Qt 6.8.2 Application does not show SVGs when deployed

[Christian Ehrlicher]

@Ja_n said in Qt 6.8.2 Application does not show SVGs when deployed:

I added my Qt installation to PATH and when i click my Application i get (no SVGs visible):

Why do you add Qt to your PATH? I told you not to do...

[Ja_n]

I found my solution (without Qt in PATH):

This does not work:

QIcon i(":/SvgTest/help_h.svg");

SvgTest::SvgTest(QWidget *parent) : QWidget(parent)
{
	lay = new QVBoxLayout(this);
	l = new QPushButton("hi",this);
	lay->addWidget(l);
	l->setIcon(i);
}

This does work:

QIcon* i = nullptr;

SvgTest::SvgTest(QWidget *parent) : QWidget(parent)
{
	lay = new QVBoxLayout(this);
	l = new QPushButton("hi",this);
	lay->addWidget(l);
	i = new QIcon(":/SvgTest/help_h.svg");
	l->setIcon(*i);
}

I guess there is something like QApplication has to be created first?

[JonB]

@Ja_n
Without a QApplication currently instantiated I imagine code cannot resolve :/SvgTest/help_h.svg? In your original case did you check QIcon::isNull() prior to attempting to use it? In general you should not try to create global UI objects (like your QIcon i(...)) in code, these are instantiated before your main() is even entered or a QApplication has been created, it often leads to impenetrable error messages.

[Ja_n]

I did not check isNull(). It would have been true. But i dont understand why it changed when i deleted Qt6Core.dll.

[JonB]

@Ja_n
I don't know, but the immediate suspicion is that it uses an external Qt6core.dll which it finds somewhere else and is not the same as the one copied by windeployqt. Search your whole disk for Qt6core*.dll?

I don't know how QIcon sits in this, but I still would not create an external QIcon(....) prior to QApplication. I don't know whether it tries to to resolve the path/create the icon at construction rather than usage time, but a runtime call to new QIcon(":/SvgTest/help_h.svg") after QApplication instantiation seems much safer.

[Christian Ehrlicher]

a new QIcon() is wrong in 99,9% of all cases. No need to create it on the heap (and leak it afterwards). And it's for sure not the solution for your problem. You have a mix of different Qt dlls in your PATH.

[Ja_n]

I’d prefer not to put all my icons on the heap, but I tested my 'solution' in Windows Sandbox and the behavior is exactly the same. There is no Qt in my PATH. I checked every entry in PATH and none contain any Qt DLLs. The only way Qt gets into my PATH is via Visual Studio. If you search my logs for "dll" there are only C:/Qt/6.8.3/msvc2022_64 and C:/MyApp/Release — that’s it.

[JonB]

@Christian-Ehrlicher
Would you care to comment on how, say, QIcon(":/SvgTest/help_h.svg") behaves if called before a QApplication has been created? The OP's code simply shows this as a global variable, cannot tell whether this is what they really have. Do :-paths really get resolved without a QApplication object??

[Christian Ehrlicher]

@JonB said in Qt 6.8.2 Application does not show SVGs when deployed:

QIcon(":/SvgTest/help_h.svg") behaves if called before a QApplication has been created?

I would say it doesn't work as the resource system is not yet properly set up. But I would have to try it out to be sure.

[JonB]

@Christian-Ehrlicher That was my guess too :)