Building my own NSView from the ground up

I recently began work on a spreadsheet app, then, after a couple of weeks, abandoned it. I found that the off-the-peg cocoa components didn't give the behaviour I wanted. For example, I couldn't support the thousands of rows/hundereds of columns design I was after without encountering painfully long pauses for redrawing during resize operations. No doubt my design approach contributed significantly to these problems, but I'm clearly not the only one who has found Cocoa's off-the-peg components wanting at times; Microsoft for example don't appear to have used NSScrollView as the basis for Excel, and TextMate's designers seemed to have turned their nose up at NSTextView as the basis for their text editor.

My question then is how do the likes of Microsoft and TextMate set about creating their own view-side components which nevertheless ultimately become part of a native cocoa app? What's their way into Cocoa's drawing and events system if they aren't using NSView derivatives?