Alternative to QWidget's "Promote to" feature?

[Leutzig]

Hi Forum,

I'm having this weird problem with my color picker that I will eventually use to control RGB LEDs. I found a color wheel (see link) for my project that I wanted to connect to my palette so that when I change the color wheel's current color, the palette will display that color (updatePalette is called from the color wheel's MouseMoveEvent function). But this only works when the color wheel is given its own window (using show() in main). Whenever I try using the QWidget's "Promote to" feature, the program instantly crashes when I move the color wheel cursor.

You can check out the attached pictures for further understanding. But I'm mostly interested in hearing if there are alternative ways to add this color wheel to my UI without having it as a separate window or without using the QWidget's "Promote to" feature?

Color wheel with colorwheel.cpp and colorwheel.h:
https://forum.qt.io/topic/19261/colorwheel

//Leutzig