scrollbar: improve visibility animation - #2737
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August 16, 2026 09:44
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Base played the scrollbar entrance and exit with its own hardcoded durations, curves, and per-mode choreography, which put product motion below the gpui-base seam. Base now plays a transition it does not own. ScrollbarMotion carries the idle hold, enter, exit, and expand durations plus a ScrollbarEntrance choreography, and defaults to motionless: an unstyled scrollbar appears and disappears with no fade or slide. crates/ui projects the product timing through ScrollbarTheme::motion, on the full theme projection and on set_scrollbar_mode alike, so a runtime mode change cannot leave a stale entrance behind. A zero duration is now the only way to say "adopt the target now", which also covers reduced motion and always-visible scrollbars. That replaces the separate immediate flag, and settles a transition that was already in flight when the policy changed — the flag used to let it run on, because set_visible returned early on an unchanged target. Rendered behavior under the styled theme is unchanged. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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Description
Improve scrollbar appearance and disappearance motion across the shared
gpui-baseimplementation.This implementation was AI-assisted, then reviewed, visually tested in the Scrollbar story, and covered with test-first regression tests.
Screenshot
The change is temporal rather than a static layout change. It was manually exercised in the Scrollbar story across Scrolling, Hover, and Always modes.
How to Test
cargo fmt --all -- --check cargo test -p gpui-base cargo run -p gpui-component-story -- ScrollbarIn the story, switch between Scrolling, Hover, and Always and verify the entrance/exit directions, visible fade, interruption reversal, and stationary Always behavior.
Checklist
cargo runfor story tests related to the changes.