David T. Lewis uploaded a new version of ST80 to project The Inbox:
http://source.squeak.org/inbox/ST80-dtl.250.mcz

==================== Summary ====================

Name: ST80-dtl.250
Author: dtl
Time: 12 April 2020, 3:57:39.533465 pm
UUID: 427795eb-1858-4bd4-a28f-546b4a95eb62
Ancestors: ST80-eem.249

Do not burn CPU if there is nothing to do. If the ScreenController is the only scheduled controller available, then call interActivityPause before rescheduling it.

=============== Diff against ST80-eem.249 ===============

Item was changed:
  ----- Method: ControlManager>>nextActiveController (in category 'private') -----
  nextActiveController
  	"Answer the controller that would like control.  
  	If there was a click outside the active window, it's the top window
  	that now has the mouse, otherwise it's just the top window."
  
  	(newTopClicked notNil and: [newTopClicked])
  		ifTrue: [newTopClicked := false.
  				^ scheduledControllers 
  					detect: [:aController | aController isControlWanted]
  					ifNone: [scheduledControllers first]]
+ 		ifFalse: [^ scheduledControllers first interActivityPause]!
- 		ifFalse: [^ scheduledControllers first]!