Nvim documentation: nvim_terminal_emulator

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*terminal_emulator.txt*   Nvim


		 NVIM REFERENCE MANUAL    by Thiago de Arruda



Terminal emulator				*terminal* *terminal-emulator*

Nvim embeds a VT220/xterm terminal emulator based on libvterm. The terminal is
presented as a special 'buftype', asynchronously updated as data is received
from the connected program.

Terminal buffers behave like normal buffers, except:
- With 'modifiable', lines can be edited but not deleted.
- 'scrollback' controls how many lines are kept.
- Output is followed if the cursor is on the last line.
- 'modified' is the default. You can set 'nomodified' to avoid a warning when
  closing the terminal buffer.
- 'bufhidden' defaults to "hide".

				      Type |gO| to see the table of contents.

==============================================================================

Start						*terminal-start*

There are several ways to create a terminal buffer:

- Invoke the |:terminal| command.
- Call the |termopen()| function.
- Edit a file with a name matching `term://(.{-}//(\d+:)?)?\zs.*`.
  For example:

    :edit term://bash
    :vsplit term://top
 
    Note: The "term://" pattern is handled by a BufReadCmd handler, so the
    |autocmd-nested| modifier is required to use it in an autocmd.
        autocmd VimEnter * ++nested split term://sh
     This is only mentioned for reference; use |:terminal| instead.

When the terminal starts, the buffer contents are updated and the buffer is
named in the form of `term://{cwd}//{pid}:{cmd}`. This naming scheme is used
by |:mksession| to restore a terminal buffer (by restarting the {cmd}).

==============================================================================

Input						*terminal-input*

To send input, enter |Terminal-mode| using any command that would enter "insert
mode" in a normal buffer, such as |i| or |:startinsert|. In this mode all keys
except <C-\><C-N> are sent to the underlying program. Use <C-\><C-N> to return
to normal-mode. |CTRL-\_CTRL-N|

Terminal-mode has its own |:tnoremap| namespace for mappings, this can be used
to automate any terminal interaction.

To map <Esc> to exit terminal-mode:
    :tnoremap <Esc> <C-\><C-n>

To simulate |i_CTRL-R| in terminal-mode:
    :tnoremap <expr> <C-R> '<C-\><C-N>"'.nr2char(getchar()).'pi'

To use `ALT+{h,j,k,l}` to navigate windows from any mode:
    :tnoremap <A-h> <C-\><C-N><C-w>h
    :tnoremap <A-j> <C-\><C-N><C-w>j
    :tnoremap <A-k> <C-\><C-N><C-w>k
    :tnoremap <A-l> <C-\><C-N><C-w>l
    :inoremap <A-h> <C-\><C-N><C-w>h
    :inoremap <A-j> <C-\><C-N><C-w>j
    :inoremap <A-k> <C-\><C-N><C-w>k
    :inoremap <A-l> <C-\><C-N><C-w>l
    :nnoremap <A-h> <C-w>h
    :nnoremap <A-j> <C-w>j
    :nnoremap <A-k> <C-w>k
    :nnoremap <A-l> <C-w>l

Mouse input has the following behavior:

- If the program has enabled mouse events, the corresponding events will be
  forwarded to the program.
- If mouse events are disabled (the default), terminal focus will be lost and
  the event will be processed as in a normal buffer.
- If another window is clicked, terminal focus will be lost and nvim will jump
  to the clicked window
- If the mouse wheel is used while the mouse is positioned in another window,
  the terminal wont lose focus and the hovered window will be scrolled.

==============================================================================

Configuration					*terminal-configuration*

Options:		'modified', 'scrollback'
Events:			|TermOpen|, |TermClose|
Highlight groups:	|hl-TermCursor|, |hl-TermCursorNC|

Terminal sets local defaults for some options, which may differ from your
global configuration.

- 'list' is disabled
- 'wrap' is disabled

You can change the defaults with a TermOpen autocommand:
    au TermOpen * setlocal list

TERMINAL COLORS 

The `{g,b}:terminal_color_x` variables control the terminal color palette,
where `x` is the color index between 0 and 255 inclusive.  The variables are
read during |TermOpen|. The value must be a color name or hexadecimal string.
Example:
    let g:terminal_color_4 = '#ff0000'
    let g:terminal_color_5 = 'green'
Only works for RGB UIs (see 'termguicolors'); for 256-color terminals the
color index is just forwarded.

Editor highlighting (|syntax-highlighting|, |highlight-groups|, etc.) has
higher precedence: it is applied after terminal colors are resolved.

