This is a Sublime Text 3 plugin that makes an adjusted multiline C-macro

C-make-multiline-macro.py

# The MIT License (MIT)
# Copyright (c) 2016 Leonid Edrenkin
#
# This is a Sublime Text 3 plugin that makes an adjusted multiline C-macro.
# You should select some code and apply one of commands:
#   view.run_command('make_multi_line_macro')
#   view.run_command('unmake_multi_line_macro')

import sublime, sublime_plugin

class MakeMultiLineMacroCommand(sublime_plugin.TextCommand):
  def run(self, edit):
    v = self.view
    ruler_size = 80
    regions = [ s for s in self.view.sel() if not s.empty() ]

    if len(regions) == 0:
      return

    for region in regions:
      region = v.full_line(region)
      new_lines = []

      lines = v.split_by_newlines(region)
      for i, line in enumerate(lines):
        s = v.substr(line)
        if (i < len(lines)-1):
          s = s.rstrip()
          if len(s) > 0 and s[-1] == '\\': s = s[:-1].rstrip()
          space_size = ruler_size - len(s) - 1
          if space_size < 0 : space_size = 1
          s += " " * space_size +  "\\\n"
        else:
          s += "\n"
        new_lines.append(s)

      p = region.begin()
      v.erase(edit, region)
      v.insert(edit, p, ''.join(new_lines))


class UnmakeMultiLineMacroCommand(sublime_plugin.TextCommand):
  def run(self, edit):
    v = self.view
    ruler_size = 80
    regions = [ s for s in self.view.sel() if not s.empty() ]

    if len(regions) == 0:
      return

    for region in regions:
      region = v.full_line(region)
      new_lines = []

      lines = v.split_by_newlines(region)
      for i, line in enumerate(lines):
        s = v.substr(line)
        if (i < len(lines)-1):
          s = s.rstrip()
          if len(s) > 0 and s[-1] == '\\':
            s = s[:-1].rstrip() + '\n'
          else:
            s += '\n'
        else:
          s += '\n'
        new_lines.append(s)

      p = region.begin()
      v.erase(edit, region)
      v.insert(edit, p, ''.join(new_lines))