QPushButton in a sub-QMenu, change background on hover

Question

EDIT: NOTE this only occurs when the button is in a SUBMENU. (Menu in a menu.) This code works fine only on the parent menu!

Running Qt 5.0.2, on Windows 7. I have a QMenu with a QWidgetAction in it. Inside the QWidgetAction is a QPushButton. I would like to change the background color of the button when the mouse hovers over it.

Here is my code:

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QDebug>
#include <QMenu>
#include <QWidgetAction>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

}

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

void MainWindow::on_pushButton_clicked()
{
    QMenu menu;
    QMenu *subMenu = new QMenu("SubMenu text");

    QWidgetAction *widgetAction = new QWidgetAction(subMenu);
    QPushButton *btn = new QPushButton("test");
    btn->setStyleSheet("QPushButton:hover{background-color: #ff0000;}");
    widgetAction->setDefaultWidget(btn);
    subMenu->addAction(widgetAction);

    menu.addMenu(subMenu);
    menu.exec();
}

.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private slots:
    void on_pushButton_clicked();

private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

main.cpp

#include "mainwindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;

    w.show();

    return a.exec();
}

However when the cursor hovers over the QPushButton the background color doesn't change. Doesn't matter if I run it in fusion style or not.

What is going on here? Thanks for your time.

Answer 1

This sound like mouseTracking is not enabled on the widget (and/or probably on the parent widget(s)). You can enable it by calling

QWidget::setMouseTracking(bool enable);

Answer 2

1. Background may not be customized, if you don't change a border style of a button.

How to solve: use some non-default style, for example:

const auto fusion = QStyleFactory::create( "Fusion" );
QApplication::setStyle( fusion );

2. QPushButton is not designed for perfect handling hover events. For example, hover event will not change a font via stylesheet.

How to solve: use QToolButton instead.

P.S. Don't know, why it's not worked for you. Everything is OK for me...

UPDATE

Just copy-paste it and run:

#include <QApplication>
#include <QWidgetAction>
#include <QMenu>
#include <QPushButton>
#include <QToolButton>
#include <QStyleFactory>


void showMenu()
{
    const auto parent = qApp->activeWindow();
    auto menu = new QMenu( parent );
    
    auto root = new QMenu( "Root", menu );
    menu->addMenu( root );

    auto wa = new QWidgetAction( parent );
    auto tb = new QToolButton;
    tb->setText( "ToolBtn" );
    wa->setDefaultWidget( tb );

    root->addAction( wa );

    menu->exec( QCursor::pos() );
    menu->deleteLater();
}


int main(int argc, char *argv[])
{
    QApplication a( argc, argv );

    const auto fusion = QStyleFactory::create( "Fusion" );
    const auto qss =
        "QToolButton:!hover{background-color: #00ff00;}"
        "QToolButton:hover{background-color: #ff0000;}"
        ;

    QApplication::setStyle( fusion );
    qApp->setStyleSheet( qss );

    QWidget w;
    w.resize( 800, 600 );
    auto btn = new QPushButton{ "Test", &w };

    QObject::connect( btn, &QPushButton::clicked, &showMenu );
    w.show();

    return a.exec();
}