How to use JSON API to send messages from terminal to vim?

Question

In terminal.txt, there is description about terminal-api, but it seems not to give a example to show how the message is send from terminal to vim function Tapi_..., is there some examples for the usage?

Answer 1

Section :help terminal-api includes a thorough description of the API and also an example function:

function Tapi_Impression(bufnum, arglist)
  if len(a:arglist) == 2
    echomsg "impression " . a:arglist[0]
    echomsg "count " . a:arglist[1]
  endif
endfunc

Then inside a :term you can call this function by sending a special sequence starting with <Esc>]51;, then including a JSON encoded list (whose first element is the string "call", the second is the name of the function to call and the third a list of arguments to pass), finally followed by a <07>, which is the ASCII character with code 07, which is the "bell" control character.

In a shell (such as bash), you can use echo -e to have it interpret special sequences, and then \e to issue an <Esc> character, and \a for a "bell" which has ASCII code <07>. Putting it all together:

$ echo -ne '\e]51;["call", "Tapi_Impression", ["play", 14]]\a'

This will call the Tapi_Impression function, which in turn will print the following message (also available in :messages):

impression play
count 14