Transpose multiple selections

[dkeenan7]

I primarily wanted Ctrl+T to swap two selections after you Ctrl-select a second selection. I note that Multi-editing must be enabled in Preferences for Ctrl-select to work. For example, you might decide, after having written it, that some code will read better if you swap the order of operands for some commutative operator, or if you swap the if and else parts of a conditional.

But then it seems a shame not to make Ctrl+T also do something with more than 2 selections, and with rectangular selections (Alt-select). Rotating them seems the obvious generalisation.

When there is only 1 selection, Ctrl+T can do what it does now, transpose lines.

I made a Notepad++ feature request:
https://github.com/notepad-plus-plus/notepad-plus-plus/issues/6226
and a Scintilla feature request:
https://sourceforge.net/p/scintilla/feature-requests/1316/

Then dinkumoil kindly wrote a Lua script for one way of doing this, which you can see here:
https://github.com/notepad-plus-plus/notepad-plus-plus/issues/6226#issuecomment-546368744
and I agree with dinkumoil that any scripts for solving this problem need to be known and discussed here in the community forum.

Dinkumoil’s script first sorts the multiple selections by their order in the document, and so requires separate commands for rotating forwards and backwards (or down and up). I have simplified it below, to a version that rotates selections in the order they were selected, and so only requires one command. Thanks @dinkumoil! This probably would have taken me several days if I’d had to learn Lua and its Notepad++ and Scintilla APIs and do it myself.

Can anyone explain how to get the Ctrl+T shortcut to work from the script, or why it doesn’t work as written?

-- ================================================================================
-- Add a menu entry (intended for Ctrl+T shortcut) to transpose multiple selections 
-- by rotating them in the order they were selected.
-- Modified from a script kindly written by Andreas Heim (dinkumoil), 2019-10-25
-- ================================================================================

-- Get text of selection with index idx
local function getSelectionNText(idx)
  local retVal = editor:textrange(editor.SelectionNStart[idx], editor.SelectionNEnd[idx])
  if not retVal then retVal = "" end

  return retVal
end


-- Set text of selection with index idx and readjust its span
local function setSelectionNText(idx, str)
  editor:SetTargetRange(editor.SelectionNStart[idx], editor.SelectionNEnd[idx])
  editor:ReplaceTarget(str)

  editor.SelectionNCaret[idx] = editor.SelectionNAnchor[idx] + #str
end


-- Transpose selections
-- If there are less than 2 selections, the standard Line Transpose function is used
-- If there are 2 or more selections, they get rotated in the order they were selected
local function transposeSelections()
  local lastIdx, bufStr

  lastIdx = editor.Selections-1

  -- Process special case:
  --   Less than 2 selections  -> perform SCI_LINETRANSPOSE
  if lastIdx < 1 then
    npp.SendEditor(SCI_LINETRANSPOSE)
    return
  end

  -- Set start of undo sequence
  editor:BeginUndoAction()

  -- Perform transpose operation
  bufStr = getSelectionNText(lastIdx)
  for idx = lastIdx, 1, -1 do
    setSelectionNText(idx, getSelectionNText(idx-1))
  end
  setSelectionNText(0, bufStr)

  -- Set end of undo sequence
  editor:EndUndoAction()
end


-- Add menu entry for transposing selections or lines.
-- The Ctrl+T shortcut must be added manually via 
-- Settings->Shortcut Mapper->Plugin commands->Transpose Selections->Modify.
-- Ignore the conflict with the shortcut for Scintilla SCI_LINETRANSPOSE.
npp.AddShortcut("Transpose Selections", "Ctrl+T", function()
  transposeSelections()
end)

[dinkumoil]

@dkeenan7

Back from garden work (ouch, my back!).

Thank you for creating this topic here in the community forum and for providing an alternative solution.

Can anyone explain how to get the Ctrl+T shortcut to work from the script, or why it doesn’t work as written?

The only idea I have is, that you should go to (menu) Settings -> Shortcut Mapper and ensure that CTRL+T is not already assigned to another function of Notepad++, a plugin or Scintilla. Usually CTRL+T is assigned to the the Scintilla command SCI_LINETRANSPOSE (no. 92 of the Scintilla commands at Shortcut Mappers’s Scintilla register card).

[dkeenan7]

@dinkumoil Thanks for the suggestion. It wasn’t easy to remove the existing assignment of Ctrl+T to SCI_LINETRANSPOSE. Thanks go to @sasumner for describing the workaround here:
https://community.notepad-plus-plus.org/topic/13687/bug-unable-to-clear-or-remove-shortcuts-for-scintilla-commands

But it made no difference. And if I try a shortcut key that was never assigned, e.g.
npp.AddShortcut("Transpose Selections", "Ctrl+E", transposeSelections)
that doesn’t work either.

On another matter: Neil Hodgson mentioned another operation performed by Ctrl+T in some editors. When the selection is empty (only a blinking vertical line representing an insertion point) then Ctrl+T swaps the two characters on either side of the insertion point. This may be useful for correcting common typos.

Would it be easy for you to add that to your script? I suppose we should also allow for multiple selections, all empty, and do the same to all of them.

I notice Scintilla has:
SCI_GETSELECTIONEMPTY → bool
Return 1 if every selected range is empty else 0.
which, in Lua, is:
Editor.SelectionEmpty

[dkeenan7]

If an empty selection is at the start or end of a line, then the characters either side of it should not be swapped. If there is only one selection and it is empty and it is at the start or end of a line, then Ctrl+T should revert to transposing lines.

