How to implement collapsible sidebar with QSplitter that can be toggled with a button

tsup

I am trying to implement a type of collapsible sidebar with a QSplitter and a QButton that collapses/expands the sidebar (the leftmost widget in my QSplitter. However, I am having problem to make the "sidebar" collapse to the width of the button for collapse/expand. I tried void QSplitter::setSizes(const QList<int> &list) and I do not even remember what else, but up to now I was not able to figure out how to do it. Does anybody have an idea, what is missing?

This is my code:

// main.cpp
#include "mainwindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

// mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

class QSplitter;
class QPushButton;
class QVBoxLayout;
class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private slots:
    void collapseExpand(bool checked);

private:
    QVBoxLayout* verticalLayout;
    QPushButton * button;
    QString buttonText;
    QSplitter * splitter;
};
#endif // MAINWINDOW_H

//mainwindow.cpp
#include "mainwindow.h"

#include <QDebug>
#include <QListView>
#include <QLabel>
#include <QSplitter>
#include <QVBoxLayout>
#include <QHBoxLayout>
#include <QPushButton>
#include <QIcon>
#include <QSpacerItem>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent),
      buttonText("Collapse")
{
    QWidget* cWidget = new QWidget(this);
    verticalLayout = new QVBoxLayout(cWidget);
    verticalLayout->setObjectName("verticalLayout");

    button = new QPushButton(QIcon("apple.jpg"), buttonText, cWidget);
    button->setCheckable(true);
    button->setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Fixed);
    QSpacerItem* spacerItem = new QSpacerItem(1, 1, QSizePolicy::Fixed, QSizePolicy::MinimumExpanding);

    verticalLayout->addWidget(button);
    verticalLayout->addWidget(new QLabel("This is the first label which is very long"));
    verticalLayout->addWidget(new QLabel("This is the second label which is very long"));
    verticalLayout->addWidget(new QLabel("This is the third label which is very long"));
    verticalLayout->addWidget(new QLabel("This is another label that is very long"));
    verticalLayout->addItem(spacerItem);

    splitter = new QSplitter(this);    
    QLabel * myLabel = new QLabel("My label");
    setCentralWidget(splitter);
    splitter->addWidget(cWidget);
    splitter->addWidget(myLabel);
    splitter->setCollapsible(0, false);

    for (int i=0; i<splitter->sizes().count(); i++) {
        splitter->setStretchFactor(i, 0);
    }

    QObject::connect(button, &QPushButton::clicked, this, &MainWindow::collapseExpand);
}

MainWindow::~MainWindow()
{
}

void MainWindow::collapseExpand(bool checked)
{
    for (int i = 0; i < verticalLayout->count(); ++i) {
        QWidget * wdg = verticalLayout->itemAt(i)->widget();
        if (wdg && button != wdg) {
            wdg->setVisible(!checked);
        }
    }
    if (checked) {
        button->setText("");
    } else {
        button->setText(buttonText);
    }
}

Zbigniew-Sch

I use the following and it works:
pcoSplitter->setSizes({ pcoSplitter->size().width(), 0 });