settled-reach/client/tests/test_step_canvas_viewer.gd

## T-1182 tests: StepCanvasViewer — the rung transport state machine
## (enter() lands on the Global opener, scroll steps through the ladder,
## overlay toggle wiring, pan-edge re-request, edge-scroll) and
## RegionalScreen's re-entry guard against the new viewer. test_mode
## (SimBridge default outside SR_LIVE=1) means request_step_canvas() is a
## silent no-op — these tests exercise client-side state only, no live
## server needed.
class_name TestStepCanvasViewer
extends GdUnitTestSuite

const StepCanvasTransport := preload("res://ui/implant/apps/atlas/step_canvas/step_canvas_transport.gd")

## GJ1c's own region-grid shape from the T-1183 eyeball (177x88) — reused
## across the T-1189/T-1192 section below so every test is grounded in the
## actual regression captured in
## .cache/screenshots/t1183-eyeball-run2/02-region.png.
const GJ1C_GLOBAL_EXTENT := Vector2i(177, 88)


func test_enter_lands_on_the_global_opener() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.enter({"body_id": "GJ380c", "body_radius_km": 6238.4}, {})
	assert_str(v.get_held_rung()).is_equal(StepCanvasTransport.RUNG_GLOBAL)


func test_get_body_id_reflects_the_entered_body() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	assert_str(v.get_body_id()).is_equal("")
	v.enter({"body_id": "GJ380c", "body_radius_km": 6238.4}, {})
	assert_str(v.get_body_id()).is_equal("GJ380c")


## Scrolling one notch descends the ladder — cursor-anchored, so a cursor
## position must be supplied; the rung index advances by exactly one.
func test_scroll_rung_descends_one_notch() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.enter({"body_id": "GJ380c", "body_radius_km": 6238.4}, {})
	v._scroll_rung(1, Vector2(400.0, 300.0))
	assert_str(v.get_held_rung()).is_equal(StepCanvasTransport.RUNG_REGION)


func test_scroll_rung_clamps_at_the_deepest_rung() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.enter({"body_id": "GJ380c", "body_radius_km": 6238.4}, {})
	for _i in range(10):
		v._scroll_rung(1, Vector2(400.0, 300.0))
	assert_str(v.get_held_rung()).is_equal(StepCanvasTransport.RUNG_CHUNK)


func test_reset_to_global_returns_from_a_deep_rung() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.enter({"body_id": "GJ380c", "body_radius_km": 6238.4}, {})
	v._scroll_rung(1, Vector2(400.0, 300.0))
	v._scroll_rung(1, Vector2(400.0, 300.0))
	v._reset_to_global()
	assert_str(v.get_held_rung()).is_equal(StepCanvasTransport.RUNG_GLOBAL)


## PR #203 review (Hoshe finding 2): the hard full-zoom-out reset — a
## scroll-out gesture while ALREADY at Global (rung 0), with the view
## drifted from the canonical un-panned frame, must snap the view back to
## center (Jeroen's explicit HARD condition, carried from the retired
## viewer's own _maybe_reset_to_canonical_frame()). Behavioral, through the
## real input entry point (_scroll_rung with direction=-1), not a direct
## _reset_to_global() call — this is what would have caught the dead-code
## regression (scroll_step() clamping at index 0 meant _scroll_rung()
## returned before ever reaching a reset call).
func test_scroll_out_at_global_after_a_pan_resets_the_view() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.enter({"body_id": "GJ380c", "body_radius_km": 6238.4}, {})
	assert_str(v.get_held_rung()).is_equal(StepCanvasTransport.RUNG_GLOBAL)

	v._apply_pan_delta(Vector2(1.0, 0.0), 1.0)  # drift the view off-center
	assert_bool(v._is_global_view_drifted()).override_failure_message(
		"test setup: a pan at Global must actually drift the view"
	).is_true()

	v._scroll_rung(-1, Vector2(400.0, 300.0))  # scroll OUT — already at rung 0

	assert_str(v.get_held_rung()).is_equal(StepCanvasTransport.RUNG_GLOBAL)
	assert_bool(v._is_global_view_drifted()).override_failure_message(
		"a scroll-out past the top of the ladder must hard-reset the drifted"
		+ " Global view back to its canonical (centered) frame"
	).is_false()


