Fixes #470

…ndowing (#485)

* Port TabSwitcher over to libxfce4windowing

This PR ports our TabSwitcher over to libxfce4windowing from using libwnck directly. To facilitate this, considerable amounts of the code was gutted or rewritten, for example wm no longer does any sort of cur_tabs tracking. That is left up to TabSwitcher.

Instead of rebuilding tabswitcher contents every single time we invoke it, we allow it to handle its own state and handle changes based on libxfce4windowing events. Windows are added / removed automatically, workspace handling is done to support show-all-windows function and workspace swapping, and we leverage sort with our recency list and filter to know when to hide items.

* ci: change package name for libxfce4windowing devel

* Port Show Desktop applet to libxfce4windowing

Fixes #471

* Port Workspace applet

Fixes #470

* Fix typo in signal

Co-authored-by: Evan Maddock <[email protected]>

* Use construct on TabSwitcherWindow

Co-authored-by: Evan Maddock <[email protected]>

* Remove unnecessary workspace switch code.

Use warning and document backwards / forwards logic.

* Make TabSwitcherSwitch sub-class Gtk.FlowBoxChild

* Clean up bit mask checking

Co-authored-by: Evan Maddock <[email protected]>

* Use down var already defined

Co-authored-by: Evan Maddock <[email protected]>

* Cleanup extra newline

Co-authored-by: Evan Maddock <[email protected]>

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Co-authored-by: Evan Maddock <[email protected]>