[PortLoadView / LayerMappedView] rename/add new views

MIGRATION.md

@@ -599,17 +599,23 @@ old Nx4 form.
 `BuildReport` mapping fields are now defensively copied and read-only. Copy a
 field to a new `dict` before adding or removing report entries.
 
-`PortsLibraryView`, `OverlayLibrary`, and source-backed outputs returned by
-`LibraryBuilder.build()` borrow their sources. They do not close source resources, and
-`PortsLibraryView` is not a context manager. Keep each lazy source open and
-unchanged until every borrowing view or overlay is finished, then close the
-owning source explicitly. An eager `build(output='library')` result is detached
-and does not need its sources afterward.
+`PortLoadView`, `LayerMappedView`, `OverlayLibrary`, and source-backed outputs
+returned by `LibraryBuilder.build()` borrow their sources. They do not close
+source resources, and the views are not context managers. Keep each lazy
+source open and unchanged until every borrowing view or overlay is finished,
+then close the owning source explicitly. An eager `build(output='library')`
+result is detached and does not need its sources afterward.
 
 Lazy GDS sources no longer provide `with_ports_from_data()` or
 `with_port_overrides()` convenience methods. Construct the generic view
-directly instead: `PortsLibraryView(source, layers=...)` imports port data, and
-`PortsLibraryView(source, ports=..., replace=...)` applies explicit overrides.
+directly instead: `PortLoadView(source, layers=...)` imports port data, and
+`PortLoadView(source, ports=..., replace=...)` applies explicit overrides.
+
+`LayerMappedView(source, map_layer)` lazily remaps shape and label layers while
+leaving the source untouched. Its default `copy_through=False` forces mapped
+serialization of every cell. Set `copy_through=True` only when source-aware
+writers may copy untouched cells unchanged and intentionally skip their layer
+mapping; persistently accessed cells are mapped and no longer copied through.
 
 Generic borrowing views no longer expose GDS-specific `raw_struct_bytes()`,
 `can_copy_raw_struct()`, or forwarded `library_info` attributes. Keep the
@@ -697,11 +703,12 @@ through `source_cell()`; format writers decide whether that provenance permits
 raw copy-through. Raw GDS structure access remains confined to GDS sources and
 writers.
 
-`LibraryBuilder`, `OverlayLibrary`, and `PortsLibraryView` are new additive
-library implementations. `LibraryBuilder` supports declarative `@cell` recipes
-and dependency-aware builds; `OverlayLibrary` composes source libraries without
-eagerly copying all patterns; `PortsLibraryView` overlays port metadata on a
-read-only source.
+`LibraryBuilder`, `OverlayLibrary`, `PortLoadView`, and `LayerMappedView` are new
+additive library implementations. `LibraryBuilder` supports declarative `@cell`
+recipes and dependency-aware builds; `OverlayLibrary` composes source libraries
+without eagerly copying all patterns; `PortLoadView` loads port metadata from
+labels and/or explicit mappings; `LayerMappedView` remaps shape and label layers
+on detached materialization.
 
 Flattening with `flatten_ports=True` now rejects repeated refs whose target has
 ports, because expanding them would create duplicate port names. Resolve the
@@ -797,7 +804,7 @@ scikit-image implementation. The `arrow` and `boolean` extras are also new.
 These are additive, but available now from `masque` and `masque.builder`:
 
 - from `masque`: `RectCollection`, `boolean`, `OverlayLibrary`,
-  `PortsLibraryView`, `IMaterializable`, `IBorrowing`, `LibraryBuilder`,
+  `PortLoadView`, `LayerMappedView`, `IMaterializable`, `IBorrowing`, `LibraryBuilder`,
   `BuildReport`, `CellProvenance`, and `cell`
 - from `masque.builder`: `CostCallable`, `RenderStepKind`, the concrete
   primitive-offer classes, structured route error/status types,

examples/tutorial/library.py

@@ -11,7 +11,7 @@ from typing import Any
 from pprint import pformat
 
 
-from masque import ILibrary, LibraryBuilder, Pather, Pattern, PortsLibraryView, cell
+from masque import ILibrary, LibraryBuilder, Pather, Pattern, PortLoadView, cell
 from masque.file.gdsii import writefile
 from masque.file.gdsii.lazy import readfile
 
