# rectangle moving problem

Hi all,

In my project I’m trying to move a rectangle ( to the left & right) with pressing a right mouse button nothing more.

Here is the code :
// Rectangle para.s
float x1=10.00f ,y1=-40.00f,x2=-60.00,y2=-50.00, D=0.0;

void drawbar (void)
{

glColor3f(1.0, 1.0, 1.0);
glRectf(x1,y1,x2,y2);

}

void myGlutMouse(int button, int button_state, int x, int y )
{
switch(button)
{
case GLUT_RIGHT_BUTTON:
if (button_state == GLUT_DOWN) { x1=x1+5.5 ; x2= x2+5.5; D = x2-x1;}
break;
case GLUT_LEFT_BUTTON:
if (button_state == GLUT_DOWN) { x1=x1-5.5 ; x2= x2-5.5; D = x2-x1;}
// glutIdleFunc(drawbar);
break;
default:
break;
}
}

void myGlutMotion(int x, int y )
{
glutPostRedisplay();
}
The previous code move the rectangle using left& right mouse button , and this what I don’t aim to … I beleive that I have to use GlutMotion function to return the x,y for GlutMouse function .Moreover,My code above move the rectangle each time (anywhere !) the right button is pressed !! What I want is once the rightbutton is pressed ( in the area of the rectangle) ( and still pressed) the user can move the rectangle ( as the same manner of the scroll bar of the window) !! I try a lot to do that but still with no result till now !!!

Any help …

U basically want to implement ‘dragging’

bool dragging = false;
float lastMouseX, lastMouseY;

//register as glutMouseFunc
void onMouseButton(int button, int state, int x, int y)
{
if(button == GLUT_RIGHT_BUTTON)
{
if(state == GLUT_DOWN)
{
dragging = true;
y = WinHeight - y;//Win (0,0)
//is Left-Top
lastMouseX = x;
lastMouseY = y;
}
else
dragging = false;
}
}

//register as glutMotionFunc
void onMouseDrag(int x, int y)
{
if(dragging)
{
y = WinHeight - y;//Win (0,0)
//is Left-Top
float dragX = x - lastMouseX;
float dragY = y - lastMouseY;
lastMouseX = x;
lastMouseY = y;
//do whatever u wanna do with dragX
//and dragY
}
}

• Chetan

Hi Chetan

Thank you very much for your help …

I did the steps you mentioned above but the result was wrong . The rectangle now disappear !! I beleive I did somthing wrong somewhere … but I don’t know where exactly …

Here is my modified code :

float lastMouseX, lastMouseY;
float dragx, dragy;
bool dragging = false;

void drawbar (void)
{

glTranslateflastMouseX,lastMouseY,0.0f);
glColor3f(1.0, 1.0, 1.0);
glRectf(x1,y1,x2,y2);

}

void myGlutMouse(int button, int button_state, int x, int y )
{

switch(button)
{
case GLUT_RIGHT_BUTTON:
if (button_state == GLUT_DOWN)
{ dragging = true ;// y = 600 - y ; // Win(0,0)
// is left top
lastMouseX = x;
lastMouseY = y ;}
else
dragging = false ;

// default:
// break;
}
}

void myGlutMotion(int x, int y )
{
if (dragging) {// y = 600 - y; // win(0,0)
//is left top
dragx = x - lastMouseX;
dragy = y - lastMouseY;
glutPostRedisplay( );
lastMouseX = x;
lastMouseY = y ;}

}

Maybe you’ll ask why I changed dragx, and dragy to global variables , I do that because I want to use them in the (drawbar) function but the result I have was wrong also ( the rectangle stop moving neither left nor right !!)

What to do know

One thing I can see is that ur rectangle drawing code is not within
glPushMatrix()- glPopMatrix()pair.

Originally posted by glcrazy:
void drawbar (void)
{

glTranslateflastMouseX,lastMouseY,0.0f);
glColor3f(1.0, 1.0, 1.0);
glRectf(x1,y1,x2,y2);

}

If that doesn’t solve the problem, post complete code and I’ll try running it on my machine to see what the problem is.

-Chetan

Hi again Chetan …

There is a little bit progress ( the rectangle is shaking up, down, left & right when the right mouse button is pressed now )

Here is the complete code:

#include <string.h>
#include <GL/glut.h>
#include <GL/glaux.h>
#include <stdio.h>
//#include “glui.h”

float xy_aspect;
int last_x, last_y;
float lastMouseX, lastMouseY;
float dragx, dragy;
bool dragging = false;
int x, y;

int main_window;

// Rectangle para.s
float x1=10.00f ,y1=-40.00f,x2=-60.00,y2=-50.00, D=0.0;

/**************************************** Draw user bar **********/
void drawbar (void)
{

glPushMatrix();

``````    glTranslatef(dragx,dragy,0.0f);
glColor3f(1.0, 1.0, 1.0);
glRectf(x1,y1,x2,y2);
``````

glPopMatrix();