## The inverse guard: scrolling out while ALREADY at the canonical
## (un-drifted) Global frame must stay a no-op — the reset is edge-triggered
## on genuine drift, not a per-scroll unconditional reset.
func test_scroll_out_at_undrifted_global_is_a_no_op() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.enter({"body_id": "GJ380c", "body_radius_km": 6238.4}, {})
	v._scroll_rung(-1, Vector2(400.0, 300.0))
	assert_str(v.get_held_rung()).is_equal(StepCanvasTransport.RUNG_GLOBAL)
	assert_bool(v._is_global_view_drifted()).is_false()


func test_overlay_visibility_defaults_to_off_for_every_toggle() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	for def: Dictionary in v.get_overlay_defs():
		assert_bool(v.is_overlay_visible(def["id"])).is_false()


func test_set_overlay_visible_updates_state() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.set_overlay_visible("gen_dw_temp", true)
	assert_bool(v.is_overlay_visible("gen_dw_temp")).is_true()


func test_set_overlay_visible_unknown_id_is_a_no_op() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.set_overlay_visible("not_a_real_overlay", true)
	assert_bool(v.is_overlay_visible("not_a_real_overlay")).is_false()


# =============================================================================
# RegionalScreen re-entry guard (BUG 2 lineage, carried forward from the
# retired AtlasWindowViewer-era regression) — now against StepCanvasViewer.
# =============================================================================


func test_regional_screen_repeat_enter_for_the_same_body_is_a_no_op() -> void:
	var screen: RegionalScreen = auto_free(RegionalScreen.new())
	add_child(screen)
	var body: Dictionary = {"body_id": "GJ380c", "body_radius_km": 6238.4}
	screen.enter({"body": body, "system": {}})
	screen._viewer._scroll_rung(1, Vector2(400.0, 300.0))
	assert_str(screen._viewer.get_held_rung()).is_equal(StepCanvasTransport.RUNG_REGION)

	screen.enter({"body": body, "system": {}})

	# A no-op re-entry must NOT reset the held rung back to Global — that
	# would be the exact "repeat enter tears down in-flight state" class the
	# retired viewer's own cold-start guard existed to prevent.
	assert_str(screen._viewer.get_held_rung()).override_failure_message(
		"a repeat enter() for the SAME body must not reset the held rung"
	).is_equal(StepCanvasTransport.RUNG_REGION)


func test_regional_screen_different_body_still_re_enters() -> void:
	var screen: RegionalScreen = auto_free(RegionalScreen.new())
	add_child(screen)
	screen.enter({"body": {"body_id": "GJ380c", "body_radius_km": 6238.4}, "system": {}})

	screen.enter({"body": {"body_id": "OtherBody", "body_radius_km": 100.0}, "system": {}})

	assert_str(screen._viewer.get_body_id()).is_equal("OtherBody")


## Relocated from test_atlas_descend_entry.gd (T-1182 PR #203 review — the
## AtlasViewer cluster orphan retirement, Tyre finding). This is the one live
## regression guard from that suite: RegionalScreen must wrap StepCanvasViewer
## (the stepped ladder), never fall back to the now-deleted AtlasViewer
## heightmap-texture display — a direct type-identity check, distinct from
## the behavioral tests above (which would only fail indirectly, via a
## missing method, if this ever regressed).
func test_regional_screen_wraps_step_canvas_viewer_not_atlas_viewer() -> void:
	var screen: RegionalScreen = auto_free(RegionalScreen.new())
	add_child(screen)
	assert_object(screen._viewer).override_failure_message(
		"RegionalScreen must wrap StepCanvasViewer (the stepped ladder) since T-1182,"
		+ " not the retired AtlasViewer heightmap-texture display"
	).is_instanceof(StepCanvasViewer)