@@ -53,7 +53,7 @@ def main() -> None:
     # imported on first materialization, but the raw source remains untouched
     # until we build the final library.
     gds_lib, _properties = readfile('circuit.gds')
-    builder.add_source(PortsLibraryView(gds_lib, layers=[(3, 0)], max_depth=1))
+    builder.add_source(PortLoadView(gds_lib, layers=[(3, 0)], max_depth=1))
 
     print('Registered imported cells:\n' + pformat(list(gds_lib.keys())))
 

masque/__init__.py

@@ -67,7 +67,8 @@ from .library import (
     LibraryView as LibraryView,
     Library as Library,
     OverlayLibrary as OverlayLibrary,
-    PortsLibraryView as PortsLibraryView,
+    PortLoadView as PortLoadView,
+    LayerMappedView as LayerMappedView,
     LibraryBuilder as LibraryBuilder,
     BuildReport as BuildReport,
     CellProvenance as CellProvenance,

masque/file/gdsii/lazy.py

@@ -7,7 +7,7 @@ This module provides the non-Arrow half of Masque's lazy GDS architecture:
   struct order, and child edges without materializing every cell.
 - cells are materialized on demand through the classic `gdsii` decoder
   whenever a caller indexes the lazy view
-- the source can be wrapped in `PortsLibraryView` or merged through
+- the source can be wrapped in `PortLoadView` or merged through
   `OverlayLibrary`
 
 The public surface intentionally parallels `gdsii.lazy_arrow` closely so that

masque/library/__init__.py

@@ -23,7 +23,8 @@ from .mapping import (
 )
 from .overlay import (
     OverlayLibrary as OverlayLibrary,
-    PortsLibraryView as PortsLibraryView,
+    PortLoadView as PortLoadView,
+    LayerMappedView as LayerMappedView,
 )
 from .build import (
     LibraryBuilder as LibraryBuilder,

masque/library/overlay.py

@@ -1,4 +1,4 @@
-"""Overlay and ports-importing library views."""
+"""Overlay and lazily processed library views."""
 from __future__ import annotations
 
 from collections import defaultdict
@@ -7,7 +7,7 @@ from typing import TYPE_CHECKING, Literal, Self, cast
 import copy
 
 from ..error import LibraryError
-from ..pattern import Pattern, map_targets
+from ..pattern import Pattern, map_layers, map_targets
 from .base import ILibrary, ILibraryView
 from .capabilities import IBorrowing, IMaterializable
 from .utils import INameView, dangling_mode_t, _plan_source_names, _source_rename_map, _validate_dangling_mode
@@ -44,39 +44,17 @@ def _materialize_detached_pattern(view: ILibraryView, name: str) -> Pattern:
     return view[name].deepcopy()
 
 
-class PortsLibraryView(ILibraryView, IMaterializable, IBorrowing):
-    """
-    Read-only view which imports or applies ports on first materialization.
-
-    The wrapped source remains untouched; this view owns a separate processed
-    cache so direct-copy workflows can continue to use the raw source view.
-    The view borrows its source: callers must keep the source open for the
-    lifetime of the view and close the source themselves.
-
-    Graph queries and source ordering are delegated to the wrapped source,
-    while `source_cell()` exposes unchanged layout provenance and `__getitem__`
-    and `materialize_many()` return port-imported patterns.
-    """
+class _ProcessedLibraryView(ILibraryView, IMaterializable, IBorrowing):
+    """Shared detached-materialization behavior for read-only processing views."""
 
     def __init__(
             self,
             source: ILibraryView,
             *,
-            layers: Sequence[layer_t] = (),
-            max_depth: int = 0,
-            skip_subcells: bool = True,
-            ports: Mapping[str, Mapping[str, Port]] | None = None,
-            replace: bool = False,
+            copy_through: bool,
             ) -> None:
         self._source = source
-        self._layers = tuple(layers)
-        self._max_depth = max_depth
-        self._skip_subcells = skip_subcells
-        self._ports = {
-            name: copy.deepcopy(dict(cell_ports))
-            for name, cell_ports in (ports or {}).items()
-        }
-        self._replace = replace
+        self._copy_through = copy_through
         self._cache: dict[str, Pattern] = {}
         self._lookups_in_progress: list[str] = []
 
@@ -92,9 +70,11 @@ class PortsLibraryView(ILibraryView, IMaterializable, IBorrowing):
     def __contains__(self, key: object) -> bool:
         return key in self._source
 
