Expanding and hiding a widget

[Dauntless]

First I want to thank you for your time, I’m new to Qt and I hope I won’t bother you but I have a simple question and I hope I can get a simple answer.

The circumstances are the following:
I made a QmainWindow
That has 1+3 widgets:

// a main widget
QWidget *centralWidget;
//with a main Layout
QGridLayout *mainLayout;

//a top Widget (child of centralWidget)
QWidget *topWidget;
//with a top Layout
QGridLayout *topLayout;
//[…]more childWidgets of topWidget,
//including a moreButton that when I press it expands middle Widget

//a middle Widget (child of centralWidget)
QWidget *middleWidget;
//with a middle Layout
QVBoxLayout *middleLayout;
//[…]more childWidgets of middleWidget;

//a bottom Widget (child of centralWidget)
QWidget * bottom Widget;
//with a bottom Layout
QHBoxLayout * bottom Layout;
//[…]more childWidgets of bottom Widget;

So I hide the middleWidget->hide() in the constructor;

Then I resize the window so it will start “compressed”

QSize size(0, 0);
size = size.expandedTo(mainLayout->minimumSize());
resize(size);

QSize size(0, 0);
size = size.expandedTo(mainLayout->minimumSize());
resize(size);

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I connect the more button

connect(moreButton, SIGNAL(toggled(bool)), 
	  middleWidget, SLOT(setVisible(bool)));

connect(moreButton, SIGNAL(toggled(bool)), 
	  middleWidget, SLOT(setVisible(bool)));

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and it works well but the problem is that after I made it visible and I hide again the middleWidget the window doesn’t compress back, the MainLayout just covers the empty space left by the middleWidget.

I even made a SLOT makeSmall that I connected to the moreButton so that it will
compress again but id doesn't change the size.

QSize size(0, 0);
size = size.expandedTo(mainLayout->minimumSize());
this->resize(size);

QSize size(0, 0);
size = size.expandedTo(mainLayout->minimumSize());
this->resize(size);

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If I make the middleLayout visible again the window will keep the same size.

I want to make the window shrink when I hide the widget but I don't know how how to do it every time I hide the widget (as I sad it compresses at start but afterwards it remains big).

Sorry if the post is a bit confusing.