Farm Watch counts your animals without knowing it is Minecraft.

#include <axiom/surface.hpp>

using namespace axiom;

struct FarmWatch final : Mod {
  void on_load(Context& ctx) override {
    ctx.config().bind("radius", &radius_);
    ctx.input().bind(Key::F, "toggle");
  }

  void on_frame(Frame& f) override {
    counts_ = {};
    marks_.clear();
    if (!shown_) return;

    // one crossing for every live entity
    auto ids = f.entities().alive();
    auto pos = f.entities().positions(ids);
    auto eye = f.camera().position;

    for (std::size_t i = 0; i < ids.size(); ++i) {
      auto kind = f.entities().kind(ids[i]);
      if (!is_livestock(kind)) continue;
      if (distance(eye, pos[i]) > radius_) continue;

      counts_[kind]++;
      if (auto s = f.camera().project(pos[i]))
        marks_.push_back(*s);
    }
  }

  void on_draw(ui::Surface& ui) override {
    if (!shown_) return;
    auto p = ui.panel("Farm Watch", ui::Anchor::TopRight);
    p.text("within {} blocks", radius_);
    p.separator();
    for (auto const& [kind, n] : counts_)
      p.text("{:<10} {}", name_of(kind), n);
    for (auto const& m : marks_) p.marker(m);
    ui.submit(std::move(p));
  }

  void on_event(Event& e) override {
    if (e.binding() == "toggle") shown_ = !shown_;
  }

  bool shown_ = true;
  float radius_ = 32.0f;
  std::map<EntityKind, int> counts_;
  std::vector<ui::Point> marks_;
};

AXIOM_MOD(FarmWatch);