Module actor_call_counter 

Per-thread counter for App::read_editor / App::mutate_editor / App::mutate_editor_with calls.

Slice 3c.extension.fold-rs.test: regression-test scaffolding that asserts the per-frame paint path doesn’t reach the actor mailbox. The previous regression — frame_120_lines/200 went from 90µs to 43.73ms because 120 per-line read_editor calls crept into compose_visible_lines_inner — would have been caught by a “this path makes 0 actor calls” assertion if one had existed.

The counter is a Cell<u64> in thread-local storage; the seam methods bump() on entry. Tests call snapshot to read the current count, drive the path under test, then call snapshot again and assert the delta is bounded.

Non-test builds: one inlined thread-local increment per seam call (~ns). Negligible against the ~µs–~100µs cost the seam itself pays.

Functions

bump

Increment the per-thread call count. Called by the App::{read,mutate,mutate_with}_editor seam.

reset

Reset the count to zero. Optional — tests can also just compute deltas via snapshot() before / after.

snapshot

Read the current count. Tests use this to capture before/after snapshots around a code path under test.