EXPLANATION.org

EXPLANATION

Basic Concepts

In this section we walk through a list of basic concepts in design.

Selection

To get better understanding on movement commands in NORMAL state, it’s important to know what is a selection. We call it selection to distinguish from region.

A selection is a region with the direction (forward/backward), the type (char/word/line/etc…) and a expandable flag.

For example, we can say we have a selection which

• from point 7 to 12
• with forward direction
• with the type word
• and is expandable.

And there are 3 rules those decide the behavior of a movement

• RULE 1 commands except for char/word/symbol have no opinion on direction, they will follow current direction when meet same selection type.
• RULE 2 selection will be expanded if movement and current selection have same type, and current selection is expandable.
• RULE 3 these commands create expanble selection:
  • meow-*-expand
  • meow-mark-word
  • meow-mark-symbol
  • meow-line

It sounds complicated at first. But it will be seamless once you get used to it.

A few cases to help you understand.

CASE 1 To select 3 lines, do meow-line 3 times. meow-line will create expandable line selection.

CASE 2 To reverse select 3 lines, do negative-argument, then meow-line 3 times. line will follow the direction.

CASE 3 To select previous, current and next word, do meow-mark-word, meow-back-word and meow-next-word. Back and next will expand, because meow-mark-word create expandable word selection.

CASE 4 To select next word, do meow-next-word twices. Current word won’t be selected because meow-next-word will create nonexpandable word selection.

Secondary Selection

Emacs has built-in secondary selection support. By default, you create secondary selection by dragging with Alt + left mouse button. It can be a range or just a single point.

Since secondary selection has no relation with the cursor, there’re a lot features built on top of it.

FEATURE 1 For text swap. See command meow-swap-grab and meow-sync-grab.

FEATURE 2 To represent a range for kmacro application. See Meow BEACON state.

FEATURE 3 To mark a text to be inserted in minibuffer prompt later. See meow-grab-fill-commands.

Multiedit

Ways to multiedit

There are many ways to multiedit in Emacs. Following is the parts I know:

Evil’s n.n.n.n. (Evil built-in)

• pros: support simple transformation, no extra keys
• cons: not for complex transaformation, hard to undo

counter example:

1 2 3
=>
[| "1" |] [| "2" |] [| "3" |]

You can do, but not as simple as it should be.

Evil’s :exe (Evil built-in)

• pros: flexible, great compatibility
• cons: verbose, bad visual feedback

Same counter case with kmacro

kmacro (built-in)

• pros: no lag on recording, great compatibility, flexible, arbitrary operation, macros can be used later
• cons: verbose, can only be apply to a single position, or each lines in a region, no visual feedback, hard to undo

counter example:

x-y-foo-bar-baz
=>
x_y_foo_bar_baz

More keys(record, finish, call) make it useless in a very simple case.

query-replace (built-in)

• pros: simple, interactive application(y/n/!), fastest, good visual feedback (with anzu package)
• cons: not flexible, have to type more keys

counter example:

foo-1-bar
foo-2-bar
foo-3-bar
=>
bar-1-foo
bar-2-foo
bar-3-foo

You can do with query-replace, but type regexp foo-\([0-9]\)-bar and bar-\1-foo require more keys.

rectange-mark-mode (built-in)

• pros: easy to use for insertion
• cons: not flexible

counter example:

foo bar foo
bar foo bar
=>
foo baz foo
baz foo baz

Just can’t do things like this

iedit / evil-multiedit (package)

• pros: less keys, easy to specify affected range, good visual feedback
• cons: no arbitrary transformation, only for same occurs

counter example:

1 2 3
=>
"1" "2" "3"

multiple-cursors / evil-mc (package)

• pros: flexible, good visual feedback, intuitive
• cons: lag for many cursors, operation not re-useable, bad compatibility

counter example: whenever number of cursors > 100

After your each type, multiple cursors have to run hooks, backup/restore variables for all cursors

The answer from Meow

Meow embraces kmacro, and trying to improve the experience by collapsing undo boundary and introducing BEACON state.

