[3/4] TUI: reuse retained text measurements

[kevinyang372]

Description

Stack 3 of 4. Reuses TuiText natural measurements when retained content is laid out again at the same width, and avoids copying a viewport selection snapshot when there is no active selection and line-end trimming is disabled.

This layer targets steady-state frame overhead after stack PR 2 has already bounded paint work. Width changes still recompute text measurement, and selection snapshots remain enabled whenever selection or trimmed line-end behavior needs them.

Benchmark at 120×50 versus stack PR 2:

• Retained rich response, 1,000 rows: 0.925 → 0.129 ms (86% faster).
• Retained rich response, 10,000 rows: 8.56 → 0.598 ms (93% faster).
• Retained middle frame, 10,000 rows: 8.41 → 0.395 ms (95% faster).
• Retained streaming tail at end, 10,000 rows: 17.2 → 9.88 ms (42% faster).
• Invalidated rich response, 10,000 rows: 9.38 → 9.85 ms (~5% slower).
• Many completed blocks, 10,000: 29.2 → 31.6 µs/frame (~8% slower, still flat with history depth).

The next stack layer removes the remaining repeated streaming-height work and owns auto-scroll reconciliation.

Stack: #14575 ← #14582 ← 3/4 → oz/tui-streaming-height-reconciliation.

Agent conversation: https://staging.warp.dev/conversation/2b6af7be-b227-4b20-aaf4-23c9a8494b81
Stack plan: https://staging.warp.dev/drive/notebook/yM2YcQsILFsFzwixBDbD9p
Performance plan: https://staging.warp.dev/drive/notebook/LHzsFd1B8XbQ8AnUqB88LS

Linked Issue

N/A — Warp Agent CLI retained-frame performance.

Testing

• cargo nextest run -p warpui_core --features tui — 555 passed, 7 skipped.

• cargo nextest run -p warp_tui — 902 passed.

• Strict Clippy passed for warpui_core --features tui and warp_tui --features test-util.

• cargo bench -p warp_tui --features test-util --bench transcript_bench

• ./script/format

• Signed-in 120×40 tmux PTY: zero state and unsent input repainted correctly.

• I have manually tested my changes locally with ./script/run-tui

Agent Mode

• Warp Agent Mode - This PR was created via Warp's AI Agent Mode

CHANGELOG-NONE

[kevinyang372]

• [3/4] TUI: reuse retained text measurements #14585 : 2 dependent PRs (#14586 , #14594 ) 👈 (View in Graphite)
• [2/4] TUI: bound clipped viewport painting #14582
• [1/4] TUI: add retained transcript performance benchmarks #14575
• master

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[oz-for-oss]

@kevinyang372

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[oz-for-oss]

Overview

This PR caches TuiText natural measurements by width and skips viewport selection snapshot allocation when there is no active selection and line-end trimming is disabled.

Concerns

• The TuiText measurement cache can remain populated across measurement-affecting builder calls, allowing a later layout at the same width to reuse a stale wrapped/truncated natural size.

Verdict

Found: 0 critical, 1 important, 0 suggestions

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[harryalbert]

nice. warpy comment seems potentially real but other than that LGTM