To improve my note editing app The Archive’s responsiveness, I want to find out when the user is actively editing a note. Here’s how to create the idle switch in RxSwift/RxCocoa. A simple enum of .typing and .idle will do for a start. Of course, NSTextViewDelegate provides a textDidChange(_:) callback to hook into; it’s based on a notification, so you can also subscribe to the NSText.didChangeNotification directly if you don’t want to use a delegate. That’s the input signal I’m going to use.
If you run macOS 10.13 High Sierra, try not to use the Help menu. It will appear to freeze the app for which you invoke the Help menu: it will not accept keyboard input anymore, emitting the NSBeep “invalid action” sound in most circumstances. The reason seems to be that the nifty Search bar inside the Help menu will acquire focus so you can search for a menu item or help book entry. This is taking away focus from the app window. You notice this when the blue focus ring around an active text field in the window goes away; instead, the Help menu’s Search bar obtains focus and the accompanying blue focus ring. All this is supposed to happen. This process just isn’t reverted for some reason since at least macOS 10.13.3, maybe earlier. When you click back into the app outside of the Help menu, the key window status will not be assigned back to the window you click on. That means keyboard input will not work at all. (As a non-native English speaker, I asked if “key window” was supposed to mean “window that responds to key events” a while back. While people agreed this wasn’t the intention, I still cannot help to think that way. The app has no key window, so key events are not handled, resulting in NSBeep.)
On iOS, this does maybe not happen at all, but when you want to write syntax highlighting code for macOS apps, copying together stuff from around the web, you’ll end up with broken application behavior. In short: when you type and the attributes of the line change, the insertion point is moved to the end of the line. That sucks.
When you work with view-based NSTableViews, cells by default contain a NSTextField. You can edit cell contents with them. The headers are not designed to be edited, though. You don’t have much control over the column headings from Interface Builder. So you have to build this yourself.
