defaultcursor - bakkeby/patches GitHub Wiki
This patch makes st interpret cursor 0 as the default cursor.
According to the specification the "Set cursor style (DECSCUSR), VT520." escape sequences define both values of 0 and 1 as a blinking block, with 1 being the default.
Refer to:
This patch allows the default cursor to be set when value 0 is used, as opposed to setting the cursor to a blinking block.
This allows a command like this to restore the cursor to what st is configured with:
$ echo -ne "\e[ q"
While many terminal emulators do this it is not adhering to specification. xterm is an example terminal that sets a blinking block instead of the configured one, same as st.
Example use case is changing cursor shape in vim depending on what mode is used:
https://vim.fandom.com/wiki/Change_cursor_shape_in_different_modes
The alternative in this case would be to explicitly set the cursor back to what you expect it to be (underline, bar) in the vim configuration.