src/sprite.c

/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 * Copyright 2025 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/sprite.h"

#include "ascension/context.h"
#include "ascension/glcontext.h"
#include "ascension/error.h"
#include "ascension/mesh.h"
#include "ascension/shader.h"
#include "ascension/constants.h"

#include <GL/glew.h>


typedef struct asc_sprite_shader_s {
    AscShaderProgram program;
    GLint tex;
} AscSpriteShader;

static void *asc_sprite_shader_create(bool rect) {
    AscShaderCodes codes;
    if (asc_shader_load_code_files((AscShaderCodeInfo){
        .files.vtx = "sprite_vtx.glsl",
        .files.frag = "sprite_frag.glsl",
        .defines.frag = rect ? "#define USE_RECT" : NULL,
    }, &codes)) {
        asc_error("Loading sprite shader failed.");
        return NULL;
    }
    AscSpriteShader *shader = asc_shader_create(codes, sizeof(*shader));
    if (asc_has_error()) {
        asc_shader_free_codes(codes);
        return NULL;
    }
    shader->tex = glGetUniformLocation(shader->program.gl_id, "tex");
    asc_shader_free_codes(codes);

    asc_error_catch_all_gl();

    return shader;
}

static AscShaderProgram *asc_sprite_shader_rect_create() {
    return asc_sprite_shader_create(true);
}

static AscShaderProgram *asc_sprite_shader_uv_create() {
    return asc_sprite_shader_create(false);
}

static const AscSpriteShader *asc_sprite_shader_rect(void) {
    return asc_shader_lookup_or_create(ASC_SHADER_SPRITE_RECT, asc_sprite_shader_rect_create);
}

static const AscSpriteShader *asc_sprite_shader_uv(void) {
    return asc_shader_lookup_or_create(ASC_SHADER_SPRITE_UV, asc_sprite_shader_uv_create);
}

static void asc_sprite_destroy(AscSceneNode *node) {
    AscSprite *sprite = (AscSprite *) node;
    asc_mesh_destroy(&sprite->mesh);
    sprite->texture->refcount--;
}

static void asc_sprite_update(AscSceneNode *node) {
    AscSprite *sprite = (AscSprite *) node;

    // calculate texture parameters
    asc_vec2f uv_scale;
    if (sprite->texture_scale_mode == ASC_TEXTURE_SCALE_REPEAT) {
        uv_scale = asc_texture_calculate_uv_scale(sprite->texture,
            asc_vec2u_new(sprite->width, sprite->height), sprite->texture_scale);
    } else {
        uv_scale = sprite->texture_scale;
    }

    // update mesh
    asc_mesh_plane_2d(&sprite->mesh,
        .size = asc_vec2f_new(sprite->width, sprite->height),
        .uv_scale = uv_scale
    );
}

void asc_sprite_draw(const AscCamera *camera, const AscSceneNode *node) {
    asc_ptr_cast(const AscSprite, sprite, node);

    // Activate shader
    // TODO: scene should know which shader we are going to activate s.t. it can pre-sort nodes
    const AscSpriteShader *shader =
            sprite->texture->target == GL_TEXTURE_RECTANGLE
                ? asc_sprite_shader_rect()
                : asc_sprite_shader_uv();
    asc_shader_use(&shader->program, camera);

    // Upload model matrix
    glUniformMatrix4fv(shader->program.model, 1,
                       GL_FALSE, node->world_transform);

    // Bind texture
    asc_texture_bind(sprite->texture, shader->tex, 0);

    // Draw mesh
    asc_mesh_draw_triangle_strip(&sprite->mesh);
}

AscSceneNode *asc_sprite_create(struct asc_sprite_create_args args) {
    AscSprite *sprite = cxZallocDefault(sizeof(AscSprite));

    // sprite parameters
    args.texture->refcount++;
    sprite->texture = args.texture;
    sprite->width = args.width;
    sprite->height = args.height;
    sprite->texture_scale_mode = args.texture_scale_mode;
    sprite->texture_scale.u = ASC_NONZERO_OR(1.f, args.texture_scale_x);
    sprite->texture_scale.v = ASC_NONZERO_OR(1.f, args.texture_scale_y);

    // basic node parameters
    AscSceneNode *node = (AscSceneNode *) sprite;
    asc_scene_node_name(node, args.name);
    node->render_group = args.opaque
                             ? ASC_RENDER_GROUP_2D_OPAQUE
                             : ASC_RENDER_GROUP_2D_BLEND;
    node->update_func = asc_sprite_update;
    node->destroy_func = asc_sprite_destroy;
    node->draw_func = asc_sprite_draw;

    node->position = asc_vec3f_new(args.x, args.y, ASC_SCENE_2D_DEPTH_OFFSET);
    node->scale = asc_vec3f_one;

    asc_node_update(node);
    return node;
}

void asc_sprite_set_size(AscSceneNode *node, unsigned width, unsigned height) {
    AscSprite *sprite = (AscSprite*) node;
    sprite->width = width;
    sprite->height = height;
    asc_node_update(node);
}