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 <cx/tree.h>

#include <assert.h>

#define child_list_off_ \
    offsetof(AscSceneNode, children), offsetof(AscSceneNode, next)

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

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

void asc_scene_add(AscScene *scene, AscSceneNode *node) {
    asc_scene_node_link(scene->root, node);
    asc_node_update(node);
}

void asc_scene_draw(AscScene const *scene) {
    CxTreeIterator iter = cx_tree_iterator(scene->root, false, child_list_off_);

    // skip the root node deliberately, we know it's just the container
    cxIteratorNext(iter);

    // update the children
    cx_foreach(AscSceneNode*, node, iter) {
        // execute behaviors, first
        AscBehaviorNode *behavior = node->behaviors;
        while (behavior) {
            behavior->func(node);
            behavior = behavior->next;
        }

        // check if geometry needs update
        if (node->need_update && node->update_func != NULL) {
            node->need_update = false;
            asc_transform_copy(node->transform, node->parent->transform);
            node->update_func(node);
        }

        // TODO: don't visit the tree for drawing, visit the render groups
        if (node->draw_func != NULL) {
            node->draw_func(node);
        }
    }
}

AscSceneNode *asc_scene_node_empty(void) {
    AscSceneNode *node = calloc(1, sizeof(AscSceneNode));
    assert(node != NULL);
    node->free_func = (asc_scene_free_func) free;
    asc_transform_identity(node->transform);
    return node;
}

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

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

    // free the entire subtree
    CxTreeIterator iter = cx_tree_iterator(node, true, child_list_off_);
    cx_foreach(AscSceneNode*, child, iter) {
        if (!iter.exiting) continue;
        if (child->free_func != NULL) {
            child->free_func(child);
        } else {
            free(child);
        }
    }
}

void asc_scene_node_link(AscSceneNode * restrict parent, AscSceneNode * restrict node) {
    cx_tree_link(
            parent, node,
            offsetof(AscSceneNode, parent),
            offsetof(AscSceneNode, children),
            offsetof(AscSceneNode, prev),
            offsetof(AscSceneNode, next)
    );
}

void asc_scene_node_unlink(AscSceneNode *node) {
    cx_tree_unlink(
            node,
            offsetof(AscSceneNode, parent),
            offsetof(AscSceneNode, children),
            offsetof(AscSceneNode, prev),
            offsetof(AscSceneNode, next)
    );
}

AscBehaviorNode *asc_scene_add_behavior(AscSceneNode *node, asc_scene_update_func behavior) {
    AscBehaviorNode *behavior_node = calloc(1, sizeof(AscBehaviorNode));
    behavior_node->func = behavior;
    cx_tree_link(
            node,
            behavior_node,
            offsetof(AscBehaviorNode, parent),
            offsetof(AscSceneNode, behaviors),
            offsetof(AscBehaviorNode, prev),
            offsetof(AscBehaviorNode, next)
    );
    return behavior_node;
}

void asc_scene_remove_behavior(AscBehaviorNode *node) {
    cx_tree_unlink(
            node,
            offsetof(AscBehaviorNode, parent),
            offsetof(AscSceneNode, behaviors),
            offsetof(AscBehaviorNode, prev),
            offsetof(AscBehaviorNode, next)
    );
}