Use of undeclared identifier 'setMode'

[charry]

the error is when I use QT6.2 run the code.

case QEvent::ApplicationPaletteChange: {
setMode(setMode);

[ChrisW67]

You have a compile-time error, not a run-time one.

The undisclosed class that this bit of code appears in does not have a setMode() function in scope (member or global) or there is no variable in scope named setMode. I am not aware of any commonly used Qt class with such a method.

In any case, having a function and variable of the same name is odd/broken.