src/scene.c

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 * Copyright 2023 Mike Becker. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *
 *   2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include "ascension/scene.h"
#include "ascension/error.h"

#include <assert.h>

void asc_scene_init(AscScene *scene) {
    if (scene->root != NULL) {
        asc_error("Scene is already initialized.");
        return;
    }
    scene->root = asc_scene_node_create(NULL);
}

void asc_scene_destroy(AscScene *scene) {
    asc_scene_node_free(scene->root);
}

AscSceneNode *asc_scene_node_create(AscSceneNode *parent) {
    // TODO: check if this can remain a calloc or if it's too expensive
    AscSceneNode *node = calloc(1, sizeof(AscSceneNode));
    assert(node != NULL);
    asc_scene_node_link(node, parent);
    return node;
}

void asc_scene_node_free(AscSceneNode *node) {
    if (node == NULL) return;

    // free the children recursively
    while (node->children != NULL) {
        asc_scene_node_free(node->children);
    }

    // remove this node from its parent
    asc_scene_node_unlink(node);

    // free the node
    free(node);
}

void asc_scene_node_link(
        AscSceneNode *node,
        AscSceneNode *parent
) {
    if (node->parent == parent) return;
    if (node->parent != NULL || parent == NULL) asc_scene_node_unlink(node);
    if (parent != NULL) {
        if (parent->children == NULL) {
            parent->children = node;
        } else {
            parent->children->prev = node;
            node->next = parent->children;
        }
        node->parent = parent;
    }
}

void asc_scene_node_unlink(AscSceneNode *node) {
    if (node->parent == NULL) return;
    AscSceneNode *left = node->prev;
    AscSceneNode *right = node->next;
    assert(left == NULL || node->parent->children != node);
    if (left != NULL) {
        left->next = right;
    } else {
        node->parent->children = right;
    }
    if (right != NULL) right->prev = left;
    node->parent = node->prev = node->next = NULL;
}