Learn-Vim/ch20_views_sessions_viminfo.md

# Views, Sessions, and Viminfo

After you worked on a project for a while, you may find that the project to gradually take shape with its own settings, folds, buffers, layouts, etc. It's like decorating your apartment to make it feel like home.

The problem is, when you close Vim, you lose those changes. Wouldn't it be nice if you can keep those changes so the next time you open Vim, it looks just like you had never left?

Vim has three tools for this: View, Session, and Viminfo. In this chapter, you will learn how to leverage all three to take a "snapshot" of your project.

# Views

A View is the smallest subset of the three (View, Session, Viminfo). A Vim View is a collection of settings for one window. If you spend a long time working on a window and you want to preserve the mappings and folds, you can use a View.

Let's create a file called `foo.txt`:

```
foo1
foo2
foo3
foo4
foo5
foo6
foo7
foo8
foo9
foo10
```

In this file, create three changes:

1. On line 1, create a manual fold `zf4j` (fold the next 4 lines).
2. Change the `number` setting: `setlocal nonumber norelativenumber`.
3. Create a local mapping to go down two lines each time you press `j` instead of one: `:nnoremap <buffer> j jj`.

Your file should look like this:

```
+-- 5 lines: foo1 -----
foo6
foo7
foo8
foo9
foo10
```

Now, your display won't have any numbers on the left side and pressing the `j` key goes down two lines instead of one line.

## Configuring View Attributes

Run:

```
:set viewoptions?
```

By default it should say:

```
viewoptions=folds,cursor,curdir
```

Yours might look different. Let's configure `viewoptions`. The three attributes you want to preserve are the folds, the mapping, and the local set option. If your setting looks like mine, you already have the `folds` option. You need to tell View to remember the `localoptions`. Run:

```
:set viewoptions+=localoptions
```

To learn what other options are available for `viewoptions`, check out `:h viewoptions`. Now if you run `:set viewoptions?`, you should see:

```
viewoptions=folds,cursor,curdir,localoptions
```

## Saving the View

With the `foo.txt` window properly folded and having `nonumber norelativenumber` options, let's save the View. Run:

```
:mkview
```

Vim creates a View file.

## View Files

You might wonder, "Where did Vim save this View file?" To see where Vim saves it, run:

```
:set viewdir?
```

The default should say `~/.vim/view` (if you have a different OS, it might show a different path. Check out `:h viewdir` for more). If you want to change it to a different path, add this into your vimrc:

```
set viewdir=$HOME/else/where
```

## Loading the View File

Close the `foo.txt` if you haven't, then open `foo.txt` again. You should see the original text without the changes. That's expected. Let's load the View file. Run:

```
:loadview
```

Now you should see:

```
+-- 5 lines: foo1 -----
foo6
foo7
foo8
foo9
foo10
```

The folds, local settings, and local mappings are restored. If you notice, your cursor should also be on the line where you left it when you ran `:mkview`. As long as you have the `cursor` option, View also remembers your cursor position.

## Multiple Views

Vim lets you save 9 numbered Views (1-9).

Suppose you want to make an additional fold (say you want to fold the last two lines) with `:9,10 fold`. Let's save this as View 1. Run:

```
:mkview 1
```

If you want to make one more fold with `:6,7 fold` and save it as a different View, run:

```
:mkview 2
```

Close the file. When you open `foo.txt` and you want to load View 1, run:

```
:loadview 1
```

To load View 2, run:

```
:loadview 2
```

To load the original View, run:

```
:loadview
```

## Automating View Creation

One of the worst things that can happen is, after spending countless hours organizing a large file with folds, you accidentally close the window and lose all fold information. To prevent this, you might want to automatically create a View each time you close a buffer. Add this in your vimrc:

```
au BufWinLeave *.txt mkview
```

Additionally, it might be nice to load View when you open a buffer:

```
au BufWinEnter *.txt silent loadview
```

Now you don't have to worry about creating and loading View anymore when you are working with `txt` files. Keep in mind that over time, your `~/.vim/view` might start to accumulate View files. It's good to clean it up once every few months.

# Sessions

If a View saves the settings of a window, a Session saves the information of all windows (including the layout).

## Creating a New Session

Suppose you are working with these 3 files in a `foobarbaz` project:

`foo.txt`:

```
foo1
foo2
foo3
foo4
foo5
foo6
foo7
foo8
foo9
foo10
```

`bar.txt`:

```
bar1
bar2
bar3
bar4
bar5
bar6
bar7
bar8
bar9
bar10
```

and `baz.txt`:

```
baz1
baz2
baz3
baz4
baz5
baz6
baz7
baz8
baz9
baz10
```

And you've been working on these 3 files for a while, so that your windows layout look like (using strategically placed `split` and `vsplit`):

![./img/session-layout.png](./img/session-layout.png)

To save the Session, run:

```
:mksession
```

Unlike `mkview` where it saves to `~/.vim/view` by default, `mksession` saves a Session file (`Session.vim`) in the current directory. Check out the file if you're curious what's inside.

If you want to save the Session file somewhere else, you can pass an argument to `mksession`:

```
:mksession ~/some/where/else.vim
```

If you want to overwrite the existing Session file, call the command with a `!` (`:mksession! ~/some/where/else.vim`).

