fix: split action respects segment timescale (speed)

[pmartinonales]

Fix: Split action respects segment timescale (speed)

Problem

#1445 When using the split tool (scissors) on the timeline, if a previous segment had a modified playback speed (timescale), the split would occur at the wrong position instead of where the user clicked.

Root Cause

The code was mixing two different time representations:

Time Space	Formula	Description
Timeline time	(end - start) / timescale	Visual duration on the timeline
Recording time	end - start	Raw source video duration

The splitClipSegment function searched for the target segment using recording time durations instead of timeline time, causing incorrect segment detection when earlier segments had modified speeds.

Example

Consider this timeline:

• Segment 0: 100 frames at 2x speed → 50s visible on timeline
• Segment 1: 100 frames at 1x speed → 100s visible on timeline

When clicking to split at 25% into Segment 1 (which is at 75s into the timeline):

	Before Fix	After Fix
Result	❌ Splits Segment 0 at frame 75	✅ Splits Segment 1 at frame 25

Changes

apps/desktop/src/routes/editor/context.ts

• Account for timescale when calculating segment duration during search
• Convert timeline time back to recording time when setting the split position

apps/desktop/src/routes/editor/Timeline/ClipTrack.tsx

• Calculate splitTime in timeline time (divide by timescale) to be consistent with prevDuration()

Testing

• Split works correctly when all segments are at 1x speed
• Split works correctly when previous segments have modified speed (0.5x, 2x, 4x, etc.)
• Split at current playhead position (C key) works correctly with modified speeds
• Click-to-split in split mode works correctly with modified speeds

Summary by CodeRabbit

• Bug Fixes
  • Clip splitting now accounts for each segment's timescale, ensuring splits occur at the correct absolute position for clips with varying playback rates — improving timeline accuracy and editing reliability.
• Style
  • Updated track button background styling for a more consistent appearance in the editor UI.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

---

Note

Ensure clip splitting uses timeline time and converts to recording time so splits occur at correct positions with speed-adjusted segments; minor add-button style tweak.

• Bug fix — clip splitting respects timescale
  • Update projectActions.splitClipSegment in apps/desktop/src/routes/editor/context.ts to search by timeline duration (end - start) / timescale and convert split position back to recording time (* timescale).
  • In apps/desktop/src/routes/editor/Timeline/ClipTrack.tsx, compute splitTime as fraction * (end - start) / timescale before calling splitClipSegment.
• UI
  • Tweak apps/desktop/src/routes/editor/Timeline/TrackManager.tsx add button styling (class changes).

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[coderabbitai]

Walkthrough

Split and duration calculations for clip segments were made timescale-aware: splitting now normalizes computed times against the segment's timescale, and segment start/end updates use timescale-adjusted values. A minor UI style tweak updated a TrackManager button background class.

Changes

Cohort / File(s)	Summary
Timescale-aware split logic apps/desktop/src/routes/editor/Timeline/ClipTrack.tsx, apps/desktop/src/routes/editor/context.ts	Split and duration math updated to account for segment.timescale. splitTime/duration are normalized by timescale; split position is computed in recording units and used to update segment start/end.
TrackManager styling apps/desktop/src/routes/editor/Timeline/TrackManager.tsx	Button background class changed from bg-gray-2/60 to bg-gray-1 (visual/style-only change).

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20–30 minutes

• Verify arithmetic and unit consistency around timescale conversions in both files.
• Check for off-by-one/rounding and boundary conditions when splitting at segment edges.
• Validate UI behavior in split mode across varied timescales and playback rates.
• Confirm the style change has no unintended visual regressions (dark mode variants).

Possibly related PRs

• Fix trimming behavior #1273 — Modifies clip segment start/end calculations to be timescale-aware (closely related changes).
• fix(editor): show scissors cursor when clip tool is active #1218 — Alters clip-splitting behavior and split-mode handling in the timeline UI (related to split handlers).
• improvement: support cutting during playback #969 — Adjusts callers/use of splitClipSegment with playback time considerations (touches same split logic).

Suggested labels

Desktop

Suggested reviewers

• Brendonovich

Poem

🐰 I hopped through code with careful paws,

split times now heed their silent laws.
Segments line up, neat and kind,
each timescale tick now well aligned.
✨

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 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 fix: enabling the split action to respect segment timescale (speed), which directly addresses the core bug being fixed across all modified files.

✨ Finishing touches

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[richiemcilroy]

Amazing!

[coderabbitai]

Actionable comments posted: 0

🧹 Nitpick comments (1)

apps/desktop/src/routes/editor/Timeline/TrackManager.tsx (1)

60-60: Consider moving unrelated UI styling to a separate PR.

This background color change appears unrelated to the PR's stated objective of fixing the timescale bug in the split tool. Mixing cosmetic UI changes with bug fixes can make code review and git history less clear.

Additionally, note that TrackIcon at line 72 still uses bg-gray-2/60. If this background change is intentional, verify whether TrackIcon should be updated for visual consistency.

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Reviewing files that changed from the base of the PR and between 5761eab and 73b4b71.

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• apps/desktop/src/routes/editor/Timeline/TrackManager.tsx (1 hunks)

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