Sublime Text - Extended Add Line command, allowing column selection even on shorter lines.

Default (OSX).sublime-keymap

[
  { "keys": ["ctrl+alt+up"], "command": "smart_select_lines", "args": {"forward": false} },
  { "keys": ["ctrl+alt+down"], "command": "smart_select_lines", "args": {"forward": true} }
]

smart_select_lines_command.py

import sublime_plugin
from sublime import Region


class SmartSelectLinesCommand(sublime_plugin.TextCommand):
    """
        Upgraded version of default Add Previous/Next Line commands
        Pads new lines with empty spaces to allow column editing
        as if there are virtual spaces.
    """

    def run(self, edit, forward):
        region = self.view.sel()[-1 if forward else 0]
        caret_position = region.b
        row_position, col_position = self.view.rowcol(caret_position)

        total_rows = self.view.rowcol(self.view.size())[0]
        skip_on_row = [0, total_rows]

        if(row_position == skip_on_row[forward]):
            return

        curr_line_region = self.view.line(caret_position)

        if forward:
            next_line_offset = (curr_line_region.size() - col_position + 1)
        else:
            next_line_offset = -(col_position + 1)

        next_line_region = self.view.line(caret_position + next_line_offset)
        diff = col_position - next_line_region.size()

        if diff > 0:
            fill = diff * ' '
            self.view.insert(edit, next_line_region.end(), fill)

        new_caret_position = next_line_region.begin() + col_position
        new_region = Region(new_caret_position, new_caret_position)

        self.view.sel().add(new_region)

caret_position = region.begin() if region.empty() else (region.a if region.a < region.b else region.b)
is actually
caret_position = region.begin()

Thanks for letting me know.
I had something in mind right there but probably didn't get the api documentation right.
Anyway, what i wanted to address there was extending the selection even if the first region was not empty.
I was falling back to the default 'select_lines' command for region placement, which is not working correctly in the case i wanted to address.
Here comes the update.

Works perfectly in Sublime Text 3 :o)

Thank you for this neat piece of software :o)

You can enhance this to extend selections up and down as well as just the caret:

change:

    caret_position = region.b

to:

    caret_position = region.end()
    caret_offset   = region.b - caret_position
    caret_size = region.a - region.b

and also change:

    new_region = Region(new_caret_position, new_caret_position)

to:

    new_region = Region( new_caret_position+caret_offset+caret_size, new_caret_position+caret_offset )