xyf_display_opengl
    
    
    
      xyf_display_opengl,
      a C++ code which 
      reads XYF information defining points and faces in 2D,
      and draws a picture using OPENGL.
    
    
      The point and face information is stored in a pair of files,
      called the XYF format.  Essentially, the first file
      stores a list of point coordinates, and the second lists point indices
      which can be connected to form faces.
    
    
      Usage:
    
    
      
        xyf_display_opengl prefix
      
      where
      
        - 
          prefix is the common prefix for the point coordinate data in
          prefix.xy and the
          point index lists in prefix.xyf.
        
 
      
    
    
      Licensing:
    
    
      The information on this web page is distributed under the MIT license.
    
    
      Languages:
    
    
      xyf_display_opengl is available in
      a C++ version.
    
    
      Related Data and Programs:
    
    
      
      opengl_test,
      a C++ code which
      uses opengl() to display graphic images on the screen;
    
    
      Reference:
    
    
      
        - 
          Edward Angel,
          Interactive Computer Graphics, 
          a Top-Down Approach with OpenGL,
          Addison-Wesley, 2000,
          ISBN: 0-201-38597-X,
          LC: T385.A514.
         
        - 
          Renate Kempf, Chris Frazier, editors,
          OpenGL Reference Manual,
          Fourth Edition,
          Addison-Wesley, 2004,
          ISBN: 032117383X,
          LC: T385.O642
         
        - 
          Mason Woo, Jackie Neider, Tom Davis,
          OpenGL Programming Guide,
          Addison-Wesley, 1997,
          ISBN: 0-201-46138-2,
          LC: T385.N435
         
        - 
          Richard Wright, Michael Sweet,
          OpenGL Superbible,
          Third Edition,
          Sams, 2004,
          ISBN: 0672326019,
          LC: T385.W73
         
        - 
          
                     https://www.opengl.org/  
          The official OpenGL site.
         
      
    
    
      Source Code:
    
    
      
    
    
      Examples and Tests:
    
    
      
    
    
      List of Routines:
    
    
      
        - 
          MAIN is the main program for XYF_DISPLAY_OPENGL.
        
 
        - 
          CH_EQI is true if two characters are equal, disregarding case.
        
 
        - 
          CH_TO_DIGIT returns the integer value of a base 10 digit.
        
 
        - 
          DISPLAY generates the graphics output.
        
 
        - 
          I4VEC_MAX returns the value of the maximum element in an I4VEC.
        
 
        - 
          I4VEC_MIN returns the value of the minimum element in an I4VEC.
        
 
        - 
          MYINIT initializes OpenGL state variables dealing with viewing and attributes.
        
 
        - 
          R8_MAX returns the maximum of two R8.
        
 
        - 
          R82VEC_MAX returns the maximum value in a R82VEC.
        
 
        - 
          R82VEC_MIN returns the minimum value in a R82VEC.
        
 
        - 
          S_CAT concatenates two strings to make a third string.
        
 
        - 
          S_LEN_TRIM returns the length of a string to the last nonblank.
        
 
        - 
          S_TO_I4 reads an I4 from a string.
        
 
        - 
          S_TO_I4VEC reads an I4VEC from a string.
        
 
        - 
          S_TO_R8 reads an R8 from a string.
        
 
        - 
          S_TO_R8VEC reads an R8VEC from a string.
        
 
        - 
          S_WORD_COUNT counts the number of "words" in a string.
        
 
        - 
          TIMESTAMP prints the current YMDHMS date as a time stamp.
        
 
        - 
          XY_DATA_READ reads the data in an XY file.
        
 
        - 
          XY_HEADER_READ reads the header of an XY file.
        
 
        - 
          XYF_DATA_READ reads the data in an XYF file.
        
 
        - 
          XYF_HEADER_READ determines the number of face items in an XYF file.
        
 
      
    
    
    
      Last revised on 07 January 2009.