git.sur5r.net Git - cc65/blob - libsrc/tgi/tgi_arc.c

   1 /*****************************************************************************/
   2 /*                                                                           */
   3 /*                                 tgi_arc.c                                 */
   4 /*                                                                           */
   5 /*                            Draw an ellipse arc                            */
   6 /*                                                                           */
   7 /*                                                                           */
   8 /*                                                                           */
   9 /* (C) 2002-2009, Ullrich von Bassewitz                                      */
  10 /*                Roemerstrasse 52                                           */
  11 /*                D-70794 Filderstadt                                        */
  12 /* EMail:         uz@cc65.org                                                */
  13 /*                                                                           */
  14 /*                                                                           */
  15 /* This software is provided 'as-is', without any expressed or implied       */
  16 /* warranty.  In no event will the authors be held liable for any damages    */
  17 /* arising from the use of this software.                                    */
  18 /*                                                                           */
  19 /* Permission is granted to anyone to use this software for any purpose,     */
  20 /* including commercial applications, and to alter it and redistribute it    */
  21 /* freely, subject to the following restrictions:                            */
  22 /*                                                                           */
  23 /* 1. The origin of this software must not be misrepresented; you must not   */
  24 /*    claim that you wrote the original software. If you use this software   */
  25 /*    in a product, an acknowledgment in the product documentation would be  */
  26 /*    appreciated but is not required.                                       */
  27 /* 2. Altered source versions must be plainly marked as such, and must not   */
  28 /*    be misrepresented as being the original software.                      */
  29 /* 3. This notice may not be removed or altered from any source              */
  30 /*    distribution.                                                          */
  31 /*                                                                           */
  32 /*****************************************************************************/
  33
  34
  35
  36 #include <tgi.h>
  37 #include <tgi/tgi-kernel.h>
  38 #include <cc65.h>
  39
  40
  41
  42 /*****************************************************************************/
  43 /*                                   Code                                    */
  44 /*****************************************************************************/
  45
  46
  47
  48 void __fastcall__ tgi_arc (int x, int y, unsigned char rx, unsigned char ry,
  49                            unsigned sa, unsigned ea)
  50 /* Draw an ellipse arc with center at x/y and radii rx/ry using the current
  51 ** drawing color. The arc covers the angle between sa and ea (startangle and
  52 ** endangle), which must be in the range 0..360 (otherwise the function may
  53 ** bevave unextectedly).
  54 */
  55 {
  56     int x1, y1, x2, y2;
  57     unsigned char inc;
  58     unsigned char done = 0;
  59
  60     /* Bail out if there's nothing to do */
  61     if (sa > ea) {
  62         return;
  63     }
  64
  65     /* Determine the number of segments to use. This may be refined ... */
  66     if (rx + ry >= 25) {
  67         inc = 12;
  68     } else {
  69         inc = 24;
  70     }
  71
  72     /* Calculate the start coords */
  73     x1 = x + tgi_imulround (rx, _cos (sa));
  74     y1 = y - tgi_imulround (ry, _sin (sa));
  75     do {
  76         sa += inc;
  77         if (sa >= ea) {
  78             sa = ea;
  79             done = 1;
  80         }
  81         x2 = x + tgi_imulround (rx, _cos (sa));
  82         y2 = y - tgi_imulround (ry, _sin (sa));
  83         tgi_line (x1, y1, x2, y2);
  84         x1 = x2;
  85         y1 = y2;
  86     } while (!done);
  87 }
  88
  89
  90