only some of the widgets are resizing properly

[Yi Gin]

Hi all,
I have created a custom widget, A, which I assign as the central widget.
In its constructor I create and assign to it two other custom widgets - B and C.
in A's constructor I put B and C inside a QVBoxLayout and add this layout to widget A.

When I run the application and resize the window the B widget resizes properly but the C widget does not.
I am attaching the redacted .h files and constructors of all these widgets.

Any help will be appreciated.

A.h:

class A : public QWidget
{
    Q_OBJECT

public:
    explicit A(QWidget *parent = 0);
    ~A();
    virtual int heightForWidth ( int w ) const { return w*535/1645;}

private:
    Ui::A *ui;
    B* header_widget;
    C* body_widget;
    QVBoxLayout* main_layout;
    void setMainLayout();
};

A.cpp:

A::A(QWidget *parent) : QWidget(parent), ui(new Ui::A)
{
    ui->setupUi(this);
    setMainLayout();
    this->setLayout(main_layout);
}

A::~A()
{
    delete ui;
}


void A::setMainLayout(){
    main_layout = new QVBoxLayout();

    header_widget = new B(this);
    body_widget = new C(this);

    main_layout->addWidget(B);
    main_layout->addWidget(C);
}

B.h:

class B : public QWidget
{
    Q_OBJECT

public:
    explicit B(QWidget *parent = 0);
    ~B();
    virtual int heightForWidth ( int w ) const { return w*535/1645;}


private:
    Ui::B *ui;
};

C.h:

class C : public QStackedWidget
{
    Q_OBJECT

public:
    explicit C(QWidget *parent = 0);
    ~C();  
    virtual int heightForWidth ( int w ) const { return w*535/1645;}

private:
    Ui::C *ui;
    A *widgetParent;
};