-    def materialize(self, name: str, *, persist: bool = True) -> Pattern:
-        from ..utils.ports2data import data_to_ports        # noqa: PLC0415
+    def _process_pattern(self, name: str, pattern: Pattern) -> Pattern:
+        """Apply this view's processing to one detached source pattern."""
+        raise NotImplementedError
 
+    def materialize(self, name: str, *, persist: bool = True) -> Pattern:
         if name in self._cache:
             return self._cache[name]
 
@@ -108,28 +88,14 @@ class PortsLibraryView(ILibraryView, IMaterializable, IBorrowing):
 
         self._lookups_in_progress.append(name)
         try:
-            pat = _materialize_detached_pattern(self._source, name)
-            if self._layers:
-                pat = data_to_ports(
-                    layers=self._layers,
-                    library=self,
-                    pattern=pat,
-                    name=name,
-                    max_depth=self._max_depth,
-                    skip_subcells=self._skip_subcells,
-                )
-            if name in self._ports:
-                ports = copy.deepcopy(self._ports[name])
-                if self._replace:
-                    pat.ports = ports
-                else:
-                    pat.ports.update(ports)
+            pattern = _materialize_detached_pattern(self._source, name)
+            pattern = self._process_pattern(name, pattern)
         finally:
             self._lookups_in_progress.pop()
 
         if persist:
-            self._cache[name] = pat
-        return pat
+            self._cache[name] = pattern
+        return pattern
 
     def source_order(self) -> tuple[str, ...]:
         return self._source.source_order()
@@ -138,7 +104,7 @@ class PortsLibraryView(ILibraryView, IMaterializable, IBorrowing):
         return (self._source,)
 
     def source_cell(self, name: str) -> tuple[ILibraryView, str] | None:
-        if name not in self._source or name in self._cache:
+        if not self._copy_through or name not in self._source or name in self._cache:
             return None
         return self._source, name
 
@@ -162,6 +128,88 @@ class PortsLibraryView(ILibraryView, IMaterializable, IBorrowing):
         return super().find_refs_local(name, parent_graph=parent_graph, dangling=dangling)
 
 
+class PortLoadView(_ProcessedLibraryView):
+    """
+    Read-only view which loads or applies ports on first materialization.
+
+    The wrapped source remains untouched; this view owns a separate processed
+    cache so direct-copy workflows can continue to use the raw source view.
+    The view borrows its source: callers must keep the source open for the
+    lifetime of the view and close the source themselves.
+
+    Graph queries and source ordering are delegated to the wrapped source,
+    while `source_cell()` exposes unchanged layout provenance and `__getitem__`
+    and `materialize_many()` return port-imported patterns.
+    """
+
+    def __init__(
+            self,
+            source: ILibraryView,
+            *,
+            layers: Sequence[layer_t] = (),
+            max_depth: int = 0,
+            skip_subcells: bool = True,
+            ports: Mapping[str, Mapping[str, Port]] | None = None,
+            replace: bool = False,
+            ) -> None:
+        super().__init__(source, copy_through=True)
+        self._layers = tuple(layers)
+        self._max_depth = max_depth
+        self._skip_subcells = skip_subcells
+        self._ports = {
+            name: copy.deepcopy(dict(cell_ports))
+            for name, cell_ports in (ports or {}).items()
+        }
+        self._replace = replace
+
+    def _process_pattern(self, name: str, pattern: Pattern) -> Pattern:
+        from ..utils.ports2data import data_to_ports        # noqa: PLC0415
+
+        if self._layers:
+            pattern = data_to_ports(
+                layers=self._layers,
+                library=self,
+                pattern=pattern,
+                name=name,
+                max_depth=self._max_depth,
+                skip_subcells=self._skip_subcells,
+                )
+        if name in self._ports:
+            ports = copy.deepcopy(self._ports[name])
+            if self._replace:
+                pattern.ports = ports
+            else:
+                pattern.ports.update(ports)
+        return pattern
+
+
+class LayerMappedView(_ProcessedLibraryView):
+    """
+    Read-only view which remaps shape and label layers on materialization.
+
+    The wrapped source remains untouched. By default, source-aware writers
+    must materialize and serialize every mapped cell. With `copy_through=True`,
+    unmaterialized cells may instead be copied unchanged from their source;
+    persistent access maps and caches a cell, disabling copy-through for it.
+    """
+
+    def __init__(
+            self,
+            source: ILibraryView,
+            map_layer: Callable[[layer_t], layer_t],
+            *,
+            copy_through: bool = False,
+            ) -> None:
+        super().__init__(source, copy_through=copy_through)
+        self._map_layer = map_layer
+
+    def _process_pattern(self, name: str, pattern: Pattern) -> Pattern:
+        _ = name
+        pattern.shapes = map_layers(pattern.shapes, self._map_layer)
+        pattern.labels = map_layers(pattern.labels, self._map_layer)
+        return pattern
+
+
 class OverlayLibrary(ILibrary, IMaterializable, IBorrowing):
     """
     Mutable overlay over one or more source libraries.