[dinkumoil]

@dkeenan7

I have tried to integrate a slightly modified version of your code above in my LuaScript plugin startup script using CTRL+ALT+0 and Ctrl+Alt+0 (note the different case) as keyboard shortcuts because this shortcut is unused in my Notepad++ installation - it worked. The modifications I made were only to rename the functions to avoid conflicts with my own version of the script (provided in the GitHub issue) I already use. But IMO it should be avoided to set a keyboard shortcut by script anyway because of possible conflicts with existing shortcuts.

Would it be easy for you to add that to your script?

Since you seem not to be a novice in programming, how about doing it yourself? Thus you will learn something useful.

Hint: Visit the >>> documentation site of the LuaScript plugin <<<, there you will find all information you need. Beyond the functions I’ve used in my script I guess the following functions could be useful for that task as well:

• editor.CurrentPos
• editor:LineFromPosition
• editor.LineEndPosition

Please note:

1. Don’t confuse Editor and editor. The first one is the class name and the second one is the instance name. Lua is case sensitive.
2. In Lua calling a method is different from using a property. The first one requires a colon as delimiter between instance and method name (thus editor:LineFromPosition) and the latter one requires a dot as delimiter (thus editor.CurrentPos).
3. In Lua there is no difference between arrays and lists, both are implemented as dictionaries with the index as the key. The routines of the runtime assume that indices are 1-based. That’s the reason why I wrote a sort function by myself.

For further information about the Lua language visit the >>> online version of “Programming in Lua” <<< written by the author of the language.

[dkeenan7]

@dinkumoil Ctrl+Alt+0 is also unused in my Notepad++ installation. I tried
npp.AddShortcut("Transpose Selections", "Ctrl+Alt+0", transposeSelections)
npp.AddShortcut("Transpose Selections", "CTRL+ALT+0", transposeSelections)
Neither of them added the keyboard shortcut for me. Are you sure they worked for you? I fooled myself for a while, that “Ctrl+Shift+T” had worked, but it was merely that I had previously set it manually, using Shortcut Mapper.

But IMO it should be avoided to set a keyboard shortcut by script anyway because of possible conflicts with existing shortcuts.

In this case, we expect there to be a conflict as we are deliberately extending the function of the likely existing Ctrl+T. The script could first remove the existing assignment of Ctrl+T. Ideally it would only do this if it was the shortcut for SCI_LINETRANSPOSE. But I see no way to determine that. And I tried
editor:ClearCmdKey(string.byte("T"), SCMOD_CTRL)
but this had no effect. I also tried substituting editor1, editor2, console and input for editor. Still no effect.

Yes, I will add the character-transpose function and post the script. Thanks for the hints.

[dinkumoil]

@dkeenan7 said in Transpose multiple selections:

I tried
npp.AddShortcut("Transpose Selections", "Ctrl+Alt+0", transposeSelections)

The correct syntax is:

npp.AddShortcut("Transpose Selections", "Ctrl+Alt+0", function()
  transposeSelections()
end)

The third parameter of AddShortcut is called a closure or anonymous function. It calls the actual handler function transposeSelections. See >>> here <<<.

[dkeenan7]

@dinkumoil said in Transpose multiple selections:

The third parameter of AddShortcut is called a closure or anonymous function. It calls the actual handler function transposeSelections. See >>> here <<<.

Because transposeSelections has no parameters, it works just fine as a closure here without being anonymised. I only have to drop the trailing empty parentheses “()”.

[dkeenan7]

Here is a Transpose script that includes transposing characters either side of insertion points.

You will see that I have also added code to handle virtual space, when transposing the rows of a rectangular selection. If you apply it to sasumner’s example you will see that it does give a visual improvement, but still does not give the result I want. I believe my desired result can be achieved by inserting and removing real spaces. But that’s enough work for one day. :-)

-- Startup script for LuaScript plugin
-- Changes will take effect once Notepad++ is restarted

-- ================================================================================
-- Add a menu entry (intended for Ctrl+T shortcut) to transpose multiple selections 
-- by rotating them in the order they were selected, 
-- and to transpose characters either side of an insertion point, 
-- and to transpose lines if neither of the above apply.
-- Modified from a script kindly written by Andreas Heim (dinkumoil), 2019-10-25
-- ================================================================================

-- Get text and virtual space of selection with index idx
local function getSelectionNTextVirtual(idx)
	local str = editor:textrange(editor.SelectionNStart[idx], editor.SelectionNEnd[idx])
	if not str then str = "" end
	local aVirt = editor.SelectionNAnchorVirtualSpace[idx]
	local cVirt = editor.SelectionNCaretVirtualSpace[idx]

	return str, aVirt, cVirt
end


-- Set text and virtual space of selection with index idx and readjust its span
local function setSelectionNTextVirtual(idx, str, aVirt, cVirt)
	editor:SetTargetRange(editor.SelectionNStart[idx], editor.SelectionNEnd[idx])
	editor:ReplaceTarget(str)

	editor.SelectionNCaret[idx] = editor.SelectionNAnchor[idx] + #str
	editor.SelectionNAnchorVirtualSpace[idx] = aVirt
	editor.SelectionNCaretVirtualSpace[idx] = cVirt
end


-- Is the given position at the start or end of a line?
local function isStartOrEndOfLine(pos)
	local line, lineStart, lineEnd
	line = editor:LineFromPosition(pos)
	lineStart = editor:PositionFromLine(line)
	lineEnd = editor.LineEndPosition[line]
	return pos == lineStart or pos == lineEnd
end


-- Transpose the characters either side of the given position
local function transposeCharactersAt(pos)
	local before = editor:PositionBefore(pos) -- Allow for multi-byte characters
	local after = editor:PositionAfter(pos)
	local str = editor:textrange(pos, after) -- Save the character to the right of the insertion point
	editor:SetTargetRange(pos, after) -- Target the character to the right of the insertion point
	editor:ReplaceTarget(editor:textrange(before, pos)) -- Replace the char to the right with the char to the left
	editor:SetTargetRange(before, pos) -- Target the character to the left of the insertion point
	editor:ReplaceTarget(str) -- Replace the char to the left with the saved char from the right
end


