Draw a triangle to the screen

src/main.cpp

@@ -1,12 +1,116 @@
 #include <stdio.h>
+#include <string.h>
 #include <GL/glew.h>
 #include <GLFW/glfw3.h>
 
 // Window dimensions
 const GLint WIDTH = 800, HEIGHT = 600;
 
+// Vertex Shader
+static const char *vertex_shader = "              \n\
+#version 330                                      \n\
+                                                  \n\
+layout (location = 0) in vec3 pos;                \n\
+                                                  \n\
+void main() {                                     \n\
+    gl_Position = vec4(pos.x, pos.y, pos.z, 1.0); \n\
+}";
+
+// Fragment shader
+static const char *fragment_shader =  "           \n\
+#version 330                                      \n\
+                                                  \n\
+out vec4 color;                                   \n\
+                                                  \n\
+void main() {                                     \n\
+    color = vec4(1.0, 0.0, 0.0, 1.0);             \n\
+}";
+
+bool add_shader(GLuint *program, const char *shader_code, GLenum shader_type) {
+    GLuint shader = glCreateShader(shader_type);
+    const GLchar *code[1];
+    code[0] = shader_code;
+
+    GLint code_length[1];
+    code_length[0] = strlen(shader_code);
+
+    glShaderSource(shader, 1, code, code_length);
+    glCompileShader(shader);
+
+    GLint result = 0;
+    GLchar errors[1024] = { 0 };
+
+    glGetShaderiv(shader, GL_COMPILE_STATUS, &result);
+    if (!result) {
+        glGetShaderInfoLog(shader, sizeof(errors), NULL, errors);
+        printf("Error compiling the %d shader: '%s'\n", shader_type, errors);
+        return false;
+    }
+
+    glAttachShader(*program, shader);
+    return true;
+}
+
+bool compile_shaders(GLuint *shader_program) {
+    *shader_program = glCreateProgram();
+
+    if (!shader_program) {
+        printf("Error creating shader program!\n");
+        return false;
+    }
+
+    add_shader(shader_program, vertex_shader, GL_VERTEX_SHADER);
+    add_shader(shader_program, fragment_shader, GL_FRAGMENT_SHADER);
+
+    GLint result = 0;
+    GLchar errors[1024] = { 0 };
+
+    glLinkProgram(*shader_program);
+    glGetProgramiv(*shader_program, GL_LINK_STATUS, &result);
+
+    if (!result) {
+        glGetProgramInfoLog(*shader_program, sizeof(errors), NULL, errors);
+        printf("Error linking program: '%s'\n", errors);
+        return false;
+    }
+
+    glValidateProgram(*shader_program);
+    glGetProgramiv(*shader_program, GL_VALIDATE_STATUS, &result);
+
+    if (!result) {
+        glGetProgramInfoLog(*shader_program, sizeof(errors), NULL, errors);
+        printf("Error validating program: '%s'\n", errors);
+        return false;
+    }
+
+    return true;
+}
+
+void create_triangle(GLuint *VAO, GLuint *VBO) {
+    GLfloat vertices[] = {
+        -1.0f, -1.0f, 0.0f,
+        1.0f, -1.0f, 0.0f,
+        0.0f, 1.0f, 0.0f
+    };
+
+    glGenVertexArrays(1, VAO);
+    glBindVertexArray(*VAO);
+
+    glGenBuffers(1, VBO);
+    glBindBuffer(GL_ARRAY_BUFFER, *VBO);
+    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
+
+    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
+    glEnableVertexAttribArray(0);
+
+    // Unbinding
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+    glBindVertexArray(0);
+}
 
 int main() {
+    GLuint VAO, VBO, shader_program;
+
     // Initialize GLFW
     glfwInitHint(GLFW_PLATFORM, GLFW_PLATFORM_WAYLAND);
 
@@ -19,7 +123,6 @@ int main() {
 
     // Setup GLFW window properties
     // OpenGL version
-    // @Reminder Look into making it work on Wayland
     glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
     glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 6);
     // Core profile means it will not be backwards compatible
@@ -63,21 +166,33 @@ int main() {
     // Setup viewport size
     glViewport(0, 0, buffer_width, buffer_height);
 
+    // Create our triangle
+    create_triangle(&VAO, &VBO);
+    compile_shaders(&shader_program);
+
     // Loop until window is closed
     while (!glfwWindowShouldClose(window)) {
         // Get and handle user input events
         glfwPollEvents();
 
         // Clear window
-        glClearColor(1.0f, 0.9f, 0.4f, 1.0f);
+        glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
         glClear(GL_COLOR_BUFFER_BIT);
 
+        glUseProgram(shader_program);
+        glBindVertexArray(VAO);
+        glDrawArrays(GL_TRIANGLES, 0, 3);
 
-        // We usually have two buffers, the first is hidden and that's the one
-        // we draw to. The second is the one we display, so when we're done drawing
-        // we call this glfwSwapBuffers() to swap the buffers to show the one we've
-        // been drawing to so that it now shows. We then can start drawing on the
-        // other buffer.
+        glBindVertexArray(0);
+        glUseProgram(0);
+
+
+        // We usually have two buffers, the first is hidden and that's
+        // the one we draw to. The second is the one we display, so
+        // when we're done drawing we call this glfwSwapBuffers() to
+        // swap the buffers to show the one we've been drawing to so
+        // that it now shows. We then can start drawing on the other
+        // buffer.
         glfwSwapBuffers(window);
     }