Draw a square in opengl at mouse position - opengl

Question

I am trying to draw a simple square wherever I press the left mouse button using opengl/glut. My program runs perfectly except for the part where it does not draw the square where I click the left mouse button :). Can someone point out what I am doing wrong?
#include <stdlib.h>
#include <glut.h>
GLsizei WIDTH = 1300, HEIGHT = 700;
GLsizei MOUSEx, MOUSEy;
GLfloat SIDE=1;
GLfloat RED[3] = {1,0,0};
GLfloat GREEN[3] = {0,1,0};
GLfloat BLUE[3] = {0,0,1};
GLfloat WHITE[3] = {1,1,1};
GLfloat BLACK[3] = {0,0,0};
GLfloat YELLOW[3] = {1,1,0};
GLfloat CYAN[3] = {0,1,1};
GLfloat MAGENTA[3] = {1,0,1};
void drawSquare(int x, int y)
{
glColor3fv(YELLOW);
glBegin(GL_POLYGON);
glVertex3f(x+SIDE, y+SIDE,0);
glVertex3f(x-SIDE, y+SIDE,0);
glVertex3f(x-SIDE, y-SIDE,0);
glVertex3f(x+SIDE, y-SIDE,0);
glEnd();
glFlush();
}
void drawSquare1()
{
int x=0,y=0;
glColor3fv(BLUE);
glBegin(GL_POLYGON);
glVertex3f(x+SIDE, y+SIDE,0);
glVertex3f(x-SIDE, y+SIDE,0);
glVertex3f(x-SIDE, y-SIDE,0);
glVertex3f(x+SIDE, y-SIDE,0);
glEnd();
glFlush();
}
void display (void) {
glClearColor (0.0,0.0,0.0,1.0);
glClear (GL_COLOR_BUFFER_BIT);
glLoadIdentity();
glTranslatef(0,0,-5);
drawSquare1();
glFlush();
}
void reshape (int w, int h) {
glViewport (0, 0, (GLsizei)w, (GLsizei)h);
glMatrixMode (GL_PROJECTION);
glLoadIdentity ();
gluPerspective (60, (GLfloat)w / (GLfloat)h, 1.0, 100.0);
glMatrixMode (GL_MODELVIEW);
WIDTH=w;
HEIGHT=h;
}
void setX(int x)
{
MOUSEx=x;
}
void setY(int y)
{
MOUSEy=y;
}
void mouse(int btn, int state, int x, int y)
{
if(btn==GLUT_LEFT_BUTTON && state==GLUT_DOWN)
{
setX(x);
setY(y);
drawSquare(MOUSEx,HEIGHT-MOUSEy);
glutPostRedisplay();
}
if(btn==GLUT_RIGHT_BUTTON && state==GLUT_DOWN)
{
exit(1);
}
}
int main (int argc, char **argv) {
glutInit (&argc, argv);
glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize (WIDTH, HEIGHT);
glutInitWindowPosition (10, 10);
glutCreateWindow ("New Window");
glutDisplayFunc (display);
glutReshapeFunc (reshape);
glutMouseFunc(mouse);
//glutMotionFunc(drawSquare);
glutMainLoop ();
return 0;
}

Answer 1

In short words: OpenGL is not a scene graph. That means that those drawing commands issued in the mouse handler don't create some kind of "persistency".
Instead clicking the mouse you should store the position in a list/array and draw the squares from the values in that list in the display function.

