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explorer: a restored snapshot loses to a folder's running animation

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Active
Tech stack
zig
Domain
desktop, testing

Research direction

Start with core/widgets/TreeWidget.zig (the branch's expanded and the _expanded data around lines 468 and 890) and plugins/workbench/src/files.zig (carryBack and the expander near line 1150), then find where setExplorerBranchOpen is called. Replay #293's property test with seed 0x6 to reproduce the failure. Done when the tree draws open or closed from the caller's value each frame, the expander reports toggles instead of writing back, and both the seed test and a new test that sets open state mid-close-animation pass.

Written by the indexing model from the issue text.

Description

bug

Found by #293 (#280 step B1), whose property test replays a demo and seeks to random moments. With seed 0x6 it fails in the tour's explorer, on seeks to 46937, 13890 and 17830 ms: after a snapshot restore, the explorer's open folders aren't the ones the snapshot holds. The checked-in seed and nine others pass, so this shows up only when a seek lands during a folder's open or close animation.

Cause: open state lives in two places that copy each other

  • core.widgets.TreeWidget's branch keeps its own expanded, stored per widget as _expanded in dvui's data (core/widgets/TreeWidget.zig:468, :890). It eases toward the caller's value through an animation.
  • The workbench keeps the explorer's open folders on the host (setExplorerBranchOpen, the per-branch open state the snapshot captures and restores). Each frame it writes the branch's expanded back into that state (plugins/workbench/src/files.zig, carryBack and the expander around :1150).

So a restore that sets the host's open state while a branch's own animation is still running loses: the next frame copies the widget's in-flight value back over the restored one. Nothing is wrong with the snapshot or the player. The model has two writers.

Fix

Give the open state one owner. The tree should draw open or closed from the caller's value each frame, keeping only the animation's progress as its own state, and never write it back. Clicking the expander reports a toggle to the caller, which changes its state. Then a restore, or anything else that sets the open folders (a reveal-in-explorer, a demo keyframe), takes effect on the next frame with no race.

Test: #293's property test with seed 0x6 must pass, plus a focused integration test: start a folder's close animation, set the open state from outside, run frames, and check the branch ends open.

Part of #280.

🤖 Generated with Claude Code

Dominant language
Zig
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Forks
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Avg merge
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Merged PRs (30d)
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