import VTSequence from "@/components/VTSequence";

# Insert Character (ICH)

<VTSequence sequence={["CSI", "Pn", "@"]} />

Insert `n` blank characters at the current cursor position and shift
existing cell contents right.

The parameter `n` must be an integer greater than or equal to 1. If `n` is less than
or equal to 0, adjust `n` to be 1. If `n` is omitted, `n` defaults to 1.

This sequence always unsets the pending wrap state.

If the cursor position is outside of the [left and right margins](#TODO),
this sequence does not change the screen, but the pending wrap state is
still reset.

Existing cells shifted beyond the right margin are deleted. Inserted cells
are blank with the background color colored according to the current SGR state.

If a multi-cell character (such as "橋") is shifted so that the cell is split
in half, the multi-cell character can either be clipped or erased. Typical
behavior is to clip at the right edge of the screen and erase at a right
margin, but either behavior is acceptable.

## Validation

### ICH V-1: No Scroll Region, Fits on Screen

```bash
printf "ABC"
printf "\033[1G"
printf "\033[2@"
```

```
|XcABC_____|
```

### ICH V-2: SGR State

```bash
printf "ABC"
printf "\033[1G"
printf "\033[41m"
printf "\033[2@"
printf "X"
```

```
|c_ABC_____|
```

The `c_` cells should both have a red background. The `ABC` cells should
remain unchanged in style.

### ICH V-3: Shifting Content Off the Screen

```bash
cols=$(tput cols)
printf "\033[${cols}G"
printf "\033[2D"
printf "ABC"
printf "\033[2D"
printf "\033[2@"
printf "X"
```

```
|_______XcA|
```

### ICH V-4: Inside Left/Right Scroll Region

```bash
printf "\033[1;1H" # move to top-left
printf "\033[0J" # clear screen
printf "\033[?69h" # enable left/right margins
printf "\033[3;5s" # scroll region left/right
printf "\033[3G"
printf "ABC"
printf "\033[3G"
printf "\033[2@"
printf "X"
```

```
|__XcA_____|
```

### ICH V-5: Outside Left/Right Scroll Region

```bash
printf "\033[1;1H" # move to top-left
printf "\033[0J" # clear screen
printf "\033[?69h" # enable left/right margins
printf "\033[3;5s" # scroll region left/right
printf "\033[3G"
printf "ABC"
printf "\033[1G"
printf "\033[2@"
printf "X"
```

```
|XcABC_____|
```

### ICH V-6: Split Wide Character

```bash
cols=$(tput cols)
printf "\033[${cols}G"
printf "\033[1D"
printf "橋"
printf "\033[2D"
printf "\033[@"
printf "X"
```

```
|_______Xc_|
```

In this case, it is valid for the last cell to be blank or to clip the
multi-cell character. xterm clips the character but many other terminals
erase the cell.
