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fix(drawer): tolerate fractional scroll metrics #36520

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Mohd Saif (mohd-saif-1850) wants to merge 1 commit into
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fix(drawer): tolerate fractional scroll metrics #36520

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3 changes: 2 additions & 1 deletion packages/react-components/react-drawer/library/src/components/DrawerBody/useDrawerBody.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,7 @@ import { useFluent_unstable as useFluent } from '@fluentui/react-shared-contexts
* @param element - HTMLElement to check scroll state of

@github-actions github-actions Bot Aug 6, 2026

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🕵🏾‍♀️ visual changes to review in the Visual Change Report

vr-tests-react-components/Avatar Converged 1 screenshots
Image Name Diff(in Pixels) Image Type
vr-tests-react-components/Avatar Converged.badgeMask.normal.chromium.png 5 Changed
vr-tests-react-components/Positioning 2 screenshots
Image Name Diff(in Pixels) Image Type
vr-tests-react-components/Positioning.Positioning end.chromium.png 882 Changed
vr-tests-react-components/Positioning.Positioning end.updated 2 times.chromium.png 16 Changed
vr-tests-react-components/ProgressBar converged 3 screenshots
Image Name Diff(in Pixels) Image Type
vr-tests-react-components/ProgressBar converged.Indeterminate + thickness - Dark Mode.default.chromium.png 59 Changed
vr-tests-react-components/ProgressBar converged.Indeterminate + thickness - High Contrast.default.chromium.png 69 Changed
vr-tests-react-components/ProgressBar converged.Indeterminate + thickness.default.chromium.png 27 Changed
vr-tests-react-components/Skeleton converged 1 screenshots
Image Name Diff(in Pixels) Image Type
vr-tests-react-components/Skeleton converged.Opaque Skeleton with rectangle - Dark Mode.default.chromium.png 9 Changed
vr-tests-react-components/TagPicker 2 screenshots
Image Name Diff(in Pixels) Image Type
vr-tests-react-components/TagPicker.disabled - RTL.disabled input hover.chromium.png 635 Changed
vr-tests-react-components/TagPicker.disabled - Dark Mode.disabled input hover.chromium.png 658 Changed

There were 2 duplicate changes discarded. Check the build logs for more information.

*/
const getScrollState = ({ scrollTop, scrollHeight, clientHeight }: HTMLElement): DrawerScrollState => {
const epsilon = 1;

@PaulGMardling PaulGMardling Aug 6, 2026

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The change is reasonable, browser layout values can be fractional, so strict equality may fail near the bottom.

Main criticisms:

epsilon = 1 is unexplained and could classify the drawer as bottom while still 1px away. Name it descriptively or document why 1px is acceptable.

The top check remains strict. For consistency, consider scrollTop <= epsilon, especially if fractional or slightly negative values can occur.

Prefer comparing the remaining distance

I'd suggest

const scrollTolerance = 1;

if (scrollHeight <= clientHeight) return 'none';
if (scrollTop <= scrollTolerance) return 'top';
if (scrollHeight - clientHeight - scrollTop <= scrollTolerance) return 'bottom';
return 'middle';

Tests should be added to cover fractional values, exact boundaries, and values within/outside the tolerance.

if (scrollHeight <= clientHeight) {
return 'none';
}
Expand All @@ -31,7 +32,7 @@ const getScrollState = ({ scrollTop, scrollHeight, clientHeight }: HTMLElement):
return 'top';
}

if (scrollTop + clientHeight === scrollHeight) {
if (scrollTop + clientHeight >= scrollHeight - epsilon) {
return 'bottom';
}

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