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.

[wysota]

Use QLayout::setSizeConstraint(). If in doubt, search the forum for the method name, there has recently been a thread about the same problem.

[Dauntless]

Thank you, I search and found this thread regarding the same issue. But I still don't know why the window doesn't shrink back .

I made this little project, maybe you can tell me what I forget to do:

main.cpp:

#include <QtGui/QApplication>
#include "testclass.h"
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    TestClass w;
    w.show();
    a.connect(&a, SIGNAL(lastWindowClosed()), &a, SLOT(quit()));
    return a.exec();
}

#include <QtGui/QApplication>
#include "testclass.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    TestClass w;
    w.show();
    a.connect(&a, SIGNAL(lastWindowClosed()), &a, SLOT(quit()));
    return a.exec();
}

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testclass.h

#ifndef TESTCLASS_H
#define TESTCLASS_H
 
#include <QtGui/QMainWindow>
#include <QtGui/QWidget>
#include <QtGui/QVBoxLayout>
#include <QtGui/QHBoxLayout>
#include <QtGui/QLabel>
#include <QtGui/QPushButton>
#include <QtGui/QCheckBox>
 
class TestClass : public QMainWindow
{
    Q_OBJECT
 
public:
    TestClass(QWidget *parent = 0, Qt::WFlags flags = 0);
    ~TestClass();
 
private:
	QWidget *mainWidget;
	QVBoxLayout *mainLayout;
 
	QWidget *topWidget;
	QHBoxLayout *topLayout;
	QLabel *topLabel;
	QPushButton *moreButton;
 
	QWidget *middleWidget;
	QVBoxLayout *middleLayout;
	QLabel *middleLabel;
	QCheckBox *checkBox;
 
	QWidget *bottomWidget;
	QVBoxLayout *bottomLayout;
	QLabel *bottomLabel;
};
 
#endif // TESTCLASS_H

#ifndef TESTCLASS_H
#define TESTCLASS_H

#include <QtGui/QMainWindow>
#include <QtGui/QWidget>
#include <QtGui/QVBoxLayout>
#include <QtGui/QHBoxLayout>
#include <QtGui/QLabel>
#include <QtGui/QPushButton>
#include <QtGui/QCheckBox>

class TestClass : public QMainWindow
{
    Q_OBJECT

public:
    TestClass(QWidget *parent = 0, Qt::WFlags flags = 0);
    ~TestClass();

private:
	QWidget *mainWidget;
	QVBoxLayout *mainLayout;

	QWidget *topWidget;
	QHBoxLayout *topLayout;
	QLabel *topLabel;
	QPushButton *moreButton;

	QWidget *middleWidget;
	QVBoxLayout *middleLayout;
	QLabel *middleLabel;
	QCheckBox *checkBox;

	QWidget *bottomWidget;
	QVBoxLayout *bottomLayout;
	QLabel *bottomLabel;
};

#endif // TESTCLASS_H

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testclass.cpp

#include "testclass.h"
 
TestClass::TestClass(QWidget *parent, Qt::WFlags flags)
    : QMainWindow(parent, flags)
{
	mainWidget = new QWidget(this);
	mainLayout = new QVBoxLayout(mainWidget);
 
	//topWidget
 
	topWidget = new QWidget(mainWidget);
	topLayout = new QHBoxLayout(topWidget);
 
	topLabel = new QLabel(topWidget);
	topLabel->setText("This is the top widget");
	moreButton = new QPushButton(topWidget);
	moreButton->setText("Press to see the middle widget");
	moreButton->setCheckable(true);
 
	topLayout->setSizeConstraint(QLayout::SetFixedSize);
	topLayout->addWidget(topLabel);
	topLayout->addWidget(moreButton);
 
	//middleWidget
 
	middleWidget = new QWidget(mainWidget);
	middleLayout = new QVBoxLayout(middleWidget);
 
	middleLabel = new QLabel(middleWidget);
	middleLabel->setText("This is the middle widget");
	checkBox = new QCheckBox(middleWidget);
	checkBox->setText("Extra Option");
 
	middleLayout->setSizeConstraint(QLayout::SetFixedSize);
	middleLayout->addWidget(middleLabel);
	middleLayout->addWidget(checkBox);
 
