Need for setWIndowIcon()/setIcon()

[Perdrix]

If a Windows application has a .rc file that specifies a .ico file, or a macOS bundle contains a .icns file, do I need to call QWidget::setWindowIcon() or QWindow::setIcon()?

Or perhaps better put under what circumstances do I need/not need to use these?

Thanks
David

[Asperamanca]

@Perdrix Docs on QWidget::setWindowIcon:

This property only makes sense for windows. If no icon has been set, windowIcon() returns the application icon

So you need to set if you want a diverging icon (e.g. for applications with multiple windows)

[Chris Kawa]

If you have a resource icon set up properly it will be used by default for all your windows. Usually you don't need to call these functions. You only call them when you want to change the icon at runtime, e.g. have different icon for one of the windows, like @Asperamanca said, or change the icon to indicate some state change in your app (logged in, connected to something etc.). There's usually a more idiomatic way to do the latter on most OSes though, so it's sometimes a bit of an abuse. Generally if you don't have an immediate idea how you could use that runtime change in a meaningful way don't use it.

[Perdrix]

So, if I read that correctly, then I would normally only call QWindow::setIcon() on Linux?

Is that right?

[Asperamanca]

I haven't done it, but it seems possible to set application icons on Linux, too....if you know the desktop environment beforehand.
For full reference, please see https://doc.qt.io/qt-6/appicon.html