I think these … “noobs” just haven’t spent the time to truly understand why they are asking questions at all. wx.stc.EVT_STC_UPDATEUI or *_MODIFIED would scare the shit out of most listening folks … Folks that do have the knowledge to build a complete undo/redo structure do not respond here mainly… Because…
To see the effect of yielding as you do run these two modules and move them around on the screen as the counter is running down 
fs_timer_thread.py (1.8 KB) fs_timer_yield.py (1.4 KB)