Qt DoubleSpin Box value changed slot has called twice

[Wael11]

The double call to slot happened in my case only with a breakpoint in the slot function, otherwise it is called once only. The second call was triggered by a timer event

[JonB]

@Wael11
For anyone reading this: This is known behaviour, which I stumbled across a long time ago and it was infuriating.

With a QSpinbox Qt Internal code uses a timer on clicks/presses. If you step through in debugger you exceed the timeout and get bad/double behaviour.

Simplest: change all connect() to QSpinbox click/key to pass Qt::QueuedConnection as last parameter for connection type, not default Qt::DirectConnection. Now you can use debugger breakpoints and all will be well. I wrote a method to connect all my spinboxes like this.