Remove wheel-scroll tab/pane navigation (rollback #80/#83)

[GeneralD]

Rolls back and completely removes the mouse-wheel tab/pane navigation
feature (scroll + scroll_cooldown_ms, #80/#83). Closes #103.

Why

zellij delivers ScrollUp/ScrollDown with no device identity and no
physical detent, so a notched wheel and a stepless device (Magic Mouse,
trackpad) are indistinguishable at the event level. A stepless device emits a
burst of events per flick, and no single rate-limiter value reconciles both
classes — a short cooldown still races through many tabs/panes, a long one locks
out deliberate input and lets momentum tails add stray steps. The successive
attempts each only moved the failure mode:

• scroll: configurable wheel sensitivity (too fast — one flick jumps several steps) #83 — leading-edge cooldown (raced on long bursts)
• scroll_cooldown_ms anchors the cooldown to the first event, so momentum scrolling races then freezes #96 / fix: debounce the wheel cooldown to the last event so momentum scrolling steps once (#96) #97 — debounce to the last event (locked out continuous scrolling)
• Wheel throttle locks out continuous scrolling — rejects every step until you stop (regression from #96) #100 / fix: reopen the wheel cooldown on every timer so continuous scrolling paces, not locks out (#100) #101 — reopen-on-timer throttle (stepless devices still flood, then stall)

On a Magic Mouse / trackpad the bar still receives a flood of scroll events up
front and then stops responding. There is no scroll_cooldown_ms value that
behaves correctly for both device classes, so the feature is removed rather than
tuned further. Full rationale in #103.

What's removed

• src/scroll.rs — deleted in full (traversal + gate rate-limiter).
• src/lib.rs — scroll_cooling state, the ScrollUp/ScrollDown/Timer
  handlers, the EventType::Timer subscription, scroll / arm_scroll_cooldown
  / scroll_tabs / scroll_panes / focused_pane_id / pane_focus_order, and
  the wheel test suite + helpers.
• src/config.rs — the scroll and scroll_cooldown_ms keys, their defaults,
  parsing, and tests.
• src/projection.rs — pane_ids_in_reading_order (scroll-only) and its tests;
  is_tiled_terminal stays (still used by project).
• README.md — the scroll / scroll_cooldown_ms documentation.

Compatibility / breaking

Config parsing is total, so existing layouts that still set scroll /
scroll_cooldown_ms keep loading — the now-unknown keys are simply ignored and
have no effect. The wheel over the bar returns to inert (pre-#80). No permission
change: wheel navigation needed nothing beyond the default set
(ReadApplicationState + ChangeApplicationState).

Verification

• cargo build --target wasm32-wasip1 — ✓
• cargo test --lib (host triple) — 268 passed, 0 failed ✓
• cargo clippy --lib — clean ✓
• cargo fmt --check — clean ✓

Related

#80 (feature), #83 (cooldown), #96 / #97, #100 / #101 (fix attempts),
#77 (mouse-interaction tracking).

Summary by CodeRabbit

• Documentation
  • Updated configuration examples and option descriptions: removed scroll/cooldown settings; added tab gap and pane fill gradient controls, plus inactive-tab dimming and active-tab depth lift.
• Removed Features
  • Removed mouse wheel navigation for switching tabs and panes, along with related cooldown gating.
  • Removed tab drag/reorder behavior and the associated configuration option.
• Permissions
  • Simplified the permission request to a fixed two-permission set.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: a0528c31-f35f-4793-af7c-aea2f9277a5f

📥 Commits

Reviewing files that changed from the base of the PR and between 1f595df and 8c216fd.

📒 Files selected for processing (5)

• README.md
• cliff.toml
• src/config.rs
• src/lib.rs
• src/line.rs

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📝 Walkthrough

Walkthrough

The PR removes mouse-wheel tab/pane navigation and drag-to-reorder features entirely. src/config.rs drops scroll, scroll_cooldown_ms, and reorder fields with parsing and tests. src/lib.rs removes the scroll module export, scroll_cooling and drag state fields, timer subscription, and all scroll/drag handlers and helpers. src/line.rs removes Shift enum and drag_steps gesture API. src/projection.rs deletes pane_ids_in_reading_order helper. Tests across all files are updated or removed. README.md and cliff.toml documentation are revised.

