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/*
* libcucul Canvas for ultrafast compositing of Unicode letters
* Copyright (c) 2002-2006 Sam Hocevar <sam@zoy.org>
* All Rights Reserved
*
* $Id: triangle.c 1026 2006-11-11 16:29:39Z sam $
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the Do What The Fuck You Want To
* Public License, Version 2, as published by Sam Hocevar. See
* http://sam.zoy.org/wtfpl/COPYING for more details.
*/
/*
* This file contains triangle drawing functions, both filled and outline.
*/
#include "config.h"
#include "common.h"
#if !defined(__KERNEL__)
# include <stdlib.h>
#endif
#include "cucul.h"
#include "cucul_internals.h"
/** \brief Draw a triangle on the canvas using the given character.
*
* This function never fails.
*
* \param cv The handle to the libcucul canvas.
* \param x1 X coordinate of the first point.
* \param y1 Y coordinate of the first point.
* \param x2 X coordinate of the second point.
* \param y2 Y coordinate of the second point.
* \param x3 X coordinate of the third point.
* \param y3 Y coordinate of the third point.
* \param ch UTF-32 character to be used to draw the triangle outline.
* \return This function always returns 0.
*/
int cucul_draw_triangle(cucul_canvas_t *cv, int x1, int y1, int x2, int y2,
int x3, int y3, unsigned long int ch)
{
cucul_draw_line(cv, x1, y1, x2, y2, ch);
cucul_draw_line(cv, x2, y2, x3, y3, ch);
cucul_draw_line(cv, x3, y3, x1, y1, ch);
return 0;
}
/** \brief Draw a thin triangle on the canvas.
*
* This function never fails.
*
* \param cv The handle to the libcucul canvas.
* \param x1 X coordinate of the first point.
* \param y1 Y coordinate of the first point.
* \param x2 X coordinate of the second point.
* \param y2 Y coordinate of the second point.
* \param x3 X coordinate of the third point.
* \param y3 Y coordinate of the third point.
* \return This function always returns 0.
*/
int cucul_draw_thin_triangle(cucul_canvas_t *cv, int x1, int y1,
int x2, int y2, int x3, int y3)
{
cucul_draw_thin_line(cv, x1, y1, x2, y2);
cucul_draw_thin_line(cv, x2, y2, x3, y3);
cucul_draw_thin_line(cv, x3, y3, x1, y1);
return 0;
}
/** \brief Fill a triangle on the canvas using the given character.
*
* This function never fails.
*
* \param cv The handle to the libcucul canvas.
* \param x1 X coordinate of the first point.
* \param y1 Y coordinate of the first point.
* \param x2 X coordinate of the second point.
* \param y2 Y coordinate of the second point.
* \param x3 X coordinate of the third point.
* \param y3 Y coordinate of the third point.
* \param ch UTF-32 character to be used to fill the triangle.
* \return This function always returns 0.
*/
int cucul_fill_triangle(cucul_canvas_t *cv, int x1, int y1, int x2, int y2,
int x3, int y3, unsigned long int ch)
{
int x, y, xmin, xmax, ymin, ymax;
long int xx1, xx2, xa, xb, sl21, sl31, sl32;
/* Bubble-sort y1 <= y2 <= y3 */
if(y1 > y2)
return cucul_fill_triangle(cv, x2, y2, x1, y1, x3, y3, ch);
if(y2 > y3)
return cucul_fill_triangle(cv, x1, y1, x3, y3, x2, y2, ch);
/* Compute slopes and promote precision */
sl21 = (y2 == y1) ? 0 : (x2 - x1) * 0x10000 / (y2 - y1);
sl31 = (y3 == y1) ? 0 : (x3 - x1) * 0x10000 / (y3 - y1);
sl32 = (y3 == y2) ? 0 : (x3 - x2) * 0x10000 / (y3 - y2);
x1 *= 0x10000;
x2 *= 0x10000;
x3 *= 0x10000;
ymin = y1 < 0 ? 0 : y1;
ymax = y3 + 1 < (int)cv->height ? y3 + 1 : (int)cv->height;
if(ymin < y2)
{
xa = x1 + sl21 * (ymin - y1);
xb = x1 + sl31 * (ymin - y1);
}
else if(ymin == y2)
{
xa = x2;
xb = (y1 == y3) ? x3 : x1 + sl31 * (ymin - y1);
}
else /* (ymin > y2) */
{
xa = x3 + sl32 * (ymin - y3);
xb = x3 + sl31 * (ymin - y3);
}
/* Rasterize our triangle */
for(y = ymin; y < ymax; y++)
{
/* Rescale xa and xb, recentering the division */
if(xa < xb)
{
xx1 = (xa + 0x800) / 0x10000;
xx2 = (xb + 0x801) / 0x10000;
}
else
{
xx1 = (xb + 0x800) / 0x10000;
xx2 = (xa + 0x801) / 0x10000;
}
xmin = xx1 < 0 ? 0 : xx1;
xmax = xx2 + 1 < (int)cv->width ? xx2 + 1 : (int)cv->width;
for(x = xmin; x < xmax; x++)
cucul_put_char(cv, x, y, ch);
xa += y < y2 ? sl21 : sl32;
xb += sl31;
}
return 0;
}
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