frame_clock.hpp

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#pragma once

 
#include <functional>
#include <memory>
#include <vector>
#include <cstdint>
 
namespace pulp::view {
 
class FrameClock {
public:
    void tick(float dt);

    float time() const { return time_; }

    float dt() const { return dt_; }

    uint64_t frame() const { return frame_; }

    int subscribe(std::function<bool(float dt)> callback);

    void unsubscribe(int id);

    bool has_active_subscribers() const;
 
    // ── Activity channel (wake-from-idle probes) ────────────────────────────
    // Distinct from the render subscribers above. An activity subscriber is an
    // idle probe: the host calls pump_activity() every host tick REGARDLESS of
    // render state, so a view can decide each tick whether it now needs
    // continuous frames (e.g. flip set_continuous_repaint when a meter starts
    // moving) WITHOUT the subscription itself counting as render-liveness. This
    // separation is what lets an editor idle at 0 fps yet still wake: render
    // subscribers (subscribe / has_active_subscribers) mean "keep painting";
    // activity subscribers mean "let me look each tick, but don't paint for me".
    // A wake-from-idle liveness flag driven from here is why a per-tick View
    // vtable hook is unnecessary — self-subscribe via View::on_frame_clock_changed.

    int subscribe_activity(std::function<void(float dt)> callback);

    void unsubscribe_activity(int id);

    bool has_activity_subscribers() const;

    void pump_activity(float dt);

    void reset();

    std::weak_ptr<const void> liveness_token() const { return alive_; }
 
private:
    struct Subscriber {
        int id;
        std::function<bool(float dt)> callback;
        bool active = true;
    };
    struct ActivitySubscriber {
        int id;
        std::function<void(float dt)> callback;
        bool active = true;
    };
 
    std::vector<Subscriber> subscribers_;
    std::vector<ActivitySubscriber> activity_subscribers_;
    float time_ = 0;
    float dt_ = 0;
    uint64_t frame_ = 0;
    int next_id_ = 1;
    std::shared_ptr<const void> alive_ = std::make_shared<const char>('\0');
};
 
} // namespace pulp::view