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 /**********************************************************************
  14  *           LineDDA   (GDI32.@)
  15  */
  16 BOOL WINAPI LineDDA(INT nXStart, INT nYStart, INT nXEnd, INT nYEnd,
  17                         LINEDDAPROC callback, LPARAM lParam )
  18 {
  19     INT xadd = 1, yadd = 1;
  20     INT err,erradd;
  21     INT cnt;
  22     INT dx = nXEnd - nXStart;
  23     INT dy = nYEnd - nYStart;
  24
  25     if (dx < 0)  {
  26       dx = -dx; xadd = -1;
  27     }
  28     if (dy < 0)  {
  29       dy = -dy; yadd = -1;
  30     }
  31     if (dx > dy) { /* line is "more horizontal" */
  32       err = 2*dy - dx; erradd = 2*dy - 2*dx;
  33       for(cnt = 0;cnt <= dx; cnt++) {
  34         callback(nXStart,nYStart,lParam);
  35         if (err > 0) {
  36           nYStart += yadd;
  37           err += erradd;
  38         } else  {
  39           err += 2*dy;
  40         }
  41         nXStart += xadd;
  42       }
  43     } else  { /* line is "more vertical" */
  44       err = 2*dx - dy; erradd = 2*dx - 2*dy;
  45       for(cnt = 0;cnt <= dy; cnt++) {
  46         callback(nXStart,nYStart,lParam);
  47         if (err > 0) {
  48           nXStart += xadd;
  49           err += erradd;
  50         } else  {
  51           err += 2*dx;
  52         }
  53         nYStart += yadd;
  54       }
  55     }
  56     return TRUE;
  57 }