Here are a few hints for finding your way around the source code. This doesn't make it less complex than it is, but it gets you started.
You might also want to read
:help development.
First of all, use :make tags to generate a tags file, so that you can jump
around in the source code.
To jump to a function or variable definition, move the cursor on the name and
use the CTRL-] command. Use CTRL-T or CTRL-O to jump back.
To jump to a file, move the cursor on its name and use the gf command.
Most code can be found in a file with an obvious name (incomplete list):
| File name | Description |
|---|---|
| alloc.c | memory management |
| arglist.c | handling argument list |
| autocmd.c | autocommands |
| blob.c | blob data type |
| buffer.c | manipulating buffers (loaded files) |
| bufwrite.c | writing a buffer to file |
| change.c | handling changes to text |
| cindent.c | C and Lisp indentation |
| clientserver.c | client server functionality |
| clipboard.c | handling the clipboard |
| cmdexpand.c | command-line completion |
| cmdhist.c | command-line history |
| debugger.c | vim script debugger |
| diff.c | diff mode (vimdiff) |
| drawline.c | drawing a window line |
| drawscreen.c | drawing the windows |
| eval.c | expression evaluation |
| evalbuffer.c | buffer related built-in functions |
| evalfunc.c | built-in functions |
| evalvars.c | vim variables |
| evalwindow.c | window related built-in functions |
| fileio.c | reading and writing files |
| filepath.c | dealing with file names and paths |
| findfile.c | search for files in 'path' |
| fold.c | folding |
| getchar.c | getting characters and key mapping |
| help.c | vim help related functions |
| highlight.c | syntax highlighting |
| indent.c | text indentation |
| insexpand.c | Insert mode completion |
| locale.c | locale/language handling |
| map.c | mapping and abbreviations |
| mark.c | marks |
| match.c | highlight matching |
| float.c | floating point functions |
| mbyte.c | multi-byte character handling |
| memfile.c | storing lines for buffers in a swapfile |
| memline.c | storing lines for buffers in memory |
| menu.c | menus |
| message.c | (error) messages |
| mouse.c | handling the mouse |
| ops.c | handling operators ("d", "y", "p") |
| option.c | options |
| optionstr.c | handling string options |
| popupmenu.c | popup menu |
| popupwin.c | popup window |
| profiler.c | vim script profiler |
| quickfix.c | quickfix commands (":make", ":cn") |
| regexp.c | pattern matching |
| register.c | handling registers |
| scriptfile.c | runtime directory handling and sourcing scripts |
| screen.c | lower level screen functions |
| search.c | pattern searching |
| session.c | sessions and views |
| sign.c | signs |
| spell.c | spell checking core |
| spellfile.c | spell file handling |
| spellsuggest.c | spell correction suggestions |
| strings.c | string manipulation functions |
| syntax.c | syntax and other highlighting |
| tag.c | tags |
| term.c | terminal handling, termcap codes |
| testing.c | testing: assert and test functions |
| textformat.c | text formatting |
| textobject.c | text objects |
| textprop.c | text properties |
| time.c | time and timer functions |
| typval.c | vim script type/value functions |
| undo.c | undo and redo |
| usercmd.c | user defined commands |
| userfunc.c | user defined functions |
| viminfo.c | viminfo handling |
| window.c | handling split windows |
If you have a reasonable recent version of gdb, you can use the :Termdebug
command to debug Vim. See :help :Termdebug.
When something is time critical or stepping through code is a hassle, use the channel logging to create a time-stamped log file. Add lines to the code like this:
ch_log(NULL, "Value is now %02x", value);
After compiling and starting Vim, do:
:call ch_logfile('debuglog', 'w')
And edit debuglog to see what happens. The channel functions already have
ch_log() calls, thus you always see that in the log.
The current mode is stored in State. The values it can have are NORMAL,
INSERT, CMDLINE, and a few others.
The current window is curwin. The current buffer is curbuf. These point
to structures with the cursor position in the window, option values, the file
name, etc. These are defined in
structs.h.
All the global variables are declared in
globals.h.
This is conveniently called main_loop(). It updates a few things and then
calls normal_cmd() to process a command. This returns when the command is
finished.
The basic idea is that Vim waits for the user to type a character and
processes it until another character is needed. Thus there are several places
where Vim waits for a character to be typed. The vgetc() function is used
for this. It also handles mapping.
Updating the screen is mostly postponed until a command or a sequence of
commands has finished. The work is done by update_screen(), which calls
win_update() for every window, which calls win_line() for every line.
See the start of
screen.c
for more explanations.
When typing a :, normal_cmd() will call getcmdline() to obtain a line
with an Ex command. getcmdline() contains a loop that will handle each typed
character. It returns when hitting CR or Esc or some other character that
ends the command line mode.
Ex commands are handled by the function do_cmdline(). It does the generic
parsing of the : command line and calls do_one_cmd() for each separate
command. It also takes care of while loops.
do_one_cmd() parses the range and generic arguments and puts them in the
exarg_t and passes it to the function that handles the command.
The : commands are listed in ex_cmds.h. The third entry of each item is
the name of the function that handles the command. The last entry are the
flags that are used for the command.
The Normal mode commands are handled by the normal_cmd() function. It also
handles the optional count and an extra character for some commands. These
are passed in a cmdarg_t to the function that handles the command.
There is a table nv_cmds in
normal.c
which lists the first character of every command. The second entry of each
item is the name of the function that handles the command.
When doing an i or a command, normal_cmd() will call the edit()
function. It contains a loop that waits for the next character and handles it.
It returns when leaving Insert mode.
There is a list with all option names in
option.c,
called options[].
Most of the GUI code is implemented like it was a clever terminal. Typing a
character, moving a scrollbar, clicking the mouse, etc. are all translated
into events which are written in the input buffer. These are read by the
main code, just like reading from a terminal. The code for this is scattered
through gui.c.
For example, gui_send_mouse_event() for a mouse click and gui_menu_cb() for
a menu action. Key hits are handled by the system-specific GUI code, which
calls add_to_input_buf() to send the key code.
Updating the GUI window is done by writing codes in the output buffer, just
like writing to a terminal. When the buffer gets full or is flushed,
gui_write() will parse the codes and draw the appropriate items. Finally the
system-specific GUI code will be called to do the work.
Remember to prevent that gvim forks and the debugger thinks Vim has exited,
add the -f argument. In gdb: run -f -g.
When stepping through display updating code, the focus event is triggered
when going from the debugger to Vim and back. To avoid this, recompile with
some code in gui_focus_change() disabled.
If you would like to help making Vim better, see the
CONTRIBUTING.md
file.
This is README.md for version 9.0 of the Vim source code.