Xcode 6 code editor erratic behaviour
Equalise all font sizes and remove any italics and bolds in your colour theme.
The answer to this issue I discovered in the Apple Developer forums. Unfortunately, I cannot find the thread there. It basically said that the behaviour I was experiencing was the result of a colour theme I was using having different sized fonts and a combination of italics and bolds. The thing is that there were no more comments after this guy's post, confirming or disproving the solution. For me, it did the thing. And now that @Kirby Todd has confirmed it, I am posting it as an answer.
This was happening to me in Xcode 7.1.1 (7B1005). It got so bad I went back to vi for a while!
I considered the discussion above, but I never adjusted my fonts and was using the defaults. I'm on an MacBook Air. There wasn't enough memory pressure or memory used to suggest it was swapping and couldn't keep up, which is another reasonable cause.
However, in my case at least deleting all the "Derived Data" made the problem go away. I didn't even have to quit Xcode!
This is simple to do (provided here for anyone who might possibly not know):
- From Xcode's Window menu select Projects.
- Make sure the project highlighted on the left is your project (or click on your project to make it so)
- Click on the Delete... buttonnext to "Derived Data".
I finally solved this.
I had a large project with lots of lines and some deprecated warnings due to me using things like UIAlertView which are no longer supported. It turns out it was the warnings that were causing the line jumps. Editor seems to run on a timer checking for new warnings at an insane rate like every 5 seconds, so every 5 seconds it would see if my code updated and if it did it would run through the whole thing again marking all of the yellow warning tags, which especially was erratic if the number of lines in my project changed since the warning windows would then have to shift down (or up). This would cause rendering issues and the line I was editing would shift up and down, very obnoxious.
Long story short I turned off the deprecated warnings by simply wrapping my .m in #pragma marks and it all went away (also editor became significantly less laggy (this was a 30k line of code .m file btw) very laggy to begin with).