When this was originally introduced, it handled single clicks on a list entry
(treating them similar to a double-click by checking whether the click was on
the selected entry). Arguably it should have been called OnDoubleClick back then
already; but when we later changed it to do actual double-click detection (see
37197b8e9a), we should have renamed the methods.
This begins a big refactor of moving more code out of the Gui struct into contexts, controllers, and helpers. We also move some code into structs in the
gui package purely for the sake of better encapsulation