-- Transpose selections or characters or lines.
-- If there is only one selection and it is non-empty or at the start or end of a line, then 
-- transpose the line with the one above it (the pre-existing Ctrl+T behaviour).
-- If all selections are empty insertion points, then transpose the characters on either side of them 
-- unless they are at the start or end of a line
-- If there are less than 2 selections, the standard Line Transpose function is used
local function transposeSelectionsCharactersLines()
	-- According to the Scintilla documentation, there is always at least one selection
	local lastIdx = editor.Selections-1 -- Indexes for multiple selections are zero-based
  
	if editor.SelectionEmpty then -- If all selections are empty, i.e. consist only of an insertion point
		if lastIdx == 0 and isStartOrEndOfLine(editor.CurrentPos) then -- If there is only one selection and it's at the start or end of a line
			editor:LineTranspose() -- Transpose the current line with the one before
		else -- Else multiple empty selections or a single empty selection not at the start or end of a line
			editor:BeginUndoAction() -- Begin the sequence of actions to be undone or redone as a unit
			
			-- Transpose the characters on either side of each insertion point that is not at the start or end of a line
			for idx = 0, lastIdx do
				local pos = editor.SelectionNCaret[idx]
				if not isStartOrEndOfLine(pos) then -- If this empty selection is not at the start or end of a line
					transposeCharactersAt(pos) -- Transpose the characters either side of the given position
					-- For some unknown reason, the insertion point will now be to the left of both characters 
					-- Put the insertion point back in between them, allowing for different numbers of bytes per character
					pos = editor:PositionAfter(editor.SelectionNCaret[idx])
					editor.SelectionNAnchor[idx] = pos
					editor.SelectionNCaret[idx] = pos
				end
			end
			
			editor:EndUndoAction() -- End the sequence of actions to be undone or redone as a unit
		end
	else -- Else selections are not all empty
		if lastIdx == 0 then -- If there is only 1 selection
			editor:LineTranspose() -- Transpose the current line with the one before
		else -- Else there are 2 or more selections
			editor:BeginUndoAction() -- Begin the sequence of actions to be undone or redone as a unit
			
			-- Rotate selection contents between selections
			local lastStr, lastAVirt, lastCVirt = getSelectionNTextVirtual(lastIdx) -- Save the last selection including any virtual space			
			for idx = lastIdx, 1, -1 do -- Shift the other selections along
				setSelectionNTextVirtual(idx, getSelectionNTextVirtual(idx-1))
			end
			setSelectionNTextVirtual(0, lastStr, lastAVirt, lastCVirt) -- Make the first selection be the saved last selection
			
			editor:EndUndoAction() -- End the sequence of actions to be undone or redone as a unit
		end
	end
end


-- Add menu entry for transposing selections, characters or lines.
-- The Ctrl+T shortcut may need to be added manually via 
-- Settings -> Shortcut Mapper -> Plugin commands -> Transpose Selections/Characters/Lines -> Modify.
-- You can ignore the conflict with the shortcut for Scintilla SCI_LINETRANSPOSE.
-- editor:ClearCmdKey(string.byte("T"), SCMOD_CTRL)
npp.AddShortcut("Transpose Selections/Characters/Lines", "Ctrl+T", transposeSelectionsCharactersLines)

[dinkumoil]

@dkeenan7

Nice!

I believe my desired result can be achieved by inserting and removing real spaces.

I stay tuned!

[dkeenan7]

@dinkumoil @sasumner That was waaay harder than I expected. I was tearing out what little hair I have left, while debugging it. :-) I eventually started over from scratch with a blank sheet of paper on which I mapped out a grid of all the possible combinations of virtual space to the left and right of the selection and the replacement, and what should be done in each case, then simplified it Karnaugh-map style. And it finally does what I expect it to do with rectangular selections that include virtual space.

So, please install this script, map it to Ctrl+T, take your most ragged set of line endings, alt-select a rectangle through the middle of them and rotate them to your heart’s content.

That was a lot of work for a feature probably no-one will ever use. But I couldn’t let it beat me. :-)

But everyone can benefit from this script’s basic Ctrl+T functions of swapping two adjacent characters or swapping two disjoint selections. I used these myself several times while writing, and rewriting, the virtual rectangle code.

Thanks again dinkumoil, for introducing me to Lua and scripting of Notepad++. Here’s the final code:

-- Startup script for LuaScript plugin
-- Changes will take effect once Notepad++ is restarted

-- ================================================================================
-- Add a menu entry (intended for Ctrl+T shortcut) to transpose multiple selections 
-- (disjoint or rectangular) by rotating them in the order they were selected, 
-- and to transpose characters either side of an insertion point, 
-- and to transpose lines if neither of the above apply.
-- Modified from a script kindly written by Andreas Heim (dinkumoil), 2019-10-25
-- ================================================================================

-- Get text of selection with index idx, converting any trailing virtual space to real spaces
local function getSelectionNTextVirtual(idx)
	local startVirt = editor.SelectionNAnchorVirtualSpace[idx] -- Number of positions virtual anchor is past real anchor 
	local endVirt = editor.SelectionNCaretVirtualSpace[idx] -- Number of positions virtual caret is past real caret
	if startVirt > endVirt then startVirt, endVirt = endVirt, startVirt end -- Ensure startVirt < endVirt
	
	local selStart = editor.SelectionNStart[idx]
	local selEnd = editor.SelectionNEnd[idx]
	local str = editor:textrange(selStart, selEnd)
	if not str then str = "" end
	
