[Usability] Drag handles for dialogs and other windows

[Gregory Merchan <merchan phys lsu edu>]

On Microsoft Windows and (iirc) MacOS, resizable dialogs usually have
drag handles in the bottom right corner.

The only widget in Gtk+ that can, without extra hackery, show a drag handle
is GtkStatusbar. Dialogs, of course, should not contain status bars.

Here are the questions for the GUP:

  Should GNOME dialogs and similar resizable windows provide a drag handle?
  How large should the drag handle be?
  Do the HIG spacing guidelines need adjustment for the drag handle?

Once these are answered, the GUP needs to pass a recommendation on to the
Gtk+ team.

At the risk of starting a flame war, I have another question. Right now,
the GtkStatusbar drag handle looks like a few diagonal lines. I've seen
one somewhere (maybe MacOS) that looks like either bumps or holes. What
should these drag handles look like?  (It may be themable. I haven't checked.)

Cheers,
Greg