Changes

Gesture feature removal

Layer / File(s)	Summary
Config: scroll and reorder settings removal src/config.rs	Removes ScrollMode import, scroll, scroll_cooldown_ms, and reorder struct fields with defaults and doc comments; removes parsing branches in from_configuration; updates test assertions and deletes parsing-specific unit tests.
State struct and subscription initialization changes src/lib.rs	Removes pub mod scroll export, scroll_cooling and drag fields from State, DragState type definition; updates load() to use Self::permissions() without arguments and removes EventType::Timer subscription.
Permissions function and event handler cleanup src/lib.rs	Simplifies State::permissions() to a zero-arg function with fixed return value; removes mouse wheel scroll/navigation and timer-driven cooldown handling from update() dispatch; strips drag gesture arms.
Helper implementation and impl block cleanup src/lib.rs	Deletes scroll dispatcher, cooldown arming, tab/pane scroll helpers, focused-pane lookup, and pane-order traversal functions from impl State block.
Event and interaction test updates and removals src/lib.rs	Updates permission test for fixed two-permission request; changes load test input to remove reorder config; removes drag-reorder expectations from mouse interaction tests; deletes scroll/cooldown and wheel event tests; adjusts close-button click test; removes scroll/drag test helpers.
Line module gesture API removal src/line.rs	Updates module documentation to clarify click-to-focus behavior and remove drag references; removes Shift enum and drag_steps function with drop-resolution helpers; deletes drag_steps test suite.
Projection helper removal src/projection.rs	Removes pane_ids_in_reading_order public function and tests; is_tiled_terminal remains intact.
Documentation and changelog updates README.md, cliff.toml	Removes scroll/cooldown example and documentation; adds tab_gap and gradient rendering options (gradient, gradient_shape, gradient_angle, gradient_radial), inactive_dim, and perspective; updates changelog note about reorder permissions and adds note on releases/latest/download/ permission keying.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~60 minutes

Possibly related PRs

• GeneralD/zellij-tabmap#21: Inverse change that introduces Shift enum and drag_steps function to src/line.rs for drag-to-reorder gesture calculation.
• GeneralD/zellij-tabmap#22: Inverse change that adds drag-to-reorder state (drag: Option<DragState>) and handler logic to src/lib.rs with MoveTabByTabId permission.
• GeneralD/zellij-tabmap#90: Introduces the wheel-scroll cooldown implementation (scroll_cooldown_ms, cooldown gate logic) that this PR deletes across config, scroll module, and state handling.

Poem

🐇 Two gestures spun beyond our reach,
Scroll bursts and drag reorder teach
That some code paths belong in dreams.
We hop back clean—no middle schemes!
The bar stays still, the drags are gone,
Simplicity: our best new dawn. ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main objective: removing wheel-scroll navigation and rolling back prior changes (#80/#83), which aligns with all the significant code deletions across multiple files.
Linked Issues check	✅ Passed	All code changes align with #103 requirements: src/scroll.rs deleted, scroll state/handlers removed from src/lib.rs, scroll config removed from src/config.rs, pane_ids_in_reading_order removed from src/projection.rs, and documentation updated in README.md, with backward compatibility maintained.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to removing wheel-scroll navigation as specified in #103; no unrelated modifications detected beyond the intended removal scope.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch revert/103-remove-wheel-scroll

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[Copilot]

Pull request overview

This PR reverts and removes the previously added mouse-wheel tab/pane navigation feature, returning wheel behavior over the tab bar to inert (pre-#80) and eliminating the associated config surface and traversal logic.

Changes:

• Deletes the wheel traversal + cooldown limiter implementation and its unit tests (src/scroll.rs).
• Removes wheel event handling/state and all scroll-specific helpers/tests from the plugin state machine (src/lib.rs).
• Removes scroll / scroll_cooldown_ms config keys (and their docs/tests), and drops the now-scroll-only reading-order helper from projection (src/config.rs, src/projection.rs, README.md).

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/scroll.rs	Removes the pure traversal + cooldown-gate module and its tests.
src/lib.rs	Removes wheel event handling, cooldown state, and pane/tab traversal helpers/tests.
src/config.rs	Removes scroll-related config keys, defaults, parsing, and tests.
src/projection.rs	Removes the scroll-only pane reading-order helper and its tests; keeps the tiled-pane filter.
README.md	Removes documentation for scroll and scroll_cooldown_ms.

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