Debugging NSTextView performance problem when editing multiple languages


I’m trying to figure out why some text (seems to be when mixing languages) is so slow to edit in NSTextView. You can reproduce the problem in TextEdit (I’m reproducing it on OS X 10.11.1) with the attached document:

EnglishChineseHebrewGreek.txt (31.0 KB)

  1. Open the document in TextEdit

  2. Zoom that document’s window to full-screen mode.

  3. Type fast in the 16th paragraph where it says “TYPE IN THIS PARAGRAPH”. And notice there’s a noticeable lag when typing. In full screen mode for me it seems there’s a lag most anywhere that I type. If I size the window smaller editing some lines presents a smaller or no lag, while other lines (such as the 16th line) present a noticeable lag.

For any developers who might have an idea of what is causing this I’ve created an example project with some console logging. The underlying problem seems to be that when I type a single character in that paragraph these things happen for each keystroke:


2015-12-08 12:13:16.734 TextTest[71365:32040704] layoutCharactersInRange: {729, 69}
2015-12-08 12:13:16.735 TextTest[71365:32040704] layoutCharactersInRange: {798, 17045}
2015-12-08 12:13:16.736 TextTest[71365:32040704] layoutCharactersInRange: {1370, 16473}
2015-12-08 12:13:16.736 TextTest[71365:32040704] layoutCharactersInRange: {1639, 16204}
2015-12-08 12:13:16.737 TextTest[71365:32040704] layoutCharactersInRange: {1877, 15966}
2015-12-08 12:13:16.738 TextTest[71365:32040704] setFrameSize: {809, 4290}
2015-12-08 12:13:16.738 TextTest[71365:32040704] setNeedsDisplayInRect: rect=self.bounds
2015-12-08 12:13:16.740 TextTest[71365:32040704] layoutCharactersInRange: {2742, 15101}
2015-12-08 12:13:16.740 TextTest[71365:32040704] setFrameSize: {809, 4276}
2015-12-08 12:13:16.740 TextTest[71365:32040704] layoutCharactersInRange: {2535, 207}
2015-12-08 12:13:16.741 TextTest[71365:32040704] layoutCharactersInRange: {2742, 15101}
2015-12-08 12:13:16.741 TextTest[71365:32040704] setFrameSize: {809, 4248}
2015-12-08 12:13:16.744 TextTest[71365:32040704] setNeedsDisplayInRect: rect=self.bounds
2015-12-08 12:13:16.746 TextTest[71365:32040704] layoutCharactersInRange: {3027, 14816}
2015-12-08 12:13:16.746 TextTest[71365:32040704] setFrameSize: {809, 4234}
2015-12-08 12:13:16.746 TextTest[71365:32040704] layoutCharactersInRange: {3215, 14628}
2015-12-08 12:13:16.747 TextTest[71365:32040704] setFrameSize: {809, 4220}
2015-12-08 12:13:16.750 TextTest[71365:32040704] setNeedsDisplayInRect: rect=self.bounds

NSTypesetter method layoutCharactersInRange is called a bunch with many different and overlapping ranges.

NSTextView’s setFrameSize method is called multiple times.

And as a result NSTextView is asked to do a full repaint on each keystroke.

Does anyone know why this would be happening, and how I might avoid it?

Here’s the example project with that logging: (255.8 KB)

Laggy UI on MacBook Pro (15-inch, 2016)
TaskPaper 3.5 Korean text performance
TP 3 will get stuck when i typing in Chinese sometimes

If anyone tries the example document and doesn’t see a performance lag please let me know too.


EDIT: I’m on 10.10.5 I thought I would just check it out, I run through Text Edit and Taskpaper and there is noticeable lag in full-screen mode, it doesn’t seem to be related to any specific language, there’s just too much text to redraw. I can’t run your project through XCode as I kind of don’t use it.

[Is there a possibility to add .txt as a bundle extension for Taskpaper, I use the context menus all the time and it’s not there for me?]

I just rechecked TextEdit I can’t see the problem any more I must have been mistaken. I use Menlo in TextEdit.


Interesting… I just tried on OS X 10.10 also and don’t see the problem in TextEdit. Seems to be only in 10.11 in TextEdit.


is there any progress on this issue?


I reported it to Apple and the report got marked as a duplicate. So at least they know about it. After that the process is pretty much a black box, I have no idea when/if a fix is planned.