Re: Question and possibly bugs about string encoding in gtk-perl

On 16.12.2016 20:02, Dominique Dumont wrote:
On Wednesday, 14 December 2016 10:54:16 CET Boyuan Yang wrote:
The original messy output, as indicated in screenshot in the Ubuntu bug,
looks  like treating a latin-1-encoded binary data as UTF-8-encoded data
and showing them anyway.

In more details, the problematic code boils down to:

  my $wnck_screen = Gnome2::Wnck::Screen->get_default;
  my $win= $wnck_screen->get_windows_stacked; # Gnome2::Wnck object
  my $name = $win->get_name;
  my $window_item = Gtk2::ImageMenuItem->new_with_label( $name );

$name contains window name apparently in octet format instead of an utf8
string. As a consequence, the list of windows shown by shutter contains

Yes, Gnome2::Wnck does not do any decoding at all in get_name. This is probably by accident, not by intention, but if you look at what wnck_window_get_name boils down to, <>, you see that it returns UTF8-encoded strings in most cases, but sometimes also strings in X11's compound text encoding, according to <>.

So it seems like the safest bet would be to try to decode the window name from UTF8, and if that fails, try Encode::X11 and its 'x11-compound-text' (Hi Kevin!).

The hacky patch proposed (by me) is using
Encode::_utf8_on() to turn on the internal flag for string and mark it as

And I'm worried that shutter may crash if used in a non-utf8 environment.

After some experimentation, I've come up with a safer solution:

  use 5.12.0;
  use Encode::Locale;
  use Encode qw/decode/;
  # ...
  my $name = decode( 'locale' , $win->get_name);

This works in utf8 locale and is safer than turning utf8 flag on.

It seems like this would fail in a non-UTF8 locale, however, as gnome_wnck_window_get_name seems to always return UTF8 strings, regardless of locale.

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