Add a togglable rectangle and toggable wireframe.

.vscode/settings.json

@@ -0,0 +1,5 @@
+{
+	"clangd.arguments": [
+		"-header-insertion=never"
+	]
+}

src/main.cc

@@ -4,6 +4,7 @@
 
 void framebuffer_size_callback(GLFWwindow* window, int width, int height);
 void process_input(GLFWwindow* window);
+void key_pressed(GLFWwindow *window, int key, int scancode, int action, int mods);
 int check_shader_compilation_status(unsigned int shaderId);
 
 const char* vertexShaderCode = R"(
@@ -26,6 +27,98 @@ void main() {
 }
 )";
 
+bool wireframe;
+bool rectangleToggled;
+
+struct GlRenderObjects {
+	unsigned int vertexBufferObject;
+	unsigned int vertexArrayObject;
+	unsigned int elementBufferObject;
+	void Destroy() {
+		glDeleteBuffers(1, &vertexBufferObject);
+		glDeleteVertexArrays(1, &vertexArrayObject);
+		glDeleteBuffers(1, &elementBufferObject);
+	}
+};
+
+GlRenderObjects triangle() {
+	// An array of verticies containing data for a triangle.
+	float vertices[] = {
+		-0.5f, -0.5f, 0.0f,
+		0.5f, -0.5f, 0.0f,
+		0.0f, 0.5f,  0.0f
+	};
+
+	unsigned int vertexBufferObject, vertexArrayObject;
+	// Create a Vertex Array Object.
+	glGenVertexArrays(1, &vertexArrayObject);
+	// Create a Vertex Buffer Object and write the id to the vertexBufferObject variable.
+	glGenBuffers(1, &vertexBufferObject);
+	// Bind the vertex array object so the attributes are stored in that object.
+	glBindVertexArray(vertexArrayObject);
+
+	// Bind the GL_ARRAY_BUFFER target to the verterBufferObject object id.
+	glBindBuffer(GL_ARRAY_BUFFER, vertexBufferObject);
+	// Copy the verticies data into the vertexBufferObject object and tell the GPU it will only be written once but read many times.
+	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
+
+	// Tell OpenGL how to process the Vertex attributes so it can pass it to the Vertex shader.
+	// This will pass the vertex to the location "0". We tell OpenGL the size of the array is 3 elements.
+	// We tell OpenGL that we're using floating point types.
+	// We tell OpenGL we don't want our data to be normalized as its already normalized.
+	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
+	glEnableVertexAttribArray(0);
+
+	glBindBuffer(GL_ARRAY_BUFFER, 0);
+	glBindVertexArray(0);
+
+	return {vertexBufferObject, vertexArrayObject, 0};
+}
+
+GlRenderObjects rectangle() {
+	float vertices[] = {
+		0.5f,  0.5f, 0.0f,
+		0.5f, -0.5f, 0.0f,
+		-0.5f, -0.5f, 0.0f,
+		-0.5f,  0.5f, 0.0f
+	};
+
+	unsigned int indices[] = {
+		0, 1, 3,
+		1, 2, 3
+	};
+
+	unsigned int vertexBufferObject, vertexArrayObject, elementBufferObject;
+
+	// Create a Vertex Array Object.
+	glGenVertexArrays(1, &vertexArrayObject);
+	// Create a Vertex Buffer Object.
+	glGenBuffers(1, &vertexBufferObject);
+	// Create a Element Buffer Object;
+	glGenBuffers(1, &elementBufferObject);
+
+	// Bind the Vertex Array Object to the state.
+	glBindVertexArray(vertexArrayObject);
+	// Bind the Vertex Buffer Object to the GL_ARRAY_BUFFER target on the state.
+	glBindBuffer(GL_ARRAY_BUFFER, vertexBufferObject);
+	// Copy verticies into the GPU's memory.
+	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
+	// Bind the Element Buffer Object to the GL_ELEMENT_ARRAY_BUFFER target on the state.
+	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementBufferObject);
+	// Copy indicies into the GPU's memory.
+	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
+	// Tell OpenGL on how to process the verticies.
+	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void *)0);
+	glEnableVertexAttribArray(0);
+
+	// Unbind the current buffers and arrays from the state.
+	glBindBuffer(GL_ARRAY_BUFFER, 0);
+	glBindVertexArray(0);
+	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
+
+	return {vertexBufferObject, vertexArrayObject, elementBufferObject};
+}
+
 int main() {
 	glfwInit();
 