}

/**************************************** myGlutKeyboard() **********/

void myGlutKeyboard(unsigned char Key, int x, int y)
{
switch(Key)
{
case 27:
case ‘q’:
case ‘Q’:
case ‘x’:
case ‘X’:
exit(0);
break;
};

glutPostRedisplay();
}

{
myGlutKeyboard( value, 0, 0 );
}

/***************************************** myGlutIdle() ***********/

void myGlutIdle( void )
{
/* According to the GLUT specification, the current window is
undefined during an idle callback. So we need to explicitly change
it if necessary */
if ( glutGetWindow() != main_window )
glutSetWindow(main_window);

glutPostRedisplay();
}

/***************************************** myGlutMouse() **********/

void myGlutMouse(int button, int button_state, int x, int y )
{

switch(button)
{
case GLUT_RIGHT_BUTTON:
if (button_state == GLUT_DOWN)
{ dragging = true ; y = 600 - y ; // Win(0,0)
// is left top
lastMouseX = x;
lastMouseY = y ;}
else
dragging = false ;

// default:
// break;
}
}

/***************************************** myGlutMotion() **********/

void myGlutMotion(int x, int y )
{
if (dragging) {// y = 600 - y; // win(0,0)
//is left top
dragx = x - lastMouseX;
dragy = y - lastMouseY;
glutPostRedisplay( );
lastMouseX = x;
lastMouseY = y ;}

}

/**************************************** myGlutReshape() *************/

void myGlutReshape( int x, int y )
{
int tx, ty, tw, th;
//viewport_area( &tx, &ty, &tw, &th );
glViewport( tx, ty, tw, th );

xy_aspect = (float)tw / (float)th;

glutPostRedisplay();
}

/***************************************** myGlutDisplay() *****************/

void myGlutDisplay( void )
{

glViewport(0, 0, 580, 600);
glMatrixMode(GL_PROJECTION);
gluPerspective(45.0f, (GLfloat)580/(GLfloat)600, 1.0f, 1000.0f);

glMatrixMode(GL_MODELVIEW); // Sets the projection matrix.
glLoadIdentity(); // Reset the modelview matrix.

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clears the screen.
glLoadIdentity(); // Reset modelview matrix for new frame.
glTranslatef(0.0f,0.0f, -200.0f); //zoom the “camera” out a bit

drawbar ( ) ;

glutSwapBuffers();
}

/**************************************** main() ********************/

void main(int argc, char* argv[])
{
//
/
Initialize GLUT and create window /
/
/

glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH );
glutInitWindowPosition( 50, 50 );
glutInitWindowSize( 800, 600 );

main_window = glutCreateWindow( "My New Game " );
glutDisplayFunc( myGlutDisplay );
glutReshapeFunc( myGlutReshape );
glutKeyboardFunc( myGlutKeyboard );
glutSpecialFunc( NULL );
glutMouseFunc( myGlutMouse );
glutMotionFunc( myGlutMotion );

//
/
Enable z-buferring /
/
/

glEnable(GL_DEPTH_TEST);

glutIdleFunc( myGlutIdle );

/**** Regular GLUT main loop ****/

glutMainLoop();

}

Thanks a lot Chetan ,even if you can’t solve the problem .

[This message has been edited by glcrazy (edited 11-20-2003).]

Originally posted by glcrazy:

What do u mean ???

• Chetan

Hi ,

I faced a problem with my browser for that I wrote (…) to check the it’s acceptance for posting replies here

U r using dragx and dragy as values for translation, ie. in glTranslatef.

In the code u posted,

1)y value should be subtracted from window height before using.

1. drag values should be accumulated,
i.e. instead of drag =, use drag +=
• Chetan

Hi Chetan …

Originally posted by virtualchetan:
[b]U r using dragx and dragy as values for translation, ie. in glTranslatef.

In the code u posted,

… OK! … I did that because you wrote "//do whatever u wanna do with dragX
//and dragY " … if you didn’t mean to translate the rectangle … what did you mean then … ??

1)y value should be subtracted from window height before using.

I did that ,

1. drag values should be accumulated,
i.e. instead of drag =, use drag +=
• Chetan[/b]

… Also No result … I don’t know where is my mistake exactly !!! ???

