well i was able to solve it on my own
thanks for the help guys
turns out after passing the connect statement through lambda, a different issue arrised
instead of

self.animation.endValue(widthExtend)

i had to write

self.animation.setEndValue(widthExtend)

To quote the wiki page, "You may use this code without any warranty. "

The code is from 2011, when Qt 4 was the latest. Attempting to compile the Git code with Qt 5 or 6 will not work as-is. The error in DocumentWindow::winEvent() is simply because Qt5 changed the API and removed QPaintDevice::winEvent() (and by inheritance from QWidget and QMainWindow). Look at QWidget::nativeEvent() when you are porting.

There are a few typos in the Wiki page source code and a now broken link to the source on Gitorious.
Gitorious ceased to be in 2015 when taken over by Gitlab. The source still exists there. The simple typos are not present in the Git sources.

When you have finished porting to Qt5 and Qt6 feel free to update the wiki page with code that uses include guards to handle version differences.

Fixed. This errors was because of Qt 6. I downloaded and linked previous version of QT - 5.15, and this errors disappeared