Sublime Text 3 Plugin for iterating through selected regions

sel_iterate.py

import sublime
import sublime_plugin
import weakref

from weakref import WeakValueDictionary

view_selection_iterators = WeakValueDictionary()
class ViewSelectionIterator(sublime_plugin.ViewEventListener):
	current_item = None

	def __init__(self, view):
		super().__init__(view)
		global view_selection_iterators
		view_selection_iterators[self.view.id()] = self

	@staticmethod
	def find_by_view(view):
		global view_selection_iterators
		return view_selection_iterators.get(view.id())

	def on_query_context(self, key, operator, operand, match_all):
		if key == "has_selection_iterator":
			return self.has_regions()
		return False

	def sel(self):
		return self.view.get_regions("selection_iterator")

	def has_regions(self):
		return self.current_item is not None

	def start(self, sel):
		self.view.add_regions("selection_iterator", sel, "string", "", sublime.DRAW_EMPTY_AS_OVERWRITE)
		self.current_item = 0
		return sel[0]

	def next(self):
		n = self.current_item + 1
		region = self.sel()[n]
		self.current_item = n
		return region

	def clear(self):
		self.view.erase_regions("selection_iterator")
		self.current_item = None


class SelIterateCommand(sublime_plugin.TextCommand):
	def run(self, edit):
		iterator = ViewSelectionIterator.find_by_view(self.view)
		sel = self.view.sel()

		if iterator.has_regions():
			sel.clear()
			try:
				region = iterator.next()
				sel.add(region)
				self.view.show(region)
			except IndexError:
				sel.add_all(iterator.sel())
				iterator.clear()
		else:
			try:
				region = iterator.start(sel)
				sel.clear()
				sel.add(region)
				self.view.show(region)
			except IndexError:
				pass


class SelIterateCancelCommand(sublime_plugin.TextCommand):
	def run(self, edit):
		iterator = ViewSelectionIterator.find_by_view(self.view)
		if iterator.has_regions():
			sel = self.view.sel()
			sel.clear()
			sel.add_all(iterator.sel())
			iterator.clear()