/*
 * paint.c
 * 
 * Sweep out rectangles using the mouse.
 *
 *   Left button: sweep out a new rectangle
 *   Middle button: clear the screen
 *
 * Pat Hanrahan 1/97
 */

#include <stdlib.h>
#include <glut.h>

int Width = 512, Height = 512;
int Start = 0; 
int StartX, StartY;

void
Reshape(GLint w, GLint h)
{
    Width = w;
    Height = h;

    glViewport(0, 0, w, h);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0, w, 0, h, 0.0, 1.0);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

void
Display()
{
    glClearColor(0, 0, 0, 1);
    glClear(GL_COLOR_BUFFER_BIT);
}

void
DrawRect( float x1, float y1, float x2, float y2 )
{
    glBegin(GL_QUADS);
	glVertex2f(x1, y1);
	glVertex2f(x2, y1);
	glVertex2f(x2, y2);
	glVertex2f(x1, y2);
    glEnd();
}

void
Mouse(int button, int state, int x, int y)
{
    Start = 0;
    if( state == GLUT_DOWN ) 
	switch( button ) {
	    case GLUT_LEFT_BUTTON:
		glColor3f( drand48(), drand48(), drand48() );
		StartX = x;
		StartY = Height - y;
		Start = 1;
	    break;
        case GLUT_MIDDLE_BUTTON:
	    glutPostRedisplay();
	    break;
    }
}

void
MouseDrag( int x, int y )
{
    DrawRect( StartX, StartY, x, Height - y );
}


void
Keyboard( unsigned char key, int x, int y )
{
#define ESCAPE '\033'

    if( key == ESCAPE )
        exit(0);
}


main(int argc, char *argv[])
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGB);
    glutInitWindowSize(512, 512);
    glutCreateWindow("Paint");

    glutDisplayFunc(Display);
    glutReshapeFunc(Reshape);
    glutKeyboardFunc(Keyboard);
    glutMouseFunc(Mouse);
    glutMotionFunc(MouseDrag);

    glutMainLoop();
}