src: add vertex_color

build.sh

@@ -1,9 +1,7 @@
 set -eux
 
-CFLAGS="-Wall -Werror -Wfatal-errors -g -Og -std=gnu23 -Iinclude $(pkg-config --libs --cflags glfw3) -lm"
+CFLAGS="-Wall -Werror -Wfatal-errors -g -Og -std=gnu23 -Iinclude $(pkg-config --libs --cflags glfw3) -lm -lGL"
 
-if [ -f src/glad.o ]; then
-    gcc $CFLAGS src/main.c src/glad.o
-else
-    gcc $CFLAGS src/main.c src/glad.c
-fi
+#gcc $CFLAGS src/main.c
+
+gcc $CFLAGS src/vertex_color.c

src/main.c

@@ -7,8 +7,8 @@
 #include <time.h>
 #include <math.h>
 
-#include <glad/glad.h>
 #include <GLFW/glfw3.h>
+#include <GLES2/gl2.h>
 
 static void * read_file(const char * filename)
 {
@@ -180,11 +180,6 @@ int main()
   }
   glfwMakeContextCurrent(window);
 
-  if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) {
-    printf("Failed to initialize GLAD\n");
-    return -1;
-  }
-
   glViewport(0, 0, 800, 600);
   glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
 

src/vertex_color.c

@@ -0,0 +1,207 @@
+#include <fcntl.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <math.h>
+
+#include <GLFW/glfw3.h>
+#include <GLES2/gl2.h>
+
+static void * read_file(const char * filename)
+{
+  int fd = open(filename, O_RDONLY);
+  if (fd == -1) {
+    fprintf(stderr, "open(%s): %s\n", filename, strerror(errno));
+    return NULL;
+  }
+
+  off_t size = lseek(fd, 0, SEEK_END);
+  if (size == (off_t)-1) {
+    fprintf(stderr, "lseek(%s, SEEK_END): %s\n", filename, strerror(errno));
+    return NULL;
+  }
+
+  off_t start = lseek(fd, 0, SEEK_SET);
+  if (start == (off_t)-1) {
+    fprintf(stderr, "lseek(%s, SEEK_SET): %s\n", filename, strerror(errno));
+    return NULL;
+  }
+
+  void * buf = malloc(size+1);
+
+  ssize_t read_size = read(fd, buf, size);
+  if (read_size == -1) {
+    fprintf(stderr, "read(%s): %s\n", filename, strerror(errno));
+    return NULL;
+  }
+  ((char*)buf)[read_size] = 0;
+
+  return buf;
+}
+
+void framebuffer_size_callback(GLFWwindow* window, int width, int height)
+{
+  glViewport(0, 0, width, height);
+}
+
+unsigned int compile_shaders()
+{
+  void * vertexShaderSource = read_file("src/vertex_color.vp.glsl");
+  unsigned int vertexShader;
+  vertexShader = glCreateShader(GL_VERTEX_SHADER);
+  glShaderSource(vertexShader, 1, (const char **)&vertexShaderSource, NULL);
+  glCompileShader(vertexShader);
+  {
+    int  success;
+    char infoLog[512];
+    glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
+    if(!success) {
+      glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
+      printf("vertex shader compile failed:\n%s\n", infoLog);
+    }
+  }
+  free(vertexShaderSource);
+
+  void * fragmentShaderSource = read_file("src/vertex_color.fp.glsl");
+  unsigned int fragmentShader;
+  fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
+  glShaderSource(fragmentShader, 1, (const char **)&fragmentShaderSource, NULL);
+  glCompileShader(fragmentShader);
+  {
+    int  success;
+    char infoLog[512];
+    glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
+    if(!success) {
+      glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
+      printf("fragment shader compile failed:\n%s\n", infoLog);
+    }
+  }
+  free(fragmentShaderSource);
+
+  unsigned int shaderProgram;
+  shaderProgram = glCreateProgram();
+
+  glAttachShader(shaderProgram, vertexShader);
+  glAttachShader(shaderProgram, fragmentShader);
+  glLinkProgram(shaderProgram);
+
+  {
+    int  success;
+    char infoLog[512];
+    glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
+    if(!success) {
+      glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