# =============================================================================
# PR #203 review (Hoshe notes): pan-edge re-request (_maybe_refloat) and
# edge-scroll pan — previously untested. _maybe_refloat() only does anything
# once the terrain layer holds a real texture (get_footprint_px() is
# ZERO/inert until then), so these tests drive StepCanvasTerrainLayer.
# rebuild_from_canvas() directly (bypassing the network — a decoded canvas
# dict is all it needs) to put the viewer into the "holding a real canvas"
# state _maybe_refloat's early-out guards against.
# =============================================================================


static func _synthetic_canvas(width: int, height: int) -> Dictionary:
	return {
		"width": width,
		"height": height,
		"morphology": null,
		"elev_q": null,
		"moisture_q": null,
		"vegetation": null,
		"glaciation": null,
		"temp_dc": [],
		"settlement_id": [],
		"courses": [],
		"cliffs": [],
	}


func test_maybe_refloat_is_inert_before_any_canvas_has_arrived() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.enter({"body_id": "GJ380c", "body_radius_km": 6238.4}, {})
	v._scroll_rung(1, Vector2(400.0, 300.0))  # District — footprint still ZERO, nothing arrived
	var world_center_before: Vector2 = v._world_center
	v._maybe_refloat()
	assert_that(v._world_center).is_equal(world_center_before)


## A small pan (well under half the canvas footprint) must NOT re-float —
## the held canvas keeps drawing, no re-request (§4/§5's "only when a pan
## carries the view past the held window's edge").
func test_maybe_refloat_does_not_refloat_on_a_small_pan() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.size = Vector2(800.0, 600.0)  # a real viewport size — _maybe_refloat's
	# drift math is relative to get_rect().size's own center; leaving this at
	# the default ZERO would make screen_center ZERO too, so even a tiny
	# view_offset reads as "drifted past the canvas's own half-footprint"
	# (drift = view_offset + half, threshold = half*0.5) — a test-harness
	# artifact, not the behavior under test.
	v.enter({"body_id": "GJ380c", "body_radius_km": 6238.4}, {})
	v._scroll_rung(1, Vector2(400.0, 300.0))  # District
	v._terrain_layer.rebuild_from_canvas(_synthetic_canvas(64, 64), v.get_held_rung(), "")
	# _scroll_rung() re-centers view_offset to ZERO on arrival, which under a
	# real 800x600 viewport already puts the canvas center near screen center
	# (both small relative to the viewport) — center the canvas explicitly so
	# "small pan" starts from a known-centered baseline.
	v._view_offset = v.size * 0.5 - v._terrain_layer.get_footprint_px() * 0.5

	var world_center_before: Vector2 = v._world_center
	v._view_offset += Vector2(2.0, 0.0)  # tiny drift, far under half the footprint
	v._maybe_refloat()

	assert_that(v._world_center).override_failure_message(
		"a small pan must not re-float the held canvas"
	).is_equal(world_center_before)


## A large pan (past half the canvas footprint) DOES re-float — new
## world_center, view_offset reset to ZERO (the canvas re-centers under the
## new request).
func test_maybe_refloat_refloats_once_the_pan_crosses_the_edge_threshold() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.enter({"body_id": "GJ380c", "body_radius_km": 6238.4}, {})
	v._scroll_rung(1, Vector2(400.0, 300.0))  # District
	v._terrain_layer.rebuild_from_canvas(_synthetic_canvas(64, 64), v.get_held_rung(), "")

	var world_center_before: Vector2 = v._world_center
	var footprint: Vector2 = v._terrain_layer.get_footprint_px()
	v._view_offset = Vector2(footprint.x, 0.0)  # far past half the footprint
	v._maybe_refloat()

	assert_that(v._world_center).override_failure_message(
		"a pan past the edge threshold must re-float (new world_center)"
	).is_not_equal(world_center_before)
	assert_that(v._view_offset).override_failure_message(
		"re-floating resets view_offset to ZERO (the canvas re-centers)"
	).is_equal(Vector2.ZERO)


