mouse wheel zooming is not well controlled, can't recover

I often use CTRL+mousewheel to zoom in web browsers and it works well. However when using the Arduino IDE there are big problems, it zooms erratically and jumps in and out almost randomly and recently it zoomed very far out and I could not get back to the default zoom in the output window, and it didn't reset when I restarted the IDE. How do you change the output window font size??

Are you using Arduino IDE 1.8.5? A previous IDE version allowed you to set the font size to 0 via the mouse wheel shortcut, which caused some problems but that has since been fixed.

Yes, it's 1.8.5 Effectively I can't use mouse controlled zooming, I am running typical Win10 64 home with a typical mouse.

Well all I can say is it works fine for me on Window 10, Arduino IDE 1.8.5. You can also change the font via File > Preference > Editor Font Size or Edit > Increase/Decrease Font Size. Ctrl+minus is the keyboard shortcut for decreasing the font size but they haven't been able to get the Ctrl+plus keyboard shortcut for increasing the font size working on Windows.