/* -*- C++ -*-
 * Copyright ©2005 Hugo Mills <hugo@carfax.org.uk>
 *
 * This software is distributed under the terms of the GNU GPL v3
 * For more information on the GPL, see the file COPYING or 
 * visit http://www.gnu.org/
 *
 * This software is distributed without warranty
 */

#include "magellan/output.h"

void Output::drawline(const ivec2& from, const ivec2& to,
					  int r, int g, int b)
{
	int STATE = 0;

	ivec2 d = std::valarray<int>(to-from); // Eurgh. Hacky.
	ivec2 p0;
	p0[0] = p0[1] = 0;
	ivec2 p1 = d;

	// Normalise to first octant
	// Flip in y axis
	if(d[0] < 0)
	{
		STATE |= 0x1;
		d[0] = -d[0];
		p1[0] = -p1[0];
	}
	// Flip in x axis
	if(d[1] < 0)
	{
		STATE |= 0x2;
		d[1] = -d[1];
		p1[1] = -p1[1];
	}
	// Flip in x=y
	if(d[0] < d[1])
	{
		STATE |= 0x4;
		std::swap(d[0], d[1]);
		std::swap(p0[0], p0[1]);
		std::swap(p1[0], p1[1]);
	}

	// Now run Bresenham's algorithm
	int err = 0;
	ivec2 pos;
	for(; p0[0]<p1[0]; p0[0]++)
	{
		err += d[1];
		if(err > d[0])
		{
			p0[1]++;
			err -= d[0];
		}
		// Transform coords back to something sensible to plot
		switch(STATE)
		{
		case 0:
			pos[0] = p0[0];
			pos[1] = p0[1];
			break;
		case 1:
			pos[0] = -p0[0];
			pos[1] = p0[1];
			break;
		case 2:
			pos[0] = p0[0];
			pos[1] = -p0[1];
			break;
		case 3:
			pos[0] = -p0[0];
			pos[1] = -p0[1];
			break;
		case 4:
			pos[0] = p0[1];
			pos[1] = p0[0];
			break;
		case 5:
			pos[0] = -p0[1];
			pos[1] = p0[0];
			break;
		case 6:
			pos[0] = p0[1];
			pos[1] = -p0[0];
			break;
		case 7:
			pos[0] = -p0[1];
			pos[1] = -p0[0];
			break;
		}
		pos += from;
		setpixel(pos, r, g, b);
	}
}