masque/test/test_gdsii_lazy.py

@@ -11,7 +11,10 @@ from ..file.gdsii import lazy_write as gdsii_lazy_write
 from ..error import LibraryError
 from ..pattern import Pattern
 from ..ports import Port
-from ..library import IBorrowing, IMaterializable, LazyLibrary, Library, LibraryView, OverlayLibrary, PortsLibraryView
+from ..library import (
+    IBorrowing, IMaterializable, LayerMappedView, LazyLibrary, Library, LibraryView,
+    OverlayLibrary, PortLoadView,
+    )
 
 
 def _make_lazy_port_library() -> Library:
@@ -201,13 +204,13 @@ def test_gdsii_lazy_overlay_subtree_preserves_source_laziness(tmp_path: Path) ->
     assert set(roundtrip) == {'leaf', 'child', 'top'}
 
 
-def test_gdsii_lazy_ports_view_keeps_raw_source_unmodified(tmp_path: Path) -> None:
+def test_gdsii_lazy_port_load_view_keeps_raw_source_unmodified(tmp_path: Path) -> None:
     gds_file = tmp_path / 'lazy_ports.gds'
     src = _make_lazy_port_library()
     gdsii.writefile(src, gds_file, meters_per_unit=1e-9, library_name='classic-ports')
 
     raw, _ = gdsii_lazy.readfile(gds_file)
-    processed = PortsLibraryView(raw, layers=[(10, 0)], max_depth=2)
+    processed = PortLoadView(raw, layers=[(10, 0)], max_depth=2)
     assert not hasattr(processed, 'library_info')
 
     top = processed['top']
@@ -219,14 +222,14 @@ def test_gdsii_lazy_ports_view_keeps_raw_source_unmodified(tmp_path: Path) -> No
     assert not raw_top.ports
 
 
-def test_gdsii_lazy_ports_view_detaches_previously_cached_source(tmp_path: Path) -> None:
+def test_gdsii_lazy_port_load_view_detaches_previously_cached_source(tmp_path: Path) -> None:
     gds_file = tmp_path / 'lazy_cached_ports.gds'
     src = _make_lazy_port_library()
     gdsii.writefile(src, gds_file, meters_per_unit=1e-9, library_name='classic-cached-ports')
 
     raw, _ = gdsii_lazy.readfile(gds_file)
     raw_top = raw['top']
-    processed = PortsLibraryView(raw, ports={
+    processed = PortLoadView(raw, ports={
         'top': {
             'P': Port((1, 2), rotation=0, ptype='wire'),
         },
@@ -247,7 +250,7 @@ def test_gdsii_lazy_port_overrides_without_data_stay_lazy(tmp_path: Path) -> Non
     gdsii.writefile(src, gds_file, meters_per_unit=1e-9, library_name='classic-overrides')
 
     raw, _ = gdsii_lazy.readfile(gds_file)
-    processed = PortsLibraryView(raw, ports={
+    processed = PortLoadView(raw, ports={
         'top': {
             'P': Port((1, 2), rotation=0, ptype='wire'),
         },
@@ -270,7 +273,7 @@ def test_gdsii_lazy_port_overrides_apply_after_extraction(tmp_path: Path) -> Non
     gdsii.writefile(src, gds_file, meters_per_unit=1e-9, library_name='classic-override-extracted')
 
     raw, _ = gdsii_lazy.readfile(gds_file)
-    processed = PortsLibraryView(
+    processed = PortLoadView(
         raw,
         layers=[(10, 0)],
         max_depth=2,
@@ -299,7 +302,7 @@ def test_gdsii_lazy_port_overrides_replace_extracted_ports(tmp_path: Path) -> No
     gdsii.writefile(src, gds_file, meters_per_unit=1e-9, library_name='classic-replace-ports')
 