@@ -103,40 +196,15 @@ int main() {
 	glDeleteShader(vertexShader);
 	glDeleteShader(fragmentShader);
 
-	// An array of verticies containing data for a triangle.
+	GlRenderObjects triangleRenderObjs = triangle();
-	float vertices[] = {
+	GlRenderObjects rectangleRenderObjs = rectangle();
-		-0.5f, -0.5f, 0.0f,
-		0.5f, -0.5f, 0.0f,
-		0.0f, 0.5f,  0.0f
-	};
-
-	unsigned int vertexBufferObject, vertexArrayObject;
-	// Create a Vertex Array Object.
-	glGenVertexArrays(1, &vertexArrayObject);
-	// Create a Vertex Buffer Object and write the id to the vertexBufferObject variable.
-	glGenBuffers(1, &vertexBufferObject);
-	// Bind the vertex array object so the attributes are stored in that object.
-	glBindVertexArray(vertexArrayObject);
-
-	// Bind the GL_ARRAY_BUFFER target to the verterBufferObject object id.
-	glBindBuffer(GL_ARRAY_BUFFER, vertexBufferObject);
-	// Copy the verticies data into the vertexBufferObject object and tell the GPU it will only be written once but read many times.
-	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
-
-	// Tell OpenGL how to process the Vertex attributes so it can pass it to the Vertex shader.
-	// This will pass the vertex to the location "0". We tell OpenGL the size of the array is 3 elements.
-	// We tell OpenGL that we're using floating point types.
-	// We tell OpenGL we don't want our data to be normalized as its already normalized.
-	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
-	glEnableVertexAttribArray(0);
-
-	glBindBuffer(GL_ARRAY_BUFFER, 0);
-	glBindVertexArray(0);
 
 	// Create a render loop, which keeps the program open until glfw tells the loop that the window should close.
 	while (!glfwWindowShouldClose(window)) {
 		// Process input.
 		process_input(window);
+		// Set a callback to trigger whenever a key is pressed.
+		glfwSetKeyCallback(window, key_pressed);
 		
 		// Set the GL state to use this color when clearing the screen.
 		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
@@ -145,10 +213,17 @@ int main() {
 
 		// Use the shaderProgram shader program for drawing verticies.
 		glUseProgram(shaderProgram);
-		// Bind the state to use the vertexArrayObject object so OpenGL knows what to do with the verticies.
+		if (!rectangleToggled) {
-		glBindVertexArray(vertexArrayObject);
+			// Bind the state to use the vertexArrayObject object so OpenGL knows what to do with the verticies.
-		// Draw the verticies.
+			glBindVertexArray(triangleRenderObjs.vertexArrayObject);
-		glDrawArrays(GL_TRIANGLES, 0, 3);
+			// Draw the verticies.
+			glDrawArrays(GL_TRIANGLES, 0, 3);
+			glBindVertexArray(0);
+		} else {
+			glBindVertexArray(rectangleRenderObjs.vertexArrayObject);
+			glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
+			glBindVertexArray(0);
+		}
 
 		// This swaps completely drawn frames from the "second buffer" to the front one which is displayed on the screen.
 		glfwSwapBuffers(window);
@@ -156,6 +231,11 @@ int main() {
 		glfwPollEvents();
 	}
 
+	// Clean up objects from memory.
+	triangleRenderObjs.Destroy();
+	rectangleRenderObjs.Destroy();
+	glDeleteProgram(shaderProgram);
+
 	glfwTerminate();
 	return 0;
 }
@@ -176,3 +256,23 @@ int check_shader_compilation_status(unsigned int shaderId) {
 	glGetShaderiv(shaderId, GL_COMPILE_STATUS, &success);
 	return success;
 }
+
+void key_pressed(GLFWwindow *window, int key, int scancode, int action, int mods) {
+	// If the W key is pressed, toggle wireframe mode.
+	if (key == GLFW_KEY_W && action == GLFW_PRESS) {
+		if (!wireframe) {
+			// Render polygons in wireframe mode.
+			glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
+			wireframe = true;
+		} else {
+			// Render polygons in fill mode.
+			glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
+			wireframe = false;		
+		}
+	}
+
+	// Flip a boolean indicating the rectangle should be rendered.
+	if (key == GLFW_KEY_R && action == GLFW_PRESS) {
+		rectangleToggled = !rectangleToggled;
+	}
+}