click button to add multiple tabs
the selected tab does not scroll into view.
tab scrolls into view when selected
problem became visible after fixing
the left position is calculated while the new tab is still breaking to the next line
using styles to avoid the line breaking in the first place can avoid this (see workaround: float replaced by inline block, nowrap )
It even looks like recalculating the z-tabs-content width seems to become unnecessary, allowing for simpler JS code.
additional/specific style rules might be necessary for z-tabbox-bottom
adding theme specific styles e.g. for breeze:
tested on chrome/ff/IE11 (10-8 emulated),edge