`GetWidth`/`GetHeight` answer against current layout, so they resolve first — and
a resolve that follows any `CreateFrame` re-derives the whole layout graph, because
minting a frame id drops the cached one (`Model::frame_id` → `touch_layout`). A UI
load is nothing but creation interleaved with reads, so the player's interface paid
**839 whole-roster derivations in one load, 2.84 ms each: 2.4 s**, against 650
`GetWidth` calls. `WOW_LAYOUT_DERIVE_TRACE` named the giver-up: every sampled one
was `create_frame`.
Most of those reads cannot learn anything from a resolve. An edge takes its anchor
scan first and only then `combineEdge(center, opposite, size · scale)`
(`resolve_left`, `resolve_right`), so an authored size IS the span unless the
anchors pin **both** of that axis's edges. `LayoutInput::authored_span` is that
rule, written beside the solver whose precedence it mirrors, and it refuses the two
cases where only the solver knows: both edges anchored, and a clamped frame, whose
rect the screen can squeeze.
Measured on the player's own 91 addons through the harness's `--together` load,
three passes each:
```
derives per load 839 → 235
preamble per load 2,414 → 560 ms
frame:GetWidth 686 µs → 60 µs per call (1,241 ms → 118 ms over three loads)
```
**1.85 seconds off every login and every `/reload`**, and the steady state gains
the same way: an addon reading a size it set in an `OnUpdate` no longer walks the
roster for it.
Proven as well as measured: six UI captures (character, bag, merchant, quest, quest
log, tooltip) are **pixel-identical** before and after, MAE 0.000, max 0; the
layout suite passes under `WOW_LAYOUT_VERIFY`, which re-derives every frame from
scratch and demands the same rects; and `resolve_bench` now asserts both halves —
an authored, singly-anchored span answers with no gate walk, while one whose
anchors pin both edges still forces the resolve and reports the anchors' distance,
not the authored number.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SgstFWtn1RxEJ5kVrpgYwn
gromandClaude Opus 5
0fe0a99d8a