## Global never re-floats on pan (D-255(a): its canvas is the whole body,
## no edge to cross) — even with a real texture held and a huge drift.
func test_maybe_refloat_is_a_no_op_at_global_rung() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.enter({"body_id": "GJ380c", "body_radius_km": 6238.4}, {})
	v._terrain_layer.rebuild_from_canvas(_synthetic_canvas(200, 100), v.get_held_rung(), "")

	var world_center_before: Vector2 = v._world_center
	v._view_offset = Vector2(9_999.0, 9_999.0)
	v._maybe_refloat()

	assert_that(v._world_center).is_equal(world_center_before)


# =============================================================================
# Edge-scroll: suppression conditions + direction.
# =============================================================================


func test_edge_scroll_suppressed_without_application_focus() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.size = Vector2(800.0, 600.0)
	v._app_has_focus = false
	v._last_mouse_pos = Vector2(2.0, 300.0)  # well inside the edge margin
	assert_bool(v._is_cursor_edge_scrolling()).is_false()


func test_edge_scroll_suppressed_when_cursor_has_never_moved_over_the_control() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.size = Vector2(800.0, 600.0)
	# _last_mouse_pos defaults to (-1, -1) — an impossible in-bounds position,
	# so edge-scroll never fires before the mouse has moved over the control
	# at least once (matches the retired viewer's own documented contract).
	assert_bool(v._is_cursor_edge_scrolling()).is_false()


func test_edge_scroll_active_near_the_left_edge() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.size = Vector2(800.0, 600.0)
	v._app_has_focus = true
	v._last_mouse_pos = Vector2(2.0, 300.0)
	assert_bool(v._is_cursor_edge_scrolling()).is_true()
	var direction: Vector2 = v._edge_scroll_direction()
	assert_float(direction.x).is_less(0.0)
	assert_float(direction.y).is_equal(0.0)


func test_edge_scroll_active_near_the_right_edge() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.size = Vector2(800.0, 600.0)
	v._app_has_focus = true
	v._last_mouse_pos = Vector2(798.0, 300.0)
	var direction: Vector2 = v._edge_scroll_direction()
	assert_float(direction.x).is_greater(0.0)


func test_edge_scroll_inactive_well_inside_the_viewport() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.size = Vector2(800.0, 600.0)
	v._app_has_focus = true
	v._last_mouse_pos = Vector2(400.0, 300.0)  # dead center — far from any edge
	assert_bool(v._is_cursor_edge_scrolling()).is_false()


# =============================================================================
# T-1183: disk-cache sweep-trigger wiring
# =============================================================================


## enter() must invoke the disk cache's (2a) visit sweep for the entered
## body — a smoke test that the wiring exists and doesn't crash; the sweep
## LOGIC itself (what gets evicted and why) is covered exhaustively by
## test_step_canvas_disk_cache.gd. Uses a distinctive body_id with nothing
## ever cached under it, so the sweep is a true no-op read (no writes to the
## real user://atlas_cache/ directory this test could leak).
func test_enter_runs_the_disk_cache_visit_sweep_without_crashing() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.enter({"body_id": "T1183_sweep_smoke_test_body", "body_radius_km": 6238.4}, {})
	# If the wiring is broken (e.g. calling a method that doesn't exist), the
	# enter() call itself would already have failed above — reaching here
	# with the expected held rung is the assertion.
	assert_str(v.get_held_rung()).is_equal(StepCanvasTransport.RUNG_GLOBAL)


