quadtree.h

/*
 * This code was initially authored by the Stackoverflow user dragon-energy and
 * posted under following page:
 * https://stackoverflow.com/questions/41946007/efficient-and-well-explained-implementation-of-a-quadtree-for-2d-collision-det
 *
 * As for the license, the author has kindly noted:
 *
 * "Oh and feel free to use this code I post however you want, even for
 * commercial projects. I would really love it if people let me know if they
 * find it useful, but do as you wish."
 *
 * And generally all Stackoverflow-posted code is by default licensed with CC
 * BY-SA 4.0: https://creativecommons.org/licenses/by-sa/4.0/
 */
#pragma once
 
#include "intlist.h"
 
typedef struct Quadtree Quadtree;
 
struct Quadtree {
   // Stores all the nodes in the quadtree. The first node in this
   // sequence is always the root.
   IntList nodes;
 
   // Stores all the elements in the quadtree.
   IntList elts;
 
   // Stores all the element nodes in the quadtree.
   IntList enodes;
 
   // Stores the quadtree extents.
   int root_mx, root_my, root_sx, root_sy;
 
   // Maximum allowed elements in a leaf before the leaf is subdivided/split
   // unless the leaf is at the maximum allowed tree depth.
   int max_elements;
 
   // Stores the maximum depth allowed for the quadtree.
   int max_depth;
 
   // Temporary buffer used for queries.
 
   char *temp;
 
   // Stores the size of the temporary buffer.
   int temp_size;
};
 
// Function signature used for traversing a tree node.
typedef void QtNodeFunc( Quadtree *qt, void *user_data, int node, int depth,
                         int mx, int my, int sx, int sy );
 
// Creates a quadtree with the requested extents, maximum elements per leaf, and
// maximum tree depth.
void qt_create( Quadtree *qt, int x1, int y1, int x2, int y2, int max_elements,
                int max_depth );
 
// Destroys the quadtree.
void qt_destroy( Quadtree *qt );
 
// Clears the quadtree making it empty.
void qt_clear( Quadtree *qt );
 
// Inserts a new element to the tree.
// Returns an index to the new element.
int qt_insert( Quadtree *qt, int id, int x1, int y1, int x2, int y2 );
 
// Removes the specified element from the tree.
void qt_remove( Quadtree *qt, int element );
 
// Cleans up the tree, removing empty leaves.
void qt_cleanup( Quadtree *qt );
 
// Outputs a list of elements found in the specified rectangle.
void qt_query( Quadtree *qt, IntList *out, int x1, int y1, int x2, int y2 );
 
// Traverses all the nodes in the tree, calling 'branch' for branch nodes and
// 'leaf' for leaf nodes.
void qt_traverse( Quadtree *qt, void *user_data, QtNodeFunc *branch,
                  QtNodeFunc *leaf );