Saving and restoring colors#
It is often useful for a full screen application with its own color themes to set the default foreground, background, selection and cursor colors and the ANSI color table. This allows for various performance optimizations when drawing the screen. The problem is that if the user previously used the escape codes to change these colors themselves, then running the full screen application will lose those changes even after it exits. To avoid this, kitty introduces a new pair of OSC escape codes to push and pop the current color values from a stack:
<ESC>]30001<ESC>\ # push onto stack
<ESC>]30101<ESC>\ # pop from stack
These escape codes save/restore the colors, default background, default foreground, selection background, selection foreground and cursor color and the 256 colors of the ANSI color table.
In July 2020, after several years, xterm copied this protocol extension, without acknowledgement, and using incompatible escape codes (XTPUSHCOLORS, XTPOPCOLORS, XTREPORTCOLORS). And they decided to save not just the dynamic colors but the entire ANSI color table. In the interests of promoting interoperability, kitty added support for xterm’s escape codes as well, and changed this extension to also save/restore the entire ANSI color table.