## The coarse background sweep timer exists, is not per-frame (a real
## Timer node, not a _process()-driven counter), autostarts, and is set to
## the documented coarse interval — never a sub-frame or per-frame value.
func test_disk_sweep_timer_is_coarse_and_autostarts() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	var timer: Timer = v.get_node("DiskSweepTimer")
	assert_object(timer).is_not_null()
	# Godot resets Timer.autostart to false once the timer has actually
	# started after entering the tree (documented engine behavior — the flag
	# is a one-shot "start me on _ready()" instruction, not a persistent
	# state mirror). The real behavioral guarantee is "the timer is running,
	# unpaused, without anyone having to call start() explicitly" —
	# is_stopped() == false is the correct read of that.
	assert_bool(timer.is_stopped()).override_failure_message(
		"the disk sweep timer must autostart running, no explicit start() call needed"
	).is_false()
	assert_float(timer.wait_time).override_failure_message(
		"the disk sweep timer must be coarse (minutes), never a per-frame interval"
	).is_greater_equal(60.0)


## The timer's timeout must actually route to the disk cache's
## run_background_sweep() for the currently-entered body — verified by
## invoking the private handler directly (the same "call the handler, don't
## wait on a real Timer" pattern used elsewhere in this cluster for
## non-blocking test speed) against an injected-root request so this test
## touches no real cache files.
func test_disk_sweep_timeout_handler_runs_background_sweep_for_the_current_body() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.enter({"body_id": "T1183_sweep_smoke_test_body", "body_radius_km": 6238.4}, {})
	# No live server, no cached entries for this body — the assertion is
	# that calling the handler does not crash and leaves the (empty) cache
	# consistent, mirroring the enter()-sweep smoke test above.
	v._on_disk_sweep_timeout()
	assert_int(v.get_request().get_disk_cache().entry_count("T1183_sweep_smoke_test_body")).is_equal(0)


# =============================================================================
# T-1189: extent cap wired end-to-end (viewer -> transport), plus the
# cache-key consistency the ticket calls out explicitly ("capping happens
# BEFORE the request is issued so keys stay consistent"). No live server —
# a Global canvas is landed via the SAME Tier-1 cache-hit path
# StepCanvasRequest's own tests use (get_cache().put() + request_now()'s
# synchronous cache-hit emit), so the full _on_canvas_ready wiring runs for
# real rather than being shortcut.
# =============================================================================


## Land a Global canvas of the given size into the viewer's OWN cache (Tier
## 1), then fire the request that the real cache-hit path serves
## synchronously — same mechanism test_step_canvas_request.gd's own
## cache-hit tests use, now driven through the viewer so _on_canvas_ready()
## and _global_body_extent actually populate through the real signal wiring.
static func _land_global_canvas(v: StepCanvasViewer, width: int, height: int) -> void:
	var req: Variant = v.get_request()
	req.get_cache().put(
		v.get_body_id(),
		"Global",
		Vector2i.ZERO,
		Vector2i.ZERO,
		TestStepCanvasViewer._synthetic_canvas(width, height)
	)
	v._fire_request()  # Global's own request — served from the cache hit just landed


func test_global_canvas_arrival_populates_the_body_extent_cap_source() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.enter({"body_id": "T1189_extent_letterbox_test_body", "body_radius_km": 6371.0}, {})
	TestStepCanvasViewer._land_global_canvas(v, GJ1C_GLOBAL_EXTENT.x, GJ1C_GLOBAL_EXTENT.y)

	assert_that(v._global_body_extent).is_equal(GJ1C_GLOBAL_EXTENT)


