The output log is our most extreme example of a multi-line editable text, however it shouldn’t be causing that level of performance degradation. Given that it only happens when the log is visible, it’s most likely something in OnPaint() - I’ll take a look. For reference, what spec is your machine?

[4.5] The Output Log degrades performance

Development Platform & Builds Debugging, Optimization, & Profiling

TS100101 (TS100101) December 2, 2014, 3:40pm 15

I think I got it! Looks like unplugging my Wacom tablet solves the issue.