Athanasius / tk-radio-buttons

Test code for a tk radio button Windows scaling bug

Introduction

During development of the Elite Dangerous Market Connector (EDMC) project we were made aware of an issue when using Windows 10 UI Scaling. This appears to be a Tk bug with python tkinter.ttk.RadioButton elements when using some level of UI scaling if the executable involved has the dpiAware manifest setting set true.

Windows UI Scaling

Some users with high resolution/DPI monitors don't want a small application window so they make use of a Windows 10 feature to scale their UI up.

Specifically this is accessed via:

1. Right-click desktop.
2. Select Display settings.
3. Ensure the desired display is selected.
4. Scroll down to Scale and layout.
5. Change the scaling option Change the size of text, apps and other items to e.g. 150%.

Any application run after changing this setting will respect that new setting.

dpiAware manifest option

There is a manifest option you can set on Windows executables, as per Application Manifests, which informs the OS that the application is DPI aware.

The effect of this in practice is that, when used in conjunction with UI Scaling as documented above, the rendered text and other UI elements will be much sharper than without it.

The EDMC application is processed into a .exe using py2exe upon which the manifest is then set.

The bug

Unfortunately when you have some UI Scaling set along with dpiAware set true you might find that radio buttons are mis-rendered. The usual manifestation of this is that the last button will be properly sized initially, with the others being undersized. If you even only mouse-over the 'correct' radio button it will then become undersized as well.

This does not occur either without UI Scaling active (have it set to 100%), or if dpiAware is not set true. So far all other UI elements appear to always scale correctly with the combination of UI Scaling > 100% and dpiAware true.

Reproducing the bug

In order to more simply reproduce the bug the edmc.py script in this repository was created. In EDMC we observe this in the Settings/Preferences dialog, so this edmc.py script re-creates the same circumstances with a main window that has a File menu with a Prefs entry that then opens a new ttk.TopLevel window to contain a ttk.Notebook which then contains a frame with the test ttk.RadioButton elements.

As the bug depends on dpiAware being true you can't just run the script with a normal python.exe. Instead you will need to:

1. Make a copy of python.exe into your clone of this project.

   copy "c:\Program Files (x86)\Python39-32\python.exe" python-390.exe

2. Use mt.exe to set an alternate manifest on it:

   "c:\Program Files (x86)\Windows Kits\10\bin\10.0.18362.0\x86\mt.exe" -manifest python_dpiAware.manifest -outputresource:python-390.exe

   That manifest file was produced by using:

   "c:\Program Files (x86)\Windows Kits\10\bin\10.0.18362.0\x86\mt.exe " -inputresource:python-390.exe -out:python.manifest

   to extract the default manifest, then adding:

   <dpiAware xmlns="http://schemas.microsoft.com/SMI/2005/WindowsSettings">true</dpiAware>

   to the <windowsSettings> section.

   mt.exe comes from the Windows SDK, such as Windows 10 SDK, version 2004 (10.0.19041.0).

3. Now you need to set PYTHONPATH so that your copied python.exe can find its libraries.

   1. Run the actually installed python.exe (so change directory out of this project).

      python.exe -i
      >>> import sys
      >>> sys.path
      

   2. Then use set PYTHONPATH=<that output without the [] brackets>

   The file python-390-local-edmc.bat contains an example of this, but specific to my setup.

4. Run the script either with an edited version of python-390-local-edmc.bat or directly with:

   python-390.exe edmc.py

Now use the File menu and select the Prefs option to open the additional window and observe the state of the radio buttons. You should see something like tk-radio-buttons_python-exe_dpiAware_edmc.png shows.