	-- The following line was added to give the behaviour I expect when transposing rectangular selections
	-- that contain virtual space. Dave Keenan, 2019-10-30
	str = str .. string.rep(" ", endVirt - startVirt) -- Convert virtual space at the end of the selection into real spaces at the end of the string

	return str
end


-- Set text of selection with index idx, converting any trailing real spaces to virtual space
local function setSelectionNTextVirtual(idx, str)
	local selStart = editor.SelectionNStart[idx] -- The start of the selection
	local selEnd = editor.SelectionNEnd[idx] -- The end of the selection
	local lineEnd = editor.LineEndPosition[editor:LineFromPosition(selEnd)] -- The end of the line that the selection ends on
	
	local startVirt = editor.SelectionNAnchorVirtualSpace[idx] -- The number of positions virtual anchor is past real anchor
	local endVirt = editor.SelectionNCaretVirtualSpace[idx] -- The number of positions virtual caret is past real caret
	if startVirt > endVirt then startVirt = endVirt end -- Ensure startVirt really is the starting virtual space
	
	-- The following section was added to give the behaviour I expect when transposing rectangular selections
	-- that contain virtual space. Dave Keenan, 2019-10-30
	-- It has the unavoidable side effect of leaving no trailing spaces on any line that ends with a selection.
	-- This (fairly benign) side effect could be eliminated if Rotate Selections was implemented as a Scintilla method.

	-- If there is no text after the selection, convert any trailing spaces in the replacement into end virtual space
	-- and if the replacement is then empty, convert spaces before the selection into start virtual space, otherwise do the opposite conversion.
	endVirt = 0 -- Set end virtual space to a default value of zero
	if selEnd == lineEnd then -- If there is no text after the selection
		-- Convert any spaces at the end of the replacement string, into virtual space at the end of the new selection
		local origStrLen = #str -- Save the original string length
		str = string.gsub(str, " +$", "") -- Remove any trailing spaces
		endVirt = origStrLen - #str -- Set end virtual to the number of spaces removed. Assumes start virtual will be zero. May be modified below.
		-- If the replacement is now empty, convert spaces before the selection into start virtual space, otherwise do the opposite conversion
		if #str == 0 then -- If the replacement string is now empty
			-- Convert any real spaces before the selection, into virtual space
			local before = editor:PositionBefore(selStart) -- Get the character position before the present selection start
			while editor:textrange(before, selStart) == " " do -- While the character before the selection is a space
				editor:SetTargetRange(before, selStart) -- Target the space
				editor:ReplaceTarget("") -- Delete the space
				selStart = selStart - 1 -- Shift the real selection start back
				selEnd = selEnd - 1 -- Shift the real selection end back
				startVirt = startVirt + 1 -- Increment the start virtual space
				before = editor:PositionBefore(selStart) -- Get the character position before the new selection start
			end
			endVirt = endVirt + startVirt -- End virtual previously assumed start virtual was zero
		else -- Else the replacement string is not now empty
			-- Convert any virtual space before the selection, into real spaces
			editor:SetTargetRange(selStart, selStart) -- Target the start of the selection
			editor:ReplaceTarget(string.rep(" ", startVirt)) -- Insert a number of spaces corresponding to start virtual
			selStart = selStart + startVirt -- New start is old start plus the number of spaces inserted
			selEnd = selEnd + startVirt -- New end is old end plus the number of spaces inserted
			startVirt = 0 -- New start virtual is zero. End virtual is unchanged.
		end
	end
	
	-- Update the text and position and virtual space of the selection
	editor:SetTargetRange(selStart, selEnd) -- Target the existing selection position
	editor:ReplaceTarget(str) -- Replace the selection contents with the possibly-modified replacement string
	editor.SelectionNStart[idx] = selStart -- Set the selection start
	selEnd = selStart + #str -- Set the new selection end based on the length of the replacement string
	editor.SelectionNEnd[idx] = selEnd -- Set the selection end
	editor.SelectionNAnchorVirtualSpace[idx] = startVirt -- Update the selection start virtual space
	editor.SelectionNCaretVirtualSpace[idx] = endVirt  -- Update the selection end virtual space
end


-- Is the given position at the start or end of a line?
local function isStartOrEndOfLine(pos)
	local line, lineStart, lineEnd
	line = editor:LineFromPosition(pos)
	lineStart = editor:PositionFromLine(line)
	lineEnd = editor.LineEndPosition[line]
	return pos == lineStart or pos == lineEnd
end


-- Transpose the characters either side of the given position
local function transposeCharactersAt(pos)
	local before = editor:PositionBefore(pos) -- Allow for multi-byte characters
	local after = editor:PositionAfter(pos)
	local str = editor:textrange(pos, after) -- Save the character after the insertion point
	editor:SetTargetRange(pos, after) -- Target the character after the insertion point
	editor:ReplaceTarget(editor:textrange(before, pos)) -- Replace the char before with the char after
	editor:SetTargetRange(before, pos) -- Target the character before the insertion point
	editor:ReplaceTarget(str) -- Replace the char before with the saved char from after
end


-- Transpose selections or characters or lines.
-- If there is only one selection and it is non-empty or at the start or end of a line, then 
-- transpose the line with the one above it (the pre-existing Ctrl+T behaviour).
-- If all selections are empty insertion points, then transpose the characters on either side of them 
-- unless they are at the start or end of a line.
-- If there are 2 or more selections that are not all empty, rotate the selection contents between selections.
local function transposeSelectionsCharactersLines()
	-- According to the Scintilla documentation, there is always at least one selection
	local lastIdx = editor.Selections-1 -- Indexes for multiple selections are zero-based
  
	if editor.SelectionEmpty then -- If all selections are empty, i.e. consist only of an insertion point
		if lastIdx == 0 and isStartOrEndOfLine(editor.CurrentPos) then -- If there is only one selection and it's at the start or end of a line
			editor:LineTranspose() -- Transpose the current line with the one before
		else -- Else multiple empty selections or a single empty selection not at the start or end of a line
			editor:BeginUndoAction() -- Begin the sequence of actions to be undone or redone as a unit
			
