QtConcurrent::run()'s return type is marked with [[nodiscard]], which is
not nice to code that just needs to move some tasks to a worker thread.
On the other hand, QThreadPool satisfies our needs too and Qt doesn't
need to construct futures that we won't use.
One remark about the screenshot plugin: the task lambda is mutable so it
cannot be represented using a std::function.
Counter part for the copyClient test app: the pasteClient test app
creates and maps a shell surface and waits for selection announce,
initiates the copy/paste mechanismn and prints out what got pasted.
After success it closes itself.
The test application copyClient creates a ShellSurface, maps it as
fullscreen, renders a green buffer and when it gets pointer focus it
sets "foo" in mimetype "text/plain" into the selection.
Vlad Zahorodnii
Alexander Lohnau
Aleix Pol
Andreas Cord-Landwehr
Frederik Gladhorn
Martin Gräßlin