Add Meld compare menu to Nautilus file manager on Ubuntu 22.04

meld-compare-menu-nautilus-ubuntu-2204.md

Sources:

• https://askubuntu.com/questions/1417245/nautilus-compare-on-22-04
• https://gist.github.com/Erriez/08f461cb8a8fc6872426f3b5f2e268ae

Install the nautilus python3 bindings

$ sudo apt-get install python3-nautilus

Download the source

# Original link:
$ wget https://launchpad.net/~boamaod/+archive/ubuntu/nautilus-compare/+sourcefiles/nautilus-compare/1.0.0~focal1/nautilus-compare_1.0.0~focal1.tar.xz

# Extract
$ tar -xvf nautilus-compare_1.0.0~focal1.tar.xz 

Install the source files

$ cd nautilus-compare-1.0.0/src
$ sudo cp nautilus-compare.py /usr/share/nautilus-python/extensions/

$ sudo mkdir /usr/share/nautilus-compare
$ sudo cp utils.py /usr/share/nautilus-compare
$ sudo cp nautilus-compare-preferences.py /usr/share/nautilus-compare

Restart nautilus

$ nautilus -q && nautilus &

Usage

1. Open a directory in Nautilus
2. Select two files
3. Right mouse click on the selected files: Compare

This automatically opens Meld for file comparison:

nautilus-compare-preferences.py

#!/usr/bin/python3
# -*- coding: utf-8 -*-
#    nautilus-compare --- Context menu extension for Nautilus file manager
#    Copyright (C) 2011, 2015, 2020  Märt Põder <tramm@infoaed.ee>
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <http://www.gnu.org/licenses/>.

import gi
gi.require_version('Gtk', '3.0')

from gi.repository import Gtk, GObject
import os
import gettext
import locale

import utils

def combo_add_and_select(combo, text):
	'''Convenience function to add/selct item in ComboBoxEntry'''
	combo.append_text(text)
	model=combo.get_model()
	iter=model.get_iter_first()
	while model.iter_next(iter):
		iter=model.iter_next(iter)
	combo.set_active_iter(iter)

class NautilusCompareExtensionPreferences:
	'''The main class for preferences dialog using PyGTK'''

	combo = None
	combo_3way = None
	combo_multi = None

	def cancel_event(self, widget, event, data = None):
		'''This callback quits the program'''
		Gtk.main_quit()
		return False

	def changed_cb(self, combo):
		'''Any of the comboboxes has changed, change the data accordingly'''
		model = combo.get_model()
		index = combo.get_active()
		entry = combo.get_child().get_text()

		selection=""

		if len(entry)>0:
			selection=entry
		elif index:
			selection=model[index][0]

		if combo is self.combo:
			self.config.diff_engine = selection
		elif combo is self.combo_3way:
			self.config.diff_engine_3way = selection
		elif combo is self.combo_multi:
			self.config.diff_engine_multi = selection

		return

	def save_event(self, widget, event, data = None):
		'''This callback saves the settings and quits the program.'''
		self.config.save()
		Gtk.main_quit()
		return False

	def __init__(self):
		'''Load config and create UI'''

		self.config = utils.NautilusCompareConfig()
		self.config.load()

		# find out if some new engines have been installed
		self.config.add_missing_predefined_engines()

		# initialize i18n
		locale.setlocale(locale.LC_ALL, '')
		gettext.bindtextdomain(utils.APP)
		gettext.textdomain(utils.APP)
		_ = gettext.gettext

		self.window = Gtk.Window(type=Gtk.WindowType.TOPLEVEL)
		self.window.set_resizable(False)
		self.window.set_title(_("Nautilus Compare Extension Preferences"))
		self.window.connect("delete_event",self.cancel_event)
		self.window.set_border_width(15)

		main_vbox = Gtk.Box(orientation=Gtk.Orientation.VERTICAL)
		self.window.add(main_vbox)

		# normal diff
		frame = Gtk.Frame(label=_("Normal Diff"))
		self.combo = Gtk.ComboBoxText.new_with_entry()
		for text in self.config.engines:
			if text == self.config.diff_engine:
				combo_add_and_select(self.combo, text)
			else:
				self.combo.append_text(text)
		self.combo.connect('changed', self.changed_cb)
		frame.add(self.combo)
		main_vbox.pack_start(frame, True, True, 0)

