On 8 Feb 2017, at 17:48, Konstantin Suvorov wrote:

Does anybody experience random selections while clicking on tabs or other
textmate windows (like search dialog) on Sierra?

Yes — this happened to me 1-2 weeks ago, never noticed it before, but it happened all the time for a day or so, until I rebooted (due to a software update), and now it does not seem to happen anymore.

I was very puzzled as to why it would happen, and I did try all sorts of things to reproduce the steps, but like you, I was unsuccessful.

One thing that was a little atypical compared to my normal workflow is that the project I worked on at the time had saveOnBlur = true in its .tm_properties and I was regularly switching away/back to TextMate. Although definitely not the first time I have used this workflow, but first time I noticed the selection issue.

FYI I am now on 10.12.3, so if you are on less, then definitely check for an OS update.

I would also suggest trying to reboot. I don’t exactly see how it could happen, but perhaps some sort of stuck modifier flag for the activation mouse event, making TextMate think there was a shift-click to extend the selection.