objects/linedda.c

   1 /*
   2  * LineDDA
   3  *
   4  * Copyright 1993 Bob Amstadt
   5  */
   6
   7 #include <stdlib.h>
   8 #include "windows.h"
   9
  10
  11 /**********************************************************************
  12  *           LineDDA16   (GDI.100)
  13  */
  14 void WINAPI LineDDA16( INT16 nXStart, INT16 nYStart, INT16 nXEnd, INT16 nYEnd,
  15                        LINEDDAPROC16 callback, LPARAM lParam )
  16 {
  17     LineDDA32( nXStart, nYStart, nXEnd, nYEnd,
  18                (LINEDDAPROC32)callback, lParam );
  19 }
  20
  21
  22 /**********************************************************************
  23  *           LineDDA32   (GDI32.248)
  24  */
  25 BOOL32 WINAPI LineDDA32(INT32 nXStart, INT32 nYStart, INT32 nXEnd, INT32 nYEnd,
  26                         LINEDDAPROC32 callback, LPARAM lParam )
  27 {
  28     INT32 xadd = 1, yadd = 1;
  29     INT32 err,erradd;
  30     INT32 cnt;
  31     INT32 dx = nXEnd - nXStart;
  32     INT32 dy = nYEnd - nYStart;
  33
  34     if (dx < 0)  {
  35       dx = -dx; xadd = -1;
  36     }
  37     if (dy < 0)  {
  38       dy = -dy; yadd = -1;
  39     }
  40     if (dx > dy) { /* line is "more horizontal" */
  41       err = 2*dy - dx; erradd = 2*dy - 2*dx;
  42       for(cnt = 0;cnt <= dx; cnt++) {
  43         callback(nXStart,nYStart,lParam);
  44         if (err > 0) {
  45           nYStart += yadd;
  46           err += erradd;
  47         } else  {
  48           err += 2*dy;
  49         }
  50         nXStart += xadd;
  51       }
  52     } else  { /* line is "more vertical" */
  53       err = 2*dx - dy; erradd = 2*dx - 2*dy;
  54       for(cnt = 0;cnt <= dy; cnt++) {
  55         callback(nXStart,nYStart,lParam);
  56         if (err > 0) {
  57           nXStart += xadd;
  58           err += erradd;
  59         } else  {
  60           err += 2*dx;
  61         }
  62         nYStart += yadd;
  63       }
  64     }
  65     return TRUE;
  66 }