fix: open latched link on release with press-time chord + defer-clear latch (#71 follow-up)

[austinywang]

Two review follow-ups (codex) on the link-under-mouse-reporting work (#71/#74/#75/#76/#77, manaflow-ai/cmux#5128), unifying the link-click decision so the open path and the report-suppression path use the same press-time chord.

1. Swallowed click (P2). When the ctrl/super modifier was released before the left button, the report was still suppressed (latched at press), but processLinks re-derived linkAtPos from the now-empty live mods — so the link no longer matched and the click was swallowed (link never opened, nothing reached the program). linkAtPos now uses the latched chord while link_click_active is set, and the release path attempts processLinks whenever the click is latched (not only while over_link is still set). The latched click opens its link instead of being dropped.

2. Stale latch (P3). The unconditional reset was placed after the report block, but the successful-link (if (processed) return true) and prompt-click branches return early and never reached it. The latch is now cleared with a function-level defer, so it resets on every left-release return path. The press remains the only setter.

Net: a single press-time decision drives press/drag/release suppression and link opening, consistently — closing the modifier-timing edge cases. zig fmt/ast-check clean; behavior is integration-level, verified by cmux dogfood.

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AI disclosure (per AI_POLICY.md): developed with Claude Code (Claude Opus 4.8); reviewed by a maintainer.

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Summary by cubic

Fixes swallowed link clicks when ctrl/super is released before the left mouse button. We latch the press-time chord for the full click and always clear it on release, so latched clicks open reliably. Addresses manaflow-ai/cmux#5128.

• Bug Fixes
  • Use the press-time modifier chord while link_click_active to resolve linkAtPos, and attempt open on release even if over_link changed.
  • Clear the latch on every left-button release via a function-level defer to avoid stale suppression on early returns.

^{Written for commit 9f014e9. Summary will update on new commits.}

Summary by CodeRabbit

• Bug Fixes
  • Improved consistency of modifier-key link clicking. Fixed an issue where Ctrl/Cmd-clicking links could fail if hover state changed between mouse press and release events.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 09e74927-6da4-4d2d-92fe-6fdbd66da717

📥 Commits

Reviewing files that changed from the base of the PR and between dcc611b and 9f014e9.

📒 Files selected for processing (1)

• src/Surface.zig

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📝 Walkthrough

Walkthrough

This PR modifies src/Surface.zig to fix link activation when ctrl/super is held at mouse-button press. It latches the modifier state at press time, ensures cleanup on release via a deferred statement, and makes link resolution use consistent effective modifiers throughout the interaction.

Changes

Link activation latch and dispatch

Layer / File(s)	Summary
Press-time latch capture and release-time dispatch src/Surface.zig	At left-button press, link_click_active is set based on ctrl/super state; a defer ensures cleanup on release. Link-click dispatch now checks over_link or link_click_active to trigger even when the mouse has moved off the link. Prior unconditional reset is removed.
Effective modifier resolution for consistent link matching src/Surface.zig	linkAtPos computes effective modifiers using the latched ctrl/super while link_click_active is true, otherwise using live mouse modifiers. This keeps OSC8 and link matching consistent with the press-time latch during release handling.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• manaflow-ai/ghostty#74: Both PRs modify src/Surface.zig's mouseButtonCallback link-activation handling for ctrl/super (Cmd) clicks—fix: suppress mouse reporting for the full cmd-clicked link click (follow-up to #71) #74 suppresses mouse press/release reporting for cmd-clicked links, while this PR latches that modifier state to drive consistent link handling through release.
• manaflow-ai/ghostty#71: Both PRs modify src/Surface.zig link handling to correctly honor the ctrl/super "link-activation" chord during mouse interaction (this PR via press-time latch and effective modifiers, the other PR via ctrl/super-aware link/hover refresh gating).

