使用键盘输入暂停c ++ GLUT程序

Question

I am trying to pause my GLUT program during its execution by pressing a key on the keyboard. It seems to not recognize my entry. Here are the relevant sections of my code:

static bool paused = false;
void handleKeypress(unsigned char key, //The key that was pressed                                                                                                           
                                        int x, int y) {    //The current mouse coordinates                                                                                  
        switch (key) {
                case 27: //Escape key                                                                                                                                       
                  exit(0); //Exit the program                                                                                                                               
                case 'p':
                  paused = !paused;
                  break;
        }
}

int main(int argc, char** argv) {
        //Initialize GLUT                                                                                                                                                   
        glutInit(&argc, argv);
        glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
        glutInitWindowSize(600, 400); //Set the window size                                                                                                                 

        //Create the window                                                                                                                                                 
        glutCreateWindow("Fractals in Motion");
        initRendering(); //Initialize rendering                                                                                                                             

        //Set handler functions for drawing, keypresses, and window resizes                                                                                                 
        if(!paused)
          {
            glutDisplayFunc(drawScene);       //drawScene draws everything does the real work
            glutTimerFunc(10, update, 0); //Add a timer                                                                                                                     
          }
        //glutKeyboardFunc(handleKeypress);                                                                                                                                 
        glutReshapeFunc(handleResize);

        glutMainLoop(); //Start the main loop.  glutMainLoop doesn't return.                                                                                                
        return 0; //This line is never reached                                                                                                                              
}

I actually got the skeleton of this code from this very will written tutorial:

http://www.videotutorialsrock.com/opengl_tutorial/basic_shapes/home.php

However, I cannot seem to get the program to pause when I press the 'p' key. If you have better methods please let me know!

Answer 1

its not working because glutKeyboardFunc(handleKeypress) is commented out for some reason. uncomment and it should work.

Answer 2

Your program runs in two stages:

• Initialization
• Main loop

Everything before glutMainLoop is initialization, telling GLUT all the different settings and callbacks you want to use. During the main loop, GLUT will call all your callbacks and you can draw.

The problem is that you're setting paused during the main loop and checking it during the initialization. Since initialization always happens before the main loop, setting paused won't actually do anything.

The solution is to not rely on checking paused during initialization, but instead modify your callbacks to immediately return if paused is true .

Answer 3

# include<GL/glut.h>
void keys(unsigned char key, int x, int y)    
{    
    if (key == 'a')     paused = 1;    
    if (key == 'A')     paused = 0;    
    glutPostRedisplay();    
}

add this function in your program for keyboard function and wherever u are using glutPostRedisplay() in program add if(paused == 0) above it