[Interest] Detecting any desktop state change

[Alexander Syvak]

Hello,

the requirement is to detect a desktop window visual change starting from a
defined time moment.

In the QPaintEvent
documentation<http://qt-project.org/doc/qt-4.8/qpaintevent.html#details>there's
no exact information when it should be sent.
However, I assume that it is sent whenever a widget is
- resized;
- moved;
- exposed because a covering widget was moved.

N.B. !!!
I do not make assumptions whether a widget should be repainted in Qt if it
is either partially or fully covered by a widget.
However, since the desktop widget is the widget constituting the area for
all widgets after an user is logged in and assumed that the widgets are
children of the desktop widget, the desktop widget is the first QPaintEvent
receival point. Hence, it should receive the QPaintEvent message when it is
partially or fully covered.

The idea is to use the QDesktopWidget class with an event filter expecting
a paint event.

I need thorough information (with sources) whether the assumptions are
correct.

If there is an input regarding the idea or another solution it would  be
greatly appreciated.
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