Keyboard input doesn't work, works when clicking the mouse - c++

Question

I have this code:
#include <iostream>
#include <GL/glut.h>
using namespace std;
bool* Keys = new bool[256];
void keyboardDown(unsigned char key, int x, int y)
{
Keys[key] = true;
}
void keyboardUp(unsigned char key, int x, int y)
{
Keys[key] = false;
}
void reshape(int width, int height)
{
GLfloat fieldOfView = 90.0f;
glViewport(0, 0, (GLsizei)width, (GLsizei)height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(fieldOfView, (GLfloat)width / (GLfloat)height, 0.1, 500.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
void draw()
{
if (Keys['e'])
cout << "e" << endl;
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glBegin(GL_QUADS);
glColor3f(0.1, 0.1, 0.1); glVertex3f(1.0, 1.0, -1.0);
glColor3f(0.1, 0.9, 0.1); glVertex3f(1.0, -1.0, -1.0);
glColor3f(0.9, 0.1, 0.1); glVertex3f(-1.0, -1.0, -1.0);
glColor3f(0.1, 0.1, 0.9); glVertex3f(-1.0, 1.0, -1.0);
glEnd();
glFlush();
glutSwapBuffers();
}
void initGL(int width, int height)
{
reshape(width, height);
glClearColor(0.1f, 0.5f, 0.7f, 1.0f);
glClearDepth(1.0f);
glOrtho(0, 1, 0, 1, 1, 10);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LEQUAL);
}
/* initialize GLUT settings, register callbacks, enter main loop */
int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH);
glutInitWindowSize(800, 800);
glutInitWindowPosition(100, 100);
glutCreateWindow("Perspective's GLUT Template");
glutKeyboardFunc(keyboardDown);
glutKeyboardUpFunc(keyboardUp);
glutSpecialFunc(keyboardSpecialDown);
glutSpecialUpFunc(keyboardSpecialUp);
glutReshapeFunc(reshape);
glutDisplayFunc(draw);
glutIgnoreKeyRepeat(true); // ignore keys held down
initGL(800, 600);
glutMainLoop();
return 0;
}
When I start the program, it writes 'e' only when I press on the mouse. I can't find the problem. Why does it only work when the mouse is held down?

Answer 1

You dont have mouse functions in your code, thats why it is not working. Insert from here : http://www.zeuscmd.com/tutorials/glut/03-MouseInput.php
#include <iostream>
#include <gl/glut.h>
using namespace std;
bool lbuttonDown = false;
bool init()
{
return true;
}
void display()
{
}
void mouse(int button, int state, int x, int y)
{
if (button == GLUT_RIGHT_BUTTON)
{
if (state == GLUT_DOWN)
cout << "Right button pressed"
<< endl;
else
cout << "Right button lifted "
<< "at (" << x << "," << y
<< ")" << endl;
}
else if (button == GLUT_LEFT_BUTTON)
{
if (state == GLUT_DOWN)
lbuttonDown = true;
else
lbuttonDown = false;
}
}
void motion(int x, int y)
{
if (lbuttonDown)
cout << "Mouse dragged with left button at "
<< "(" << x << "," << y << ")" << endl;
}
void motionPassive(int x, int y)
{
cout << "Mouse moved at "
<< "(" << x << "," << y << ")" << endl;
}
void entry(int state)
{
if (state == GLUT_ENTERED)
cout << "Mouse Entered" << endl;
else
cout << "Mouse Left" << endl;
}
int main(int argc, char *argv[])
{
glutInit(&argc, argv);
glutInitWindowPosition(200, 200);
glutInitWindowSize(200, 200);
glutCreateWindow("03 - Mouse Input");
glutDisplayFunc(display);
glutMouseFunc(mouse);
glutMotionFunc(motion);
glutPassiveMotionFunc(motionPassive);
glutEntryFunc(entry);
if (!init())
return 1;
glutMainLoop();
return 0;
}

Answer 2

I had the same problem [using freeglut] and calling 'draw()' [or whatever display callback you use] right after glutPostRedisplay() in the key callback function forced it to do the redraw. I actually don't know why it behaves like this. After data is changed by keyboard input and the key callback returned, a redraw is expected but not executed.