Answer 2

I am fresh to this Coding But I done it.
Here is My Code It will Work.
#include <GL/glut.h>
GLsizei MOUSEx=0, MOUSEy=0;
GLfloat SIDE=50;
GLfloat BLUE[3] = {0,0,1};
void drawSquare1()
{
glColor3fv(BLUE);
glBegin(GL_POLYGON);
glVertex3f(MOUSEx, MOUSEy,0);
glVertex3f(MOUSEx+SIDE, MOUSEy,0);
glVertex3f(MOUSEx+SIDE, MOUSEy+SIDE,0);
glVertex3f(MOUSEx, MOUSEy+SIDE,0);
glEnd();
glFlush();
}
void display(void)
{
glClearColor (0.0,0.0,0.0,1.0);
glClear (GL_COLOR_BUFFER_BIT);
glLoadIdentity();
drawSquare1();
glFlush();
}
void reshape(int w, int h)
{
glViewport(0,0,(GLsizei)w,(GLsizei)h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
//gluPerspective (60, (GLfloat)w / (GLfloat)h, 1.0, 100.0);
glOrtho(0.0,1368,768,0,-1.0,1.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
void spindisplay(void)
{
glutPostRedisplay();
}
void setX(int x)
{
MOUSEx=x;
}
void setY(int y)
{
MOUSEy=y;
}
void mouse(int btn, int state, int x, int y)
{
if(btn==GLUT_LEFT_BUTTON && state==GLUT_DOWN)
{
setX(x);
setY(y);
//drawSquare(MOUSEx,HEIGHT-MOUSEy);
glutPostRedisplay();
}
if(btn==GLUT_RIGHT_BUTTON && state==GLUT_DOWN)
{
exit(1); // To Exit the Program
}
}
int main(int argc, char **argv)
{ glutInit(&argc,argv);
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
glutInitWindowSize(1366,768);
glutInitWindowPosition(0,0);
glutCreateWindow("Moving squares");
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutMouseFunc(mouse);
glutIdleFunc(spindisplay);
glutMainLoop();
}

Answer 3

Below is the sample code taken from OpenGL Projects. Try to execute this and I think the problem with your drawing squares in OpenGL would be solve easily. If any question kindly ask.
#include<stdlib.h>
#include<glut.h>
GLsizei wh=500,ww=500;
GLfloat size=3.0;
void display()
{
glFlush();
}
void myInit()
{
glViewport(0,0,ww,wh);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0,(GLdouble)ww,0.0,(GLdouble)wh);
glMatrixMode(GL_MODELVIEW);
glClearColor(0.0,0.0,0.0,1.0);
glColor3f(1.0,0.0,0.0);
}
void myReshape(GLsizei w,GLsizei h)
{
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0,(GLdouble)w,0.0,(GLdouble)h);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glViewport(0,0,w,h);
ww=w;
wh=h;
}
void drawSquare(int x,int y)
{
y=wh-y;
glBegin(GL_POLYGON);
glVertex2f(x+size,y+size);
glVertex2f(x-size,y+size);
glVertex2f(x-size,y-size);
glVertex2f(x+size,y-size);
glEnd();
glFlush();
}
void size_menu(int id)
{
switch(id)
{
case 2: size=size*2;
break;
case 3:if(size>1) size=size/2;
break;
}
glutPostRedisplay();
}
void top_menu(int id)
{
switch(id)
{
case 1:exit(0);break;
}
glutPostRedisplay();
}
void myMouse(int button,int state,int x,int y)
{
if(button==GLUT_LEFT_BUTTON&&state==GLUT_DOWN)
drawSquare(x,y);
if(button==GLUT_RIGHT_BUTTON&&state==GLUT_DOWN)
exit(0);
}
int main(int argc,char **argv)
{
int sub_menu;
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
glutInitWindowSize(500,500);
glutCreateWindow("Hierarchical Menus to Draw Squares");
glutDisplayFunc(display);
myInit();
glutMouseFunc(myMouse);
sub_menu=glutCreateMenu(size_menu);
glutAddMenuEntry("Increase Square Size",2);
glutAddMenuEntry("Decrease Square Size",3);
glutCreateMenu(top_menu);
glutAddMenuEntry("Quit",1);
glutAddSubMenu("Resize",sub_menu);
glutAttachMenu(GLUT_RIGHT_BUTTON);
glutReshapeFunc(myReshape);
glClear(GL_COLOR_BUFFER_BIT);
glutMainLoop();
return 0;
}