docs/misc-protocol.rst
These are a few small protocol extensions kitty implements, primarily for use by its own kitten, they are documented here for completeness.
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 <https://vt100.net/docs/vt510-rm/DECOM.html>__ and DECCOLM <https://vt100.net/docs/vt510-rm/DECCOLM.html>__.
This allows TUI applications to easily save and restore emulator state without needing to maintain lists of modes.
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.
.. _mouse_leave_window:
kitty extends the SGR Pixel mouse reporting protocol created by xterm to also report when the mouse leaves the window. This 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.
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.
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).