Boundary trace (seed point)

// Seed-point boundary: two overlapping rectangles; the tracer must split the
// edges at their crossings and return the minimal face around the seed.
static void feat_boundary(bool filled) {
    samp_clear();
    feat_rect_lines(0, 0, 60, 40);
    feat_rect_lines(30, 20, 90, 70);
    const double sx = 45, sy = 30;                       // seed inside the overlap
    int h = filled ? CadAddBoundPolygon(g_hDwg, sx, sy, 0)
                   : CadAddBoundary(g_hDwg, sx, sy, 0);
    if (h) CadEntityPutColor(h, CAD_COLOR_RED);
    int mark = CadAddCircle(g_hDwg, sx, sy, 0, 1.2);     // show the seed
    CadEntityPutColor(mark, CAD_COLOR_YELLOW);
    CadUpdate(g_hDwg); samp_zoom_ext();
    set_status(h ? (filled ? L"CadAddBoundPolygon: filled minimal region around the seed (red)"
                           : L"CadAddBoundary: traced contour around the seed (red)")
                 : L"Boundary trace FAILED (seed not enclosed?)");
}

    1, 2:                                        // Boundary / BoundPolygon
      begin
        CadPurge(FhDwg, CAD_CLEAR_ENTITIES);
        FeatRectLines(0, 0, 60, 40);             // two overlapping rectangles:
        FeatRectLines(30, 20, 90, 70);           // edges split at crossings
        if TMenuItem(Sender).Tag = 2 then
          h := CadAddBoundPolygon(FhDwg, 45, 30, 0)
        else
          h := CadAddBoundary(FhDwg, 45, 30, 0);
        if h <> 0 then CadEntityPutColor(h, CAD_COLOR_RED);
        m := CadAddCircle(FhDwg, 45, 30, 0, 1.2);   // show the seed
        CadEntityPutColor(m, CAD_COLOR_YELLOW);
        CadUpdate(FhDwg); CadExecute(FhDwg, FCadHwnd, CAD_CMD_ZOOM_EXT);
        if h <> 0 then
          StatusBar.SimpleText := 'CadAddBoundary/BoundPolygon: minimal region around the seed (red)'
        else
          StatusBar.SimpleText := 'Boundary trace FAILED (seed not enclosed?)';
      end;

    private void FeatBoundary(bool filled)
    {
        SampleClear();
        FeatRectLines(0, 0, 60, 40);            // two overlapping rectangles: the
        FeatRectLines(30, 20, 90, 70);          // tracer splits edges at crossings
        const double sx = 45, sy = 30;          // seed inside the overlap
        var h = filled ? YuCadApi.CadAddBoundPolygon(_hDwg, sx, sy, 0)
                       : YuCadApi.CadAddBoundary(_hDwg, sx, sy, 0);
        if (h != 0) YuCadApi.CadEntityPutColor(h, YuCadApi.CAD_COLOR_RED);
        var mark = YuCadApi.CadAddCircle(_hDwg, sx, sy, 0, 1.2);
        YuCadApi.CadEntityPutColor(mark, YuCadApi.CAD_COLOR_YELLOW);
        YuCadApi.CadUpdate(_hDwg); SampleZoomExt();
        SetStatus(h != 0 ? (filled ? "CadAddBoundPolygon: filled minimal region around the seed (red)"
                                   : "CadAddBoundary: traced contour around the seed (red)")
                         : "Boundary trace FAILED (seed not enclosed?)");
    }