Texture Displaying

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___API  glutBitmapCharacter
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URL: https://www.opengl.org/documentation/specs/glut/spec3/node76.html
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___ VARIOUS WAYS WITH SOURCE DEMO
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URL: https://www.opengl.org/archives/resources/features/fontsurvey/
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___ ONLY LETTERS
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URL: https://mycodelog.com/tag/glutbitmapcharacter/

This can be done by using C’s va_list type, which is C’s approach to defining functions with variables number of arguments.

• In the function prototype, place ellipsis (…) as the last argument

• Define a variable argument list: va_list args;

• Call va_start on the args list and the first real argument in the function prototype preceding the ellipsis:va_start(args, format);

• Use _vscprintf to get the number of characters that would be generated if the string pointed to by the list of arguments was printed using the specified format

• Allocate memory for a string with the specified number of characters

• Call vsprintf_s to build the string we want from the list of arguments

• Call va_end to end the use of the variables argument list

• Draw our beautified string

• Free allocated memory

Function implementation with full comments shown below:

//-------------------------------------------------------------------------

//  Draws a string at the specified coordinates.

//-------------------------------------------------------------------------

   #include <stdio.h>    //  Standard Input\Output C Library

#include <stdarg.h>   //  To use functions with variables arguments

#include <stdlib.h>   //  for malloc

#include <gl/glut.h>  //  Include GLUT, OpenGL, and GLU libraries




//-------------------------------------------------------------------------

//  Draws a string at the specified coordinates.

//-------------------------------------------------------------------------

void printw (float x, float y, float z, char* format, ...)

{

    va_list args;   //  Variable argument list

    int len;        // String length

    int i;          //  Iterator

    char * text;    // Text

    //  Initialize a variable argument list

    va_start(args, format);

    //  Return the number of characters in the string 

// referenced the list of arguments.

    // _vscprintf doesn't count terminating '\0' (that's why +1)

    len = _vscprintf(format, args) + 1;

    //  Allocate memory for a string of the specified size

    text = malloc(len * sizeof(char));

    //  Write formatted output using a pointer to the list of arguments

    vsprintf_s(text, len, format, args);

    //  End using variable argument list

    va_end(args);

    //  Specify the raster position for pixel operations.

    glRasterPos3f (x, y, z);

    //  Draw the characters one by one

    for (i = 0; text[i] != '\0'; i++) {

     glutBitmapCharacter(font_style, text[i]);

}

    //  Free the allocated memory for the string

    free(text);

}