objects/linedda.c

   1 /*
   2  * LineDDA
   3  *
   4  * Copyright 1993 Bob Amstadt
   5  */
   6
   7 #include <stdlib.h>
   8 #include "windef.h"
   9 #include "wingdi.h"
  10 #include "wine/wingdi16.h"
  11
  12 /**********************************************************************
  13  *           LineDDA16   (GDI.100)
  14  */
  15 void WINAPI LineDDA16( INT16 nXStart, INT16 nYStart, INT16 nXEnd, INT16 nYEnd,
  16                        LINEDDAPROC16 callback, LPARAM lParam )
  17 {
  18     LineDDA( nXStart, nYStart, nXEnd, nYEnd,
  19                (LINEDDAPROC)callback, lParam );
  20 }
  21
  22
  23 /**********************************************************************
  24  *           LineDDA32   (GDI32.248)
  25  */
  26 BOOL WINAPI LineDDA(INT nXStart, INT nYStart, INT nXEnd, INT nYEnd,
  27                         LINEDDAPROC callback, LPARAM lParam )
  28 {
  29     INT xadd = 1, yadd = 1;
  30     INT err,erradd;
  31     INT cnt;
  32     INT dx = nXEnd - nXStart;
  33     INT dy = nYEnd - nYStart;
  34
  35     if (dx < 0)  {
  36       dx = -dx; xadd = -1;
  37     }
  38     if (dy < 0)  {
  39       dy = -dy; yadd = -1;
  40     }
  41     if (dx > dy) { /* line is "more horizontal" */
  42       err = 2*dy - dx; erradd = 2*dy - 2*dx;
  43       for(cnt = 0;cnt <= dx; cnt++) {
  44         callback(nXStart,nYStart,lParam);
  45         if (err > 0) {
  46           nYStart += yadd;
  47           err += erradd;
  48         } else  {
  49           err += 2*dy;
  50         }
  51         nXStart += xadd;
  52       }
  53     } else  { /* line is "more vertical" */
  54       err = 2*dx - dy; erradd = 2*dx - 2*dy;
  55       for(cnt = 0;cnt <= dy; cnt++) {
  56         callback(nXStart,nYStart,lParam);
  57         if (err > 0) {
  58           nXStart += xadd;
  59           err += erradd;
  60         } else  {
  61           err += 2*dx;
  62         }
  63         nYStart += yadd;
  64       }
  65     }
  66     return TRUE;
  67 }