From 3a2d18f7310c4429dd2072707611a587722a82bb Mon Sep 17 00:00:00 2001
From: sigonasr2 <sigonasr2@gmail.com>
Date: Wed, 25 Oct 2023 18:26:11 -0500
Subject: [PATCH] Create basic vertex and fragment shader. Error handling.

---
 OpenGLTemplate/OpenGLTemplate.vcxproj         |   3 +
 OpenGLTemplate/OpenGLTemplate.vcxproj.filters |   5 +
 OpenGLTemplate/ShaderError.h                  |  39 +++++++
 OpenGLTemplate/main.cpp                       | 100 +++++++++++++++++-
 4 files changed, 145 insertions(+), 2 deletions(-)
 create mode 100644 OpenGLTemplate/ShaderError.h

diff --git a/OpenGLTemplate/OpenGLTemplate.vcxproj b/OpenGLTemplate/OpenGLTemplate.vcxproj
index dae2e99..f06f70c 100644
--- a/OpenGLTemplate/OpenGLTemplate.vcxproj
+++ b/OpenGLTemplate/OpenGLTemplate.vcxproj
@@ -141,6 +141,9 @@
   <ItemGroup>
     <ClCompile Include="main.cpp" />
   </ItemGroup>
+  <ItemGroup>
+    <ClInclude Include="ShaderError.h" />
+  </ItemGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>
diff --git a/OpenGLTemplate/OpenGLTemplate.vcxproj.filters b/OpenGLTemplate/OpenGLTemplate.vcxproj.filters
index ce0c35c..62b6244 100644
--- a/OpenGLTemplate/OpenGLTemplate.vcxproj.filters
+++ b/OpenGLTemplate/OpenGLTemplate.vcxproj.filters
@@ -19,4 +19,9 @@
       <Filter>Source Files</Filter>
     </ClCompile>
   </ItemGroup>
+  <ItemGroup>
+    <ClInclude Include="ShaderError.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+  </ItemGroup>
 </Project>
\ No newline at end of file
diff --git a/OpenGLTemplate/ShaderError.h b/OpenGLTemplate/ShaderError.h
new file mode 100644
index 0000000..8ae7d47
--- /dev/null
+++ b/OpenGLTemplate/ShaderError.h
@@ -0,0 +1,39 @@
+#pragma once
+#include <GL/glew.h>
+#include <cstdlib>
+#include <iostream>
+
+namespace ErrorCheck{
+    inline void printShaderLog(GLuint shader) {
+       int len = 0;
+       int chWrittn = 0;
+       char *log;
+       glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &len);
+       if (len > 0) {
+            log = (char *)malloc(len);
+            glGetShaderInfoLog(shader, len, &chWrittn, log);
+            std::cout << "Shader Info Log: " << log << std::endl;
+            free(log);
+    }  }
+    inline void printProgramLog(int prog) {
+       int len = 0;
+       int chWrittn = 0;
+       char *log;
+       glGetProgramiv(prog, GL_INFO_LOG_LENGTH, &len);
+       if (len > 0) {
+            log = (char *)malloc(len);
+            glGetProgramInfoLog(prog, len, &chWrittn, log);
+            std::cout << "Program Info Log: " << log << std::endl;
+            free(log);
+    } }
+    inline bool checkOpenGLError() {
+      bool foundError = false;
+      int glErr = glGetError();
+      while (glErr != GL_NO_ERROR) {
+          std::cout << "glError: " << glErr << std::endl;
+          foundError = true;
+          glErr = glGetError();
+      }
+      return foundError;
+    }
+}
\ No newline at end of file
diff --git a/OpenGLTemplate/main.cpp b/OpenGLTemplate/main.cpp
index eac2b6e..3db875b 100644
--- a/OpenGLTemplate/main.cpp
+++ b/OpenGLTemplate/main.cpp
@@ -1,5 +1,101 @@
+#include <GL/glew.h>
+#include <GLFW/glfw3.h>
 #include <iostream>
+#include "ShaderError.h"
 
-int main(){
-	std::cout<<"It works!"<<std::endl;
+#define numVAOs 1
+
+GLuint renderingProgram;
+GLuint vao[numVAOs];
+
+GLuint createShaderProgram(){
+    GLint vertCompiled;
+    GLint fragCompiled;
+    GLint linked;
+    // catch errors while compiling shaders
+
+    const char*vShaderSource=
+        "#version 430 \n"
+        "void main(void) \n"
+        "{gl_Position=vec4(0.0,0.0,0.0,1.0);}";
+    const char*fShaderSource=
+        "#version 430 \n"
+        "out vec4 color; \n"
+        "void main(void) \n"
+        "{ color=vec4((gl_FragCoord.x-300)/5.f,0.0,5-(gl_FragCoord.x-300)/5.f,1.0); }";
+
+    GLuint vShader=glCreateShader(GL_VERTEX_SHADER);
+    GLuint fShader=glCreateShader(GL_FRAGMENT_SHADER);
+
+    glShaderSource(vShader,1,&vShaderSource,NULL);
+    glShaderSource(fShader,1,&fShaderSource,NULL);
+
+    glCompileShader(vShader);
+    ErrorCheck::checkOpenGLError();
+    glGetShaderiv(vShader,GL_COMPILE_STATUS,&vertCompiled);
+    if(vertCompiled!=1){
+        std::cout<<"Vertex Compilation Failed!"<<std::endl;
+        ErrorCheck::printShaderLog(vShader);
+        throw;
+    }
+
+    glCompileShader(fShader);
+    ErrorCheck::checkOpenGLError();
+    glGetShaderiv(fShader,GL_COMPILE_STATUS,&fragCompiled);
+    if(fragCompiled!=1){
+        std::cout<<"Fragment Compilation Failed!"<<std::endl;
+        ErrorCheck::printShaderLog(fShader);
+        throw;
+    }
+
+    //catch errors while linking shaders
+
+    GLuint vfProgram=glCreateProgram();
+
+    glAttachShader(vfProgram,vShader);
+    glAttachShader(vfProgram,fShader);
+
+    glLinkProgram(vfProgram);
+    ErrorCheck::checkOpenGLError();
+    glGetProgramiv(vfProgram,GL_LINK_STATUS,&linked);
+    if(linked!=1){
+        std::cout<<"Linking Failed!"<<std::endl;
+        ErrorCheck::printProgramLog(vfProgram);
+    }
+
+    return vfProgram;
+}
+
+void init(GLFWwindow* window) {
+    renderingProgram=createShaderProgram();
+    glGenVertexArrays(numVAOs,vao);
+    glBindVertexArray(vao[0]);
+}
+
+void display(GLFWwindow* window, double currentTime) {
+    glUseProgram(renderingProgram);
+    glPointSize(30);
+    glDrawArrays(GL_POINTS,0,1);
+}
+
+int main(void) {
+    if (!glfwInit()) { exit(EXIT_FAILURE); }
+    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
+    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
+    GLFWwindow* window = glfwCreateWindow(600, 600, "My First OpenGL Program!", NULL, NULL);
+    glfwMakeContextCurrent(window);
+    if (glewInit() != GLEW_OK) { exit(EXIT_FAILURE); }
+    glfwSwapInterval(1);
+
+    init(window);
+
+    while (!glfwWindowShouldClose(window)) {
+        display(window,glfwGetTime());
+        glfwSwapBuffers(window);
+        glfwPollEvents();
+    }
+
+    glfwDestroyWindow(window);
+    glfwTerminate();
+    exit(EXIT_SUCCESS);
 }
\ No newline at end of file