The two-layer client rebuild per D-255(a)(b)(e), replacing the
_canvas.scale continuous-zoom model with one viewer, one path, all six
rungs:
- step_canvas_protocol.gd: StepCanvasRequest/Response codec against
the T-1181 wire contract — incl. the discovered png_bytes subtlety
(rmp_serde without serde_bytes emits a msgpack int-array, not bin;
decode repacks via PackedByteArray before load_png_from_buffer) and
the extent-echo rule (read the server-clamped extent, never assume
the requested one).
- step_canvas/ component: transport (six-rung ladder, cursor-anchored
scroll steps, edge-scroll/WASD pan with re-request on edge crossing,
hard reset-to-Global), RTT terrain layer (Image.set_pixel colorize
per the c1 measured ruling, texture.update reuse on step-cross,
NEAREST coarse / LINEAR fine per rung), unscaled screen-space
annotation sibling (courses + settlement markers at literal px),
in-memory LRU cache (Tier 1; T-1183 layers the disk tiers beneath),
request lifecycle (pending retry, staleness gate, extent echo).
- Full _canvas.scale retirement in the same change: the zoom-scaled
canvas model, the _zs compensation family, select_rung /
MAX_COVERAGE_M / compute_tile_grid, the orbital-mosaic-vs-window
two-path split, _view_zoom/_canonical_fit_zoom — 10 source files
deleted; their 14 test suites deleted with them (T-1157 dead-goldens
rule; replacement visual-capture coverage is re-scoped T-1157).
- Surviving surfaces kept per the ticket: atlas_window_cache.gd's LRU
shape (the ticket's named file atlas_window_tile_set.gd was the
retiring orchestrator; the real LRU shape lives in
atlas_window_cache.gd — cited in step_canvas_cache.gd), overlay
colors, legend/overlay-bar chrome, AtlasViewer descend geometry.
Determinism boundary per D-255(e): the client interpolates only within
the closed server-supplied input set. 7 new gdUnit suites (164 cases)
incl. a real extent-echo bug caught by its own test during
implementation. Full client suite green (exit 0) with the live-gated
suites running against a worktree server build.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
jpmschweitzerandClaude Fable 5
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