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Problems with a simple program in OpenGL

Started by Himura-San Nov 15, 2004 at 7:10 AM 2 replies 400+ views

Original Post

Nov 15, 2004 at 7:10 AM

Hi, i´m extremely noob in OpenGL API and i got a big problem in coordinates.Well, i wanna make a program that highlight a square if the user clicks on it and set the default color if he clicks out.The problem in my code is : if the user click on the top of square it doesn´t highlight!!! Here is the code, please tell what´s wrong.


#include <GL\glut.h>

void Draw()
  {
      //Aplica as alterações ao modelo      
      glMatrixMode(GL_MODELVIEW);
      glLoadIdentity();
      
      glClear(GL_COLOR_BUFFER_BIT);
     
      
      glBegin(GL_POLYGON);
        {
            //glColor3f(1.0f,1.0f,1.0f);
            glVertex2i(100,150);
            glVertex2i(100,100);
            glVertex2i(150,100);
            glVertex2i(150,150);
        }
       glEnd();
       glFlush();
   }    

void Mouse(int button , int state, int x , int y)
  {
      if (button == GLUT_LEFT_BUTTON)
         if (state == GLUT_DOWN)
            if ( (x >= 100) && (x <= 150) && (y >= 100) && (y <= 150) ) glColor3f(1.0f,0.0f,0.0f);
            else glColor3f(1.0f,1.0f,1.0f);
         //if (state == GLUT_UP) glColor3f(1.0f,1.0f,1.0f);      
      glutPostRedisplay();      
  }    

void Reshape(GLint w, GLint h)
  {
      glViewport(0,0,(GLsizei)w,(GLsizei)h);
      glMatrixMode(GL_PROJECTION);
      glLoadIdentity();
      gluOrtho2D(0.0,(GLdouble)w,0.0,(GLdouble)h);
  }


int main()
  {
      //Cria a Janela
      glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
      glutInitWindowSize(320,240);
      glutInitWindowPosition(10,10);
      glutCreateWindow("My Program :p");
      
      //Seta a cor de fundo como preta
      glClearColor(0.0,0.0,0.0,0.0);
      
      glutDisplayFunc(Draw);      
      glutReshapeFunc(Reshape);
      glutMouseFunc(Mouse);
      glutMainLoop();
       
   }

[Edited by - Himura-San on November 15, 2004 3:24:26 PM]

Roboguy

Nov 15, 2004 at 7:35 AM

works fine for me, but I had to fix you main function, it should look like this:

int main(int argc, char* argv[]){//Cria a JanelaglutInit(&argc, argv);glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);glutInitWindowSize(320,240);glutInitWindowPosition(10,10);glutCreateWindow("My Program :p");//Seta a cor de fundo como pretaglClearColor(0.0,0.0,0.0,0.0);glutDisplayFunc(Draw);glutReshapeFunc(Reshape);glutMouseFunc(Mouse);glutMainLoop();}

Himura-San

Author

Himura-San

Nov 15, 2004 at 3:12 PM

Thanks Roboguy , but it doesn´t work fine.Just try to click on top of square, the color doesn´t change!!!

Is this a coordinate problem?Is there any difference between passing arguments in the main function main and passing void?

Roboguy

Nov 15, 2004 at 3:34 PM

the arguments describe the arguments passed to the program, for example, if you ran:

C:\path\to\myOpenGLProg.exe this is a test

the arguments in main would be setup like this:
argc: 5(I think)
contents of argv:
argv[0] = "C:\path\to\myOpenGLProg.exe"
argv[1] = "this"
argv[2] = "is"
argv[3] = "a"
argv[4] = "test"

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