---
jupyter:
  description: 'Closing small gaps in planex2d: CloseGaps joins ends that miss each other within a tolerance, and the same
    step runs on export and when reading DXF.'
---

# Small gaps

Ends that should meet but miss each other by a small distance keep a wire open. `CloseGaps(tol)` moves them
together.

```python
import planex as px
```

```python nbsphinx="hidden"
from docs_figures import Row, Vertices
```

## A square that does not close

The example is a unit square whose right side starts 10⁻⁴ above the end of the bottom (Figure 1a). Magnified at that
corner, the two open ends are marked (Figure 1b). `Wire.Add` refuses an edge that misses the wire's end, so the four
loose edges go through `px.Wires`, which chains them into one open wire.

```python
corners = [((0, 0), (1, 0)), ((1, 1e-4), (1, 1)), ((1, 1), (0, 1)), ((0, 1), (0, 0))]
(w,) = px.Wires([px.Line(a, b) for a, b in corners])
print(w.IsClosed(), w.OpenEnds())
```

```python nbsphinx="hide-input"
Row((w, "The wire", {"fill": False}),
    (w, "Magnified at (1, 0)", {"fill": False, "marks": [(1, 0), (1, 1e-4)], "view": ((1 - 3e-4, 1 + 3e-4), (-2e-4, 3e-4))}),
    caption="A square whose ends miss by 10⁻⁴")
```

Closed with a tolerance of 10⁻³, the two ends meet in one vertex, marked in the same magnified view, and the wire
bounds a face (Figure 2). The ends meet halfway, at (1, 5·10⁻⁵), so the area is 1 − 5·10⁻⁵.

```python
w.CloseGaps(1e-3)
square = w.Face()
print(w.IsClosed(), square.mass)
```

```python nbsphinx="hide-input"
Row((square, "The face"),
    (w, "Magnified at (1, 0)", {"fill": False, "marks": Vertices(w), "view": ((1 - 3e-4, 1 + 3e-4), (-2e-4, 3e-4))}),
    caption="Closed with a tolerance of 10⁻³")
```

## On export and when reading

The exports take `close_gaps_smaller`, and `FromDXF` takes `tol` for the same step:

```python
print(w.Simplified(close_gaps_smaller=1e-3).IsClosed())
```