Adding widgets dynamically to layout, causes to them to be misplaced

  • In the third picture of the link, there is a layout selected which is called verticalLayout_Widgets. The widget is supposed to be placed there and only once but that is something I took care with some code.

  • Lifetime Qt Champion

    Why not in designer using the promotion feature ?

  • @SGaist What is the promotion feature?

  • Lifetime Qt Champion

    Promotion feature is a super replace at runtime.
    During design, you say this QWidget should become this type when run.
    Designer will then use the actual type so when app is run, your control is
    used and not the plain widget.

    This allows light integration where you can desgin with your custom widget but do not have to make a full
    plugin for integration.

  • @mrjj I will read about this. I didn't know this thing even existed.

  • What happens it that my widget is now loaded upon startup, while I need it to be loaded if and when the use clicks a checkbox. I guess I wan't clear about the term dynamic loading...

  • Lifetime Qt Champion


    • my widget is now loaded upon startup

    you mean, after you used promotion, they are constructed with the main window
    or where you promoted them ?
    This is expected and often you can just hide them, and then show if enabled in checkbox.
    If you strictly really need only to construct them on demand, you cant use promotion directly.

  • @mrjj Yes, I think so too. Right now I managed to put the widget on the layout with the use of a vertical spacer (enabled and shown here). After the widget is created and shown, the whole window expands a little so the layout and it's widget can be visible.

    The thing is that I can't "resize" the layout(?) and the whole window to it's original, smaller size. It seems that once the layout is "stretched" to show the widget, it stays that way when the widget is deleted. This leaves an ugly void space where the widget was placed.

  • Lifetime Qt Champion

    Normally layouts will "contract". I have yet to experience
    one that leaves a hole if i remove widget. Maybe boxlayout.

  • @mrjj

    Maybe boxlayout.

    You mean I should try boxlayout? Designer doesn't have one though...

    @Global-Moderators Please, correct my title. I meant to write "...causes them to be misplaced".

  • Lifetime Qt Champion

    no, no i mean maybe box layout would / might/perhaps leave a hole but all other layouts would
    contract if you remove a widget.

    There is something else wrong.
    Do you use TakeAt to remove from layout ?
    Its the only valid way to remove a widget.

  • Well, one thing I know is that the custom widget's size constraints had to set to a minimum. It used quite a lot of space so it was centered on top of another layout/widget. Now it's loaded where it should, but after it's deletion there still is a void space.

    That's the code:

    void QtDice::enableUserWidget()
    	userwidget = new UserWidget(this);
    void QtDice::deleteUserWidget()
    	delete userwidget;

    Other suspects could be the main form (i.e. the QtDice qmainwindow) and it's size policies or the vertical spacer. I tried almost every combination and I am out of ideas.

    Do you use TakeAt to remove from layout ?

    Ebook Mastering Qt5, suggested the QLayout::removeWidget, so...

  • Lifetime Qt Champion

    Oh, yes, removeWidget seems better in this case and you do change parent.
    Hmm, i would also suspect spacer.
    Sorry i cant spot it. All seems pretty dandy with code shown.

  • @mrjj Yeah, it's ok, thank you very much!

    For the moment I just create unconditionally the userwidget and all that clicking the checkbox does, is to enable or disable it. But it's always visible.

    It's not what I like, but it gives the functionality I am working on without an ugly ui. Until I find and post what the missing part of this puzzle is, I will leave this as UNSOLVED.

  • Lifetime Qt Champion

    What about hiding it while the condition to use it are not met ?

  • Why use an empty QVBoxLayout as a placeholder for your userwidget? Why not just simply put your userwidget into the layout of your Mainwindow?

    I guess you are using another QVBoxLayout as the Layout of your Mainwindow so you could use:

    m_ui->yourmainlayoutname->insertWidget( 1, userwidget);

    On a sidenote: You don't need to put your textlabel-placeholder for your dice into a QGridLayout too, just put it into your Mainwindow-Layout and maybe set stretch-factors to your likeing.

  • @SGaist One reason is that I want to learn about creating custom widgets or working with spacers and layouts.
    @MCam Aren't the widgets supposed to be -pretty much- always on top of a layout?

  • So, at first the window is at it's most minimum size. After enabling the widget it resizes a little, but after closing the widget again, the window doesn't resize back but rather the QLabel that shows the red dice expands.

    I can't find some way to alter this. I have tried every combination for QLabel about it's SizePolicy but nothing changed.

  • @Petross404_Petros-S
    This is the default behavior of the layout-system here but you can get what you want by readjusting the size of your MainWindow after deleting the userwidget. In your case you have two QWidgets involved: your QtDice-MainWindow and its centralWidget(). So you need to adjust both of them!

    Try adding


    after removing the userwidget.

  • @MCam Thank you, I was using plain adjustSize() that's why it didn't resize. Although there is problem that remains even when resizing both layouts :

    After unmaximising the window, adjustSize gives this result. I will mark the thread as solved because I can make the window to not be able to get maximized, but for completeness shake it would be nice if this result could be avoided.

    Either way, you saved my day and I thank you very much for that :)

Log in to reply

Looks like your connection to Qt Forum was lost, please wait while we try to reconnect.