# `RasterExRatatui.Patch`
[🔗](https://github.com/mcass19/raster_ex_ratatui/blob/v0.4.0/lib/raster_ex_ratatui/patch.ex#L1)

A rectangle of packed pixels to write to a panel.

`RasterExRatatui.Raster.apply/2` answers a cell diff with a list of patches: one per run of changed cells on a row, one per pixel region that is new or changed, and the margins on a full repaint. A panel driver writes each patch at `(x, y)`, **in list order** (a region patch may overlap cells painted by an earlier patch).

## Fields

  * `:x`, `:y` — top-left corner, in panel pixels
  * `:width`, `:height` — size, in pixels
  * `:data` — `width * height` pixels, row-major from the top-left, each packed by the raster's `RasterExRatatui.PixelFormat`. There is no stride padding: row `r` starts at byte `r * width * bytes_per_pixel`.

# `t`

```elixir
@type t() :: %RasterExRatatui.Patch{
  data: binary(),
  height: non_neg_integer(),
  width: non_neg_integer(),
  x: non_neg_integer(),
  y: non_neg_integer()
}
```

# `blit`

```elixir
@spec blit(binary(), pos_integer(), pos_integer(), t()) :: binary()
```

Writes `patch` into `frame`, a row-major buffer `frame_width` pixels wide with `bytes_per_pixel` bytes per pixel, and returns the new buffer.

For consumers that keep a full frame and apply patches to it (a panel that only accepts whole frames, a PNG snapshot), and for tests. The patch must lie inside the frame.

## Examples

    iex> frame = :binary.copy(<<0>>, 4 * 3)
    iex> patch = %RasterExRatatui.Patch{x: 1, y: 1, width: 2, height: 2, data: <<1, 2, 3, 4>>}
    iex> RasterExRatatui.Patch.blit(frame, 4, 1, patch)
    <<0, 0, 0, 0, 0, 1, 2, 0, 0, 3, 4, 0>>

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