algo/VLine.algo.h

   1 /*****************************************************************************
   2  * This file is part of gfxprim library.                                     *
   3  *                                                                           *
   4  * Gfxprim is free software; you can redistribute it and/or                  *
   5  * modify it under the terms of the GNU Lesser General Public                *
   6  * License as published by the Free Software Foundation; either              *
   7  * version 2.1 of the License, or (at your option) any later version.        *
   8  *                                                                           *
   9  * Gfxprim is distributed in the hope that it will be useful,                *
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of            *
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU         *
  12  * Lesser General Public License for more details.                           *
  13  *                                                                           *
  14  * You should have received a copy of the GNU Lesser General Public          *
  15  * License along with gfxprim; if not, write to the Free Software            *
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor,                        *
  17  * Boston, MA  02110-1301  USA                                               *
  18  *                                                                           *
  19  * Copyright (C) 2009-2010 Jiri "BlueBear" Dluhos                            *
  20  *                         <jiri.bluebear.dluhos@gmail.com>                  *
  21  *                                                                           *
  22  * Copyright (C) 2009-2010 Cyril Hrubis <metan@ucw.cz>                       *
  23  *                                                                           *
  24  *****************************************************************************/
  25
  26 /* A vertical line drawing algorithm. */
  27
  28 /* Ensures that coordinates are in correct order, and clips them.
  29  * Exits immediately if the line is completely clipped out.
  30  */
  31 #define ORDER_AND_CLIP_COORDS do { \
  32         if (y0 > y1) GP_SWAP(y0, y1); \
  33         if (x < (int) context->clip_w_min \
  34             || x > (int) context->clip_w_max \
  35             || y1 < (int) context->clip_h_min \
  36             || y0 > (int) context->clip_h_max) { \
  37                 return; \
  38         } \
  39         y0 = GP_MAX(y0, (int) context->clip_h_min); \
  40         y1 = GP_MIN(y1, (int) context->clip_h_max); \
  41 } while (0)
  42
  43 /*
  44  * This macro defines a horizontal line drawing function.
  45  * Arguments:
  46  *     CONTEXT_T - user-defined type of drawing context (passed to PUTPIXEL)
  47  *     PIXVAL_T  - user-defined pixel value type (passed to PUTPIXEL)
  48  *     PIXEL_ADDRESS  - a function that returns a pointer to a pixel in memory,
  49  *                      in form f(context, y, x)
  50  *     WRITE_PIXELS   - a function that fills a linear block with pixel value,
  51  *                      in form f(start, length, pixel)
  52  *     FN_NAME   - name of the function to be defined
  53  */
  54 #define DEF_VLINE_FN(FN_NAME, CONTEXT_T, PIXEL_T, PUT_PIXEL) \
  55 void FN_NAME(CONTEXT_T context, int x, int y0, int y1, PIXEL_T pixel) \
  56 { \
  57         ORDER_AND_CLIP_COORDS; \
  58         int y; \
  59 \
  60         for (y = y0; y <= y1; y++) \
  61                 PUT_PIXEL(context, x, y, pixel); \
  62 }