Broken horizontal scrolling in Firefox #1164
Description
It has 2 manifestations:
- If you drag the bottom scrollbar and your cursor moves beneath the bottom of the grid, it will scroll vertically at the same time (and vice versa).
- If you have a cell selected when you start scrolling, the selection changes with your scrolling.
Screen.Recording.2025-12-09.at.11.45.35.AM.mov
We've traced the issue to this old PR #1063