From fe96bc501c56fa8ef4eb11b72a7ce5516140094f Mon Sep 17 00:00:00 2001
From: GuilhermeWerner <guilhermeqwerner@gmail.com>
Date: Thu, 14 Jan 2021 15:11:53 -0300
Subject: [PATCH] Craete Custom Shader

---
 OpenGL/Source/Application.cpp | 81 +++++++++++++++++++++++++++++++++--
 1 file changed, 78 insertions(+), 3 deletions(-)

diff --git a/OpenGL/Source/Application.cpp b/OpenGL/Source/Application.cpp
index 2cda635..ec26bac 100644
--- a/OpenGL/Source/Application.cpp
+++ b/OpenGL/Source/Application.cpp
@@ -3,6 +3,56 @@
 
 #include <iostream>
 
+static unsigned int CompileShader(unsigned int type, const std::string &source)
+{
+    unsigned int id = glCreateShader(type);
+    const char *src = source.c_str();
+
+    glShaderSource(id, 1, &src, nullptr);
+    glCompileShader(id);
+
+    int result;
+    glGetShaderiv(id, GL_COMPILE_STATUS, &result);
+
+    if (result == GL_FALSE)
+    {
+        int lenght;
+        glGetShaderiv(id, GL_INFO_LOG_LENGTH, &lenght);
+
+        char *message = (char *)alloca(lenght + sizeof(char));
+
+        glGetShaderInfoLog(id, lenght, &lenght, message);
+
+        std::cout << "Failed to compile " << (type == GL_VERTEX_SHADER ? "vertex" : "fragment") << " shader!" << std::endl;
+        std::cout << message << std::endl;
+
+        glDeleteShader(id);
+
+        return 0;
+    }
+
+    return id;
+}
+
+static unsigned int CreateShader(const std::string &vertexShader, const std::string &fragmentShader)
+{
+    unsigned int program = glCreateProgram();
+
+    unsigned int vs = CompileShader(GL_VERTEX_SHADER, vertexShader);
+    unsigned int fs = CompileShader(GL_FRAGMENT_SHADER, fragmentShader);
+
+    glAttachShader(program, vs);
+    glAttachShader(program, fs);
+
+    glLinkProgram(program);
+    glValidateProgram(program);
+
+    glDeleteShader(vs);
+    glDeleteShader(fs);
+
+    return program;
+}
+
 int main()
 {
     GLFWwindow *window;
@@ -31,9 +81,8 @@ int main()
 
     float positions[6] = {
         -0.5f, -0.5f,
-         0.0f, 0.5f,
-         0.5f, -0.5f
-    };
+        0.0f, 0.5f,
+        0.5f, -0.5f};
 
     unsigned int buffer;
     glGenBuffers(1, &buffer);
@@ -43,6 +92,30 @@ int main()
     glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, sizeof(float) * 2, 0);
     glEnableVertexAttribArray(0);
 
+    std::string vertexShader =
+        "#version 330 core\n"
+        "\n"
+        "layout(location = 0) in vec4 position;\n"
+        "\n"
+        "void main()\n"
+        "{\n"
+        "   gl_Position = position;\n"
+        "}\n";
+
+    std::string fragmentShader =
+        "#version 330 core\n"
+        "\n"
+        "layout(location = 0) out vec4 color;\n"
+        "\n"
+        "void main()\n"
+        "{\n"
+        "   color = vec4(0.0, 1.0, 0.0, 1.0);\n"
+        "}\n";
+
+    unsigned int shader = CreateShader(vertexShader, fragmentShader);
+
+    glUseProgram(shader);
+
     /* Loop until the user closes the window */
     while (!glfwWindowShouldClose(window))
     {
@@ -58,6 +131,8 @@ int main()
         glfwPollEvents();
     }
 
+    glDeleteProgram(shader);
+
     glfwTerminate();
 
     return 0;