The Cat That Ate the Rat…

Writing bugs often makes me more productive.

That, or writing requests for help.

For instance, I have a custom NSView, whose contents, mostly text, are completely laid out by a cross-platform engine, i.e. not by Cocoa. So I can’t use NSTextView.

But I want it to act like an NSTextView. For instance, I want to be able to select text just like an NSTextView, and I want a blinking cursor just like an NSTextView.

So I started writing up a query to the Cocoa-dev mailing list about this. But you don’t get much respect, or much help, if you aren’t as specific about what you need as you can be.

So first, I had to determine what I didn’t know. Which meant trying to implement it, and documenting where I got stuck.

Turns out, I didn’t get stuck, at least for the first part.

How do I get started learning about something new? Well, if I can guess an API name, I’ll start with the documentation, but usually I can’t. So I search based on the words I do know, like “selected text color”. If there are a lot of false matches from other frameworks, I’ll restrict the search to Cocoa-dev, but sometimes the answer is, say, a Carbon API, so I’m inclusive at first.

I find that the spare, high-level style of Apple’s developer documentation sometimes leaves me scratching my head. Is this really what I need? The mailing lists are great for this sort of clarification.

So I find out the API I need for the selected text background is the appropriately-named:

-[NSColor selectedTextBackgroundColor]

And the post that gave me that also pointed me to the “Accessing System Colors” documentation topic, which helpfully mentioned the notification:


which allows me to change the color in my application immediately if the user chooses a different highlight color from System Preferences.

But I wasn’t done because, when an application window is no longer foremost, the selection color changes from the user-choosable highlight color to a gray color.

I was unable to find a specific question about that, but I found another post that talked about matching API colors via the Developer color palette in the color panel. (Cmd-Shift-C in TextEdit.) There isn’t a nonForemostSelectedTextBackgroundColor system color, but there is a secondarySelectedControlColor that matches the non-foremost selected text color in TextEdit, and has a name that at least could apply to my situation.

So I have something that works, and gets its information as much from the system as possible, so it’s as future-proof as possible while still being custom. And I didn’t need to ask any questions! Except…

The same routine didn’t get me an answer as to the best, most system-friendly way to show a blinking caret. I could do the whole thing myself, but that might look weird in the radically overhauled UI in Mac OS X 10.9 “Puddy Tat,” eh? And I’d rather not have an NSTextView whose sole function is to show that caret – seems like a fragile, hacky solution.

So I have a question after all.