh_rate)
+int pump_info::ticks()
 {
-	if(!ticks_ && !(refresh_counter && ++*refresh_counter % refresh_rate)) {
+	if(!ticks_) {
 		ticks_ = ::SDL_GetTicks();
 	}
 

src/events.hpp

@@ -153,7 +153,7 @@ inline void pump_and_draw() { pump(); draw(); }
 struct pump_info {
 	pump_info() : resize_dimensions(), ticks_(0) {}
 	std::pair<int,int> resize_dimensions;
-	int ticks(unsigned *refresh_counter=nullptr, unsigned refresh_rate=1);
+	int ticks();
 private:
 	int ticks_; //0 if not calculated
 };

src/sound.cpp

@@ -20,6 +20,7 @@
 #include "random.hpp"
 #include "serialization/string_utils.hpp"
 #include "sound_music_track.hpp"
+#include "utils/rate_counter.hpp"
 
 #include <SDL2/SDL.h> // Travis doesn't like this, although it works on my machine -> '#include <SDL2/SDL_sound.h>
 #include <SDL2/SDL_mixer.h>
@@ -50,8 +51,7 @@ namespace
 {
 bool mix_ok = false;
 int music_start_time = 0;
-unsigned music_refresh = 0;
-unsigned music_refresh_rate = 20;
+utils::rate_counter music_refresh_rate{20};
 bool want_new_music = false;
 int fadingout_time = 5000;
 bool no_fading = false;
@@ -790,8 +790,8 @@ void music_thinker::process(events::pump_info& info)
 			fadingout_time = 0;
 		}
 
-		if(music_start_time && info.ticks(&music_refresh, music_refresh_rate) >= music_start_time - fadingout_time) {
-			want_new_music = true;
+		if(music_start_time && music_refresh_rate.poll()) {
+			want_new_music = info.ticks() >= music_start_time - fadingout_time;
 		}
 
 		if(want_new_music) {

src/utils/rate_counter.hpp

@@ -0,0 +1,32 @@
+/*
+	Copyright (C) 2003 - 2024
+	Part of the Battle for Wesnoth Project https://www.wesnoth.org/
+
+	This program is free software; you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation; either version 2 of the License, or
+	(at your option) any later version.
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY.
+
+	See the COPYING file for more details.
+*/
+
+#pragma once
+
+namespace utils
+{
+class rate_counter
+{
+public:
+	explicit rate_counter(unsigned rate) : rate_(rate) {}
+
+	/** Increments the counter by one and checks whether it is now a multiple of the chosen rate. */
+	bool poll() { return (++counter_ % rate_) == 0; }
+
+private:
+	unsigned counter_ = 0;
+	unsigned rate_ = 1;
+};
+
+} // end namespace utils