## The T-1183 eyeball regression itself: once the Global echo has landed,
## scrolling to Region and firing its request must produce a CAPPED extent
## — never the raw viewport-fit 384x216 that overran the body on both axes.
func test_region_request_extent_is_capped_to_the_landed_global_extent() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.size = Vector2(1920.0, 1080.0)  # the T-1183 eyeball's own viewport
	v.enter({"body_id": "T1189_extent_letterbox_test_body", "body_radius_km": 6371.0}, {})
	TestStepCanvasViewer._land_global_canvas(v, GJ1C_GLOBAL_EXTENT.x, GJ1C_GLOBAL_EXTENT.y)

	v._scroll_rung(1, Vector2(960.0, 540.0))  # descend to Region — fires the capped request
	var extent: Vector2i = v._request_extent()

	assert_int(extent.x).override_failure_message(
		"Region's requested extent must never exceed the body's own region-grid width"
	).is_less_equal(GJ1C_GLOBAL_EXTENT.x)
	assert_int(extent.y).override_failure_message(
		"Region's requested extent must never exceed the body's own region-grid height"
	).is_less_equal(GJ1C_GLOBAL_EXTENT.y)
	assert_that(extent).is_equal(GJ1C_GLOBAL_EXTENT)  # 1920x1080 viewport-fit exceeds 177x88 on both axes


## Cold-start fallback (documented on StepCanvasViewer._request_extent()):
## before ANY Global response has landed, `_global_body_extent` is still
## ZERO — the Region request must go out UNCAPPED (server clamps
## independently) rather than silently collapsing to a zero-cell request.
func test_region_request_extent_is_uncapped_before_the_global_echo_lands() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.size = Vector2(1920.0, 1080.0)
	v.enter({"body_id": "T1189_extent_letterbox_test_body", "body_radius_km": 6371.0}, {})
	# No _land_global_canvas() call — simulates scrolling in before the
	# FIRST (Global) request's response has arrived.

	v._scroll_rung(1, Vector2(960.0, 540.0))
	var extent: Vector2i = v._request_extent()

	var uncapped: Vector2i = StepCanvasTransport.viewport_fit_extent(v.size, "Region")
	assert_that(extent).override_failure_message(
		"before the Global echo lands, the Region request must be the ordinary"
		+ " uncapped viewport-fit extent, not silently zeroed"
	).is_equal(uncapped)


## Cache-key discipline (T-1182/T-1183, ticket's own explicit call-out): the
## cap must be applied BEFORE _fire_request() builds the request, so the
## extent that becomes part of the cache key is the SAME capped value that
## gets served — a request for "the same spot" must always resolve to the
## same key, capped or not, never a key built from one extent and served
## under another.
func test_capped_extent_matches_what_the_request_actually_sends() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.size = Vector2(1920.0, 1080.0)
	v.enter({"body_id": "T1189_extent_letterbox_test_body", "body_radius_km": 6371.0}, {})
	TestStepCanvasViewer._land_global_canvas(v, GJ1C_GLOBAL_EXTENT.x, GJ1C_GLOBAL_EXTENT.y)
	v._scroll_rung(1, Vector2(960.0, 540.0))  # Region — fires _fire_request() internally

	# _request_extent() is the SAME function _fire_request() calls to build
	# the outbound request/cache key — calling it again here must be
	# idempotent and match what was actually requested (no separate,
	# divergent cap path).
	var extent_now: Vector2i = v._request_extent()
	assert_that(extent_now).is_equal(GJ1C_GLOBAL_EXTENT)

	# The Tier-1 cache key StepCanvasCache builds from this SAME extent must
	# be a real, findable key once a response for it lands — proving the
	# capped extent (not the raw viewport-fit one) is what keys the cache.
	var req: Variant = v.get_request()
	var center: Vector2i = StepCanvasTransport.snap_to_gridunit(v._world_center, "Region")
	var canvas := TestStepCanvasViewer._synthetic_canvas(GJ1C_GLOBAL_EXTENT.x, GJ1C_GLOBAL_EXTENT.y)
	req.get_cache().put("T1189_extent_letterbox_test_body", "Region", center, extent_now, canvas)
	assert_bool(
		req.get_cache().has("T1189_extent_letterbox_test_body", "Region", center, GJ1C_GLOBAL_EXTENT, 0)
	).override_failure_message(
		"a cache entry stored under the CAPPED extent must be reachable"
		+ " under that same capped extent — key consistency"
	).is_true()


