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# Miscellaneous protocol extensions

These are a few small protocol extensions kitty implements, primarily for use by its own kitten, they are documented here for completeness.

## Simple save/restore of all terminal modes

XTerm has the XTSAVE/XTRESTORE escape codes to save and restore terminal private modes. However, they require specifying an explicit list of modes to save/restore. kitty extends this protocol to specify that when no modes are specified, all side-effect free modes should be saved/restored. By side-effects we mean things that can affect other terminal state such as cursor position or screen contents. Examples of modes that have side effects are: DECOM and DECCOLM.

This allows TUI applications to easily save and restore emulator state without needing to maintain lists of modes.

## Independent control of bold and faint SGR properties

In common terminal usage, bold is set via SGR 1 and faint by SGR 2. However, there is only one number to reset these attributes, SGR 22, which resets both. There is no way to reset one and not the other. kitty uses 221 and 222 to reset bold and faint independently.

## Reporting when the mouse leaves the window

kitty extends the SGR Pixel mouse reporting protocol created by xterm to also report when the mouse leaves the window. This is event is delivered encoded as a normal SGR pixel event except that the eight bit is set on the first number. Additionally, bit 5 is set to indicate this is a motion related event. The remaining bits 1-7 (except 5) are used to encode button and modifier information. When bit 8 is set it means the event is a mouse has left the window event, and all other bits should be ignored. The pixel position values must also be ignored as they may not be accurate.

## An escape code to move the contents of the screen into the scrollback

The escape code is `\x1b [ 22 J` (ignoring spaces present for clarity). It moves all screen contents (text and images) into the scrollback leaving the screen in the same state as it would be if the standard screen clear escape code had been used `\x1b [ 2 J`.

## kitty specific private escape codes

These are a family of escape codes used by kitty for various things including remote control. They are all DCS (Device Control String) escape codes starting with `\x1b P @ kitty-` (ignoring spaces present for clarity).