@SGaist thank you, I took QFormLayout into account.
@VRonin also thank you!
I can not believe that it would take so much code to get this done...
After starting over and over again I came up with this:

GeneralTab::GeneralTab(QWidget *parent) :QWidget(parent) { QLineEdit *lineEdit = new QLineEdit("/dev/video0"); QGroupBox *groupBox = new QGroupBox("Settings",this); groupBox->setSizePolicy(QSizePolicy::Expanding,QSizePolicy::Expanding); QFormLayout *formLayout = new QFormLayout(groupBox); formLayout->addRow("Video Device: ",lineEdit); }

and this looks exactly what I wanted, two widgets with a nice group box border sized to minimal space usage:
https://pauledd.files.wordpress.com/2016/08/pat4.png
I dont really know If this code is correct or might produce trouble but at least I dont find any errors at the moment.

@NIXIN
have you set QScrollArea's widgetResizeable property set to true?
If not it should be enough to resize the QScrollArea's content widget to it's sizeHint.

@Wieland
Ah. thank you.
Ok, you are right - spacer wont do it.
He could set Alignment to right. (for edit)
Then they stay same with all the time.
Not sure its 100% the wanted effect?
https://www.dropbox.com/s/px3t6ir6d767nn7/keepright.zip?dl=0

@Bart_Vandewoestyne

I see you used a QVBoxLayout, but if I understand things correctly, it could've as well been a QHBoxLayout or QGridLayout because there's only one widget added?

Yes of course, you can use whatever layout suits your needs. Also there is no restriction that you have to put one single widget in it, it can as easily accomodate many child widgets. QMainWindow is bit different in that respect, as it doesn't have a layout itself, but instead relies on a central widget (the client area) to do the laying out. I hope that clears things. :)

@SGaist I am just using the .ui (Qt Designer).

@marlenet15

instructionsScrollArea1 and ReplaceNow() should be
in same object or same file at least.

that what scope means.

so where is instructionsScrollArea1 declared and where
is void ReplaceNow() ?

Also
the * in
removeWidget(*instructionsScrollArea1);
is wrong.

If possible,post whole code here and its easier for us to help.

Hi,

You can add a stretch before or after the button so it will be pushed against a border.

For your second question, you can again use the stretch like described here

Hi
Checkbox is a QAbstractButton child.
I think QButtonGroup is the one doing the real work of "exclusive" so I wonder if its possible to
create a child of QButtonGroup and teach it to handle new types.
But for QGroupBox, I did not trip over anything that suggest it can use another QButtonGroup. :(

Hi, and thank you.

For improve appearance might to add it

"QGroupBox {margin-bottom: 3px;}" "QGroupBox::title { subcontrol-position: bottom; " " top: 3px; }"

I mean't: call the addStretch method form QXXXLayout