## Shape-generic guard: District's spacing differs from Global's, so its
## request extent must be completely unaffected by a landed Global canvas —
## proving the cap is spacing-keyed, not applied indiscriminately to every
## rung once a Global extent is known.
func test_district_request_extent_is_never_capped_by_the_global_extent() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.size = Vector2(1920.0, 1080.0)
	v.enter({"body_id": "T1189_extent_letterbox_test_body", "body_radius_km": 6371.0}, {})
	TestStepCanvasViewer._land_global_canvas(v, GJ1C_GLOBAL_EXTENT.x, GJ1C_GLOBAL_EXTENT.y)

	v._scroll_rung(1, Vector2(960.0, 540.0))  # Region
	v._scroll_rung(1, Vector2(960.0, 540.0))  # District
	var extent: Vector2i = v._request_extent()

	var uncapped: Vector2i = StepCanvasTransport.viewport_fit_extent(v.size, "District")
	assert_that(extent).is_equal(uncapped)


# =============================================================================
# T-1189/T-1192: shared letterbox mechanism — centering + Global fit scale.
# =============================================================================


## T-1192's own headline defect: the Global canvas must no longer draw
## top-left-anchored at Vector2.ZERO — once a canvas lands, the viewer must
## have computed a non-zero centering offset (unless the canvas happens to
## exactly fill the viewport, not the case here).
func test_global_canvas_arrival_centers_the_view_not_top_left() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.size = Vector2(1920.0, 1080.0)
	v.enter({"body_id": "T1189_extent_letterbox_test_body", "body_radius_km": 6371.0}, {})
	TestStepCanvasViewer._land_global_canvas(v, GJ1C_GLOBAL_EXTENT.x, GJ1C_GLOBAL_EXTENT.y)

	assert_that(v._view_offset).override_failure_message(
		"a landed Global canvas smaller than the viewport must be CENTERED,"
		+ " never left at the raw top-left Vector2.ZERO anchor"
	).is_not_equal(Vector2.ZERO)


## D-255 texel-exactness (T-1192): at a large (4K-class) viewport, GJ1c's
## 885x440 raw footprint (177x88 texels x 5x5 shallow display ratio) clears
## the coverage bar even AFTER the legend column is reserved, so the
## INTEGER fit wins outright — verified end-to-end through the real viewer
## wiring, not just the pure transport function this mirrors. (The T-1183
## reference 1920x1080 viewport is deliberately NOT used here — at that
## size the legend-column reservation starves the integer candidate below
## the coverage bar and the fractional escape hatch fires instead, covered
## separately by test_global_canvas_uses_fractional_fit_when_legend_column_
## starves_the_integer_fit() below.)
func test_global_canvas_scale_is_an_integer_multiple_of_the_raw_footprint() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.size = Vector2(3840.0, 2160.0)
	v.enter({"body_id": "T1189_extent_letterbox_test_body", "body_radius_km": 6371.0}, {})
	TestStepCanvasViewer._land_global_canvas(v, GJ1C_GLOBAL_EXTENT.x, GJ1C_GLOBAL_EXTENT.y)

	assert_that(v._canvas.scale).is_equal(Vector2(v._canvas_scale, v._canvas_scale))
	assert_float(v._canvas_scale).override_failure_message(
		"the Global fit scale must be a whole number of texture pixels"
		+ " when it clears the coverage bar (D-255 texel-exactness)"
	).is_equal_approx(roundf(v._canvas_scale), 0.001)


