#include <glut.h>
#include <gl.h>
#include <glu.h>

GLint TopLeftX, TopLeftY, BottomRightX, BottomRightY;

void MyDisplay() {

glViewport(0, 0, 300, 300);
glClear(GL_COLOR_BUFFER_BIT);  // 컬러버퍼에 초기화 색을 가함
glColor3f(0.1, 0.1, 0.1);   // 회색

/*
glBegin(GL_POLYGON);    // 사각형
  glVertex3f(TopLeftX/300.0, (300-TopLeftY)/300.0, 0.0);
  glVertex3f(TopLeftX/300.0, (300-BottomRightY)/300.0, 0.0);
  glVertex3f(BottomRightX/300.0, (300-BottomRightY)/300.0, 0.0);
  glVertex3f(BottomRightX/300.0, (300-TopLeftY)/300.0, 0.0);
glEnd();
*/

glFlush();

}

void MyMouseClick(GLint Button, GLint State, GLint X, GLint Y) {

if(Button == GLUT_LEFT_BUTTON && State == GLUT_DOWN) {
  TopLeftX = X;
  TopLeftY = Y;
}

}

void MyMouseMove(GLint X, GLint Y) {

BottomRightX = X;
BottomRightY = Y;
glutPostRedisplay();

}

int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB);
glutInitWindowSize(300, 300);
glutInitWindowPosition(0, 0);
glutCreateWindow("OpenGL Reshape Example Drawing");
glClearColor(1.0, 1.0, 1.0, 1.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);
glutDisplayFunc(MyDisplay);
glutMouseFunc(MyMouseClick);
glutMotionFunc(MyMouseMove);
glutMainLoop();
return 0;
}

#include <glut.h>
#include <gl.h>
#include <glu.h>
#include <stdlib.h>      // exit() 함수를 쓰기 위함

float size = 0.5;
float corR = 0.0, corG = 0.0, corB = 0.0;
float movX = 0.0, movY = 0.0;

void MyDisplay() {

glClear(GL_COLOR_BUFFER_BIT);  // 컬러버퍼에 초기화 색을 가함
glColor3f(0.5, 0.5, 0.5);   // 회색

glBegin(GL_POLYGON);    // 사각형
 glVertex3f(-0.5, -0.5, 0.0);
 glVertex3f(0.5, -0.5, 0.0);
 glVertex3f(0.5, 0.5, 0.0);
 glVertex3f(-0.5, 0.5, 0.0);
glEnd();

glFlush();

}

void MyKeyboard(unsigned char KeyPressed, int x, int y) {

switch(KeyPressed) {
 case 'Q':  case 'q':  case 27 :
  exit(0); break;
 
 case 'R': case 'r':
  glColor3f(1.0, 0.0, 0.0);   // 빨간색  
  break;
 
 case 'G': case 'g':
  glColor3f(0.0, 1.0, 0.0);   // 녹색
  break;
 
 case 'B': case 'b':
  glColor3f(0.0, 0.0, 1.0);   // 파란색
  break;

 case '+':        // 사각형 크기 늘리기
  size += 0.01;
  break;

 case '-':        // 사각형 크기 줄이기
  size -= 0.01;
  break;

 case 'i':        // 사각형을 위로 이동
  movY += 0.01;
  break;

 case 'k':        // 사각형을 아래로 이동
  movY -= 0.01;
  break;

 case 'j':        // 사각형을 왼쪽으로 이동
  movX -= 0.01;
  break;

 case 'l':        // 사각형을 오른쪽으로 이동
  movX += 0.01;
  break;

}

glClear(GL_COLOR_BUFFER_BIT);  // 컬러버퍼에 초기화 색을 가함
glBegin(GL_POLYGON);      // 사각형 그리기
 glVertex3f(-size + movX, -size + movY, 0.0);
 glVertex3f(size + movX, -size + movY, 0.0);
 glVertex3f(size + movX, size + movY, 0.0);
 glVertex3f(-size + movX, size + movY, 0.0);
glEnd();
glFlush();

}

int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB);
glutInitWindowSize(300, 300);
glutInitWindowPosition(0, 0);
glutCreateWindow("OpenGL Keyboard Example Drawing");
glClearColor(1.0, 1.0, 1.0, 1.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glutDisplayFunc(MyDisplay);
glutKeyboardFunc(MyKeyboard);
glutMainLoop();
return 0;
}

GLint TopLeftX, TopLeftY, BottomRightX, BottomRightY;

void MyDisplay() {

glViewport(0, 0, 300, 300);
glClear(GL_COLOR_BUFFER_BIT);  // 컬러버퍼에 초기화 색을 가함
glColor3f(0.5, 0.5, 0.5);   // 회색

glBegin(GL_POLYGON);    // 사각형
 glVertex3f(TopLeftX/300.0, (300-TopLeftY)/300.0, 0.0);
 glVertex3f(TopLeftX/300.0, (300-BottomRightY)/300.0, 0.0);
 glVertex3f(BottomRightX/300.0, (300-BottomRightY)/300.0, 0.0);
 glVertex3f(BottomRightX/300.0, (300-TopLeftY)/300.0, 0.0);
glEnd();

/*
glBegin(GL_LINE);
 glVertex3f(TopLeftX/300.0, (300-TopLeftY)/300.0, 0.0);
 glVertex3f(BottomRightX/300.0, (300-BottomRightY)/300.0, 0.0);
glEnd();
*/

glFlush();

}

void MyMouseClick(GLint Button, GLint State, GLint X, GLint Y) {

if(Button == GLUT_LEFT_BUTTON && State == GLUT_DOWN) {
 TopLeftX = X;
 TopLeftY = Y;
}

}

void MyMouseMove(GLint X, GLint Y) {

BottomRightX = X;
BottomRightY = Y;
glutPostRedisplay();

}

int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB);
glutInitWindowSize(300, 300);
glutInitWindowPosition(0, 0);
glutCreateWindow("OpenGL Reshape Example Drawing");
glClearColor(1.0, 1.0, 1.0, 1.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);
glutDisplayFunc(MyDisplay);
glutMouseFunc(MyMouseClick);
glutMotionFunc(MyMouseMove);
glutMainLoop();
return 0;
}