IDLE is blurry on High DPI Windows, because IDLE is not DPI aware. IDLE should be made to be DPI aware so that the text is more readable.

This is not an IDLE issue, and probably not a tkinter issue.  The display of characters on a screen is done by the OS font software under direction of tcl/tk.

What OS are you running and what version of Tk (see IDLE -> Help -> About IDLE)?

IDLE 3.5.1 on Windows 10

Westly, #31500 changed font scaling for IDLE on high DPI screens.  It also removed some hard-coding of frame sizes in terms of pixels.  Does anything look better for you with current IDLE (3.6.5, 3.7.0)?

Still blurry with 3.6.5 on Win 10 with a 2560x1600 monitor at 125% scaling (I compared it to 2.7.15, they looked identical).  If I go to the Windows properties for pythonw.exe and turn on "Override high DPI scaling behavior" it's nice and sharp.

Do any of the Windows experts know what "Override high DPI scaling behavior" on properties does?  Does it call SetProcessDpiAwareness?  It seems so. The answer would have implications for #33656 (which is about fixing this issue in IDLE, as Westly originally requested here).

This setting is on the popup when one clicks [Change high DPI settings] on the Compatibility tab.  Eric, there is a dropdown with 3 possible overrides.  Application (default), System, System [Enhanced].  Which one did you use?

In my experiments, 'Application has the same effect as SetProcessDpiAwareness(1), while 'System' is the same as SetProcessDpiAwareness(0).  I expected this from what I posted on #33656.

Since the properties settings may or not be correct for all graphics packages, but will likely be correct for all tk and tkinter apps, I think tkinter should perhaps be modified.  The question is whether SetProcessDpiAwareness(1) is correct (for tk and tkinter) for all monitors.  I suspect so but don't know for sure.

I used the default Application setting.

Elisha Paine, who prompted #33656 by posting the SetProcessDpiAwareness(1) fix to the idledev list, wrote to me that pyglet and probably pygame have similar issues.

I wonder if Python should be installed with the 'application' setting, or if DPI adjustment should be discussed in the Windows section of the Using manual. https://docs.python.org/3/using/windows.html

The fix for IDLE on Windows made it into 3.6.6rc1 and 3.7.0rc1.

Changing the python.exe and pythonw.exe default dpi settings is a possible issue for 3.8, and should have Steve.Dower nosy.