[mrramam]

Why

While a display is dimmed, displayDim.js hides scrollbars, because Chrome draws them outside the brightness filter at full brightness. Hiding the page's scrollbar gives its width back to the page, so on a browser with always-visible scrollbars the dock and anything else centered moved by half a scrollbar (4px here) on every dim, and back on every wake.

What changes

While dimmed, the page keeps the scrollbar's space (scrollbar-gutter: stable on html) and the scrollbar stays hidden. The gutter shows the dimmed page's black. Scrollbars inside widgets are hidden as before.

Testing

• Client vitest 832/832, check:i18n clean.
• Chrome with classic scrollbars, real dashboard, dimming switched on in the browser only:
  • before: the dock moves on dim;
  • after: nothing moves on dim or wake, the scroll position holds, and the gutter is black while dimmed.
• Not tested: a widget with its own scrolling area while dimmed. None overflowed on the test board.