		# 3-way diff
		frame_3way = Gtk.Frame(label=_("Three-Way Diff"))
		self.combo_3way = Gtk.ComboBoxText.new_with_entry()
		for text in self.config.engines:
			if text == self.config.diff_engine_3way:
				combo_add_and_select(self.combo_3way, text)
			else:
				self.combo_3way.append_text(text)
		self.combo_3way.connect('changed', self.changed_cb)
		frame_3way.add(self.combo_3way)
		main_vbox.pack_start(frame_3way, True, True, 0)

		# n-way diff
		frame_multi = Gtk.Frame(label=_("N-Way Diff"))
		self.combo_multi = Gtk.ComboBoxText.new_with_entry()
		for text in self.config.engines:
			if text == self.config.diff_engine_multi:
				combo_add_and_select(self.combo_multi, text)
			else:
				self.combo_multi.append_text(text)
		self.combo_multi.connect('changed', self.changed_cb)
		frame_multi.add(self.combo_multi)
		main_vbox.pack_start(frame_multi, True, True, 0)

		separator = Gtk.Box(orientation=Gtk.Orientation.HORIZONTAL, spacing=5)
		main_vbox.pack_start(separator, False, True, 5)

		# cancel / ok
		confirm_hbox = Gtk.Box(orientation=Gtk.Orientation.HORIZONTAL)
		main_vbox.pack_start(confirm_hbox, False, False, 0)
		
		cancel_button = Gtk.Button.new_with_mnemonic(_("_Cancel"))
		cancel_button.connect_object("clicked", self.cancel_event, self.window, None)  
		confirm_hbox.pack_start(cancel_button, True, True, 5)

		ok_button = Gtk.Button.new_with_mnemonic(_("_Save"))
		ok_button.connect_object("clicked", self.save_event, self.window, None)  
		confirm_hbox.pack_start(ok_button, True, True, 5)

		self.window.show_all()

	def main(self):
		'''GTK main method'''
		Gtk.main()

if __name__ == "__main__":
	prefs = NautilusCompareExtensionPreferences()
	prefs.main()

nautilus-compare.py

#!/usr/bin/python3
# -*- coding: utf-8 -*-
#    nautilus-compare --- Context menu extension for Nautilus file manager
#    Copyright (C) 2011, 2015, 2020  Märt Põder <tramm@infoaed.ee>
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <http://www.gnu.org/licenses/>.

import sys
import os
import urllib.request, urllib.parse, urllib.error
import gettext
import locale

from gi.repository import Nautilus, GObject, Gio

sys.path.insert(0, "/usr/share/nautilus-compare")

import utils

class NautilusCompareExtension(GObject.GObject, Nautilus.MenuProvider):
	'''Class for the extension itself'''

	# to hold an item for later comparison
	for_later = None

	def __init__(self):
		'''Load config'''

		GObject.Object.__init__(self)

		self.config = utils.NautilusCompareConfig()
		self.config.load()

	def menu_activate_cb(self, menu, paths):
		'''Telling from amount of paths runs appropriate comparator engine'''
		if len(paths) == 1:
			self.for_later = paths[0]
			return

		args = ""
		for path in paths:
			args += "\"%s\" " % path

		cmd = None
		if len(paths) == 2:
			cmd = (self.config.diff_engine + " " + args + "&")
		elif len(paths) == 3 and len(self.config.diff_engine_3way.strip()) > 0:
			cmd = (self.config.diff_engine_3way + " " + args + "&")
		elif len(self.config.diff_engine_multi.strip()) > 0:
			cmd = (self.config.diff_engine_multi + " " + args + "&")

		if cmd is not None:
			os.system(cmd)
		
	def valid_file(self, file):
		'''Tests if the file is valid comparable'''
		if file.get_uri_scheme() == 'file' and file.get_file_type() in (Gio.FileType.DIRECTORY, Gio.FileType.REGULAR, Gio.FileType.SYMBOLIC_LINK):
			return True
		elif self.config.diff_engine in utils.URI_COMPAT_ENGINES and file.get_location().get_path() is not None and file.get_file_type() in (Gio.FileType.DIRECTORY, Gio.FileType.REGULAR, Gio.FileType.SYMBOLIC_LINK):
			return True
		else:
			return False

	def get_file_items(self, window, files):
		'''Main method to detect what choices should be offered in the context menu'''
		paths = []
		for file in files:
			if self.valid_file(file):
				if self.config.diff_engine in utils.URI_COMPAT_ENGINES:
					path = urllib.parse.unquote(file.get_uri())
				else:
					path = urllib.parse.unquote(file.get_uri()[7:])
				paths.append(path)

