Getting textual input

OpenGL OpenGL: Basic Coding
1

Hi,
i want to take textual input in my window, rendered using glut. i have created a rectangle depicting a text box and have set it using glRasterPos2i(), so that the text gets entered in it. i have used glutBitmapCharacter(GLUT_BITMAP_9_BY_15,k); where k is the character according to the keypress. this is all working fine… my trouble is i am not able to handle the backspace… i am able to go back one character but the character already present there is not “erased”, the new keypress is written on top of the old one…
how can i erase the previous character???

my keyboard function is as follows:

void keyboard(unsigned char k,int x,int y)
{
glColor3f(0.0,0.0,0.0);
glRasterPos2f(rx,2.27);

if((inc==0)&&((int)k==13))
{
    glutSetWindow(id1);
	glutPostRedisplay();
}	
else if(int(k)!=13)// keypressed is not the return key
{
	if(int(k)==8)//key press is backspace
	{
		inc--;
		rx-=0.1;
		glColor3f(1.0,1.0,1.0);
		glutBitmapCharacter(GLUT_BITMAP_9_BY_15,s[inc]);
		glColor3f(0.0,0.0,0.0);

	}
	else
	{
		s[inc++]=k;	
		glutBitmapCharacter(GLUT_BITMAP_9_BY_15,k);
		rx+=0.1;
		glutSwapBuffers();
		glutSwapBuffers();
	}
	
}
else
{
	s[inc]='\0';
	if(!recogniz())
	{
		glutSetWindow(id);
		glutPostRedisplay();
	}
		 
	glutSetWindow(id1);
	glutPostRedisplay();
	rx=-2.5;
	inc=0;
}

}

[This message has been edited by Richa (edited 10-01-2002).]

[This message has been edited by Richa (edited 10-01-2002).]

2

Hi !

Why does everybody put two swapbuffers after each other… ?

Anyway, you can’t do it like that, you have to save the key strokes in a buffer and call redisplay, then you have to put code in your display callback function to draw the characters.

Mikael

3

The problem is the way you are drawning the text on the screen.
It is a common error to put graphics routines in your keyboard routine, it works for simple examples, but not good as you start to get a complex program.

first create a variable called

char key_input[30]; // storage for 30 charactors, if you need to have more then 30 just increase the size of the array.
int key_size; // track how may keystrokes.

void keyboard(unsigned char k,int x,int y)
{

if ( k > 31 ) // Check for a charactor not a control key
{
key_input[key_size] = k;
key_size++; // increase our number of charactors stored.
}

if ( k == 8 )
{
key_size–; //subtract key stroke
key_input[key_size] = 0; //erase charactor
}

}

Display()
{
// note normal code left out here for example

glColor3f( 1.0, 1.0, 1.0); set text color to white
Sprint( x, y, key_input); x/y is where text will start.

glutSwapBuffer();// this should be the last command you call after drawing all your objects and the only place you put this command!!! should be nowhere else in your code.
}

// my print routine…
void Sprint( int x, int y, char *st)
{
int l,i;

l=strlen( st );
glRasterPos2i( x, y);
for( i=0; i < l; i++)
	{
	glutBitmapCharacter(GLUT_BITMAP_TIMES_ROMAN_24, st[i]);
}

}

[QUOTE]Originally posted by Richa:
[b]Hi,
i want to take textual input in my window, rendered using glut. i have created a rectangle depicting a text box and have set it using glRasterPos2i(), so that the text gets entered in it. i have used glutBitmapCharacter(GLUT_BITMAP_9_BY_15,k); where k is the character according to the keypress. this is all working fine… my trouble is i am not able to handle the backspace… i am able to go back one character but the character already present there is not “erased”, the new keypress is written on top of the old one…
how can i erase the previous character???

[This message has been edited by nexusone (edited 10-02-2002).]