# `Drafter.CharacterWidth.Default`
[🔗](https://github.com/jaman/drafter/blob/main/lib/drafter/character_width/default.ex#L1)

Drafter's own width tables, and the default `Drafter.CharacterWidth`.

Used when no other implementation is configured. Call `Drafter.CharacterWidth`
rather than this module directly, so a configured implementation is honoured.

Width comes from Unicode East Asian Width (UAX #11 `W` and `F` are two
columns), Emoji Presentation (UTS #51), and the general categories that occupy
no column at all — non-spacing combining marks, format characters, and C0/C1
controls.

Measurement is per grapheme cluster, not per codepoint. A cluster's width is
the width of its base character; trailing combining marks, skin-tone
modifiers, and regional-indicator continuations add nothing. Variation
selectors override the base: `U+FE0F` forces emoji presentation (two columns)
and `U+FE0E` forces text presentation (one column). A cluster joined by
`U+200D` (ZWJ) measures two columns.

No bidirectional reordering is performed: right-to-left text is measured
correctly but emitted in logical order.

## Examples

    iex> Drafter.CharacterWidth.Default.string("ab漢")
    4

    iex> Drafter.CharacterWidth.Default.grapheme("")
    0

    iex> Drafter.CharacterWidth.Default.printable_ascii?("plain")
    true

# `codepoint`

```elixir
@spec codepoint(non_neg_integer()) :: non_neg_integer()
```

Display width in columns of a single codepoint.

# `grapheme`

```elixir
@spec grapheme(String.t()) :: non_neg_integer()
```

Display width in columns of a single grapheme cluster.

The cluster's base character determines the width; combining marks,
skin-tone modifiers and regional-indicator continuations add nothing.

# `printable_ascii?`

```elixir
@spec printable_ascii?(binary()) :: boolean()
```

Whether every byte is printable ASCII, over which display width equals byte size.

# `string`

```elixir
@spec string(String.t()) :: non_neg_integer()
```

Display width in columns of a string.

Printable-ASCII input is measured by byte size; anything else per grapheme
cluster.

---

*Consult [api-reference.md](api-reference.md) for complete listing*