Unable to change Icon::On color in Fusion style?

[CJha]

Hi, I am trying to change the QIcon::On color but I am unable to do so. Below is a test code:

MainWindow::MainWindow(QWidget* parent)
	: QMainWindow(parent)
{
	qApp->setStyle(QStyleFactory::create("Fusion"));
	ui.setupUi(this);
	ui.pushButton_2->setCheckable(true);
	QWidgetList allWidgets = qApp->allWidgets();
	for (QWidget* wid : allWidgets) {
		QString str = wid->metaObject()->className();
		if (str == "QPushButton") {
			auto btn = dynamic_cast<QPushButton*>(wid);
			if (!btn->icon().isNull()) {
				QPixmap pixOff = btn->icon().pixmap(QSize(1024, 1024));
				QPixmap pixOn(pixOff);

				QPainter painter;

				painter.begin(&pixOn);
				painter.setCompositionMode(QPainter::CompositionMode_SourceIn);
				painter.fillRect(pixOn.rect(), Qt::red);
				painter.end();

				painter.begin(&pixOff);
				painter.setCompositionMode(QPainter::CompositionMode_SourceIn);
				painter.fillRect(pixOff.rect(), Qt::green);
				painter.end();

				QIcon icon;

				icon.addPixmap(pixOff, QIcon::Normal, QIcon::Off);
				icon.addPixmap(pixOn, QIcon::Normal, QIcon::On);

				btn->setIcon(icon);
			}
		}
	}
}

The QIcon::Off state is working as expected and so is QIcon::Disabled, QIcon::Off. But none of the QIcon::On states (including QIcon::Disabled, QIcon::On) are working as I would expect them to. Why is this happening?

UPDATE: After some help, I was able to determine that the below problem is only occurring in the Fusion style. As soon as I take out the qApp->setStyle(QStyleFactory::create("Fusion")); line at the top, everything works fine.

[SGaist]

Hi,

Which version of Qt ?
On which OS ?

What happens you use a completely new QIcon ?

[CJha]

Hi @SGaist , the Qt version is 5.15.2 and it is on Windows 10 Pro (OS Build: 19043.1348). If I use completely new icon it still is the same. After some help I was able to figure out that this is not because of QIcon but because I am using Fusion style. As soon as I use the default WindowsVista style everything works as expected.

[SGaist]

So it looks like you may have found a bug in the fusion style.

[CJha]

@SGaist It looks like that, just by disabling qApp->setStyle(QStyleFactory::create("Fusion")); in my code makes everything work fine. What should I do?

[CJha]

It is a bug: https://bugreports.qt.io/browse/QTBUG-86736