src/shader.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/context.h"
#include "ascension/error.h"
#include "ascension/shader.h"
#include "ascension/filesystem.h"

#include <string.h>
#include <stdio.h>
#include <GL/glew.h>
#include <cx/buffer.h>
#include <cx/streams.h>

/**
 * Compiles a shader from the given source code.
 *
 * The ID of the returned shader will be zero when something went wrong.
 *
 * @param type the shader type (use the GL enum)
 * @param code the source code
 * @param code_pp the optional preprocessor code
 * @return the compiled shader
 */
static unsigned asc_shader_compile(unsigned int type, const char *code, const char *code_pp) {
    GLuint id = glCreateShader(type);
    if (id == 0) {
        asc_error("glCreateShader failed: %s", glGetError());
        return 0;
    }

    // some drivers don't like NULL strings, even when length is zero
    if (code_pp == NULL) code_pp = "";

    GLint success;
    const char *code_array[4] = {
        "#version 400 core\n",
        code_pp,
        "\n#line 1\n",
        code
    };
    GLint length_array[4];
    for (unsigned int i = 0; i < cx_nmemb(length_array); i++) {
        length_array[i] = (GLint) strlen(code_array[i]);
    }

    // compile
    glShaderSource(id, cx_nmemb(length_array), code_array, length_array);
    glCompileShader(id);
    glGetShaderiv(id, GL_COMPILE_STATUS, &success);
    if (success) {
        asc_dprintf("Shader %u compiled", id);
        return id;
    } else {
        char *log = malloc(1024);
        glGetShaderInfoLog(id, 1024, NULL, log);
        glDeleteShader(id);
        asc_error("Shader %u compilation failed.\n%s", id, log);
        free(log);
        return 0;
    }
}

/**
 * This function links shaders into a program.
 *
 * The ID of the returned program will be zero when something went wrong.
 *
 * @param shader the shader IDs to link
 * @param n the number of shaders
 * @param prog the struct where to store the result
 * @retval zero success
 * @retval non-zero failure
 */
static int asc_shader_link(unsigned shader[], unsigned n, AscShaderProgram *prog) {
    GLint success;
    GLint id = glCreateProgram();
    if (id <= 0) {
        asc_error("glCreateProgram failed: %s", glGetError());
        return -1;
    }
    for (unsigned i = 0; i < n; i++) {
        glAttachShader(id, shader[i]);
    }
    glLinkProgram(id);
    glGetProgramiv(id, GL_LINK_STATUS, &success);
    for (unsigned i = 0; i < n; i++) {
        glDeleteShader(shader[i]);
    }
    if (success) {
        asc_dprintf("Shader Program %u linked.", id);
        prog->gl_id = id;
        // by convention every shader shall have MVP matrices
        prog->model = glGetUniformLocation(id, "model");
        prog->view = glGetUniformLocation(id, "view");
        prog->projection = glGetUniformLocation(id, "projection");
        return 0;
    } else {
        char *log = malloc(1024);
        glGetProgramInfoLog(id, 1024, NULL, log);
        glDeleteProgram(id);
        asc_error("Linking shader program %u failed.\n%s", id, log);
        free(log);
        return -1;
    }
}

void asc_shader_free(AscShaderProgram *program) {
    if (program->gl_id > 0) {
        asc_dprintf("Delete Shader Program %u", program->gl_id);
        glDeleteProgram(program->gl_id);
    }
    if (program->destr_func) {
        program->destr_func(program);
    }
    cxFreeDefault(program);
}

void *asc_shader_create(AscShaderCodes codes, size_t mem_size) {
    AscShaderProgram *prog = cxZallocDefault(mem_size);
    unsigned shader[2];
    unsigned n = 0;
    if (codes.vtx) {
        shader[n++] = asc_shader_compile(GL_VERTEX_SHADER, codes.vtx, codes.vtx_pp);
    }
    if (codes.frag) {
        shader[n++] = asc_shader_compile(GL_FRAGMENT_SHADER, codes.frag, codes.frag_pp);
    }
    if (asc_shader_link(shader, n, prog)) {
        cxFreeDefault(prog);
        prog = NULL;
    }
    for (unsigned i = 0; i < n; i++) {
        asc_dprintf("Delete shader: %u", shader[i]);
        glDeleteShader(shader[i]);
    }
    return prog;
}

void asc_shader_use(const AscShaderProgram *shader, const AscCamera *camera) {
    if (shader == NULL) {
        asc_active_glctx->active_program = 0;
        glUseProgram(0);
        return;
    }
    if (asc_active_glctx->active_program == shader->gl_id) return;
    asc_active_glctx->active_program = shader->gl_id;
    glUseProgram(shader->gl_id);
    glUniformMatrix4fv(shader->projection, 1, GL_FALSE, camera->projection);
    glUniformMatrix4fv(shader->view, 1, GL_FALSE, camera->view);
}

static int asc_shader_load_code_file(const char *filename, char **code) {
    if (filename == NULL) {
        *code = NULL;
        return 0;
    }
    cxmutstr fpath = asc_filesystem_combine_paths(cx_strcast(asc_context.shader_path), cx_str(filename));
    asc_dprintf("Load shader code from %" CX_PRIstr, CX_SFMT(fpath));
    FILE *f = fopen(fpath.ptr, "r");
    cx_strfree(&fpath);
    if (f == NULL) return -1;
    CxBuffer buffer;
    cxBufferInit(&buffer, NULL, 1024, NULL, CX_BUFFER_AUTO_EXTEND);
    cx_stream_copy(f, &buffer, (cx_read_func) fread, cxBufferWriteFunc);
    cxBufferPut(&buffer, '\0');
    cxBufferShrink(&buffer, 0);
    *code = buffer.space;
    return *code == NULL ? -1 : 0;
}

int asc_shader_load_code_files(AscShaderCodeInfo info, AscShaderCodes *codes) {
    int ret = 0;
    ret |= asc_shader_load_code_file(info.files.vtx, &codes->vtx);
    codes->vtx_pp = info.defines.vtx;
    ret |= asc_shader_load_code_file(info.files.frag, &codes->frag);
    codes->frag_pp = info.defines.frag;
    return ret;
}

void asc_shader_free_codes(AscShaderCodes codes) {
    cxFreeDefault(codes.vtx);
    cxFreeDefault(codes.frag);
}

const void *asc_shader_register(unsigned int id, asc_shader_create_func create_func) {
    AscGLContext *glctx = asc_active_glctx;
#ifndef NDEBUG
    {
        const AscShaderProgram *prog = asc_shader_lookup(id);
        if (prog != NULL) {
            asc_error("Shader program %u already exists. This is a bug!", id);
            // still return it, so that the caller does not die immediately
            return prog;
        }
    }
#endif
    AscShaderProgram *prog = create_func();
    prog->id = id;
    cxListAdd(glctx->shaders, prog);
    return prog;
}

const void *asc_shader_lookup(unsigned int id) {
    CxIterator iter = cxListIterator(asc_active_glctx->shaders);
    cx_foreach(const AscShaderProgram *, prog, iter) {
        if (prog->id == id) return prog;
    }
    return NULL;
}

const void *asc_shader_lookup_or_create(unsigned int id, asc_shader_create_func create_func) {
    const AscShaderProgram *prog = asc_shader_lookup(id);
    if (prog == NULL) {
        return asc_shader_register(id, create_func);
    }
    return prog;
}

void asc_shader_clear_registry(void) {
    cxListClear(asc_active_glctx->shaders);
    // also clear the active program to avoid accidental matches with newly created shaders
    asc_shader_use(NULL, NULL);
}