Change Details

``` The QSignalMapper class has been deprecated since Qt 5.10. This PR replaces it by lambdas and does not change behavior. ``` Backport od core PR16706.

``` The QSignalMapper class has been deprecated since Qt 5.10. This PR replaces it by lambdas and does not change behavior. ``` Backport od core [[https://github.com/bitcoin/bitcoin/pull/16706 | PR16706]].

``` The QSignalMapper class has been deprecated since Qt 5.10. This PR replaces it by lambdas and does not change behavior. ``` Backport od core [[https://github.com/bitcoin/bitcoin/pull/16706 | PR16706]].