basic.glsl

#version 450 core                           //lower your version if GLSL 4.5 is not supported by your GPU

layout (location = 0) in vec3 VertexPosition;
uniform mat4x4 a;
 
void main()
{
	gl_Position = a * vec4(VertexPosition, 1.0);
}

frag.glsl

varying vec4 v_color;

void main() {
	gl_FragColor = v_color;
}

main.cpp

int main() {
  glViewport(0,0,800,600);
	glEnable(GL_DEPTH_TEST);
	auto projection = glm::ortho( 0.f, 800.f, 0.f, 600.f, 1.f, -1.f );
	glm::mat4 view       = glm::lookAt(
		glm::vec3(0.f,0.f,0.f),
		glm::vec3(0.f,0.f,0.f),
		glm::vec3(0.f,0.f,0.f)
	);  
	glm::mat4 model      = glm::mat4(1.0f);
	glm::mat4 MVP        = projection*view * model;
	auto program = glCreateProgram();
	auto asdf = shaders["basic.glsl"].c_str();
	auto fdsa = shaders["fragment.glsl"].c_str();
	GLuint vs = glCreateShader (GL_VERTEX_SHADER);
		glShaderSource(vs, 1, &asdf, NULL);
		glCompileShader(vs);
		int result;
		glGetShaderiv(vs, GL_COMPILE_STATUS, &result);
		if (result != GL_TRUE) {
			printf("shader fail\n");
			exit(1);
		}
		glAttachShader(program, vs);
		glLinkProgram(program);
	
	
	unsigned int vao;
	unsigned int vbo;

	glGenVertexArrays(1, &vao);
	glBindVertexArray(vao);
	
	float vertices[][3] ={
		{0.0f, 0.0f, 0.0f}, {100.0f, 0.0f, 0.0f}, {0.0f, 100.0f, 0.0f}
	};

	glGenBuffers(1, &vbo);
	glBindBuffer(GL_ARRAY_BUFFER, vbo);
	glBufferData(GL_ARRAY_BUFFER, sizeof(float) * 3 * sizeof(vertices), &vertices[0], GL_STATIC_DRAW);
	glEnableVertexAttribArray(0);
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(float) * 3, (void*)0);
	
	
	while (1) {
		poll();
		if (done) {
			glXMakeCurrent(display, None, NULL);
			glXDestroyContext(display, ctx);
			XDestroyWindow(display, win);
			XFreeColormap(display, cmap);
			XCloseDisplay(display);
			return 0;
		}
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
		glClearColor(1.0, 0.3, 0.3, 1.0);
		glUseProgram(program);
		auto projection_Location =  glGetUniformLocation(program, "a");
		printf("\nLocation: %d\n", projection_Location);
		glUniformMatrix4fv(projection_Location, 1, GL_FALSE, glm::value_ptr(MVP));
		
		glBindVertexArray(vao);
		glDrawArrays(GL_TRIANGLES, 0, 3);
		glXSwapBuffers(display, win);
		
	}
}