fix(copy-mode): harden wide-glyph h/l and align width source

[OnlineChef]

Summary

Follow-up to the CJK copy-mode horizontal motion work (upstream #1469 / #1000).

• Drive row_cell_glyphs through crate::ghostty::unicode_codepoint_width so it matches last_character_col / char_cell_width
• Harden next_cell_col / prev_cell_col when the cursor sits on a wide glyph’s trailing cell
• Add unit coverage for mid-row trailing cells and flush-right wide glyphs

Multi-model review

Addresses consensus findings from parallel Grok review of upstream #1469 (caution → ship blockers for width API + trailing-cell behavior).

Validation

Local cargo / just check are forbidden in this environment. Rely on CI (gh pr checks).

  

Greptile Summary

This PR updates copy-mode horizontal movement for wide glyphs. The main changes are:

• Uses Ghostty’s Unicode cell-width source when building row glyph maps.
• Treats wide-glyph leading and trailing cells as one glyph for h and l movement.
• Adds tests for mid-row trailing cells, flush-right wide glyphs, and combining marks.

Confidence Score: 5/5

This PR appears safe to merge.

The change is localized to copy-mode horizontal cursor stepping and uses the same width source as related helpers. The added tests cover the affected wide-glyph and combining-mark cases. No functional or security issues were identified.

No files require special attention.

T-Rex Logs

What T-Rex did

• T-Rex attempted to run gh pr checks 62 --json and encountered an unknown flag error, causing the command to exit with status 1.
• T-Rex attempted to run gh pr checks 62 again without the --json flag, but authentication was missing (GH_TOKEN), causing the command to exit with status 4.
• T-Rex executed the narrow Cargo test command; the build.rs step failed when trying to run zig build for vendored libghostty-vt, exiting with code 101.

_{Ran code and verified through T-Rex}

Important Files Changed

Filename	Overview
src/app/input/copy_mode.rs	Aligns copy-mode glyph width calculation with Ghostty width handling and updates horizontal cursor stepping and tests for wide-glyph trailing cells.

Sequence Diagram

sequenceDiagram
participant Key as h/l keypress
participant Move as move_copy_cursor
participant Row as copy_mode_visible_row_text
participant Glyphs as row_cell_glyphs
participant Step as next_cell_col/prev_cell_col

Key->>Move: horizontal copy-mode motion
Move->>Row: fetch visible row text
Row-->>Move: "Option<String>"
Move->>Glyphs: build (leading_col, width) using Ghostty width
Glyphs-->>Move: glyph cell map
Move->>Step: step from cursor_col across glyph/blank
Step-->>Move: updated cursor_col

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_{Reviews (1): Last reviewed commit: "style(copy-mode): rustfmt wide-glyph hel..." | Re-trigger Greptile}

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: c4dc30f5-dc32-46e5-9d3c-c26264144372

📥 Commits

Reviewing files that changed from the base of the PR and between 60f5fb6 and 25380a2.

📒 Files selected for processing (1)

• src/app/input/copy_mode.rs

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📝 Walkthrough

Summary by CodeRabbit

• Bug Fixes
  • Improved copy-mode cursor movement across wide characters and combining marks.
  • Corrected left and right navigation from trailing cells to keep the cursor aligned with glyph boundaries.
  • Prevented the cursor from moving beyond the pane’s right edge.

Walkthrough

Copy-mode cursor horizontal stepping now uses Ghostty’s glyph cell widths. Movement across wide and combined glyphs handles trailing cells explicitly, including right-edge behavior, with updated unit test expectations.

Changes

Copy-mode cursor movement

Layer / File(s)	Summary
Align glyph widths with terminal cells src/app/input/copy_mode.rs	row_cell_glyphs now uses Ghostty’s unicode_codepoint_width calculation.
Handle wide-glyph movement and boundaries src/app/input/copy_mode.rs	Horizontal stepping handles wide-glyph trailing cells, combined glyphs, and pane-edge limits; related tests were updated.

Estimated code review effort: 3 (Moderate) | ~15–30 minutes

Suggested reviewers: ogulcancelik, reobin, kovalov

Poem

I’m a rabbit hopping cell to cell,
Where wide glyphs make their shadows swell.
Trailing spaces? Back to the start!
No edge jumps, no cursor dart.
Ghostly widths keep paths precise. 🐇

✨ 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 cursor/fix-copy-mode-wide-glyph-85a1

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