Dialog/Drawer: lock scroll on the root element to prevent layout shift#42545
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mdo wants to merge 1 commit into
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Dialog/Drawer: lock scroll on the root element to prevent layout shift#42545mdo wants to merge 1 commit into
mdo wants to merge 1 commit into
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Apply the dialog-open scroll-lock (overflow: hidden) to the root <html> element instead of <body>, so it sits on the same element as scrollbar-gutter: stable. Co-locating them keeps the gutter reserved while the scrollbar is hidden, so the page no longer shifts (and the ::backdrop covers the gutter instead of leaving a white strip) when a dialog or drawer opens. Fixes #39221, #39972, #40908, #40659.
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Problem
Opening a dialog/drawer can shift page content sideways, and with
scrollbar-gutter: stablethe reserved gutter renders as a bare white strip instead of the dimmed overlay (#40659).Cause
scrollbar-gutter: stableis on:root(_root.scss), so the viewport scrollbar and its reserved gutter live on<html>. But the scroll-lock appliedoverflow: hiddento<body>. Because<html>'s overflow isvisible, the body→viewport overflow-propagation quirk hides the scrollbar at the viewport level while the gutter reservation stays on<html>— and in that split state browsers don't reliably honor the gutter, so content reflows and the gutter strip falls outside the native::backdrop.Fix
Apply the
dialog-openlock to the root element (<html>), co-locatingoverflow: hiddenwithscrollbar-gutter: stable. The gutter stays reserved while the scrollbar hides (no shift), and since<html>is the viewport scroller the::backdropcovers the gutter (no white strip).dialog-base.js: toggledialog-openondocument.documentElementinstead ofdocument.body._dialog.scss: scope the rule to:root.dialog-open.Fixes #39221, #39972, #40908, #40659.
Verification
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