	//bottomWidget
 
	bottomWidget = new QWidget(mainWidget);
	bottomLayout = new QVBoxLayout(bottomWidget);
 
	bottomLabel = new QLabel(bottomWidget);
	bottomLabel->setText("This is the bottom widget");
 
	bottomLayout->setSizeConstraint(QLayout::SetFixedSize);
	bottomLayout->addWidget(bottomLabel);
 
	//mainLayout
 
	mainLayout->setSizeConstraint(QLayout::SetFixedSize);
	mainLayout->addWidget(topWidget);
	mainLayout->addWidget(middleWidget);
	mainLayout->addWidget(bottomWidget);
 
	middleWidget->hide();
 
	connect(moreButton, SIGNAL(toggled(bool)), 
			middleWidget, SLOT(setVisible(bool))); 
 
	QSize size(0, 0);
	size = size.expandedTo(mainWidget->minimumSize());
    resize(size);
 
	setCentralWidget(mainWidget);
	setWindowTitle("Testing middleWidget Expansion");	
 
}
 
TestClass::~TestClass()
{
 
}

#include "testclass.h"

TestClass::TestClass(QWidget *parent, Qt::WFlags flags)
    : QMainWindow(parent, flags)
{
	mainWidget = new QWidget(this);
	mainLayout = new QVBoxLayout(mainWidget);

	//topWidget

	topWidget = new QWidget(mainWidget);
	topLayout = new QHBoxLayout(topWidget);

	topLabel = new QLabel(topWidget);
	topLabel->setText("This is the top widget");
	moreButton = new QPushButton(topWidget);
	moreButton->setText("Press to see the middle widget");
	moreButton->setCheckable(true);

	topLayout->setSizeConstraint(QLayout::SetFixedSize);
	topLayout->addWidget(topLabel);
	topLayout->addWidget(moreButton);

	//middleWidget

	middleWidget = new QWidget(mainWidget);
	middleLayout = new QVBoxLayout(middleWidget);

	middleLabel = new QLabel(middleWidget);
	middleLabel->setText("This is the middle widget");
	checkBox = new QCheckBox(middleWidget);
	checkBox->setText("Extra Option");

	middleLayout->setSizeConstraint(QLayout::SetFixedSize);
	middleLayout->addWidget(middleLabel);
	middleLayout->addWidget(checkBox);

	//bottomWidget

	bottomWidget = new QWidget(mainWidget);
	bottomLayout = new QVBoxLayout(bottomWidget);

	bottomLabel = new QLabel(bottomWidget);
	bottomLabel->setText("This is the bottom widget");

	bottomLayout->setSizeConstraint(QLayout::SetFixedSize);
	bottomLayout->addWidget(bottomLabel);

	//mainLayout

	mainLayout->setSizeConstraint(QLayout::SetFixedSize);
	mainLayout->addWidget(topWidget);
	mainLayout->addWidget(middleWidget);
	mainLayout->addWidget(bottomWidget);

	middleWidget->hide();

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

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

	setCentralWidget(mainWidget);
	setWindowTitle("Testing middleWidget Expansion");	

}

TestClass::~TestClass()
{

}

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The window size doesn't shrink back when I hide again the middleWidget.

I even tried to add a public slot:

void TestClass::makeSmall(bool r)
{
	middleWidget->setVisible(r);
 
	QSize size(0, 0);
	size = size.expandedTo(mainWidget->minimumSize());
    resize(size);
}

void TestClass::makeSmall(bool r)
{
	middleWidget->setVisible(r);

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

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and use

connect(moreButton, SIGNAL(toggled(bool)),
			this, SLOT(makeSmall(bool)));

connect(moreButton, SIGNAL(toggled(bool)),
			this, SLOT(makeSmall(bool)));

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insead but it doesn't work.

Thank you for your time.

[wysota]

The widget has to have the default size set to the size without the additional widgets. You should reimplement sizeHint() or do something simmilar.