Firstly, apologies about the original message: rereading it, it was a bit random and written in a very illogical order.

> Are you the Elisha Paine that suggested the original fix?

Yes (though I like to think I have somewhat progressed in 2 years!). The reason I am E. Paine here is solely because I prefer if Google did not index my entire life ;-) On the subject, I would like to thank you Terry 1. for all your work on IDLE and CPython more generally and 2. because you were my first experience of the devs and were very patient despite my clear incompetence (now and then!)

> tk scales on startup

When first writing this issue I saw that Tk was calling GetDeviceCaps for LOGPIXELSX/LOGPIXELSY. The Windows docs say this:
"Number of pixels per logical inch along the screen width..."

I (incorrectly) took this to mean it disregards the system dpi and returns the dpi for the monitor. In reality, increasing the zoom factor causes this value to increase, meaning Windows (in effect) declares a smaller monitor size (certainly in later versions of Windows - whether this is true in older versions I don't know).

I have checked and the scale value increases correctly with a change in system dpi (hence meaning IDLE also scales correctly).

> IDLE ... remains the same size regardless of what setting the user chooses as their scale factor

Apologies, this is complete rubbish (I think I was comparing it to the increase in size on the settings window rather than actually paying proper attention to IDLE).

I have closed this issue as not a bug.