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91 lines
3.9 KiB
C
91 lines
3.9 KiB
C
/*****************************************************************************/
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/* */
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/* tgi_arc.c */
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/* */
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/* Draw an ellipse arc */
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/* */
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/* */
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/* */
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/* (C) 2002-2009, Ullrich von Bassewitz */
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/* Roemerstrasse 52 */
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/* D-70794 Filderstadt */
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/* EMail: uz@cc65.org */
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/* */
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/* */
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/* This software is provided 'as-is', without any expressed or implied */
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/* warranty. In no event will the authors be held liable for any damages */
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/* arising from the use of this software. */
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/* */
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/* Permission is granted to anyone to use this software for any purpose, */
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/* including commercial applications, and to alter it and redistribute it */
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/* freely, subject to the following restrictions: */
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/* */
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/* 1. The origin of this software must not be misrepresented; you must not */
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/* claim that you wrote the original software. If you use this software */
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/* in a product, an acknowledgment in the product documentation would be */
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/* appreciated but is not required. */
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/* 2. Altered source versions must be plainly marked as such, and must not */
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/* be misrepresented as being the original software. */
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/* 3. This notice may not be removed or altered from any source */
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/* distribution. */
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/* */
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/*****************************************************************************/
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#include <tgi.h>
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#include <tgi/tgi-kernel.h>
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#include <cc65.h>
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/*****************************************************************************/
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/* Code */
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/*****************************************************************************/
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void __fastcall__ tgi_arc (int x, int y, unsigned char rx, unsigned char ry,
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unsigned sa, unsigned ea)
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/* Draw an ellipse arc with center at x/y and radii rx/ry using the current
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** drawing color. The arc covers the angle between sa and ea (startangle and
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** endangle), which must be in the range 0..360 (otherwise the function may
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** bevave unextectedly).
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*/
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{
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int x1, y1, x2, y2;
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unsigned char inc;
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unsigned char done = 0;
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/* Bail out if there's nothing to do */
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if (sa > ea) {
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return;
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}
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/* Determine the number of segments to use. This may be refined ... */
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if (rx + ry >= 25) {
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inc = 12;
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} else {
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inc = 24;
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}
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/* Calculate the start coords */
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x1 = x + tgi_imulround (rx, _cos (sa));
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y1 = y - tgi_imulround (ry, _sin (sa));
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do {
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sa += inc;
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if (sa >= ea) {
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sa = ea;
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done = 1;
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}
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x2 = x + tgi_imulround (rx, _cos (sa));
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y2 = y - tgi_imulround (ry, _sin (sa));
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tgi_line (x1, y1, x2, y2);
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x1 = x2;
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y1 = y2;
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} while (!done);
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}
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