// LiangBarClipViewer.cpp     
// NKU CSC 480 - Kirby
// --------------------------------------------------------------------------------
// Demonstrate Liang-Barsky clipping (in file LiBarClipLib.h, .cpp). 
// Draws many random colored lines, then clips to a rectangle. 2D only.
// ---------------------------------------------------------------------------------


#include <GL/glut.h>
#include <iostream>
#include <vector>
#include <ctime>
#include "LiBarClipLib.h"
using namespace std ;

const int  NLINES= 100 ;  // # of random lines to draw


  
inline double urand() { return  (double) rand() / RAND_MAX ;  }  // random real 0..1.



struct Line2D
// A colored line, visible or not.
{
    Line2D() 
        : visible( true )
        , xA( urand() ), yA( urand() ), xB( urand() ), yB( urand() )
        , r( urand() ), g( urand() ), b( urand() ) 
    {}
    bool visible ;
    float xA,yA,  xB,yB ;
    float r,g,b ;
} ;



// Global vector of random lines to be displayed and clipped.
vector<Line2D> G_vecLines ;



void makeLines( vector<Line2D>& vecLines, int n ) 
// Fill vecLines[] with n random, randomly colored lines.
{
    vecLines.clear() ;
    for ( int i=0 ; i < n ; ++i )
        vecLines.push_back( Line2D() ) ;
}



void clipLines( vector<Line2D>& vecLines  )
// Apply clipper to all lines in vecLines.
{
    Rect rect( 0.2, 0.6, 0.3, 0.9 ) ;
    for ( int i=0 ; i < (int) vecLines.size() ; ++i )
    {
        Line2D& ln= vecLines[i] ;
        ln.visible= clip( rect, ln.xA, ln.yA, ln.xB, ln.yB ) ;
    }
}



void drawLines( const vector<Line2D>& vecLines ) 
// Draw all the lines in vecLines.
{
    glBegin( GL_LINES ) ;
    for ( int i=0 ; i < (int) vecLines.size() ; ++i )
    {
        const Line2D& ln= vecLines[i] ;
        if ( ln.visible )
        {
            glColor3f( ln.r, ln.g, ln.b ) ;
            glVertex3f( ln.xA, ln.yA, 0 ) ;
            glVertex3f( ln.xB, ln.yB, 0 ) ;
        }
    }
    glEnd() ;
}



void display()  
// Display the lines.
{
    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT ) ;
    drawLines( G_vecLines ) ;
    glutSwapBuffers() ;
}



void kbDispatch( unsigned char ch, int x, int y )
// Toggle global state variables, or print projection matrix.
{
    switch( ch )
    {
        case 'c': clipLines( G_vecLines ) ; break ;
        case 'm': makeLines( G_vecLines, NLINES ) ; break ;
    }
    glutPostRedisplay() ;
}



int main( int argc, char** argv )
{
    // Initialize OpenGL. 
    glutInit( &argc, argv ) ;
    glutInitDisplayMode( GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH ) ; 

    // Window attributes.
    glutInitWindowSize( 700, 700 ) ;
    glutInitWindowPosition( 100, 100 ) ;
    glutCreateWindow( "Liang Barsky Clipping Demo.  Keys: m  c" ) ;

    // Register callbacks.
    glutKeyboardFunc( kbDispatch ) ;        
    glutDisplayFunc( display ) ;  
    
    // Lines
    srand( time( 0 ) ) ;
    makeLines( G_vecLines, NLINES ) ;

    // Simple orthographic projection
    glMatrixMode( GL_PROJECTION ) ;
    glOrtho( 0,1, 0,1, -1,1 ) ;
    glMatrixMode( GL_MODELVIEW ) ;

    // Go.
    glutMainLoop() ;
    
    return 0 ;
}