==============================================================================

Status Variables				*terminal-status*

Terminal buffers maintain some buffer-local variables and options. The values
are initialized before TermOpen, so you can use them in a local 'statusline'.
Example:
    :autocmd TermOpen * setlocal statusline=%{b:term_title}


- *b:term_title*  Terminal title (user-writable), typically displayed in the
  window title or tab title of a graphical terminal emulator. Terminal
  programs can set this by emitting an escape sequence.
- |'channel'|  Terminal PTY |job-id|.  Can be used with |chansend()| to send
  input to the terminal.

Use |jobwait()| to check if the terminal job has finished:
    let exited = jobwait([&channel], 0)[0] >= 0

==============================================================================

:Termdebug plugin				*terminal-debug*

The Terminal debugging plugin can be used to debug a program with gdb and view
the source code in a Vim window.  Since this is completely contained inside
Vim this also works remotely over an ssh connection.

Starting 

							*termdebug-starting*
Load the plugin with this command:
	packadd termdebug

 							*:Termdebug*
To start debugging use `:Termdebug` or `:TermdebugCommand` followed by the
command name, for example:
	:Termdebug vim

This opens two windows:

gdb window	A terminal window in which "gdb vim" is executed.  Here you
		can directly interact with gdb.  The buffer name is "!gdb".

program window	A terminal window for the executed program.  When "run" is
		used in gdb the program I/O will happen in this window, so
		that it does not interfere with controlling gdb.  The buffer
		name is "gdb program".

The current window is used to show the source code.  When gdb pauses the
source file location will be displayed, if possible.  A sign is used to
highlight the current position, using highlight group debugPC.	 

If the buffer in the current window is modified, another window will be opened
to display the current gdb position.

Focus the terminal of the executed program to interact with it.  This works
the same as any command running in a terminal window.

When the debugger ends, typically by typing "quit" in the gdb window, the two
opened windows are closed.

Only one debugger can be active at a time.

							*:TermdebugCommand*
If you want to give specific commands to the command being debugged, you can
use the `:TermdebugCommand` command followed by the command name and
additional parameters.
	:TermdebugCommand vim --clean -c ':set nu'

Both the `:Termdebug` and `:TermdebugCommand` support an optional "!" bang
argument to start the command right away, without pausing at the gdb window
(and cursor will be in the debugged window).  For example:
	:TermdebugCommand! vim --clean

To attach gdb to an already running executable or use a core file, pass extra
arguments.  E.g.:
	:Termdebug vim core
	:Termdebug vim 98343

If no argument is given, you'll end up in a gdb window, in which you need to
specify which command to run using e.g. the gdb `file` command.


Example session 

							*termdebug-example*
Start in the Vim "src" directory and build Vim:
	% make
Start Vim:
	% ./vim
Load the termdebug plugin and start debugging Vim:
	:packadd termdebug
	:Termdebug vim
You should now have three windows:
    source  - where you started
    gdb	    - you can type gdb commands here
    program - the executed program will use this window

Put focus on the gdb window and type:
	break ex_help
	run
Vim will start running in the program window. Put focus there and type:
	:help gui
Gdb will run into the ex_help breakpoint.  The source window now shows the 
ex_cmds.c file.  A red "1 " marker will appear in the signcolumn where the
breakpoint was set.  The line where the debugger stopped is highlighted.  You
can now step through the program.  You will see the highlighting move as the
debugger executes a line of source code.

Run ":Next" a few times until the for loop is highlighted.  Put the cursor on
the end of "eap->arg", then call ":Eval".  You will see this displayed:
	"eap->arg": 0x555555e68855 "gui" 
This way you can inspect the value of local variables.  You can also focus the
gdb window and use a "print" command, e.g.:
	print *eap
If mouse pointer movements are working, Vim will also show a balloon when the
mouse rests on text that can be evaluated by gdb.
You can also use the "K" mapping that will either use neovim floating windows
if available to show the results or print below the status bar.

Now go back to the source window and put the cursor on the first line after
the for loop, then type:
	:Break
You will see a "1" marker appear, this indicates the new breakpoint.  Now
run ":Cont" command and the code until the breakpoint will be executed.

You can type more advanced commands in the gdb window.  For example, type:
	watch curbuf
Now run ":Cont" (or type "cont" in the gdb window). Execution
will now continue until the value of "curbuf" changes, which is in do_ecmd().
To remove this watchpoint again type in the gdb window:
	delete 3

You can see the stack by typing in the gdb window:
	where
Move through the stack frames, e.g. with:
	frame 3
The source window will show the code, at the point where the call was made to
a deeper level.