//g++ -L/usr/X11/lib -L/usr/X11R6/lib -lglut -lGLU -lm test.C -o test

#include <GL/glut.h> // Header File For The GLUT Library
#include <GL/gl.h> // Header File For The OpenGL32 Library
#include <GL/glu.h> // Header File For The GLu32 Library

#include <string.h>
#include <GL/glut.h>
//#include <GL/glaux.h>
#include <stdio.h>
//#include “glui.h”
#include <stdlib.h>

float xy_aspect;
int last_x, last_y;
float lastMouseX, lastMouseY;
float dragx, dragy;
bool dragging = false;
int x, y;

int main_window;

// Rectangle para.s
float x1=10.00f ,y1=-40.00f,x2=-60.00,y2=-50.00, D=0.0;

/**************************************** Draw user bar **********/
void drawbar (void)
{

glPushMatrix();
glTranslatef(dragx,dragy,0.0f);
glColor3f(1.0, 1.0, 1.0);
glRectf(x1,y1,x2,y2);
glPopMatrix();

}

/**************************************** myGlutKeyboard() **********/

void myGlutKeyboard(unsigned char Key, int x, int y)
{
switch(Key)
{
case 27:
case ‘q’:
case ‘Q’:
case ‘x’:
case ‘X’:
exit(0);
break;
};

glutPostRedisplay();
}

{
myGlutKeyboard( value, 0, 0 );
}

/***************************************** myGlutIdle() ***********/

void myGlutIdle( void )
{
/* According to the GLUT specification, the current window is
undefined during an idle callback. So we need to explicitly change
it if necessary */
if ( glutGetWindow() != main_window )
glutSetWindow(main_window);

glutPostRedisplay();
}

/***************************************** myGlutMouse() **********/

void myGlutMouse(int button, int button_state, int x, int y )
{

switch(button)
{
case GLUT_RIGHT_BUTTON:
if (button_state == GLUT_DOWN)
{ dragging = true ; y = 600 - y ; // Win(0,0)
// is left top
lastMouseX = x;
lastMouseY = y ;}
else
dragging = false ;

// default:
// break;
}
}

/***************************************** myGlutMotion() **********/

void myGlutMotion(int x, int y )
{
if (dragging) {
y = 600 - y; // win(0,0)
//is left top
dragx += x - lastMouseX;
dragy += y - lastMouseY;
glutPostRedisplay( );
lastMouseX = x;
lastMouseY = y ;}

printf("drag %0.2f %0.2f
", dragx, dragy);
}

/**************************************** myGlutReshape() *************/

void myGlutReshape( int x, int y )
{
int tx, ty, tw, th;
//viewport_area( &tx, &ty, &tw, &th );
glViewport( tx, ty, tw, th );

xy_aspect = (float)tw / (float)th;

glutPostRedisplay();
}

/***************************************** myGlutDisplay() *****************/

void myGlutDisplay( void )
{

glViewport(0, 0, 580, 600);
glMatrixMode(GL_PROJECTION);
gluPerspective(45.0f, (GLfloat)580/(GLfloat)600, 1.0f, 1000.0f);

glMatrixMode(GL_MODELVIEW); // Sets the projection matrix.
glLoadIdentity(); // Reset the modelview matrix.

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clears the screen.
glLoadIdentity(); // Reset modelview matrix for new frame.
glTranslatef(0.0f,0.0f, -200.0f); //zoom the “camera” out a bit

drawbar ( ) ;

glutSwapBuffers();
}

/**************************************** main() ********************/

int main(int argc, char* argv[])
{
//
/
Initialize GLUT and create window /
/
/

glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH );
glutInitWindowPosition( 50, 50 );
glutInitWindowSize( 800, 600 );

main_window = glutCreateWindow( "My New Game " );
glutDisplayFunc( myGlutDisplay );
glutReshapeFunc( myGlutReshape );
glutKeyboardFunc( myGlutKeyboard );
glutSpecialFunc( NULL );
glutMouseFunc( myGlutMouse );
glutMotionFunc( myGlutMotion );

//
/
Enable z-buferring /
/
/

glEnable(GL_DEPTH_TEST);

glutIdleFunc( myGlutIdle );

/**** Regular GLUT main loop ****/

glutMainLoop();

return 1;
}

This code works. Still not totally correct… U have to find out whats wrong now.
A hint : u dont have to setup projection matrix and glviewport in ur display function, set them up correctly in glReshape

• Chetan

Hi Chetan

IT WORKS … Thanks millions …

I believe you mean the view port by the mistake you talked about … I can fix that … now I’m trying to let dragging of the rectangle if and only if the mouse pointer is inside the rectangle not anywhere else … I’m thinking about calculate the area of the rectangle or make comparison between x,y and the boundaries of the rectangle …
I’ll work in the tonight … and if there is no result I’ll ask your help if you don’t mind ,

Cheers …

[This message has been edited by glcrazy (edited 11-25-2003).]

Hi Chetan …

Sorry for bothering you again …
I tried to change the code as following:

void myGlutMouse(int button, int button_state, int x, int y )
{
switch(button)
{
case GLUT_RIGHT_BUTTON:
if (button_state == GLUT_DOWN)&& ( x1<=x<=x2) && (y1<=y<=y2)
{ dragging = true ;
y = 600 - y ; // Win(0,0)// is left top
lastMouseX = x;
lastMouseY = y ;
}
else dragging = false ;
}
}

It doesn’t work … and I noticed that the values of x & y are hundreds ie, something like 266, 156 , … etc whereas x1,x2,y1,y2 are fixed as shown above !!!

this confused me alot …

Do you have any idea !!
Thanks always Chetan …