HI and thanks, Lately it seems like a get a bug a month. Now when using code completion I get a flash and the viewport changes position.
After a few letters typed the screen flashes, disconnects the code completion context, and then moves the cursor to the top of the viewport and positioning the file so that the line (left-right) position you are on is the leftmost-upper location of the file. So, in other words, it re-positions the file in the viewport so that the location is now the upper left corner of the viewport. So the file has shifted to the left also.
So if you look at the image and look in the upper left corner, it would be positioned on the variable in the upper right corner in this case you see "rIds" that you were editing.
I am using Webstorm 2018.1.1 although this started in the previous release 2018.1
I am on Linux Mint 17.2
I use the Awesome tiling desktop