Bare-bones quad tree node structure.

QTreeNode.hpp

#include <list>
#include <cstdint>

// A generic object class (supporting collision) that is within the nodes.
// See here: https://github.com/Ruskiy69/IronClad/blob/master/Source/include/Entity/RigidBody.hpp
// For a real definition of the objects I use.
class CQuadTree;
class CEntity;

// This is a rectangle representation containing x, y position, and
// w, h dimensions. Something barebones could be this:
struct rect_t { float x, y; uint32_t w, h; };

// The quad tree node.
struct QTNode
{
  QTNode* pParent;
  QTNode** pChildren;

  rect_t Rect;
  uint16_t depth;

  std::list<CEntity*> nodeObjects;
};

// This defines a BAREBONES entity class. This is nowhere
// near complete, and has only the essential members 
// necessary for the quad tree to update it.
class CEntity
{
public:
  CEntity() : pCurrentNode(nullptr), needs_update(false) {}
  
  // You should know how to do this :)
  bool CheckCollision(const rect_t& Other); 

  // The class needs access to the private data members.
  friend class CQuadTree;

private:
  QTNode* pCurrentNode;
  bool needs_update;    // The entity should track if it has moved
                        // since the last frame. For example, if 
                        // CEntity::Adjust() is called with non-zero values.
                        
  float x, y;
  rect_t Dimensions;
};