draw_primitive.hpp

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#pragma once
#include "le2d/drawable/drawable.hpp"
#include <vector>
 
namespace le {
class IDrawPrimitive : public IDrawable {
  public:
    [[nodiscard]] virtual auto get_instances() const -> std::span<RenderInstance const> = 0;
    [[nodiscard]] virtual auto to_primitive() const -> Primitive = 0;
 
    void draw(IRenderer& renderer) const final { renderer.draw(to_primitive(), get_instances()); }
};
 
template <std::derived_from<IDrawPrimitive> Type>
class SingleDrawPrimitive : public Type, public RenderInstance {
  public:
    using Type::Type;
 
    [[nodiscard]] auto get_instances() const -> std::span<RenderInstance const> final { return {static_cast<RenderInstance const*>(this), 1}; }
};
 
template <std::derived_from<IDrawPrimitive> Type>
class InstancedDrawPrimitive : public Type {
  public:
    using Type::Type;
 
    [[nodiscard]] auto get_instances() const -> std::span<RenderInstance const> final { return instances; }
 
    std::vector<RenderInstance> instances{};
};
} // namespace le