TOOLS/lua: add script that pauses playback when minimizing the window

Uses functionality that was added a month ago for exactly this purpose.

Fixes #1237.

TOOLS/lua/pause-when-minimize.lua

@@ -0,0 +1,22 @@
+-- This script pauses playback when minimizing the window, and resumes playback
+-- if it's brought back again. If the player was already paused when minimizing,
+-- then try not to mess with the pause state.
+
+-- Note: currently works with X11 only.
+
+local did_minimize = false
+
+mp.observe_property("window-minimized", "bool", function(name, value)
+    local pause = mp.get_property_native("pause")
+    if value == true then
+        if pause == false then
+            mp.set_property_native("pause", true)
+            did_minimize = true
+        end
+    elseif value == false then
+        if did_minimize and (pause == true) then
+            mp.set_property_native("pause", false)
+        end
+        did_minimize = false
+    end
+end)