Improve transparency script

Transparency gets reset when the script is terminated.
Added command line option to set transparency strength without changing
the script.
Added support for multiple displays.

contrib/inactive-windows-transparency.py

@@ -3,26 +3,62 @@
 # This script requires i3ipc-python package (install it from a system package manager
 # or pip).
 # It makes inactive windows transparent. Use `transparency_val` variable to control
-# transparency strength in range of 0…1.
+# transparency strength in range of 0…1 or use the command line argument -o.
 
+import argparse
 import i3ipc
+import signal
+import sys
 
-transparency_val = '0.8';
-ipc              = i3ipc.Connection()
-prev_focused     = None
 
-for window in ipc.get_tree():
-    if window.focused:
-        prev_focused = window
-    else:
-        window.command('opacity ' + transparency_val)
-
-def on_window_focus(ipc, focused):
+def on_window_focus(ipc, event):
     global prev_focused
-    if focused.container.id != prev_focused.id: # https://github.com/swaywm/sway/issues/2859
-        focused.container.command('opacity 1')
-        prev_focused.command('opacity ' + transparency_val)
-        prev_focused = focused.container
+    global prev_workspace
 
-ipc.on("window::focus", on_window_focus)
-ipc.main()
+    focused = event.container
+    workspace = ipc.get_tree().find_focused().workspace().num
+
+    if focused.id != prev_focused.id:  # https://github.com/swaywm/sway/issues/2859
+        focused.command("opacity 1")
+        if workspace == prev_workspace:
+            prev_focused.command("opacity " + transparency_val)
+        prev_focused = focused
+        prev_workspace = workspace
+
+
+def remove_opacity(ipc):
+    for workspace in ipc.get_tree().workspaces():
+        for w in workspace:
+            w.command("opacity 1")
+    ipc.main_quit()
+    sys.exit(0)
+
+
+if __name__ == "__main__":
+    transparency_val = "0.80"
+
+    parser = argparse.ArgumentParser(
+        description="This script allows you to set the transparency of unfocused windows in sway."
+    )
+    parser.add_argument(
+        "--opacity",
+        "-o",
+        type=str,
+        default=transparency_val,
+        help="set opacity value in range 0...1",
+    )
+    args = parser.parse_args()
+
+    ipc = i3ipc.Connection()
+    prev_focused = None
+    prev_workspace = ipc.get_tree().find_focused().workspace().num
+
+    for window in ipc.get_tree():
+        if window.focused:
+            prev_focused = window
+        else:
+            window.command("opacity " + args.opacity)
+    for sig in [signal.SIGINT, signal.SIGTERM]:
+        signal.signal(sig, lambda signal, frame: remove_opacity(ipc))
+    ipc.on("window::focus", on_window_focus)
+    ipc.main()