Lab5_Doublebuffering.cpp

// Lab5 Doublebuffering 12171788 박지은

#include <gl/glut.h>
#include <gl/freeglut.h>
#include <stdio.h>

double spin = 0; // 회전값 초기화
int draw_mode = 0; // 도형 선택 변수 초기화

void init(void) {
   glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   gluOrtho2D(0.0f, 500.0f, 0.0f, 500.0f);
}

void idle(void) {
   spin = spin + 0.1; // 회전값 증가
   if (spin > 360) spin -= 360;
   // 1회전 시 회전값 초기화
   glutPostRedisplay();
}

void keyboard(unsigned char key, int x, int y) {
   printf("You pressed %c\n", key);
   if (key == 'a') {
      glutIdleFunc(idle);
   } // a 버튼 누르면 회전 실행
   else if (key == 'b') {
      glutIdleFunc(NULL);
   } // b 버튼 누르면 정지
}

void main_menu_function(int option) {
   printf("Main menu %d has been selected\n", option);
   if (option == 999) exit(0);
   else if (option == 1) draw_mode = 1; // draw_point
   else if (option == 2) draw_mode = 2; // draw_line
   else if (option == 3) draw_mode = 3; // draw_triangle
   glutPostRedisplay();
}

void draw_point(void) {
   glColor3f(1.0f, 0.0f, 0.0f);
   glPointSize(20.0f);
   glBegin(GL_POINTS);

   glVertex2i(100, 300);

   glEnd();
} // 점 그리기 함수

void draw_line(void) {
   glColor3f(1.0f, 1.0f, 0.0f);
   glBegin(GL_LINES);

   glVertex2i(50, 50);
   glVertex2i(250, 450);

   glEnd();
} // 선 그리기 함수

void draw_triangle(void) {
   glColor3f(1.0f, 1.0f, 0.0f);
   glBegin(GL_TRIANGLES);

   glVertex2i(250, 250);
   glVertex2i(150, 300);
   glVertex2i(300, 400);

   glEnd();
} // 도형(삼각형) 그리기 함수

void draw(void) {
   glClear(GL_COLOR_BUFFER_BIT);

   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();

   glTranslatef(250, 250, 0);
   glRotatef(spin, 0, 0, 1);
   glTranslatef(-250, -250, 0);

   switch (draw_mode) {
   case 1:
      draw_point();
      break;
   case 2:
      draw_line();
      break;
   case 3:
      draw_triangle();
      break;
   }
   
   glutSwapBuffers();
   // back buffer를 front buffer로 변경
}

int main(int argc, char** argv) {
   glutInit(&argc, argv);
   glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA);
   // double buffer로 변경
   glutInitWindowSize(500, 500);
   glutInitWindowPosition(300, 300);
   glutCreateWindow("12171788 박지은");
   init();

   glutCreateMenu(main_menu_function);
   glutAddMenuEntry("Quit", 999);
   glutAddMenuEntry("Point", 1);
   glutAddMenuEntry("Line", 2);
   glutAddMenuEntry("Triangle", 3);
   glutAttachMenu(GLUT_RIGHT_BUTTON);

   glutIdleFunc(idle);
   glutDisplayFunc(draw);
   glutKeyboardFunc(keyboard);
   // glut 콜백 함수

   glutMainLoop();

   return 0;
}