Qt 6.0.3 QFileIconProvider and High DPI

leoklaus

When using QFileIconProvider to retrieve a QIcon from an executable on Windows, I can't use the icon on a pushButton with scaling settings other than 100% (it's simply not displayed at all).

I've created a small sample for demonstration:

void MainWindow::on_pushButton_clicked()
{
    QFileInfo *test = new QFileInfo("C:/Qt/MaintenanceTool.exe");
    QFileIconProvider *provider = new QFileIconProvider;
    QIcon icon = provider->icon(*test);
    QPixmap pixmap = icon.pixmap(icon.actualSize((QSize(1024,1024))));
    qDebug() << icon.availableSizes() << pixmap;
    ui->pushButton->setIcon(icon);
}

Console output when scaling is set to 100% is:

QList(QSize(16, 16), QSize(32, 32)) QPixmap(QSize(32, 32),depth=32,devicePixelRatio=1,cacheKey=0x5300000001)

Console output when scaling is set to anything but 100%:

QList(QSize(24, 24), QSize(48, 48)) QPixmap(null)

I suspect this has to do with the way Qt handles Icons with high DPI displays but I obviously can't provide high DPI icons.
Is this a bug or did I miss something?

mrjj

Hi

You mean the windows text scale ?
alt text

Icon did show using Qt 5.15.1
using your code. ( also at 125% etc)

leoklaus

@mrjj Yes and yes. This only happens in 6.0.3.
5.15 doesn’t scale the app (by default).

VRonin

I’m surprised you get the icon at 100% size actually.
QFileIconProvider is to be considered broken on windows for now (6.1.0 or below) in Qt6. There is a critical priority ticket opened against it and it’s being worked on

leoklaus

@VRonin Nice, thanks for the information. Is there a platform independent alternative or should I switch development to 5.15 for now?

VRonin

Is there a platform independent alternative

See https://forum.qt.io/topic/125967/possible-qt-6-03-bug

should I switch development to 5.15 for now?

My personal opinion expressed here: https://forum.qt.io/topic/126005/qt-6-version-readiness-for-using-when