feat: create attach link shaders

Engine/engine/constants.hpp

@@ -30,6 +30,27 @@ namespace constants
         GLfloat alpha = 1.0f;
     } LEARN_OPEN_GL_COLOR;
 
+    // we write vertex shader 
+    // version of glsl (since ogl 3.3 same as ogl so we pick 330)
+    // in this shader we just forward input data to shader output
+    inline 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" } ;
+
+    // write fragment shader
+    // we set the color of each pixel to be orange
+    inline 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"
+        "}\0"
+    };
+
 }
 
 #endif

Engine/engine/match.cpp

@@ -81,6 +81,60 @@ void processInput(GLFWwindow *window)
         glfwSetWindowShouldClose(window, true);
 }
 
+int shaderProgramLinkingSuccessful(const unsigned int shaderProgram)
+{
+    // check if compilation was successful
+    // int because glGetShaderiv requires int
+    int successfulLinking;
+    // here we store info about compilation
+    char infoLog[512];
+    // check if compilation was successful 
+    glGetProgramiv(shaderProgram, GL_LINK_STATUS, &successfulLinking);
+    // if not display compilation log
+    if(!successfulLinking)
+    {
+        glGetProgramInfoLog(shaderProgram, sizeof(infoLog) / sizeof(infoLog[0]), NULL, infoLog);
+        std::cout << "ERROR shaderProgram compilation failed \n" << infoLog << std::endl;
+    }
+    return successfulLinking;
+}
+
+
+int shaderCompilationSuccessful(const unsigned int shader)
+{
+
+    
+    // check if compilation was successful
+    // int because glGetShaderiv requires int
+    int successfulCompilation;
+    // here we store info about compilation
+    char infoLog[512];
+    // check if compilation was successful 
+    glGetShaderiv(shader, GL_COMPILE_STATUS, &successfulCompilation);
+    // if not display compilation log
+    if(!successfulCompilation)
+    {
+        glGetShaderInfoLog(shader, sizeof(infoLog) / sizeof(infoLog[0]), NULL, infoLog);
+        std::cout << "ERROR vertex shader compilation failed \n" << infoLog << std::endl;
+    }
+    return successfulCompilation;
+}
+
+unsigned int compileShader(const GLenum shaderType, const char * shaderSource)
+{
+    // we create vertex shader and assign its id to shader variable
+    unsigned int shaderID;
+    shaderID = glCreateShader(GL_VERTEX_SHADER);
+
+    // attach shader source code to shader object
+    // from left: shader object to compile, how many strings as source code, actual source code (we leave the 4th as NULL)
+    glShaderSource(shaderID, 1, &shaderSource, NULL);
+    // compile shader
+    glCompileShader(shaderID);
+    if(!shaderCompilationSuccessful(shaderID)) return 0;
+    return shaderID;
+}
+
 void drawTriangle()
 {
     // we specify three vertices
@@ -108,18 +162,38 @@ void drawTriangle()
     */
     glBufferData(GL_ARRAY_BUFFER, sizeof(triangleVertices), triangleVertices, GL_STATIC_DRAW);
 
-    // we write vertex shader 
-    // version of glsl (since ogl 3.3 same as ogl so we pick 330)
-    // in this shader we just forward input data to shader output
-    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";
 
+    unsigned int vertexShader = compileShader(GL_VERTEX_SHADER, constants::vertexShaderSource);
+    if(vertexShader == 0) return;
+
+    unsigned int fragmentShader = compileShader(GL_FRAGMENT_SHADER, constants::fragmentShaderSource);
+    if(fragmentShader == 0) return;
+
+    // link shader objects into shader program 
+    // will store shader program id
+    unsigned int shaderProgram;
+    // creates program 
+    shaderProgram = glCreateProgram();
+
+    // attachShaders
+    glAttachShader(shaderProgram, vertexShader);
+    glAttachShader(shaderProgram, fragmentShader);
+
+    // link shaders
+    glLinkProgram(shaderProgram);
+    if(!shaderProgramLinkingSuccessful(shaderProgram)) return;
+
+    // activate program
+    // after that every shader and rendering call will use this program object
+    glUseProgram(shaderProgram);
+    
+    // delete shaders (they are linked into shaderProgram and we do not need them anymore)
+    glDeleteShader(vertexShader);
+    glDeleteShader(fragmentShader);
 }
 
+
+
 void renderLoop(GLFWwindow* window)
 {
     // glfwWindowShouldClose checks if GLFW was instructed to close
@@ -141,6 +215,7 @@ void renderLoop(GLFWwindow* window)
 
         // glfwPollEvents checks if any event (like mouse/keyboard input was triggered), updates window state and calls functions (which we register via callback methods)
         glfwPollEvents();    
+        drawTriangle();
 
     }
 }