## Loading a Session

To load a Session, run:

```
:source Session.vim
```

`Session.vim` is the Session file. Now Vim looks like the way you left it. Alternatively, you can also load a Session file from the terminal:

```
vim -S Session.vim
```

## Configuring Session Attributes

You can configure the attributes Session saves. To see what is currently being saved, run:

```
:set sessionoptions?
```

Mine says:

```
blank,buffers,curdir,folds,help,tabpages,winsize,terminal
```

Yours might look different. To add or remove an option, you can use `+=` or `=`.

If you don't want to save `terminal` when you save a Session, run:

```
:set sessionoptions-=terminal
```

If you want to add an `options` when you save a Session, run:

```
:set sessionoptions+=options
```

Here are some attributes that `sessionoptions` can store:

- `blank` stores empty windows
- `buffers` stores buffers
- `folds` stores folds
- `globals` stores global variables (must start with an uppercase letter and contain at least one lowercase letter)
- `options` stores options and mappings
- `resize` stores window lines and columns
- `winpos` stores window position
- `winsize` stores window sizes
- `tabpages` stores tabs
- `unix` stores files in Unix format

For the complete list check out `:h 'sessionoptions'`.

Session is a useful tool to preserve your project's external attributes. However, there are a number of internal attributes that Session doesn't save: local marks, registers, histories, etc.

To save them, you need to use Viminfo!

# Viminfo

After yanking a word into register a and quitting Vim, the next time you open Vim you can immediately paste the text from register a. This is actually one of Viminfo's features. Without it, Vim won't remember the register after you close.

If you use Vim 8 or higher, Vim enables Viminfo by default, so you may have been using Vim info this whole time without knowing it!

You might ask: "What does Viminfo save? How does it differ from Session?"

You just learned the things that Session saves from `sessionoptions`. To use Viminfo, first you need to have `+viminfo` feature available (`:version`). Viminfo stores:

- The command-line history.
- The search string history.
- The input-line history.
- Contents of non-empty registers.
- Marks for several files.
- File marks, pointing to locations in files.
- Last search / substitute pattern (for 'n' and '&').
- The buffer list.
- Global variables.

When comparing the items that can be saved for Session and Viminfo, you will notice that `sessionoptions`, in general, saves the "external" attributes while `viminfo` saves the "internal" attributes.

Unlike Session where you can have one Session file per project, you normally will use one Viminfo file per computer. Viminfo is project-agnostic.

The default Viminfo location for Unix is `$HOME/.viminfo` (`~/.viminfo`). If you use a different OS, your Viminfo location might be different. Check out `:h viminfo-file-name`. Each time you make "internal" changes, like yanking a text into a register, Vim automatically updates the Viminfo file.

*Make sure that you have `nocompatible` option set (`set nocompatible`), otherwise your Viminfo will not work.*

## Writing and Reading Viminfo

Although you will use only one Viminfo file, you can create multiple Viminfo files. To write a Viminfo file, use the `:wviminfo` command (`:wv` for short).

```
:wv ~/.viminfo_extra
```

To overwrite an existing Viminfo file, add a bang to the `wv` command:

```
:wv! ~/.viminfo_extra
```

By default Vim will read from `~/.viminfo` file. To read from a different Viminfo file, run `:rviminfo`, or `:rv` for short:

```
:rv ~/.viminfo_extra
```

You can also start Vim with a different Viminfo file from the terminal with the `i` flag:

```
vim -i viminfo_extra
```

Multiple Viminfo files can be used to create several different settings for different text editing needs:

```
vim -i viminfo_writing

vim -i viminfo_coding
```

## Starting Vim Without Viminfo

To start Vim without Viminfo data, you can run from the terminal:

```
vim -i NONE
```

To make it permanent, you can add this in your `vimrc` file:

```
set viminfo="NONE"
```

## Configuring Viminfo Attributes

Similar to `viewoptions` and `sessionoptions`, you can instruct what attributes to save with the `viminfo` option. Run:

```
:set viminfo?
```

You will get:

```
!,'100,<50,s10,h
```

This looks cryptic. Let's break it down:

- `!` saves global variables that start with an uppercase letter and don't contain lowercase letters. Recall that `g:` indicates a global variable. For example, if you call `:let g:FOO = "foo"`, Viminfo will save the global variable `FOO`. However if you do `:let g:Foo = "foo"`, Viminfo will not save this global variable because it contains lowercase letters. Without `!`, Vim won't safe those global variables.
- `'100` represents marks. In this case, Viminfo will save the local marks (a-z) of the last 100 files. Be aware that if you tell Viminfo to save too many files, Vim can start slowing down. 100-1000 files is a good range.
- `<50` tells Viminfo how many lines are saved for each registers (50 or less in this case). If I yank 100 lines of text into register a (`"ay99j`) and close Vim, the next time I open Vim and paste from register a (`"ap`), Vim will only paste 50 lines max. If you don't give it anything, *all* lines will be saved (it might slow down Vim). If you give it a 0, nothing will be saved.
- `s10` sets a size limit (in kb) for a register. In this case, any register greater than 10kb size will be excluded.
- `h` disables highlighting (from `hlsearch`) when Vim starts.

There are other options. To learn more, check out `:h 'viminfo'`.

# Using Views, Sessions, and Viminfo the Smart Way

Vim has View, Session, and Viminfo to take different level of "snapshot" of your Vim environment. For small projects, use Views. For larger projects, use Sessions. You should take your time to check out all the options that View, Session, and Viminfo offers.

Create your own View, Session, and Viminfo for your own editing style. Store them in your dotfiles. If you ever need to use Vim outside of your computer, you can just load your settings and you will immediately feel at home!