@Garry P Thanks Ivan for the comprehensive reply. I have looked at your feedback issue and raised another (Feedback Case #57361).
Do you have any code you can share about implementing a WndProc? I have experience with declares on macOS but none on Windows.
Thank you for the link to the GetSysColor function. It's really hard to find stuff in the MS API docs!
@Jean-YvesPochez I'll take a look at WFS. Thanks
For the WndProcm there is a good answer in the other thread.
As for the dark mode, I think I ddidnt explain myself, Windows 10 is now divided between the clasic apps (the ones created with xojo) and the new UWP apps.
GetSysColor and the theme messages; WM_SYSCOLORCHANGE, WM_THEMECHANGED, WM_DWMCOLORIZATIONCOLORCHANGED. work with win32 apps.
If you change the UWP dark the setting, it does not send those messages and the GetSysColor will return the exact same colors either in dark or light theme. The win32 color themes is now more used as a high contrast setting.
In the other hand, if you want to make a manual dark theme support, you can use GetSysColor in the light theme and custom colors for the dark theme.
As for your FC, xojo can refuse because dark mode is not intended for Win32 apps like those created by xojo. as a workaround, once you implement the WndProc, you just have to also listen for the WM_WININICHANGE message in windows 10 and then read the Registry key :