			-- Transpose the characters on either side of each insertion point that is not at the start or end of a line
			for idx = 0, lastIdx do
				local pos = editor.SelectionNCaret[idx]
				if not isStartOrEndOfLine(pos) then -- If this empty selection is not at the start or end of a line
					transposeCharactersAt(pos) -- Transpose the characters either side of the given position
					-- For some unknown reason, the insertion point will now be before both characters 
					-- Put the insertion point back in between them, allowing for different numbers of bytes per character
					pos = editor:PositionAfter(editor.SelectionNCaret[idx])
					editor.SelectionNAnchor[idx] = pos
					editor.SelectionNCaret[idx] = pos
				end
			end
			
			editor:EndUndoAction() -- End the sequence of actions to be undone or redone as a unit
		end
	else -- Else selections are not all empty
		if lastIdx == 0 then -- If there is only 1 selection
			editor:LineTranspose() -- Transpose the current line with the one before
		else -- Else there are 2 or more selections
			editor:BeginUndoAction() -- Begin the sequence of actions to be undone or redone as a unit
			
			-- Rotate selection contents between selections
			local lastStr = getSelectionNTextVirtual(lastIdx) -- Save the last selection including any virtual space			
			for idx = lastIdx, 1, -1 do -- Shift the other selections along
				setSelectionNTextVirtual(idx, getSelectionNTextVirtual(idx-1))
			end
			setSelectionNTextVirtual(0, lastStr) -- Make the first selection be the saved last selection
			
			editor:EndUndoAction() -- End the sequence of actions to be undone or redone as a unit
		end
	end
end


-- Add menu entry for transposing selections, characters or lines.
-- The Ctrl+T shortcut may need to be added manually via 
-- Settings -> Shortcut Mapper -> Plugin commands -> Transpose Selections/Characters/Lines -> Modify.
-- You can ignore the conflict with the shortcut for Scintilla SCI_LINETRANSPOSE.
-- editor:ClearCmdKey(string.byte("T"), SCMOD_CTRL) -- Doesn't work
npp.AddShortcut("Transpose Selections/Characters/Lines", "Ctrl+T", transposeSelectionsCharactersLines)

[dkeenan7]

I’d be pleased if a moderator would edit the above post so the code is syntax-highlighted as Lua. I learned how to do that a few minutes too late. :-) You could then delete this post. Thanks.

[dkeenan7]

For the general reader:

This script lets you correct common character-transposition typos, like “teh” instead of “the”, by clicking between the transposed characters (or arrow-keying back to between them) and hitting Ctrl+T. It also lets you swap two selections. You hold Ctrl to make the second selection. For example, you might want to swap the if and else code in a conditional.

The original function of Ctrl+T, i.e. swapping a line with the one above it, is still available by clicking at the start or end of a line, or by making a single non-empty selection anywhere in the line.

If you want to install Ctrl+T for “Transpose Selections/Characters/Lines” into Notepad++:

1. Install the “LuaScript” plugin using Plugins -> Plugins Admin.
2. Choose Plugins -> LuaScript -> Edit Startup Script, and paste in the code from this post:
   https://community.notepad-plus-plus.org/topic/18415/transpose-multiple-selections/11
3. Exit and relaunch Notepad++.
4. Use Settings -> Shortcut Mapper -> Plugin commands -> Transpose Selections/Characters/Lines -> Modify, to add Ctrl+T as the shortcut. Ignore the conflict with the shortcut for Scintilla SCI_LINETRANSPOSE.
5. Choose Settings -> Preferences -> Editing -> Multi-Edit Settings -> Enable.

Many thanks to @dinkumoil @sasumner and Neil Hodgson.

[dinkumoil]

@dkeenan7

Many thanks for that code and many respect for all the hard work!

I was tearing out what little hair I have left, while debugging it.

I thought so. ;-)

I’d be pleased if a moderator would edit the above post so the code is syntax-highlighted as Lua.

If you mean this syntax

```Lua
some code
```

it doesn’t work, the forum doesn’t support Lua syntax highlighting. Above I’ve changed it to SQL as it uses the same syntax for line comments as Lua, thus it produces a result that is closest as possible to the desired result.

[dkeenan7]

Although it’s too late to solve the problem that @X had in this thread:
https://community.notepad-plus-plus.org/topic/18448/is-it-possible-to-switch-column-lines
I have added Reverse Selections/Characters Ctrl+Alt+Shift+T to our transpose script. If you Alt-select a column, it will reverse the rows.

We now have:
Transpose Selections/Characters/Lines Ctrl+T (rotate forwards)
Rotate Backwards Selections/Characters Ctrl+Alt+T
Reverse Selections/Characters Ctrl+Alt+Shift+T

In the case of a single selection with 2 or more characters, each of the above will now rotate or reverse the characters in the selection.

It’s such a monster now, that I have to post it in two pieces. It exceeds the limit of 16 768 bytes for a post.

