fix(react-drawer): report bottom scroll state at fractional browser zoom - #36677
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`getScrollState` compared scroll offsets for exact equality, but browsers round `clientHeight` and `scrollHeight` to integers while `scrollTop` stays fractional. At non-integer browser zoom a fully scrolled DrawerBody therefore reported `middle` instead of `bottom`, which kept the divider above NavDrawerFooter visible. The same rounding can make a non-scrollable body report a pixel of overflow it cannot actually scroll, reporting `top` and showing the divider on a drawer with nothing to scroll. Compare both with a tolerance instead. Measured against Chromium across 31 zoom levels from 100% to 250%, the bottom offset falls up to 1.44px short of the computed maximum, and phantom overflow is at most 1px. Behaviour at 100% zoom is unchanged. Fixes microsoft#36331 Co-authored-by: Cursor <cursoragent@cursor.com>
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September 1, 2026 20:29
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This is the more complete fix: the tolerances are backed by measured fractional-zoom behavior, it also handles phantom 1px overflow, and it includes regression coverage.
This was referenced Sep 3, 2026
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getScrollStatecompared scroll offsets for exact equality, but browsers roundclientHeightandscrollHeightto integers whilescrollTopstays fractional. At non-integer browser zoom a fully scrolled DrawerBody therefore reportedmiddleinstead ofbottom, which kept the divider above NavDrawerFooter visible. The same rounding can make a non-scrollable body report a pixel of overflow it cannot actually scroll, reportingtopand showing the divider on a drawer with nothing to scroll.Compare both with a tolerance instead. Measured against Chromium across 31 zoom levels from 100% to 250%, the bottom offset falls up to 1.44px short of the computed maximum, and phantom overflow is at most 1px. Behaviour at 100% zoom is unchanged.
Fixes #36331
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