(text-mode is used here, no additional setup required, assuming meow-setup for Qwerty is used)

case 1

1 2 3
=>
[| "1" |] [| "2" |] [| "3" |]

• select whole content, then activate secondary selection with G(meow-grab)
• b(back-word) to create fake cursors at each word beginning
• F3 to start macro recording
• typing
• F4 to end macro recording and apply to all fake cursors

case 2

x-y-foo-bar-baz
=>
x_y_foo_bar_baz

• select whole content, then activate secondary selection with G(meow-grab)
• -(negative-argument) f(meow-find) - to backward search for character -, will create fake cursor at each -
• quick start recording and switch to insert state with c(meow-change) (character under current cursor is deleted)
• type _
• ESC to go back to NORMAL, then macro will be applied to all fake cursors.

case 3

foo-1-bar
foo-2-bar
foo-3-bar
=>
bar-1-foo
bar-2-foo
bar-3-foo

• select whole content, then activate secondary selection with G(meow-grab)
• x(meow-line) to create fake regions at each line
• F3 to start macro recording(default fake cursors are on the same column)
• select bar with w(mark-word), then activate secondary selection with G(meow-grab)
• select foo, swap with secondary selection with R(meow-swap-grab).
• F4 to end macro recording and apply to all fake cursors

case 4

foo bar foo
bar foo bar
=>
foo baz foo
baz foo baz

• select whole content, then activate secondary selection with G(meow-grab)
• move to bar, select it with w(mark-word) , create fake regions at each bar
• quick start recording and switch to insert state with c(meow-change) (current bar is deleted)
• type baz
• ESC to go back to NORMAL, then macro will be applied to all fake regions.

Reason

Why another modal editing package in Emacs?

Emacs is the one editor with most modal editing schemes in the world. Before I started working on Meow, there are a few options(Listed at the end).

Unfortunately, none of them satisfy me. I want a modal editing with following features.

• Customizable command layout
• Using existing keymap(both buit-in and third party) without modifier keys
• A set of efficient commands
• Lightweight, fast startup time

	customizable command layout	using existing keymap	efficient command set	Lightweight
evil	no	no	yes	no
xah-fly-keys	no	no	yes	yes
boon	no	yes	yes	yes
god-mode	yes	yes	no	yes
modalka	yes	possible	no	yes
ryo-modal	yes	possible	no	yes
kakoune.el	no	no	yes	yes

Why not existing package?

Evil

Evil

A complete Vim emulator in Emacs. Before Emacs, I was using Vim. So my Emacs journey was started with Evil. However, Evil have a few problems.

1. high cost on integration with other packages. Basically an editing-related package won’t play well with Evil if it doesn’t know Evil.

So there’s an evil-collection and other evil-* packages.

1. Communities like spacemacs, doom emacs prefer to organize keybindings with evil-leader. The result is pleasure, but it takes time to maintain.

Introducing another keybinding system, usually result in a complex configuration.

1. Vim is designed for Qwerty keyboard layout. H/J/K/L is meaningless on other layouts.
2. Vim is old, there are some modern alternatives, like Kakoune. We are on Emacs and we have more choices.
3. Evil is heavy, its startup time is 10X longer than other modal editing packages.

God Mode

God Mode

God mode is small, simple and easy to start with. If “no modifier keys” is all you want, god-mode is a good choice.

The only problem: it’s not a complete modal editing solution. God mode lacks a set of commands which is necessary for maximizing the benefits of sing-key commands.

Modalka

Modalka

Modalka allows user to define their own command layout. It’s more flexible than god-mode and require more configuration. It has the same problem with God Mode, it’s not a complete modal editing solution.

ryo-modal

ryo-modal

The same problem with modalka and God Mode.

Xah-fly-keys

xah-fly-keys

Xah-fly-keys is declared to be more efficient than vim, or any keybinding set in history. Personally I don’t like DWIM(Do What I Mean) style command. Of course DWIM can reduce the number of commands, but I’d rather to make commands more orthogonal.

xah-fly-keys has a pre-defined leader keymap, I don’t think it’s enough for my case.

boon

boon

Boon has a efficient command layout, a good approach to execute commands without modifier keys. It’s very close to what I want, before I started with Meow.

Boon integrates with expand-region, multiple-cursors, avy, etc. I think we can have a better way for these purpose.

Kakoune.el

kakoune.el

Kakoune.el is a package trying to bring kakoune’s command to Emacs.

I like how kakoune deal with selections, but it use a both alt & shift a lot. Since I are going to use modal edit, I prefer to avoid modifer as much as possible.