-- Copy into the startup script for the LuaScript plugin
-- Changes will take effect once Notepad++ is restarted

-- ================================================================================
-- Adds menu entries (intended for Ctrl+mod+T shortcuts) to transpose multiple selections 
-- (disjoint or rectangular) by rotating them in the order they were selected (Ctrl+T), 
-- or rotate them backwards (Ctrl+Alt+T), or reverse them (Ctrl+Alt+Shift+T), 
-- and to do the same with the characters of a single non-empty selection.
-- and to transpose characters either side of an empty selection, 
-- and to transpose lines if none of the above apply.
-- Modified from a script kindly written by Andreas Heim (dinkumoil), 2019-10-25
-- ================================================================================


-- Get the number of positions the virtual start is past the real start, for the selection with index idx
local function getSelectionNStartVirtualSpace(idx)
	local anchor = editor.SelectionNAnchor[idx]
	local caret = editor.SelectionNCaret[idx]
	local anchorVirtual = editor.SelectionNAnchorVirtualSpace[idx]
	local caretVirtual = editor.SelectionNCaretVirtualSpace[idx]
	if anchor < caret or (anchor == caret and anchorVirtual < caretVirtual) then
		return anchorVirtual
	else
		return caretVirtual
	end
end


-- Get the number of positions the virtual end is past the real end, for the selection with index idx
local function getSelectionNEndVirtualSpace(idx)
	local anchor = editor.SelectionNAnchor[idx]
	local caret = editor.SelectionNCaret[idx]
	local anchorVirtual = editor.SelectionNAnchorVirtualSpace[idx]
	local caretVirtual = editor.SelectionNCaretVirtualSpace[idx]
	if anchor < caret or (anchor == caret and anchorVirtual < caretVirtual) then
		return caretVirtual
	else
		return anchorVirtual
	end
end


-- Get text of selection with index idx, converting any trailing virtual space to real spaces
local function getSelectionNTextVirtual(idx)
	local selStart = editor.SelectionNStart[idx]
	local selEnd = editor.SelectionNEnd[idx]
	local startVirtual = getSelectionNStartVirtualSpace(idx) -- Number of positions virtual start is past real start 
	local endVirtual = getSelectionNEndVirtualSpace(idx) -- Number of positions virtual end is past real end

	local str = editor:textrange(selStart, selEnd) or ""

	-- The following section was added to give the behaviour I expect when transposing rectangular selections
	-- that contain virtual space. Dave Keenan, 2019-11-01
	if selStart == selEnd then -- If the real part of the selection is empty
		endVirtual = endVirtual - startVirtual -- The virtual part that comes after, is the difference between end and start virtual
	-- else any start virtual is on a different line and so should not be subtracted from end virtual
	end
	str = str .. string.rep(" ", endVirtual) -- Convert virtual space at the end of the selection into real spaces at the end of the string

	return str
end


-- Set text of selection with index idx, converting any trailing real spaces to virtual space
local function setSelectionNTextVirtual(idx, str)
	local selStart = editor.SelectionNStart[idx] -- The start of the selection
	local selEnd = editor.SelectionNEnd[idx] -- The end of the selection
	local lineEnd = editor.LineEndPosition[editor:LineFromPosition(selEnd)] -- The end of the line that the selection ends on
	
	local startVirt = getSelectionNStartVirtualSpace(idx) -- The number of positions virtual start is past real start
	
	-- The following section was added to give the behaviour I expect when transposing rectangular selections
	-- that contain virtual space. Dave Keenan, 2019-11-01
	-- It has the fairly benign side effect of leaving no trailing spaces on any line that ends with a selection.

	-- If there is no text after the selection, convert any trailing spaces in the replacement into end virtual space
	-- and if the replacement is then empty, convert spaces before the selection into start virtual space, otherwise do the opposite conversion.
	local endVirt = 0 -- Set end virtual space to a default value of zero
	if selEnd == lineEnd then -- If there is no text after the selection
		-- Convert any spaces at the end of the replacement string, into virtual space at the end of the new selection
		local origStrLen = #str -- Save the original string length
		str = string.gsub(str, " +$", "") -- Remove any trailing spaces
		endVirt = origStrLen - #str -- Set end virtual to the number of spaces removed. Assumes start virtual will be zero. May be modified below.
		-- If the replacement is now empty, convert spaces before the selection into start virtual space, otherwise do the opposite conversion
		if #str == 0 then -- If the replacement string is now empty
			-- Convert any real spaces before the selection, into virtual space
			local before = editor:PositionBefore(selStart) -- Get the character position before the present selection start
			while editor:textrange(before, selStart) == " " do -- While the character before the selection is a space
				editor:SetTargetRange(before, selStart) -- Target the space
				editor:ReplaceTarget("") -- Delete the space
				selStart = selStart - 1 -- Shift the real selection start back
				selEnd = selEnd - 1 -- Shift the real selection end back
				startVirt = startVirt + 1 -- Increment the start virtual space
				before = editor:PositionBefore(selStart) -- Get the character position before the new selection start
			end
			endVirt = endVirt + startVirt -- End virtual previously assumed start virtual was zero
		else -- Else the replacement string is not now empty
			-- Convert any virtual space before the selection, into real spaces
			editor:SetTargetRange(selStart, selStart) -- Target the start of the selection
			editor:ReplaceTarget(string.rep(" ", startVirt)) -- Insert a number of spaces corresponding to start virtual
			selStart = selStart + startVirt -- New start is old start plus the number of spaces inserted
			selEnd = selEnd + startVirt -- New end is old end plus the number of spaces inserted
			startVirt = 0 -- New start virtual is zero. End virtual is unchanged.
		end
	end
	
