Qt QHboxLayout cell size ssues

Question

For those of you who haven't been reading my Qt questoins, I am learning Qt for a project. I have only limited experience with GUI design at all, and not in Qt.

I've got a horizontal layout that I want to populate with some buttons. I can feed these buttons in just fine, but my formerly-square buttons are stretched horizontally to take up more space.

I want to let the layout manager determine the best way to size these buttons, but I also want their original proportions to remain intact. For instance, if I start would with 32X32 buttons that need to shrink to fit all of them in the layout, I want them to shrink proportionally so that the width to height scale is maintained. 20X20, 16X16, 12X12 would all be just fine, but 24X16 would be an example of dimensions that are unacceptable.

I've tinkered with size policies on the buttons and stretch options. I'm not seeing, even after reading the QPushButton and QHboxLayout classes how to do this. How is it accomplished?

Thanks.

Answer 1

As long as I understand the question correctly, I think what you want is QBoxLayout::addStretch(). This will add a spacer object that fills the unused space. So the buttons will have their ideal size and the spacer will fill the rest. You can try experimenting with this in Designer, it's easier than the write/compile/run cycle.

Answer 2

You should take a look at the answers to this question. This is a recap of my answer there.

You need to create a custom derivative of QLayoutItem, which overrides bool hasHeightForWidth() and int heightForWidth( int width ) to preserve the aspect ratio. You could either pass the button in and query it, or you could just set the ratio directly. You'll also need to make sure the widget() function returns a pointer to the proper button.

Once that is done, you can add a layout item to a layout in the same manner you would a widget. So when your button gets added, change it to use your custom layout item class.

I haven't actually tested any of this, so it is a theoretical solution at this point. I don't know of any way to do this solution through designer, if that was desired.