Q65590: _Floodfill() Doesn’t Completely Fill Areas with Patterns

Article: Q65590
Product(s): See article
Version(s): 6.00
Operating System(s): MS-DOS
Keyword(s): ENDUSER | s_quickc | mspl13_c
Last Modified: 24-SEP-1990

The sample code below draws two circles that are cut in half with a
line. There is a small gap (2 pixels) in the line. When _floodfill()
is used to fill the circle with a solid color, it fills the entire
circle. When _floodfill() is used to fill the circle with a pattern,
it fills only half of the circle.

In this instance, the two-pixel gap in the line corresponds to the gap
in the fill pattern. This causes _floodfill() to treat it as a solid
line and fill only half the circle.

To fill the entire circle with the pattern, create a second
_floodfill() with a point on the other side of the line, as in the
commented section of the code below:

Sample Code
-----------

#include <conio.h>
#include <graph.h>
#include <time.h>
#include <stdlib.h>
#include <stddef.h>

void main(void)
{
    unsigned char fill[] = {0x88,0x22,0x88,0x22,0x88,0x22,0x88,0x22};

    if( !_setvideomode( _MAXRESMODE ) )
       exit(1);

    _setfillmask( NULL );     /*  Fill circle with a solid color  */
    _setcolor(2);
    _ellipse( _GBORDER, 50, 100, 250, 300 );
    getch();
    _moveto( 50, 200 );
    _lineto( 248,200 );       /*  Line with a 2 pixel gap */
    getch();
    _setcolor(4);
    _floodfill( 100, 210, 2); /* Fill the circle with a solid color */
    getch();

    _setfillmask( fill );     /*  Fill circle with a pattern  */
    _setcolor(2);
    _ellipse( _GBORDER, 350, 100, 550, 300 );
    getch();
    _moveto( 350, 200 );
    _lineto( 548, 200 );      /*  Line with a 2 pixel gap */
    getch();
    _setcolor(4);
    _floodfill( 400, 210, 2); /*  Fill half of the circle with a pattern */

/*  _floodfill( 400, 180, 2);   This _floodfill() will fill in the other */
/*                              half of the circle with a pattern.       */
     getch();
    _setvideomode( _DEFAULTMODE );

}

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