SceneLink.h

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#pragma once
 
// Attaching things to scene nodes.
//
// A link keeps an external object -- a renderable, a physics body, a camera, an
// audio source -- in step with the node it hangs off. The set of kinds used to
// be a closed enum with a switch in TransformSystem, so scene had to include
// graphics, physics and audio, and no other module could ever attach to the
// tree without editing this file.
//
// Kinds are registered instead. The module that owns the target type supplies
// the three operations, keeps the casts on its own side where the type is
// complete, and scene never learns what a Renderable3D is.
//
// Dispatch is through a function-pointer table, not virtual calls: link sync
// runs for every dirty node every frame.
 
#include "common/Export.h"
 
#include <cstddef>
 
namespace eve::scene {
 
struct SceneNode;
 
struct LinkOps {
    const char* kind = nullptr;
 
    void (*pushWorld)(const SceneNode& node, void* target) = nullptr;
 
    void (*pullWorld)(SceneNode& node, void* target) = nullptr;
 
    bool (*alive)(const void* target) = nullptr;
};
 
EVENGINE_API int registerLinkKind(const LinkOps& ops);
 
EVENGINE_API int findLinkKind(const char* kind);
 
EVENGINE_API const LinkOps* linkOps(int kindId);
 
EVENGINE_API const char* linkKindName(int kindId);
 
struct SceneLink {
    int kind = -1;
    void* target = nullptr;
    int syncMode = 0;
};
 
}  // namespace eve::scene