After these changes, setAttribute is used only on Windows. I suggest to create separate functions for each attribute as it done in Qt for most platform-specific functions (desktopFileName, for example) that do nothing on other platforms.

I also noticed that you use tabs instead of spaces, which is forbidden by the Qt coding style, but you decide for yourself.

Removing the setAttribute seems like a good idea. If you want, you can add that change as well, but I can do that by myself as well.

If you are busy, then I can do :) If yes, do I need to leave the prefix Win as in enums?

Removing the setAttribute seems like a good idea. If you want, you can add that change as well, but I can do that by myself as well.

If you are busy, then I can do :) If yes, do I need to leave the prefix Win as in enums?

That would be cool. I would prefer to keep the "Win" prefix, to make clear those methods work only on windows.

Sorry for a lot of questions, I just want to implement it as you like :)

• You install event filter that used only for Windows. Maybe install it only for Windows?
• New methods instead of setAttribute will be used only for Windows. Should I make empty virtual functions in QTaskbarControlPrivate instead of pure virtual? If yes, will be better to use this approach for setWindow?
• setWindow is used only for Windows. Maybe do not use Windows prefixes for new methods too?
• In QX11TaskbarControl in createPrivate you do not specify a parent for the object. Is it a typo?

1. Sure, if it can be moved easily, why not
2. Yes please, do it for the new methods and set window as well
3. The difference is, that setWindow is required on windows, not optional. Also, it's an implementation detail, not a direct visual change. To prevent developers from "skipping" it, I would prefer to keep it as is, but still add the windows prefix for the others
4. Not a typo, the x11 simply does not need the qptr. It is not the parent, as the private implementations are not QObjects

Maybe I should add setProgress, setCounter and other methods to QTaskbarControlPrivate as with windowsBadgeIcon, windowsBadgeTextColor and windowsProgressState?

No, I would prefer those to stay pure virtual, as they are essential and available on all platforms

Sorry, it was a typo :) I meant to make getters for progressVisible, progress and other members (like progress(), counter()) instead of access to this members directly as a friend.

Still, keep it as is. The private class is just a design choice, see https://en.cppreference.com/w/cpp/language/pimpl

So it's correct that those are accessed via a friend declaration. The virtual methods are only there for the necessary platform abstraction.

Yes, I know about PIMPL, just suggested for consistency. But I think that you are right, keep it as members will be better.

The last thing that I want to suggest is to add setWindow to QTaskbarControl class as it done in QWinTaskbarButton. This will allow to avoid using extra event filter and user will must to set QWindow in showEvent as for QWinTaskbarButton. It may be useful if user already have showEvent override, custom event filter or already valid QWindow. Also it allow to avoid passing a valid QWidget to the constructor. What do you think?

The last thing that I want to suggest is to add setWindow to QTaskbarControl class as it done in QWinTaskbarButton. This will allow to avoid using extra event filter and user will must to set QWindow in showEvent as for QWinTaskbarButton. It may be useful if user already have showEvent override, custom event filter or already valid QWindow. Also it allow to avoid passing a valid QWidget to the constructor. What do you think?

I am torn on this one... I get you point, but I prefer that this is done "automagically" for widgets. Maybe it would be possible to have both? Provide setWidget which uses the widget and registers the eventfilter and a setWindow which ignores/disables the eventfilter and sets the window directly instead. What do you think about that idea

Sounds good. I will try to implement it :)

What do you think about this implementation?

I combined it into one function that checks if QWindow is valid and installs event filter if need to wait for initialization. You need to set QWindow only once, so event filter will be removed after initialization. I also changed return to QObject::eventFilter(obj, event); as it done in documentation.

And I removed extra pointer from QTaskbarControlPrivate constructor because it is not needed anymore. Because of this, I changed private members to protected and added _ prefix to avoid conflicts with functions parameters.

Is it okay?

Done! But instead of overload I created a separate QTaskbarControl::setWidget function because of ambiguous (QWidget and QWindow inherit both from QObject).

Feel free to request any other changes or refactoring.

Thank you!