How to make QWidget fill parent QWidget?

[kitfox]

I'm having trouble getting a child QWidget to fill it's parent. I've created a form using QtDesigner and added some QWidgets to it - the idea is that I want to fill these empty rectangles with custom QWidgets. In the constructor for my form, I am creating an instance of my child widget and adding it and a layout to the placeholder QWidget I have in my form, but no matter what I try my child widget is only filling a small portion in the top left corner of the widget I want it to fill entirely. How do I fix this?

sequencereditor.h

#ifndef __SEQUENCER_EDITOR_H__
#define __SEQUENCER_EDITOR_H__

#include "ui_sequencereditor.h"

class SequencerNames;

class SequencerEditor : public QDockWidget, public Ui::SequencerEditor
{
    Q_OBJECT

    Score* _score;
    SequencerNames* _seqNames;

public:
    explicit SequencerEditor(QWidget *parent = nullptr);
    ~SequencerEditor();
};

#endif // __SEQUENCER_EDITOR_H__

sequenceredtior.cpp

#include "sequencereditor.h"

#include "sequencernames.h"

SequencerEditor::SequencerEditor(QWidget *parent) :
    QDockWidget(qApp->translate("Sequencer", "Sequencer"), parent)
{
    setupUi(this);

    QHBoxLayout* nameAreaLayout = new QHBoxLayout(nameArea);

    _seqNames = new SequencerNames(nameArea);

//    _seqNames->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);

    nameAreaLayout->addWidget(_seqNames);
}

SequencerEditor::~SequencerEditor()
{
}

sequencernames.h

#ifndef __SEQUENCER_NAMES_H__
#define __SEQUENCER_NAMES_H__



class SequencerNames : public QWidget
{
    Q_OBJECT

public:
    SequencerNames(QWidget* parent = nullptr);

private:
    virtual void paintEvent(QPaintEvent*);

};

#endif // SEQUENCERNAMES_H

sequencernames.cpp

#include "sequencernames.h"

SequencerNames::SequencerNames(QWidget* parent) :
    QWidget(parent)
{

}

//---------------------------------------------------------
//   paintEvent
//---------------------------------------------------------

void SequencerNames::paintEvent(QPaintEvent* /*event*/)
{
    QPainter p(this);
    p.setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform | QPainter::TextAntialiasing);

    p.setPen(Qt::red);
    p.drawEllipse(0, 0, width(), height());
}

[Bonnie]

What is "nameArea"?
I think you need to post sequencereditor.ui, too.
Also, although I'm not familiar with QDockWidget, but I think the usual way is not subclassing it, but calling setWidget()