	-- Update the text and position and virtual space of the selection
	editor:SetTargetRange(selStart, selEnd) -- Target the existing selection position
	editor:ReplaceTarget(str) -- Replace the selection contents with the possibly-modified replacement string
	editor.SelectionNStart[idx] = selStart -- Set the selection start
	selEnd = selStart + #str -- Set the new selection end based on the length of the replacement string
	editor.SelectionNEnd[idx] = selEnd -- Set the selection end
	-- Setting SelectionNStart and SelectionNEnd above, will have ensured that the anchor is the start
	-- and the caret is the end, so that the following will be valid.
	editor.SelectionNAnchorVirtualSpace[idx] = startVirt -- Update the selection start virtual space
	editor.SelectionNCaretVirtualSpace[idx] = endVirt  -- Update the selection end virtual space
end


-- Is the given position at the start or end of a line?
local function isStartOrEndOfLine(pos)
	local line, lineStart, lineEnd
	line = editor:LineFromPosition(pos)
	lineStart = editor:PositionFromLine(line)
	lineEnd = editor.LineEndPosition[line]
	return pos == lineStart or pos == lineEnd
end


-- Transpose the characters either side of the given position
local function transposeCharactersAt(pos)
	local before = editor:PositionBefore(pos) -- Allow for multi-byte characters
	local after = editor:PositionAfter(pos)
	local str = editor:textrange(pos, after) -- Save the character after the insertion point
	editor:SetTargetRange(pos, after) -- Target the character after the insertion point. Doesn't work with different character widths if you go the other way first.
	editor:ReplaceTarget(editor:textrange(before, pos)) -- Replace the char after with the char before. 
	editor:SetTargetRange(before, pos) -- Target the character before the insertion point
	editor:ReplaceTarget(str) -- Replace the char before with the saved char from after
end


-- Rotate the characters between the given positions
local function rotateCharacters(start, endd)
	if start == endd then return end
	local after = endd
	local pos = editor:PositionBefore(endd) -- Allow for multi-byte characters
	if pos == start then return end
	local before = editor:PositionBefore(pos)
	local str = editor:textrange(pos, after) -- Save the last character
	while before > start do -- While we haven't reached the start
		editor:SetTargetRange(pos, after) -- Target the after character. Doesn't work with different character widths if you go the other way first.
		editor:ReplaceTarget(editor:textrange(before, pos)) -- Replace the after char with the before character
		-- Move backwards
		pos = before
		before = editor:PositionBefore(pos)
		after = editor:PositionAfter(pos)  -- Can't just assign the previous pos, as the character width may have changed
	end
	editor:SetTargetRange(pos, after) -- Target the after character
	editor:ReplaceTarget(editor:textrange(before, pos)) -- Replace the after char with the before character
	
	editor:SetTargetRange(before, pos) -- Target the first character
	editor:ReplaceTarget(str) -- Replace the first character with the saved last character
end


-- Rotate the characters backwards between the given positions
local function rotateCharactersBackwards(start, endd)
	-- This is tricky to make work with multi-byte characters, which include CR LF newlines.
	-- We can't simply reverse direction relative to the forward rotation function above.
	-- We still need to work backwards.
	if start == endd then return end
	local afterStart = editor:PositionAfter(start)
	if afterStart == endd then return end
	local posStr = editor:textrange(start, afterStart) -- Get the first character
	local pos = endd
	local before = editor:PositionBefore(endd) -- Allow for multi-byte characters
	while before > start do -- While we haven't reached the start
		local beforeStr = editor:textrange(before, pos) -- Save the before character
		editor:SetTargetRange(before, pos) -- Target the before character.
		editor:ReplaceTarget(posStr) -- Replace the before character with the saved present character
		posStr = beforeStr -- Replace the saved present character with the saved before character
		-- Move backwards
		pos = before
		before = editor:PositionBefore(pos)
	end
	editor:SetTargetRange(before, pos) -- Target the first character
	editor:ReplaceTarget(posStr) -- Replace the first character with the saved present character
end


-- Reverse the characters between the given positions
local function reverseCharacters(start, endd)
	if start == endd then return end
	local afterStart = editor:PositionAfter(start) -- Allow for multi-byte characters
	if afterStart == endd then return end
	local beforeEnd = editor:PositionBefore(endd)
	while afterStart <= beforeEnd do -- While we haven't reached the middle
		local str = editor:textrange(beforeEnd, endd) -- Save the character from the last half
		editor:SetTargetRange(beforeEnd, endd) -- Target the character in the last half. Doesn't work with different character widths if you go the other way first.
		editor:ReplaceTarget(editor:textrange(start, afterStart)) -- Replace the char in the last half with its opposite in the first half
		editor:SetTargetRange(start, afterStart) -- Target the character in the first half
		editor:ReplaceTarget(str) -- Replace the char in the first half with the saved char from the last half
		-- Move inward
		start = editor:PositionAfter(start) -- Can't just assign afterStart, as the character width may have changed
		endd = editor:PositionBefore(endd)
		afterStart = editor:PositionAfter(start)
		beforeEnd = editor:PositionBefore(endd)
	end
end

[dkeenan7]

-- Transpose selections or characters or lines.
-- If there is 1 empty selection at the start or end of a line, then 
-- transpose the line with the one above it (the pre-existing Ctrl+T behaviour).
-- If all selections are empty, then transpose the characters on either side of
-- any that are not at the start or end of a line.
-- If there is 1 non-empty selection, rotate its characters forward.
-- If there are 2 or more selections that are not all empty, rotate the selection contents between selections.
-- Useful for rotating the rows in a rectangular/column selection (Alt-select)
local function transposeSelectionsOrCharactersOrLines()
	-- According to the Scintilla documentation, there is always at least one selection
	local lastIdx = editor.Selections - 1 -- Indexes for multiple selections are zero-based
  
	editor:BeginUndoAction() -- Begin the sequence of actions to be undone or redone as a unit
	
