From 37827eca73d6c621d4b6a1090433f071749ae3da Mon Sep 17 00:00:00 2001
From: Jean Sirmai <jean@a-lec.org>
Date: Tue, 4 Jun 2024 22:51:07 +0200
Subject: [PATCH] WIP: idem + init  (+/- shaders...)

---
 init.c.todo | 175 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 175 insertions(+)
 create mode 100644 init.c.todo

diff --git a/init.c.todo b/init.c.todo
new file mode 100644
index 0000000..0a6c3cc
--- /dev/null
+++ b/init.c.todo
@@ -0,0 +1,175 @@
+/*
+ *      Gem-graph OpenGL experiments
+ *
+ *      Desc: GL functions
+ *
+ *  Copyright (C) 2023 Arthur Menges <arthur.menges@a-lec.org>
+ *  Copyright (C) 2023 Adrien Bourmault <neox@a-lec.org>
+ *
+ *  This file is part of Gem-graph.
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU Affero General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU Affero General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Affero General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/* -------------------------------------------------------------------------- */
+
+#include <stdlib.h>
+#include <time.h>
+#include "base.h"
+#include "contain.h" // instead of "ui.h"
+#include "graph_area.h"
+
+/* Initializes the buffer of a gl_area
+ * Calls according to the user preferences
+ * @param   gl_area, ptr to the gl_area widget
+ * @return  void
+ */
+void graphics_init_buffers(const int stack_id)
+{
+    struct graphic_stack_t *stack = &graphic_stack[stack_id];
+
+    //XXX
+    graphics_model_setup(stack_id);
+
+    GLuint vao, vertex_buffer, color_buffer;
+
+    glGenBuffers(1, &vertex_buffer);
+    glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer);
+    glBufferData(GL_ARRAY_BUFFER,
+                 stack->buffer_vertex_size *
+                    sizeof(stack->buffer_vertex_origin[0]),
+                 stack->buffer_vertex_origin,
+                 GL_STATIC_DRAW);
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+
+
+    // colors
+    glGenBuffers(1, &color_buffer);
+    glBindBuffer(GL_ARRAY_BUFFER, color_buffer);
+    glBufferData(GL_ARRAY_BUFFER, stack->buffer_colors_size *
+                    sizeof(stack->buffer_colors_origin[0]),
+                 stack->buffer_colors_origin,
+                 GL_STATIC_DRAW);
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+
+    // We only use one VAO, so we always keep it bound
+    glGenVertexArrays(1, &vao);
+    glBindVertexArray(vao);
+
+    stack->vao = vao;
+    stack->position_buffer = vertex_buffer;
+    stack->color_buffer = color_buffer;
+}
+
+/*
+ * Initializes the shaders of a gl_area and link them to a program
+ *
+ * @param   gl_area, ptr to the gl_area widget
+ *
+ * @return  true if initialized
+ */
+bool graphics_init_shaders(const int stack_id)
+{
+    struct graphic_stack_t *stack = &graphic_stack[stack_id];
+    char *vertex_shader;
+    char *fragment_shader;
+    int status;
+    GLuint vertex, fragment;
+    GLuint program = 0;
+    GLuint m = 0;
+    GLuint v = 0;
+    GLuint p = 0;
+
+    // Load vertex shader file
+    vertex_shader = read_file(VERTEX_SHADER_FILE);
+    if (vertex_shader == NULL)
+        return false;
+//////////////////////////    vertex = create_shader(stack_id, GL_VERTEX_SHADER, vertex_shader);
+
+    if(vertex == 0) {
+        stack->program = 0;
+        g_free(vertex_shader);
+        return false;
+    }
+
+    // Load fragment shader file
+    fragment_shader = read_file(FRAG_SHADER_FILE);
+    if (fragment_shader == NULL)
+        return false;
+    fragment = create_shader(stack_id, GL_FRAGMENT_SHADER, fragment_shader);
+
+    if(fragment == 0) {
+        glDeleteShader(vertex);
+        stack->program = 0;
+        g_free(vertex_shader);
+        g_free(fragment_shader);
+        return false;
+    }
+
+    // Link shaders to program
+    program = glCreateProgram();
+    glAttachShader(program, vertex);
+    glAttachShader(program, fragment);
+
+    glLinkProgram(program);
+
+    glGetProgramiv(program, GL_LINK_STATUS, &status);
+
+    if(status == GL_FALSE) {
+        int log_len;
+        char *buffer;
+
+        glGetProgramiv(program, GL_INFO_LOG_LENGTH, &log_len);
+
+        buffer = g_malloc(log_len + 1);
+        assert(buffer);
+        glGetProgramInfoLog(program, log_len, NULL, buffer);
+
+        g_warning("Linking failure:\n%s", buffer);
+
+        g_free(buffer);
+
+        glDeleteProgram(program);
+        program = 0;
+
+        glDeleteShader(vertex);
+        glDeleteShader(fragment);
+
+        g_free(vertex_shader);
+        g_free(fragment_shader);
+
+        return false;
+    }
+
+    /* Get the location of the "mvp" uniform */
+    m = glGetUniformLocation(program, "model_matrix");
+    v = glGetUniformLocation(program, "view_matrix");
+    p = glGetUniformLocation(program, "projection_matrix");
+
+    glDetachShader(program, vertex);
+    glDetachShader(program, fragment);
+
+    glDeleteShader(vertex);
+    glDeleteShader(fragment);
+
+    stack->program = program;
+    stack->m = m;
+    stack->v = v;
+    stack->p = p;
+
+    g_free(vertex_shader);
+    g_free(fragment_shader);
+
+    return true;
+}