gistfile1.py

import sublime, sublime_plugin

class ClearMarkCommand(sublime_plugin.TextCommand):
    def run(self, edit):
        self.view.run_command("clear_bookmarks", {"name": "mark"})
        self.view.settings().set('with_marker', False)

class DoAfterMarkCommand(sublime_plugin.TextCommand):
    def run(self, edit, command, args = {}):
        self.view.run_command("clear_mark")
        self.view.run_command(command)

class SetMarkCommand(sublime_plugin.TextCommand):
    def run(self, edit):
        if not self.view.get_regions("mark"):
            mark = [s for s in self.view.sel()]
            self.view.add_regions("mark", mark, "mark", "dot",
                sublime.HIDDEN | sublime.PERSISTENT)
            self.view.settings().set('with_marker', True)
        else:
            self.view.run_command("clear_mark")

class MarkDetector(sublime_plugin.EventListener):
    def on_selection_modified(self, view):
        mark = view.get_regions("mark")
        if mark:
            view.run_command("select_to_mark")

    def on_modified(self, view):
        mark = view.get_regions("mark")
        if mark:
            view.run_command("clear_mark")