mango: show focused window next to tags, fix mmsg lookup, 0.15.x compat

- new focused-window block ({icon} {app_id} - {title}) driven by the
  active_client field of mmsg watch all-monitors (mangowm >= 0.14)
- resolve program icons via freedesktop icon themes/.desktop files
  (new icon module, cairo png feature, cached per app_id)
- new show_focused_window config option (default true)
- run mmsg from PATH instead of hardcoded /usr/bin/mmsg (broken on NixOS)
- handle null active_client fields (no focused client) without failing
  to parse the whole event
- drop stale TODO comment and unused variable in mango provider
- add .justfile run recipe exporting MANGO_INSTANCE_SIGNATURE

1 files changed, 1 insertions, 0 deletions

diff --git a/src/main.rs b/src/main.rs
index 4a86593..b43443c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -8,6 +8,7 @@ mod color;
 mod config;
 mod event_loop;
 mod i3bar_protocol;
+mod icon;
 mod output;
 mod pointer_btn;
 mod protocol;