## Fixed rungs must NEVER receive the Global fit multiplier — `_canvas.scale`
## stays 1.0 once the player has descended past Global, even though a
## Global canvas was landed earlier in the same session.
func test_fixed_rung_canvas_scale_stays_one_after_descending_from_global() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.size = Vector2(1920.0, 1080.0)
	v.enter({"body_id": "T1189_extent_letterbox_test_body", "body_radius_km": 6371.0}, {})
	TestStepCanvasViewer._land_global_canvas(v, GJ1C_GLOBAL_EXTENT.x, GJ1C_GLOBAL_EXTENT.y)
	v._scroll_rung(1, Vector2(960.0, 540.0))  # Region
	v._terrain_layer.rebuild_from_canvas(
		TestStepCanvasViewer._synthetic_canvas(200, 100), v.get_held_rung(), ""
	)
	v._recompute_canvas_transform()

	assert_float(v._canvas_scale).is_equal_approx(1.0, 0.001)
	assert_that(v._canvas.scale).is_equal(Vector2.ONE)


## Legend non-overlap (T-1192: "lay the legend out beside the canvas... never
## over it"): the legend panel sits at a fixed left-column position
## (PANEL_MARGIN, ...) with a known width — once a Global canvas is landed
## and centered, its drawn rect's LEFT edge must be at or past the legend's
## own right edge, never underneath it.
func test_global_canvas_left_edge_never_overlaps_the_legend_column() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.size = Vector2(1920.0, 1080.0)
	v.enter({"body_id": "T1189_extent_letterbox_test_body", "body_radius_km": 6371.0}, {})
	TestStepCanvasViewer._land_global_canvas(v, GJ1C_GLOBAL_EXTENT.x, GJ1C_GLOBAL_EXTENT.y)

	var canvas_left_edge: float = v._view_offset.x
	assert_float(canvas_left_edge).override_failure_message(
		"the Global canvas's drawn left edge must be at or past the reserved"
		+ " legend column — the legend must never be covered by the map"
	).is_greater_equal(StepCanvasTransport.LEGEND_COLUMN_PX - 0.01)


## Resize must re-fit/re-center a HELD canvas, not just a freshly-arriving
## one — _notification(NOTIFICATION_RESIZED) wires _recompute_canvas_transform()
## for exactly this case.
func test_resize_recenters_an_already_held_global_canvas() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.size = Vector2(1920.0, 1080.0)
	v.enter({"body_id": "T1189_extent_letterbox_test_body", "body_radius_km": 6371.0}, {})
	TestStepCanvasViewer._land_global_canvas(v, GJ1C_GLOBAL_EXTENT.x, GJ1C_GLOBAL_EXTENT.y)
	var offset_before: Vector2 = v._view_offset

	v.size = Vector2(1280.0, 720.0)
	v._notification(Control.NOTIFICATION_RESIZED)

	assert_that(v._view_offset).override_failure_message(
		"a resize must re-center the held canvas for the NEW viewport size"
	).is_not_equal(offset_before)


## Small-canvas fallback (D-255's own escape hatch): once the legend column
## eats enough of the available width that the integer fit falls under
## FIT_MIN_COVERAGE_RATIO, the viewer must fall back to the fractional fit
## rather than settling for a sparse integer frame — end-to-end through the
## real viewer, mirroring test_fit_scale_falls_back_to_fractional_fit_on_
## excessive_letterboxing in test_step_canvas_transport.gd.
func test_global_canvas_uses_fractional_fit_when_legend_column_starves_the_integer_fit() -> void:
	var v: StepCanvasViewer = auto_free(StepCanvasViewer.new())
	add_child(v)
	v.size = Vector2(1920.0, 1080.0)
	v.enter({"body_id": "T1189_extent_letterbox_test_body", "body_radius_km": 6371.0}, {})
	TestStepCanvasViewer._land_global_canvas(v, GJ1C_GLOBAL_EXTENT.x, GJ1C_GLOBAL_EXTENT.y)

	# GJ1c at 1920x1080 with the legend column reserved: 2x no longer fits
	# (1770 > 1628 available), 1x covers only ~41% of the tighter axis — well
	# under the 75% coverage bar, so a non-integer fit must have been chosen.
	assert_float(v._canvas_scale).override_failure_message(
		"the reserved legend column must starve the 2x integer candidate at"
		+ " this reference viewport, forcing the fractional fit"
	).is_greater(1.0)