fix(cdk/scrolling): prevent subpixel gaps in virtual scroll viewport #31940
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Mr-KRAMA
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Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA). View this failed invocation of the CLA check for more information. For the most up to date status, view the checks section at the bottom of the pull request. |
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@Mr-KRAMA Can you remove the second commit? I think that failure was either a flake or an unrelated issue that can be fixed separately from this PR |
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@mmalerba Thanks for the feedback! I've removed the second commit as requested. How should I approach the lighthouse audit failure? Should it be a separate PR or is it expected to be handled by maintainers? |
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This PR fixes the issue where cdk-virtual-scroll-viewport renders visible gaps between items at certain zoom levels or scroll positions.
Problem:
Thin gaps (~0.5px) appear between consecutive rows when using *cdkVirtualFor
Issue occurs due to subpixel rounding in offset calculations
Most noticeable when zooming browser window or at specific scroll positions
Solution:
Added Math.round() to the offset calculation in setRenderedContentOffset()
Ensures all item positions are rounded to whole pixels
Eliminates subpixel gaps while maintaining smooth scrolling
Changes:
Single line change in fixed-size-virtual-scroll.ts
Wraps this._itemSize * newRange.start with Math.round()
Testing
Tested with different zoom levels (300%)
Verified no gaps appear between items during scrolling
Confirmed smooth scrolling behavior is preserved
Fixes #31824