fix: use tolerance for scroll bottom detection to prevent auto-scrolling breaking #9303
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taylorsilva
requested changes
Oct 9, 2025
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LGTM - I made this test pipeline to validate the fix:
jobs:
- name: job
plan:
- task: print
config:
platform: linux
image_resource:
type: mock
source: {mirror_self: true}
run:
path: bash
args:
- -c
- |
sleep 3s
for i in {1..10000}; do
sleep 0.5s
echo "Line $i"
doneOnce the text hit the bottom of the screen, shortly after the auto-scroll would stop. Re-building the frontend with this PR fixed the issue, auto-scrolling kept working.
Funnily, the related test for this PR is failing now:
$ yarn test
Compiling > Starting tests
elm-test 0.19.1-revision16
--------------------------
Running 2953 tests. To reproduce these results, run: elm-test --fuzz 100 --seed 159141073039854
↓ BuildTests
↓ build page
✗ when build is running but the user is not scrolled to the bottom it does not scroll on build event
[Scroll ToBottom "build-body"]
╷
│ Expect.equal
╵
8000
[]
TEST RUN FAILED
Duration: 637 ms
Passed: 2952
Failed: 1
Please update the test so it passes. Then this is good to merge. Thank you!
… breaking The exact equality check for detecting scroll position at bottom was failing due to sub-pixel rounding differences between scrollHeight, scrollTop, and clientHeight. This caused autoScroll to incorrectly disable during rapid content updates. Added 1px tolerance to account for browser rounding behavior. Signed-off-by: Mathias Bogaert <mathias.bogaert@gmail.com>
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The exact equality check for detecting scroll position at bottom was failing due to sub-pixel rounding differences between scrollHeight, scrollTop, and clientHeight. This caused autoScroll to incorrectly disable during rapid content updates.
Added 1px tolerance to account for browser rounding behavior.