Bug in QImage

[wostka]

When I build an run this snippet on MinGW it works, on MSCV it doesn't. Both with newest Qt6.5.2 updates. It's a known bug? I can't find anything on Internet?

extern BaseModel basemodel;
[...]
void BoardView::paintPieces(QPainter *p) {
auto w = p->window().width();  //p->viewport().width();
auto h = p->window().height(); //p->viewport().height();    
p->drawPixmap(
                  QRect(50, 50, w, h), 
                  QPixmap::fromImage(basemodel.board.pieces[0][0].img));
}
________________________
[console output on MinGW]
QImage(QSize(102, 102),format=QImage::Format_ARGB32,depth=32,devicePixelRatio=1,bytesPerLine=408,sizeInBytes=41616)

[console output on MSCV 2019]
QImage(null)

Best regards

[wostka]

One workaround: Have to add

Q_INIT_RESOURCE(res); //res = the .qrc file, e.g. res.qrc

then it run under MSVC. Not a bug, a feature... :D

see https://doc.qt.io/qt-6/resources.html#explicit-loading-and-unloading-of-embedded-resources

Thanks to @jsulm and @Chris-Kawa

[jsulm]

@wostka Where do you output anything on console?
To me it is not clear what exactly does not work.

[wostka]

@jsulm I have adapt the code.
The original code is a loop which iterates a 2-dim Array (pieces) which has stored e.g. an QImage (img)...This Array is stored in a class called board and this is stored in a class called basemodel. basemodel ist global.
The methode paintPieces is called in the paintEvent methode of a view which paints the board of a game. The methode paintPieces paints the pieces of the board.
The console output comes from

p->drawPixmap(...
qDebug() << basemodel.board.pieces[0][0].img;

The problem is, that the same code generated by different compilers one times works, and at the other time not and I dont know why.
Hope its clearer now whats the situation.

[jsulm]

@wostka said in Bug in QImage:

img

How are these QImage instances created?

[Chris Kawa]

If those are images read from files or resources you're most likely just missing the plugin for that format in your deployment directory.

[wostka]

@jsulm In the ctor of board from a struct named Piece
@Chris-Kawa The plugins seems to be on the right place. The problem arise too, if I "deploy" the exe with windeployqt. The

qDebug() << QImageReader::supportedImageFormats();

gives in both cases ".png", whats right.

Perhaps some pics:
This with MinGW-Kit

This with MSVC

If I change the Kit from MinGW to MSVC.

[Chris Kawa]

@wostka Before you jump to conclusions do a basic test:

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    qDebug() << QImage("C:/Explicit/path/to/some/file.png");
}

Does that work?

[jsulm]

@wostka said in Bug in QImage:

In the ctor of board from a struct named Piece

Why don't you show the code?

[wostka]

One workaround: Have to add

Q_INIT_RESOURCE(res); //res = the .qrc file, e.g. res.qrc

then it run under MSVC. Not a bug, a feature... :D

see https://doc.qt.io/qt-6/resources.html#explicit-loading-and-unloading-of-embedded-resources

Thanks to @jsulm and @Chris-Kawa

[Christian Ehrlicher]

@wostka said in Bug in QImage:

Not a bug, a feature... :D

No feature but a mandatory thing - otherwise there is no reference to the resource and the lnker can throw it away.