Arrange widgets in layout - qt

Question

i want to achieve following layout behavior:
| A | B | | A | |
1) |---- -----| 2) |---- D |
| C | D | | C | |
Align A,B,C,D with each other and allow D to take available space if B is hidden.
I can achieve layout behaviors 1 or 2 with multiple ways. But i cannot seem to find solution to satisfy both of these conditions without removing widgets from layouts and re-adding later when B hides/shows with qt default layouts.
I tried so far:
1) grid layout - when B is hidden, D stays in place. Can align like i want if i will start to track hide-show status of widget B.
2) combinations of hbox and vbox layouts - D will get all space, after B is hidden, but when B is shown - A and B are never aligned. Once again i'll need to rearrange all widgets to achieve behavior i want.
I suppose Grid layout best suited for my purposes, but row span is set in stone when I add widgets.
Is there simple solution i miss?

Answer 1

You could try the following code:
#include <QMainWindow>
#include "ui_mainwindow.h"
class MainWindow : public QMainWindow, public Ui::MainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
};
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
{
setupUi(this);
QWidget *left = new QWidget;
QWidget *right = new QWidget;
QHBoxLayout *hbox = new QHBoxLayout;
QVBoxLayout *vboxLeft = new QVBoxLayout;
QVBoxLayout *vboxRight = new QVBoxLayout;
vboxLeft->addWidget(new QLabel("A"));
vboxLeft->addWidget(new QLabel("C"));
auto b = new QLabel("B");
vboxRight->addWidget(b);
vboxRight->addWidget(new QLabel("D"));
left->setLayout(vboxLeft);
right->setLayout(vboxRight);
hbox->addWidget(left);
hbox->addWidget(right);
centralWidget()->setLayout(hbox);
QAction *toggleB = new QAction("Toggle B");
toggleB->setCheckable(true);
connect(toggleB, &QAction::toggled, this, [=](bool toggled) {
b->setHidden(toggled);
});
mainToolBar->addAction(toggleB);
}
You can toggle as many times as you want, it will keep the layout clean: