Taking Vim's copy/paste system beyond 'good enough'
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README.md

README.md

Cutlass.vim

Cutlass.vim is no more than a README at present. I want to share these ideas and work through any problems with them before deciding whether or not to implement the plugin. In other words, I'm practicing readme driven development.

Cutlass.vim is my attempt at addressing the problems that I discussed in Vim's registers: the good, the bad, and the ugly parts. In brief: cutlass.vim introduces a cut operator x{motion}, and redefines Vim's "delete" operations (d{motion}, D, c{motion}, C, s, and S) by making them remove text without overwriting the default register. Redefining Vim's "delete" command to not cut by default means you'll make fewer accidental cut operations. (Cutless - geddit?)

Also, cutlass.vim modifies the registers "1 through "9 (the history registers) to record the last nine yank and cut operations. The "- delete register records the most recently deleted text.

Introducing cut and delete operators

Cutlass.vim introduces a new operator command called cut, which is mapped to the x key. The cut x{motion} operator behaves much like Vim's built-in d{motion} command: it removes text from the document and writes it to a register. Pressing xx would cut an entire line. The X key is equivalent to x$, just as Vim's built-in D command is equivalent to d$.

This means that we lose two of Vim's built-in commands: x and X, but we can reproduce their functionality using xl and xh to cut a character under or behind the cursor, respectively.

Cutlass.vim changes the behavior of the d{motion} command to perform a true deletion: the specified text is removed from the document without being written to the default register. The same goes for c{motion}, s, D, C, and S too.

From here on, I'll use the delete operations as a shorthand to refer to the d{motion}, D, c{motion}, C, s, and S commands.

Redefining Vim's registers

The cut and yank operations (x{motion} and y{motion}) always write text to the default register "" and register "1. When text is written to register "1, Vim shifts the previous contents of register "1 into register "2, "2 into "3, and so forth, losing the previous contents of register "9. As a result, registers "1 through "9 represent a clipboard history of cut and yank operations. In cutlass.vim, registers "1 - "9 may be referred to collectivly as the history registers.

When the cut and yank operations are prefixed with a named register, the specified text is written to the named register, the default register, and to the history registers. For example, both "ayiw and "axiw would write the current word to "a, "", and "1.

The delete operations (d{motion}, D, c{motion}, C, s, and S) remove text from the document, writing it to register "- only. Neither the default register nor the history registers are changed by the delete operations. In cutlass.vim, register "- can be referred to as the delete register.

All delete operations can be prefixed with a named register, in which case they behave like the cut command. For example, "adiw and "axiw would both cut the current word from the document, writing it to registers "a, "", and "1, but not to the delete register "-.

This table summarizes the behaviour of Vim's registers as defined by cutlass.vim:

operations "" (default) "1 (history) "a (named) "- (delete)
y{motion}
yy
Y
x{motion}
xx
X
X X - -
"ay{motion}
"ayy
"aY
"ax{motion}
"axx
"aX
X X X -
d{motion}
dd
D
c{motion}
cc
C
s
S
- - - X
"ad{motion}
"add
"aD
"ac{motion}
"acc
"aC
"as
"aS
X X X -

See The Bad Parts for an explanation of Vim's built-in behaviour for the numbered registers.

Respecting common Vim idioms

Changing the behaviour of built-in commands such as d and x affects some common Vim idioms, such as xp and ddp. These idioms can easily be adapted to work with the operators defined by cutlass.vim.

Toggle characters: xp becomes xlp

Using Vim's built-in commands, we can toggle two characters by pressing xp. For example, with the cursor at the start of this line, xp would fix the typo, producing Roses:

oRses are red.

With cutlass.vim, this idiom becomes xlp. xl cuts the character under the cursor, saving it to the default register. p puts the contents of the default register after the cursor.

Toggle lines: ddp becomes xxp

Using Vim's built-in commands, we can toggle two lines by pressing ddp. For example, with the cursor on the first line of this block of text, the line order could be fixed by pressing ddp:

2)  Violets are blue,
1)  Roses are red,
3)  Sugar is sweet
4)  And so are you.

With cutlass.vim, this idiom becomes xxp. xx cuts the line under the cursor, saving it to the default register. p puts the contents of the default register below the cursor.

Visual put v_p writes to "-

Vim's built-in Visual mode p command overwrites the selected text with the contents of a register, then writes the old selection to the default register. Effectivly, the selected text and the default register swap values. And that allows for a neat workflow if you need to swap two chunks of text. For example, to swap the order of these arguments:

execute(second, first)

With the cursor on second, we could cut the word with diw. Then select the word first and use p to overwrite the selection with the contents of the default register. As a side-effect of the Visual mode put operation, the default register would now contain the (formerly selected) word first. Moving the cursor back to the comma, we could use Normal mode P to insert first in its correct position. This sequence of keystrokes would do the job:

diw
mm
ww
viw
p
`m
P

Would that still work with cutlass.vim? Yes - with a small modification. Cutlass.vim modifies the Visual mode put command, writing the selected text to "-, the delete register. All of the above steps would work the same way, but for the final P command we would have to prefix the "- delete register.

diw
mm
ww
viw
p
`m
"-P

That's one reason why the delete operations write text to the delete register ("-), rather than to the blackhole register ("_).

Feedback

What do you think: Should I build this? Would you use it?

Email your thoughts to drew@vimcasts.org.

The easyclip plugin by Steve Vermeulen includes similar ideas, but it's an actual working plugin that you can install and use today. Check it out!


            _,---,_
          /'_______`\
         (/'       `\|___________----------"""""""------,
          \#########||______                          /'
           ^^^^^^^^^||      """"""-----_____        /'
                     \                      """--_/'