		# no files selected
		if len(paths) < 1:
			return

		# initialize i18n
		locale.setlocale(locale.LC_ALL, '')
		gettext.bindtextdomain(utils.APP)
		gettext.textdomain(utils.APP)
		_ = gettext.gettext

		item1 = None
		item2 = None
		item3 = None

		# for paths with remembered items
		new_paths = list(paths)

		# exactly one file selected
		if len(paths) == 1:

			# and one was already selected for later comparison
			if self.for_later is not None:

				# we don't want to compare file to itself
				if self.for_later not in paths:
					item1 = Nautilus.MenuItem(
						name="NautilusCompareExtension::CompareTo",
						label=_('Compare to ') + utils.prepare_for_menu(self.for_later),
						tip=_("Compare to the file remembered before")
					)

					# compare the one saved for later to the one selected now
					new_paths.insert(0, self.for_later)

			# if only one file selected, we offer to remember it for later anyway
			item3 = Nautilus.MenuItem(
				name="NautilusCompareExtension::CompareLater",
				label=_('Compare Later'),
				tip=_("Remember file for later comparison")
			)

		# can always compare, if more than one selected
		else:
			# if we have already remembered one file and add some more, we can do n-way compare
			if self.for_later is not None:
				if self.for_later not in paths:
					# if multi compare enabled and in case of 2 files selected 3way compare enabled
					if len(self.config.diff_engine_multi.strip()) > 0 or (len(paths) == 2 and len(self.config.diff_engine_3way.strip()) > 0):
						item1 = Nautilus.MenuItem(
							name="NautilusCompareExtension::MultiCompare",
							label=_('Compare to ') + utils.prepare_for_menu(self.for_later),
							tip=_("Compare selected files to the file remembered before")
						)
						# compare the one saved for later to the ones selected now
						new_paths.insert(0, self.for_later)

			# if multi compare enabled, we can compare any number
			# if there are two files selected we can always compare
			# if three files selected and 3-way compare is on, we can do it
			if len(self.config.diff_engine_multi.strip()) > 0 or len(paths) == 2 or (len(paths) == 3 and len(self.config.diff_engine_3way.strip()) > 0):
				item2 = Nautilus.MenuItem(
					name="NautilusCompareExtension::CompareWithin",
					label=_('Compare'),
					tip=_("Compare selected files")
				)

		if item1: item1.connect('activate', self.menu_activate_cb, new_paths)
		if item2: item2.connect('activate', self.menu_activate_cb, paths)
		if item3: item3.connect('activate', self.menu_activate_cb, paths)

		items = [item1, item2, item3]

		while None in items:
			items.remove(None)

		return items

utils.py

#!/usr/bin/python3
# -*- coding: utf-8 -*-
#    nautilus-compare --- Context menu extension for Nautilus file manager
#    Copyright (C) 2011, 2015, 2020 Märt Põder <tramm@infoaed.ee>
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <http://www.gnu.org/licenses/>.

import os
import xdg.BaseDirectory
import configparser

APP = 'nautilus-compare'

# settings
CONFIG_FILES = [os.path.join(xdg.BaseDirectory.xdg_config_home, APP + ".conf"), os.path.join("/etc", APP + ".conf")]
CONFIG_FILE = CONFIG_FILES[0]
SETTINGS_MAIN = 'Settings'

DIFF_PATH = 'diff_engine_path'
DIFF_PATH_3WAY = 'diff_engine_path_3way'
DIFF_PATH_MULTI = 'diff_engine_path_multi'

