May I ask how to to do to change the bg color of the parent button of the child button when the child button is pressed, and the bg color of the child button of the parent button when the parent button is pressed?

How-to
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1

May I ask how to to do to change the bg color of the parent button of the child button when the child button is pressed, and the bg color of the child button of the parent button when the parent button is pressed?And release any button all to the default color.

2

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that is a twist on words there isn’t it?

I have to ask this silly question… you have a button inside of another button? How does that even work?

But to simplify your question into “How to change the bg color of a parent object when the child object is pressed”

My response is going to be registering an event callback for LV_EVENT_CLICKED to the child object and in that callback function set the bg color of the parent.