Investigating the cursor slowdown reported after the wash became
visible.
Confident daemon-side win: `scoped_decorations` (run every tick per
semantic frontend, in the daemon's single-threaded loop that also
serves the TUI) was materializing the whole buffer via
`buffer_source_bytes` — an O(n) rope→Vec copy — TWICE per tick: once
in the 9.2 CurrentLine branch and again in the diagnostics branch. For
an LSP buffer (diagnostics present, the common case) that doubled the
per-tick copy cost, and the daemon's tick latency gates TUI cursor
responsiveness. Now the source + line-start table is materialized at
most once per call via `get_or_insert_with` and shared between both
branches (and skipped entirely when neither branch needs it).
Consumer instrumentation to localize any remaining cost:
- `PMACS_GPU_DEBUG_FRAME=1` logs per-`render()` sub-phase timings
(background rects / minimap rects / glyph prepare+submit / total /
peer count). winit defaults to ControlFlow::Wait, so renders are
on-demand (one per coalesced redraw request), not a continuous
loop — the timing isolates the cost of a single cursor-driven frame.
- The `PMACS_GPU_DEBUG_PRESENCE` check is now one-shot via OnceLock
instead of a per-message `std::env::var_os` (which locks the global
env table); same for the new frame flag.
No behavior change to the rendered output. `render()` gains the
clippy too_many_lines allow (now 115 lines with the timing block),
matching the precedent on the other linear GPU-setup functions.
Gates green:
- cargo fmt --all -- --check
- cargo clippy --all-targets --workspace -- -D warnings
- cargo clippy --all-targets --workspace --features crdt -- -D warnings
- pmacs lib 1329 + pmacs-protocol 11; pmacs-gpu unit 15
- m4_acceptance 88, m11_5_semantic_acceptance (--features crdt) 2
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Levi Neuwirth
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