you could use @dail s script and ctypes to get the size of the fullscreen notepad++ window like this

import ctypes
from ctypes.wintypes import RECT

FindWindow = ctypes.windll.user32.FindWindowW
GetWindowRect = ctypes.windll.user32.GetWindowRect
Rect = RECT()

nppHandle = FindWindow(u'Notepad++', None)
notepad.runMenuCommand("View", "Post-It")

if GetWindowRect(nppHandle, ctypes.byref(Rect)) != 0:
    w = Rect.right
    editor.setMarginLeft(w/3)
    editor.setMarginRight(w/3)

Cheers
Claudia

I don’t have the source code any more. I just did some quick tests on an existing plugin I was working with. To get the basic functionality is easy, just set the margins wide so that it centers the text. You can do some testing with the PythonScript plugin. (Normally I would be a bit biased to use LuaScript but there is an issue using it to set the margins). So using Python:

w = 1980
editor.setMarginLeft(w/3)
editor.setMarginRight(w/3)
notepad.runMenuCommand("View", "Post-It")

That’s the general idea. Obviously the screen width is hard coded, don’t know off the top of my head how to get the width of the editor.