DolphinMainWindow: show a banner when the user presses the shortcut of a disabled action
Currently, there's no feedback when the user presses a shortcut of a disabled action, e.g. cut / paste in a read-only directory. This patch shows a banner in that case.
It's implemented by enabling a QShortcut for each disabled action. The
shortcut of the disabled action is temporarily cleared to prevent Qt from
complaining about ambiguous shortcuts. The shortcut text is added to action->text()
then, so the menu item still look the same.
Edited by Jin Liu