COMPARATORS = 'defined_comparators'
# ordered by preference
PREDEFINED_ENGINES = ['meld', 'kdiff3', 'diffuse', 'kompare', 'fldiff', 'tkdiff', 'xxdiff']
URI_COMPAT_ENGINES = ['meld']
DEFAULT_DIFF_ENGINE = 'meld'

# where comparator engines are sought
COMPARATOR_PATHS = ['/usr/bin', '/usr/local/bin']

def prepare_for_menu(item):
	'''Formats file name URI to be compared for less garbage and easier readability.'''
	prep = item.replace("_", "__") # escaping the underscores to avoid accelerators
	prep = prep.split("file://").pop() # remove default file descriptor for less garbage
	return prep

class NautilusCompareConfig:

	diff_engine = DEFAULT_DIFF_ENGINE
	diff_engine_3way = DEFAULT_DIFF_ENGINE
	diff_engine_multi = ""
	engines = []

	config = None

	def load(self):
		'''Loads config options if available. If not, creates them using the best heuristics availabe.'''
		self.config = configparser.ConfigParser()

		# allow system-wide default settings from /etc/*
		if os.path.isfile(CONFIG_FILES[0]):
			self.config.read(CONFIG_FILES[0])
		else:
			self.config.read(CONFIG_FILES[1])

		# read from start or flush from the point where cancelled
		try:
			self.diff_engine = self.config.get(SETTINGS_MAIN, DIFF_PATH)
			self.diff_engine_3way = self.config.get(SETTINGS_MAIN, DIFF_PATH_3WAY)
			self.diff_engine_multi = self.config.get(SETTINGS_MAIN, DIFF_PATH_MULTI)
			self.engines = eval(self.config.get(SETTINGS_MAIN, COMPARATORS))

		except (configparser.NoOptionError, configparser.NoSectionError):

			# maybe settings were half loaded when exception was thrown
			try:
				self.config.add_section(SETTINGS_MAIN)
			except configparser.DuplicateSectionError:
				pass

			self.add_missing_predefined_engines()

			# add choice for "engine not enabled"
			# (always needed, because at least self.engines cannot be loaded)
			self.engines.insert(0, "")

			# if default engine is not installed, replace with preferred installed engine
			if len(self.engines) > 0:
				if self.diff_engine not in self.engines:
					self.diff_engine = self.engines[0]
				if self.diff_engine_3way not in self.engines:
					self.diff_engine_3way = self.engines[0]
				if self.diff_engine_multi not in self.engines:
					self.diff_engine_multi = self.engines[0]

			self.engines.sort()

			self.config.set(SETTINGS_MAIN, DIFF_PATH, self.diff_engine)
			self.config.set(SETTINGS_MAIN, DIFF_PATH_3WAY, self.diff_engine_3way)
			self.config.set(SETTINGS_MAIN, DIFF_PATH_MULTI, self.diff_engine_multi)
			self.config.set(SETTINGS_MAIN, COMPARATORS, str(self.engines))

			with open(CONFIG_FILE, 'w') as f:
				self.config.write(f)

	def add_missing_predefined_engines(self):
		'''Adds predefined engines which are installed, but missing in engines list.'''
		system_utils = []
		for path in COMPARATOR_PATHS:
			system_utils += os.listdir(path)
		for engine in PREDEFINED_ENGINES:
			if engine not in self.engines and engine in system_utils:
				self.engines.append(engine)
	

	def save(self):
		'''Saves config options'''
		try:
			self.config.add_section(SETTINGS_MAIN)
		except configparser.DuplicateSectionError:
			pass

		self.config.set(SETTINGS_MAIN, DIFF_PATH, self.diff_engine)
		self.config.set(SETTINGS_MAIN, DIFF_PATH_3WAY, self.diff_engine_3way)
		self.config.set(SETTINGS_MAIN, DIFF_PATH_MULTI, self.diff_engine_multi)

		if self.diff_engine not in self.engines:
			self.engines.append(self.diff_engine)
		if self.diff_engine_3way not in self.engines:
			self.engines.append(self.diff_engine_3way)
		if self.diff_engine_multi not in self.engines:
			self.engines.append(self.diff_engine_multi)

		self.config.set(SETTINGS_MAIN, COMPARATORS, str(self.engines))
		with open(CONFIG_FILE, 'w') as f:
			self.config.write(f)