     raw, _ = gdsii_lazy.readfile(gds_file)
-    processed = PortsLibraryView(
+    processed = PortLoadView(
         raw,
         layers=[(10, 0)],
         max_depth=2,
@@ -323,7 +326,7 @@ def test_gdsii_lazy_overlay_add_source_stays_lazy_for_processed_view(tmp_path: P
     gdsii.writefile(src, gds_file, meters_per_unit=1e-9, library_name='classic-overlay')
 
     raw, _ = gdsii_lazy.readfile(gds_file)
-    processed = PortsLibraryView(raw, layers=[(10, 0)], max_depth=2)
+    processed = PortLoadView(raw, layers=[(10, 0)], max_depth=2)
 
     overlay = OverlayLibrary()
     overlay.add_source(processed)
@@ -341,7 +344,7 @@ def test_gdsii_lazy_overlay_add_source_sees_port_overrides(tmp_path: Path) -> No
     gdsii.writefile(src, gds_file, meters_per_unit=1e-9, library_name='classic-overlay-override')
 
     raw, _ = gdsii_lazy.readfile(gds_file)
-    processed = PortsLibraryView(raw, ports={
+    processed = PortLoadView(raw, ports={
         'top': {
             'P': Port((1, 2), rotation=0, ptype='wire'),
         },
@@ -393,7 +396,7 @@ def test_gdsii_lazy_processed_write_roundtrips_without_explicit_units(tmp_path:
     gdsii.writefile(src, gds_file, meters_per_unit=1e-9, library_name='classic-roundtrip')
 
     raw, _ = gdsii_lazy.readfile(gds_file)
-    processed = PortsLibraryView(raw, layers=[(10, 0)], max_depth=2)
+    processed = PortLoadView(raw, layers=[(10, 0)], max_depth=2)
 
     out_file = tmp_path / 'lazy_roundtrip_out.gds'
     gdsii_lazy.writefile(processed, out_file)
@@ -401,6 +404,23 @@ def test_gdsii_lazy_processed_write_roundtrips_without_explicit_units(tmp_path:
     assert out_file.read_bytes() == gds_file.read_bytes()
 
 
+def test_gdsii_lazy_layer_mapped_write_materializes_without_source_cache(tmp_path: Path) -> None:
+    gds_file = tmp_path / 'lazy_layer_source.gds'
+    src = _make_lazy_port_library()
+    gdsii.writefile(src, gds_file, meters_per_unit=1e-9, library_name='classic-layers')
+
+    raw, _ = gdsii_lazy.readfile(gds_file)
+    mapped = LayerMappedView(raw, lambda layer: (20, 0) if layer == (10, 0) else layer)
+    out_file = tmp_path / 'lazy_layer_mapped.gds'
+    gdsii_lazy.writefile(mapped, out_file)
+
+    assert not raw._cache
+    roundtrip, info = gdsii.readfile(out_file)
+    assert info['name'] == 'classic-layers'
+    assert set(roundtrip['leaf'].labels) == {(20, 0)}
+    assert (10, 0) not in roundtrip['leaf'].labels
+
+
 def test_gdsii_removed_closure_based_lazy_loader() -> None:
     assert not hasattr(gdsii, 'load_library')
     assert not hasattr(gdsii, 'load_libraryfile')

masque/test/test_gdsii_lazy_arrow.py

@@ -10,7 +10,7 @@ import pytest
 pytest.importorskip('pyarrow')
 
 from .. import PatternError
-from ..library import IBorrowing, IMaterializable, Library, OverlayLibrary, PortsLibraryView
+from ..library import IBorrowing, IMaterializable, LayerMappedView, Library, OverlayLibrary, PortLoadView
 from ..pattern import Pattern
 from ..repetition import Grid
 from ..file import gdsii
@@ -240,7 +240,7 @@ def test_gdsii_raw_copy_resolves_generic_borrowing_views(tmp_path: Path, monkeyp
     gdsii.writefile(_make_small_library(), gds_file, meters_per_unit=1e-9, library_name='provenance')
 
     raw, _ = gdsii_lazy_arrow.readfile(gds_file)
-    ports = PortsLibraryView(raw)
+    ports = PortLoadView(raw)
     subtree = ports.subtree('top')
     overlay = OverlayLibrary()
     overlay.add_source(subtree)
@@ -270,6 +270,55 @@ def test_gdsii_raw_copy_resolves_generic_borrowing_views(tmp_path: Path, monkeyp
     assert gdsii_lazy_write._resolve_raw_struct(remapped, 'mid') is None
 
