Q65200

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Q65200: _polygon() with _GFILLINTERIOR Does Not Work When Clipped

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Article: Q65200
Product(s): See article
Version(s): 6.00
Operating System(s): MS-DOS
Keyword(s): ENDUSER | buglist6.00 s_quickc setcliprgn | mspl13_c
Last Modified: 17-DEC-1990

When _polygon is called to draw a filled polygon inside a clip region
set with _setcliprgn, the polygon may not be drawn correctly. The
following program demonstrates the error:

#include <graph.h>

struct xycoord pts[4] = {{0,0}, {55,55}, {83,25}, {0,0}};

void main(void)
{
     _setvideomode(_ERESCOLOR);

/* show the polygon */
     _setcolor(3);
     _polygon(_GFILLINTERIOR, pts, 4);
     getch();

/* show the clipped region */
     _setcolor(3);
     _rectangle(_GBORDER, 0, 0, 75, 50);
     _setcliprgn(0,0, 75, 50);
     getch();

/*** polygon drawn will have portion missing with _GFILLINTERIOR ***/
     _setcolor(10);
     _polygon(_GFILLINTERIOR, pts, 4);
     getch();

/* clipped polygon drawn correctly with _GBORDER */
     _setcolor(12);
     _polygon(_GBORDER, pts, 4);
     getch();

     _setvideomode(_DEFAULTMODE);
}

Any horizontal lines that are being clipped will not be drawn at all.

Microsoft has confirmed this to be a problem with C version 6.00. We
are researching this problem and will post new information here when
it becomes available.

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