[Qt] import* rescans are not abortable and can confuse users #10992

When importing something with any of the import* commands from the qt debug window console, a progress bar appears which is uncancelable and unminimizable. Furthermore, trying to close the progress bar window simply makes it disappear, and then shortly appear again. This behavior is clearly seen in the gif below.

Rescanning also completely locks up the GUI and nothing else can be done.

Since there is an abortrescan RPC command, there should be some way to abort a rescan now through the progress bar dialog that appears, either with an additional button, or by clicking the X to close it.

Agree that one should be able to abort rescans. The fix shouldn't be to hard. The progress dialog (QProgressDialog / WalletView::showProgress) could have the optional cancel button. The cancel button then could eventually directly call AbortRescan(); or through a callback.

Rescan locks cs_main and cs_wallet. Avoiding the GUI locks will be harder (probably doable with @ryanofsky #10973).

I just tried to bitcoin-cli abortrescan a rescan caused by a cli importprivkey, and it hangs too. Maybe this is not just a GUI problem (0.15.0.1).

Fixed by #11200