Revert "Remove code-overview"

This reverts commit c6ff8c8349d7c54eeabf537aa1d7b53819fbe4ee.
dundargoc 2023-12-13 11:09:54 +01:00
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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.
## Important variables
The current mode is stored in `State`. The values it can have are `MODE_NORMAL`,
`MODE_INSERT`, `MODE_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.
All the global variables are declared in [globals.h](../blob/master/src/nvim/globals.h).
## The main loop
The main loop is implemented in state_enter. 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 [drawscreen.c](../blob/master/src/nvim/drawscreen.c) for more explanations.
## Command-line mode
When typing a `:`, `normal_cmd()` will call `getcmdline()` to obtain a line with
an Ex command. `getcmdline()` calls 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
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.lua](../blob/master/src/nvim/ex_cmds.lua).
## Normal mode commands
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](../blob/master/src/nvim/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.
## Insert mode commands
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.
## Options
There is a list with all option names in [options.lua](../blob/master/src/nvim/options.lua).