	if editor.SelectionEmpty then -- If all selections are empty, i.e. consist only of an insertion point
		if lastIdx == 0 and isStartOrEndOfLine(editor.CurrentPos) then -- If there is only one selection and it's at the start or end of a line
			editor:LineTranspose() -- Transpose the current line with the one before
		else -- Else multiple empty selections or a single empty selection not at the start or end of a line
			-- Transpose the characters on either side of each insertion point that is not at the start or end of a line
			for idx = 0, lastIdx do
				local pos = editor.SelectionNCaret[idx]
				if not isStartOrEndOfLine(pos) then -- If this empty selection is not at the start or end of a line
					transposeCharactersAt(pos) -- Transpose the characters either side of the given position
					-- The insertion point will now be before both characters 
					-- Put the insertion point back in between them, allowing for different numbers of bytes per character
					pos = editor:PositionAfter(editor.SelectionNCaret[idx])
					editor.SelectionNAnchor[idx] = pos
					editor.SelectionNCaret[idx] = pos
				end
			end
		end
	else -- Else selections are not all empty
		if lastIdx == 0 then -- If there is only 1 selection
			--[[ Alternative behaviour: 
			editor:LineTranspose() -- Transpose the current line with the one before
			--]]
			-- Rotate the characters in the selection (ignores virtual space)
			local selStart = editor.SelectionNStart[0]
			local selEnd = editor.SelectionNEnd[0]
			rotateCharacters(selStart, selEnd)
			-- Restore the selection
			editor.SelectionNStart[0] = selStart
			editor.SelectionNEnd[0] = selEnd
		else -- Else there are 2 or more selections			
			-- Rotate selection contents between selections
			local str = getSelectionNTextVirtual(lastIdx) -- Save the last selection including any virtual space			
			for idx = lastIdx, 1, -1 do -- Shift the other selections along
				setSelectionNTextVirtual(idx, getSelectionNTextVirtual(idx-1))
			end
			setSelectionNTextVirtual(0, str) -- Make the first selection be the saved last selection
		end
	end

	editor:EndUndoAction() -- End the sequence of actions to be undone or redone as a unit
end


-- Rotate selections backwards
-- Useful for rotating the rows backwards in a rectangular/column selection (Alt-select)
local function rotateSelectionsOrCharactersBackwards()
	-- According to the Scintilla documentation, there is always at least one selection
	local lastIdx = editor.Selections - 1 -- Indexes for multiple selections are zero-based

	editor:BeginUndoAction() -- Begin the sequence of actions to be undone or redone as a unit
	
	if lastIdx == 0 then -- If there is only 1 selection
		-- Rotate the characters backwards in the selection (ignores virtual space)
		local selStart = editor.SelectionNStart[0]
		local selEnd = editor.SelectionNEnd[0]
		rotateCharactersBackwards(selStart, selEnd)
		-- Restore the selection
		editor.SelectionNStart[0] = selStart
		editor.SelectionNEnd[0] = selEnd		
	else
		-- Rotate selection contents backwards between selections
		local str = getSelectionNTextVirtual(0) -- Save the first selection including any virtual space			
		for idx = 1, lastIdx do -- Shift the other selections along
			setSelectionNTextVirtual(idx-1, getSelectionNTextVirtual(idx))
		end
		setSelectionNTextVirtual(lastIdx, str) -- Make the last selection be the saved first selection
	end
	
	editor:EndUndoAction() -- End the sequence of actions to be undone or redone as a unit
end


-- Reverse selections
-- Useful for reversing the order of rows in a rectangular/column selection (Alt-select)
local function reverseSelectionsOrCharacters()
	-- According to the Scintilla documentation, there is always at least one selection
	local lastIdx = editor.Selections - 1 -- Indexes for multiple selections are zero-based
	local lastSwap = editor.Selections // 2 - 1

	editor:BeginUndoAction() -- Begin the sequence of actions to be undone or redone as a unit
	
	if lastIdx == 0 then -- If there is only 1 selection
		-- Reverse the characters in the selection (ignores virtual space)
		local selStart = editor.SelectionNStart[0]
		local selEnd = editor.SelectionNEnd[0]
		reverseCharacters(selStart, selEnd)
		-- Restore the selection
		editor.SelectionNStart[0] = selStart
		editor.SelectionNEnd[0] = selEnd
	else -- Else there are 2 or more selections
		-- Swap selection contents between opposite pairs of selections
		for idx = 0, lastSwap do
			local str = getSelectionNTextVirtual(lastIdx - idx) -- Save the later selection including any virtual space			
			setSelectionNTextVirtual(lastIdx - idx, getSelectionNTextVirtual(idx)) -- Replace later selection with the opposite earlier selection
			setSelectionNTextVirtual(idx, str) -- Make the opposite earlier selection be the saved later selection
		end
	end
	
	editor:EndUndoAction() -- End the sequence of actions to be undone or redone as a unit
end


-- Add menu entry for transposing or rotating selections, characters or lines.
-- The Ctrl+T shortcut may need to be added manually via 
-- Settings -> Shortcut Mapper -> Plugin commands -> Transpose Selections/Characters/Lines -> Modify.
-- You can ignore the conflict with the shortcut for Scintilla SCI_LINETRANSPOSE.
editor:ClearCmdKey(string.byte("T"), SCMOD_CTRL) -- This doesn't seem to work here
npp.AddShortcut("Transpose Selections/Characters/Lines", "Ctrl+T", transposeSelectionsOrCharactersOrLines)

-- Add menu entry for rotating selections backwards.
npp.AddShortcut("Rotate Selections/Characters Backwards", "Ctrl+Alt+T", rotateSelectionsOrCharactersBackwards)

-- Add menu entry for reversing selections.
npp.AddShortcut("Reverse Selections/Characters", "Ctrl+Alt+Shift+T", reverseSelectionsOrCharacters)