Getting accented characters in a custom NSView

Question

In Mac OSX text views, it's possible to enter accented characters with a sequence of key presses (e.g. option-e e to get e-acute). Is there a way to access this functionality in a custom NSView. In my case I have class derived from NSOpenGLView. I've implemented a responder for keyDown: so I can get the unicode characters that come from a single press, but with the sequences I just get events for the individual presses. I hoped that interpretKeyEvents: from NSResponder would help but it doesn't seem to.

I could implement it myself by copying what NSTextView does but I imagine it will be tricky, especially if people use a different keyboard setup to mine.

Answer 1

Calling interpretKeyEvents: is the right way to go, but you need to also implement other methods that will notify you when marked text (which I always called 'in progress text') or text to be inserted arrives in your view.

Your NSView must implement NSTextInputClient. See the Cocoa reference here. A search for some of the methods in that protocol found this chunk of code on github. which looks like a very good starting point.

For what you're asking for, it will be sufficient to test with English and at least one other Western language (French is a good one). But longer term, you'll also want to test with at least one of the Kotoeri and Hangul layouts. The code I linked to above, however, looks like it will handle the vast majority of text you can throw at it.

Answer 2

Hhhmm.. that sounds pretty tricky.

NSTextField does some pretty similar things as it does not have its own editing facilities but rather delegates them to the parent window's "field editor" which is an instance of an invisible NSTextView. You also get a lot of the NSTextView behavior without a window in NSText.

It might be worth checking how NSTextFields delegate to the field editor and see whether you can hook yourself into the field editor in the same way rather than doing your keyDown: events.

Another possibility could be to create an invisible NSTextView and delegate each key press to it and then display the NSTextStorage associated with it in your own view.

It sounds like you are in for a bit of pain, but that's what I would start by exploring.

Of course, I'm no Cocoa Text Subsystem wizard..

I hope this helps.