@Bonnie Thank you for pointing me in the right direction. I turns out the issue wasn't height, or min-height, but rather an inherited padding, that just happened to make it look like it was expanding to the full height of the QHBoxLayout.

@mpergand This works!! Thank you!!
Also resize(1,1) also works!

Great!

@Chris-Kawa, oh, pardon my blindness, it really works. I found that the stylesheet is resetting the width of the button in my case.

Thank you for the answer.
Setting a child did enable the layout selection. I don't understand the logic behind that at all but ok.

QcmEntryGuess are QWidget I've created on the side. They're only a QLabel nested in two layout 12d3bbf3-2642-4ef6-90a4-71ae4535d2d8-image.png

Althought my QGridLayout is still only consisted of one row. I'm probably missunderstanding one of its property
a3d87a05-d1dc-40b4-a478-a67c0a2a0256-image.png

@Pl45m4
"That's not possible. A widget can only have one base layout at a time."
This is what I want to know, I will look for another solution, probably I will use absolute positioning inside centralWidget.

"Why not use a HBox layout, move all your current stuff (the VBox layout) to the left and use the right for your popup widget?"
Cuse I can't change overall positioning in this app. My popup notification must pop above all contents and not to affect existing content. So this widget is not visible most of the time, under some circumstances it becomes wisible, and after few seconds it will disappeare.

@SGaist Yes Thank! It all makes sense now!

Someone on StackOverflow gave me the key that I needed. I was not setting a minimumSize for the TimeLines and as a result it was not being given enough space in the verticalLayout. Thanks for all the help!