+      printf("program link failed:\n%s\n", infoLog);
+    }
+  }
+
+  glDeleteShader(vertexShader);
+  glDeleteShader(fragmentShader);
+
+  return shaderProgram;
+}
+
+static int make_buffer(unsigned int target,
+                       const void * data,
+                       size_t size)
+{
+  unsigned int buffer;
+  glGenBuffers(1, &buffer);
+  glBindBuffer(target, buffer);
+  glBufferData(target, size, data, GL_STATIC_DRAW);
+  return buffer;
+}
+
+static const float vertex_buffer_data[] = {
+  // position          // color
+   0.5f, -0.5f, 0.0f,  1.0f, 0.0f, 0.0f,  // bottom right
+  -0.5f, -0.5f, 0.0f,  0.0f, 1.0f, 0.0f,  // bottom left
+   0.0f,  0.5f, 0.0f,  0.0f, 0.0f, 1.0f   // top
+};
+
+struct location {
+  struct {
+    unsigned int position;
+    unsigned int color;
+  } attrib;
+};
+
+int main()
+{
+  glfwInit();
+  glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 2);
+  glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 1);
+  //glfwWindowHint(GLFW_OPENGL_DEBUG_CONTEXT, GLFW_TRUE);
+
+  GLFWwindow* window = glfwCreateWindow(1600, 1200, "LearnOpenGL", NULL, NULL);
+  if (window == NULL) {
+    const char* description;
+    glfwGetError(&description);
+    printf("Failed to create GLFW window: %s\n", description);
+    glfwTerminate();
+    return -1;
+  }
+  glfwMakeContextCurrent(window);
+
+  glViewport(0, 0, 1600, 1200);
+  //glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
+
+  unsigned int vertex_buffer = make_buffer(GL_ARRAY_BUFFER,
+                                           vertex_buffer_data,
+                                           (sizeof (vertex_buffer_data)));
+
+  printf("compile start\n");
+  unsigned int shaderProgram = compile_shaders();
+  printf("compile end\n");
+
+  struct location location;
+
+  location.attrib.position = glGetAttribLocation(shaderProgram, "position");
+  location.attrib.color = glGetAttribLocation(shaderProgram, "color");
+  printf("attributes:\n  position %u\n  color %u\n",
+         location.attrib.position,
+         location.attrib.color);
+
+  while(!glfwWindowShouldClose(window)) {
+    if(glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
+      glfwSetWindowShouldClose(window, true);
+
+    //glClearColor(0.1f, 0.1f, 0.1f, 0.1f);
+    //glClear(GL_COLOR_BUFFER_BIT);
+
+    //
+    // render
+    //
+    glUseProgram(shaderProgram);
+
+    glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer);
+    glVertexAttribPointer(location.attrib.position,
+                          3,
+                          GL_FLOAT,
+                          GL_FALSE,
+                          (sizeof (float)) * 6,
+                          (void*)0
+                          );
+    glVertexAttribPointer(location.attrib.color,
+                          3,
+                          GL_FLOAT,
+                          GL_FALSE,
+                          (sizeof (float)) * 6,
+                          (void*)(3 * 4)
+                          );
+    glEnableVertexAttribArray(location.attrib.position);
+    glEnableVertexAttribArray(location.attrib.color);
+
+    glDrawArrays(GL_TRIANGLES, 0, 3);
+
+    glfwSwapBuffers(window);
+    glfwPollEvents();
+  }
+
+  glfwTerminate();
+
+  return 0;
+}

src/vertex_color.fp.glsl

@@ -0,0 +1,8 @@
+#version 120
+
+varying vec3 color_out;
+
+void main()
+{
+  gl_FragColor = vec4(color_out, 1);
+}

src/vertex_color.vp.glsl

@@ -0,0 +1,14 @@
+#version 120
+
+uniform float time;
+
+attribute vec3 position;
+attribute vec3 color;
+
+varying vec3 color_out;
+
+void main()
+{
+  gl_Position = vec4(position, 1);
+  color_out = color;
+}