Arena works better now and I can give a list of sprites to work as fixtures in a scene.

tests/animation2.cpp

@@ -0,0 +1,117 @@
+#include <catch2/catch_test_macros.hpp>
+#include <fmt/core.h>
+#include <string>
+#include <coroutine>
+#include <chrono>
+#include "rand.hpp"
+#include <thread>
+#include <vector>
+#include "components.hpp"
+#include <iostream>
+#include "stats.hpp"
+#include "simplefsm.hpp"
+#include "textures.hpp"
+#include "animation.hpp"
+
+using namespace std::chrono_literals;
+using components::Animation;
+using TheClock = std::chrono::steady_clock;
+using TimeDelta = TheClock::duration;
+using TimePoint = std::chrono::time_point<TheClock>;
+const TimeDelta MIN_TICK = 200ms;
+
+struct AnimationState {
+  Animation anim;
+  TimeDelta wait = 1s;
+  sf::Vector2f scale{1.0, 1.0};
+  sf::Vector2f pos{0.0, 0.0};
+  sf::IntRect rect{{0, 0}, {300, 300}};
+
+  void step() {
+    anim.step(scale, pos, rect);
+  }
+
+  void apply(textures::SpriteTexture& st) {
+    animation::apply(anim, *st.sprite, pos);
+  }
+};
+
+struct AnimationQueue {
+  std::vector<AnimationState> active;
+  TimePoint last_tick;
+  TimeDelta wait_for = MIN_TICK;
+  size_t in_queue = 0;
+  size_t chunk = 1000;
+
+  TimeDelta delta() {
+    return TheClock::now() - last_tick;
+  }
+
+  void tick() {
+    last_tick = TheClock::now();
+  }
+
+  size_t add(Animation& anim, int initial_wait) {
+    active.emplace_back(anim, TheClock::duration(initial_wait));
+    return active.size() - 1;
+  }
+
+  AnimationState& get(size_t id) {
+    return active.at(id);
+  }
+
+  void render() {
+    wait_for = MIN_TICK;
+    auto dt = delta();
+
+    for(size_t i = 0; i < chunk; i++) {
+      in_queue++;
+      auto& a = active[in_queue % active.size()];
+
+      if(!a.anim.playing) continue;
+
+      if(a.wait < wait_for) {
+        wait_for = a.wait;
+      }
+
+      if(a.wait < dt) {
+        // fmt::println("play animation: {} total                  ", active.size());
+        a.step();
+      }
+    }
+  }
+};
+
+TEST_CASE("simple coroutine animation test", "[coro]") {
+  AnimationQueue queue;
+  Animation anim;
+  anim.play();
+
+  for(int i = 0; i < 100; i++) {
+    int time = Random::uniform(16, 32);
+    size_t id = queue.add(anim, time);
+    auto& what = queue.get(id);
+
+    REQUIRE(what.wait == TheClock::duration(time));
+  }
+
+  dbc::check(queue.active.size() > 0, "zero size queue after adding is impossible.");
+  queue.tick();
+  Stats stats;
+
+  for(int i = 0; i < 10000; i++) {
+    auto start = stats.time_start();
+    auto delta = queue.delta();
+
+    queue.render();
+
+    if(delta > queue.wait_for) {
+      queue.add(anim, Random::uniform(100, 5000));
+      queue.tick();
+    }
+
+    stats.sample_time(start);
+  }
+
+  fmt::print("stdev: {}, mean: {}\r", stats.stddev(), stats.mean());
+}