[Sotilrac]

Summary

Adds a background_blur profile option that requests KDE KWin to blur the content behind transparent Terminator windows, creating a frosted-glass effect.

When background_blur = True and background_type is transparent or image, Terminator sets the _KDE_NET_WM_BLUR_BEHIND_REGION X11 window property via ctypes/libX11. KWin reads this property and applies its blur desktop effect behind the window.

Addresses Issue #116, but only for KDE.

Changes

• config.py: Added background_blur: False to profile defaults
• window.py: Added set_blur_behind() method (ctypes X11 property) and on_window_realize signal to apply on startup
• terminator.py: Wired blur into the reconfigure cycle so toggling the preference takes effect immediately
• prefseditor.py: Added checkbox init, callback, and sensitivity logic
• preferences.glade: Added "Blur background (KDE)" checkbox in the Background tab

Scope

• KDE KWin on X11: Full support via window property hint
• Picom/other X11 compositors: Property is safely ignored; users configure blur on the compositor side
• Wayland: Not implemented
• GNOME/Mutter: No per-window blur support in this compositor
• Default off, zero-cost when disabled, fails silently on unsupported setups

Config example

[profiles]
  [[default]]
    background_type = transparent
    background_darkness = 0.8
    background_blur = True

Testing

Tested on KDE Plasma / X11 with KWin blur desktop effect enabled. Verify with:

xprop -name Terminator | grep BLUR
# Should show: _KDE_NET_WM_BLUR_BEHIND_REGION(CARDINAL) = 0

[mattrose]

I don't have a KDE env to test this on, but this all looks good.