Used learnopengl.com triangle tutorial code to get a first triangle (with different libraries)

src/main.c

@@ -1,10 +1,29 @@
 #include "SDL3/SDL_init.h"
 #include "SDL3/SDL_log.h"
-#include "SDL3/SDL_opengl.h"
 #include "SDL3/SDL_render.h"
 #include "SDL3/SDL_video.h"
+#include <GL/glew.h>
 #include <stdlib.h>
 
+// settings
+const unsigned int SCR_WIDTH = 800;
+const unsigned int SCR_HEIGHT = 600;
+
+const char *vertexShaderSource =
+    "#version 330 core\n"
+    "layout (location = 0) in vec3 aPos;\n"
+    "void main()\n"
+    "{\n"
+    "   gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
+    "}\0";
+const char *fragmentShaderSource =
+    "#version 330 core\n"
+    "out vec4 FragColor;\n"
+    "void main()\n"
+    "{\n"
+    "   FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
+    "}\n\0";
+
 int main(int argc, char *argv[]) {
   SDL_Window *window;
   SDL_Renderer *renderer;
@@ -24,12 +43,111 @@ int main(int argc, char *argv[]) {
   window = SDL_CreateWindow("Hello SDL3", 320, 240,
                             SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE);
   if (!window) {
-    SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Couldn't create windowe: %s",
+    SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Couldn't create window: %s",
                  SDL_GetError());
     return EXIT_FAILURE;
   }
-
   SDL_GLContext glcontext = SDL_GL_CreateContext(window);
+  if (!glcontext) {
+    SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
+                 "Couldn't create OpenGL Context: %s", SDL_GetError());
+    return EXIT_FAILURE;
+  }
+
+  GLenum glewError = glewInit();
+  if (glewError != GLEW_OK) {
+    SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Error initializing GLEW! %s",
+                 glewGetErrorString(glewError));
+  }
+
+  if (!SDL_GL_MakeCurrent(window, glcontext)) {
+    SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
+                 "Couldn't make glcontext current: %s", SDL_GetError());
+  }
+
+  // vertex shader
+  unsigned int vertexShader = glCreateShader(GL_VERTEX_SHADER);
+  glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
+  glCompileShader(vertexShader);
+  // check for shader compile errors
+  int success;
+  char infoLog[512];
+  glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
+  if (!success) {
+    glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
+    SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
+                 "Failed to compile vertex shader: %s", infoLog);
+  }
+  // fragment shader
+  unsigned int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
+  glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
+  glCompileShader(fragmentShader);
+  // check for shader compile errors
+  glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
+  if (!success) {
+    glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
+    SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
+                 "Failed to compile fragment shader: %s", infoLog);
+  }
+  // link shaders
+  unsigned int shaderProgram = glCreateProgram();
+  glAttachShader(shaderProgram, vertexShader);
+  glAttachShader(shaderProgram, fragmentShader);
+  glLinkProgram(shaderProgram);
+  // check for linking errors
+  glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
+  if (!success) {
+    glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
+    SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
+                 "Failed to link shader program: %s", infoLog);
+  }
+  glDeleteShader(vertexShader);
+  glDeleteShader(fragmentShader);
+
+  // set up vertex data (and buffer(s)) and configure vertex attributes
+  float vertices[] = {
+      0.5f,  0.5f,  0.0f, // top right
+      0.5f,  -0.5f, 0.0f, // bottom right
+      -0.5f, -0.5f, 0.0f, // bottom left
+      -0.5f, 0.5f,  0.0f  // top left
+  };
+  unsigned int indices[] = {
+      // note that we start from 0!
+      0, 1, 3, // first Triangle
+      1, 2, 3  // second Triangle
+  };
+  unsigned int VBO, VAO, EBO;
+  glGenVertexArrays(1, &VAO);
+  glGenBuffers(1, &VBO);
+  glGenBuffers(1, &EBO);
+  // bind the Vertex Array Object first, then bind and set vertex buffer(s), and
+  // then configure vertex attributes(s).
+  glBindVertexArray(VAO);
+
+  glBindBuffer(GL_ARRAY_BUFFER, VBO);
+  glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
+
+  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
+  glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices,
+               GL_STATIC_DRAW);
+
+  glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void *)0);
+  glEnableVertexAttribArray(0);
+
+  // note that this is allowed, the call to glVertexAttribPointer registered VBO
+  // as the vertex attribute's bound vertex buffer object so afterwards we can
+  // safely unbind
+  glBindBuffer(GL_ARRAY_BUFFER, 0);
+
+  // remember: do NOT unbind the EBO while a VAO is active as the bound element
+  // buffer object IS stored in the VAO; keep the EBO bound.
+  // glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
+
+  // You can unbind the VAO afterwards so other VAO calls won't accidentally
+  // modify this VAO, but this rarely happens. Modifying other VAOs requires a
+  // call to glBindVertexArray anyways so we generally don't unbind VAOs (nor
+  // VBOs) when it's not directly necessary.
+  glBindVertexArray(0);
 
   while (1) {
     // handle input
@@ -39,11 +157,26 @@ int main(int argc, char *argv[]) {
     }
 
     // render
-    glClearColor(0, 0, 0, 1);
+    glClearColor(0.1f, 0.3f, 0.4f, 1.f);
     glClear(GL_COLOR_BUFFER_BIT);
+
+    // draw our first triangle
+    glUseProgram(shaderProgram);
+    glBindVertexArray(
+        VAO); // seeing as we only have a single VAO there's no need to bind it
+              // every time, but we'll do so to keep things a bit more organized
+    // glDrawArrays(GL_TRIANGLES, 0, 6);
+    glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
+    // glBindVertexArray(0); // no need to unbind it every time
+
     SDL_GL_SwapWindow(window);
   }
 
+  glDeleteVertexArrays(1, &VAO);
+  glDeleteBuffers(1, &VBO);
+  glDeleteBuffers(1, &EBO);
+  glDeleteProgram(shaderProgram);
+
   SDL_GL_DestroyContext(glcontext);
   SDL_DestroyWindow(window);