Stepping through code 

							*termdebug-stepping*
Put focus on the gdb window to type commands there.  Some common ones are:
- CTRL-C	interrupt the program
- next		execute the current line and stop at the next line
- step		execute the current line and stop at the next statement,
		entering functions
- finish	execute until leaving the current function
- where		show the stack
- frame N	go to the Nth stack frame
- continue	continue execution


						*:Run* *:Arguments*
In the window showing the source code these commands can be used to control
gdb:
 `:Run` [args]	    run the program with [args] or the previous arguments
 `:Arguments` {args}  set arguments for the next `:Run`


 *:Break*	set a breakpoint at the current line; a sign will be displayed

 *:Clear*	delete the breakpoint at the current line


 *:Step*	execute the gdb "step" command

 *:Over*	execute the gdb "next" command (`:Next` is a Vim command)

 *:Finish*	execute the gdb "finish" command

 *:Continue*	execute the gdb "continue" command

 *:Stop*	interrupt the program

If gdb stops at a source line and there is no window currently showing the
source code, a new window will be created for the source code.  This also
happens if the buffer in the source code window has been modified and can't be
abandoned.

Gdb gives each breakpoint a number.  In Vim the number shows up in the sign
column, with a red background.  You can use these gdb commands:
- info break	list breakpoints
- delete N	delete breakpoint N
You can also use the `:Clear` command if the cursor is in the line with the
breakpoint, or use the "Clear breakpoint" right-click menu entry.


Inspecting variables 

					*termdebug-variables* *:Evaluate*
 `:Evaluate`	    evaluate the expression under the cursor
 `K`		    same
 `:Evaluate` {expr}   evaluate {expr}
 `:'<,'>Evaluate`     evaluate the Visually selected text

This is similar to using "print" in the gdb window.
You can usually shorten `:Evaluate` to `:Ev`.


Other commands 

							*termdebug-commands*

 *:Gdb*	     jump to the gdb window

 *:Program*    jump to the window with the running program

 *:Source*     jump to the window with the source code, create it if there
	     isn't one


Communication 

						*termdebug-communication*
There is another, hidden, buffer, which is used for Vim to communicate with
gdb.  The buffer name is "gdb communication".  Do not delete this buffer, it
will break the debugger.

Gdb has some weird behavior, the plugin does its best to work around that.
For example, after typing "continue" in the gdb window a CTRL-C can be used to
interrupt the running program.  But after using the MI command
"-exec-continue"  pressing CTRL-C does not interrupt.  Therefore you will see
"continue" being used for the `:Continue` command, instead of using the
communication channel.


Customizing 


GDB command						 *termdebug-customizing*

To change the name of the gdb command, set the "termdebugger" variable before
invoking `:Termdebug`:
	let termdebugger = "mygdb"

To not use neovim floating windows for previewing variable evaluation, set the
`g:termdebug_useFloatingHover` variable like this:
	let g:termdebug_useFloatingHover = 0

If you are a mouse person, you can also define a mapping using your right
click to one of the terminal command like evaluate the variable under the
cursor:
      	nnoremap <RightMouse> :Evaluate<CR>
or set/unset a breakpoint:
	nnoremap <RightMouse> :Break<CR>


 							*gdb-version*
Only debuggers fully compatible with gdb will work.  Vim uses the GDB/MI
interface.  The "new-ui" command  requires gdb version 7.12 or later.  if you
get this error:
	Undefined command: "new-ui". Try "help".
Then your gdb is too old.



Colors						*hl-debugPC* *hl-debugBreakpoint*

The color of the signs can be adjusted with these highlight groups:
- debugPC		the current position
- debugBreakpoint	a breakpoint

The defaults are, when 'background' is "light":
  hi debugPC term=reverse ctermbg=lightblue guibg=lightblue
  hi debugBreakpoint term=reverse ctermbg=red guibg=red

When 'background' is "dark":
  hi debugPC term=reverse ctermbg=darkblue guibg=darkblue
  hi debugBreakpoint term=reverse ctermbg=red guibg=red



Shorcuts						*termdebug_shortcuts*

You can define your own shortcuts (mappings) to control gdb, that can work in
any window, using the TermDebugSendCommand() function.  Example:
	map ,w :call TermDebugSendCommand('where')<CR>
The argument is the gdb command.



Vim window width						*termdebug_wide*

To change the width of the Vim window when debugging starts, and use a
vertical split:
  let g:termdebug_wide = 163
This will set &columns to 163 when `:Termdebug` is used.  The value is restored
when quitting the debugger.
If g:termdebug_wide is set and &columns is already larger than
g:termdebug_wide then a vertical split will be used without changing &columns.
Set it to 1 to get a vertical split without every changing &columns (useful
for when the terminal can't be resized by Vim).



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