Poem

🐰 A latch at press, a defer at rest,
The modifier stays through mouse's zest,
Hover or not, the link knows best—
Ctrl+click consistency passes the test! ✨

🚥 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 directly and accurately describes the main technical fix: latching link-click decisions at press time and clearing the latch on release using defer, addressing modifier-timing edge cases.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix-5128-link-open-latched

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[greptile-apps]

Greptile Summary

This PR fixes two follow-up issues from the link-under-mouse-reporting work: a swallowed click when the ctrl/super modifier is released before the mouse button, and a stale latch when the early-return paths in mouseButtonCallback bypassed the unconditional reset. The link_click_active latch is now cleared via a defer (guaranteeing reset on all return paths), and processLinks is attempted whenever the latch is active (not only when over_link is set), while linkAtPos synthesizes the press-time chord when the latch is active.

• Swallowed-click fix: The condition guarding processLinks is widened from over_link to over_link or link_click_active, and linkAtPos substitutes ctrlOrSuper(.{}) for the live (possibly already-released) mods when link_click_active is true — so the latched click still resolves and opens its link instead of being silently dropped.
• Stale-latch fix: The reset of link_click_active is moved from after the report block (which early returns skip) to a defer registered immediately after the press-time setter, ensuring every left-button-release code path clears the field.

Confidence Score: 4/5

Safe to merge; changes are tightly scoped to the link-click latch lifecycle with no impact on unrelated mouse paths.

Both fixes are logically sound and the defer-based clear correctly covers all return paths. The one subtle edge case worth noting — pressing ctrl+left when not over any link still causes the click to be swallowed (report suppressed, no link opened), but this was pre-existing behaviour unchanged by the PR. The expanded processLinks guard and linkAtPos mod synthesis introduce no new code paths that could produce incorrect results.

No files require special attention; the single changed file src/Surface.zig has clear, well-commented diffs.

Important Files Changed

Filename	Overview
src/Surface.zig	Two targeted fixes to link-click latch lifecycle: defer-based clear ensures all early-return paths reset link_click_active, and the processLinks guard + linkAtPos mod synthesis handle the modifier-released-before-button edge case cleanly.

Sequence Diagram

sequenceDiagram
    participant User
    participant mouseButtonCallback
    participant processLinks
    participant linkAtPos

    Note over User,linkAtPos: Happy path: modifier held through release
    User->>mouseButtonCallback: left press (ctrl/super held)
    mouseButtonCallback->>mouseButtonCallback: "link_click_active = true"
    User->>mouseButtonCallback: left release (ctrl/super still held)
    mouseButtonCallback->>mouseButtonCallback: defer registered (clears latch on return)
    mouseButtonCallback->>processLinks: over_link OR link_click_active → call
    processLinks->>linkAtPos: linkAtPos(pos)
    linkAtPos->>linkAtPos: "link_click_active=true → use ctrlOrSuper mods"
    linkAtPos-->>processLinks: Link found
    processLinks-->>mouseButtonCallback: "processed=true → return true"
    mouseButtonCallback->>mouseButtonCallback: "defer fires: link_click_active = false"

    Note over User,linkAtPos: Edge case fix: modifier released before button
    User->>mouseButtonCallback: left press (ctrl/super held)
    mouseButtonCallback->>mouseButtonCallback: "link_click_active = true"
    User->>mouseButtonCallback: modifier released (over_link cleared)
    User->>mouseButtonCallback: "left release (modifier gone, over_link=false)"
    mouseButtonCallback->>mouseButtonCallback: defer registered
    mouseButtonCallback->>processLinks: "link_click_active=true → still enters block"
    processLinks->>linkAtPos: linkAtPos(pos)
    linkAtPos->>linkAtPos: "link_click_active=true → synthesize ctrlOrSuper mods"
    linkAtPos-->>processLinks: Link found (mods not from live state)
    processLinks-->>mouseButtonCallback: "processed=true → return true"
    mouseButtonCallback->>mouseButtonCallback: "defer fires: link_click_active = false"

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