website: ich

website/app/vt/ich/page.mdx

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+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.
+
+## 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_____|
+```