 
+def test_gdsii_layer_mapped_view_controls_raw_copy_through(
+        tmp_path: Path,
+        monkeypatch: pytest.MonkeyPatch,
+        ) -> None:
+    gds_file = tmp_path / 'layer_mapped_source.gds'
+    gdsii.writefile(_make_small_library(), gds_file, meters_per_unit=1e-9, library_name='layer-mapped')
+
+    raw, _ = gdsii_lazy_arrow.readfile(gds_file)
+    copied: list[str] = []
+    raw_reader = raw.raw_struct_bytes
+
+    def record_raw_read(name: str) -> bytes:
+        copied.append(name)
+        return raw_reader(name)
+
+    def map_layer(layer):  # noqa: ANN001,ANN202
+        return (20, 0) if layer == (1, 0) else layer
+
+    monkeypatch.setattr(raw, 'raw_struct_bytes', record_raw_read)
+
+    mapped = LayerMappedView(raw, map_layer)
+    mapped_file = tmp_path / 'layer_mapped_all.gds'
+    gdsii_lazy_arrow.writefile(mapped, mapped_file)
+
+    assert copied == []
+    assert not raw._cache
+    roundtrip, info = gdsii.readfile(mapped_file)
+    assert info['name'] == 'layer-mapped'
+    assert set(roundtrip['leaf'].shapes) == {(20, 0)}
+
+    passthrough = LayerMappedView(raw, map_layer, copy_through=True)
+    copied_file = tmp_path / 'layer_mapped_copied.gds'
+    gdsii_lazy_arrow.writefile(passthrough, copied_file)
+
+    assert copied == ['leaf', 'mid', 'top']
+    assert copied_file.read_bytes() == gds_file.read_bytes()
+    assert not raw._cache
+
+    copied.clear()
+    assert set(passthrough['leaf'].shapes) == {(20, 0)}
+    promoted_file = tmp_path / 'layer_mapped_promoted.gds'
+    gdsii_lazy_arrow.writefile(passthrough, promoted_file)
+
+    assert copied == ['mid', 'top']
+    assert not raw._cache
+    roundtrip, _ = gdsii.readfile(promoted_file)
+    assert set(roundtrip['leaf'].shapes) == {(20, 0)}
+
+
 def test_gdsii_lazy_arrow_processed_cell_edit_disables_raw_copy(
         tmp_path: Path,
         monkeypatch: pytest.MonkeyPatch,
@@ -279,7 +328,7 @@ def test_gdsii_lazy_arrow_processed_cell_edit_disables_raw_copy(
     gdsii.writefile(src, gds_file, meters_per_unit=1e-9, library_name='processed-edit')
 
     raw, _ = gdsii_lazy_arrow.readfile(gds_file)
-    processed = PortsLibraryView(raw)
+    processed = PortLoadView(raw)
     processed['top'].polygon((7, 0), vertices=[[0, 0], [4, 0], [0, 4]])
 
     copied: list[str] = []

masque/test/test_library.py

@@ -2,7 +2,10 @@ import pytest
 from collections.abc import Mapping, MutableMapping
 from typing import cast, TYPE_CHECKING
 from numpy.testing import assert_allclose
-from ..library import IBorrowing, INameView, IMaterializable, Library, LibraryView, LazyLibrary, OverlayLibrary, PortsLibraryView
+from ..library import (
+    IBorrowing, INameView, IMaterializable, LayerMappedView, Library, LibraryView,
+    LazyLibrary, OverlayLibrary, PortLoadView,
+    )
 from ..pattern import Pattern
 from ..error import LibraryError, PatternError
 from ..ports import Port
@@ -540,11 +543,11 @@ def test_overlay_add_source_callback_sees_earlier_name_reservations() -> None:
     assert set(rename_map.values()) <= set(overlay)
 
 
-def test_ports_view_detaches_already_materialized_overlay_pattern() -> None:
+def test_port_load_view_detaches_already_materialized_overlay_pattern() -> None:
     overlay = OverlayLibrary()
     overlay.add_source(Library({"top": Pattern()}))
     raw = overlay["top"]
-    processed = PortsLibraryView(
+    processed = PortLoadView(
         overlay,
         ports={"top": {"P": Port((1, 2), 0)}},
     )
@@ -557,6 +560,77 @@ def test_ports_view_detaches_already_materialized_overlay_pattern() -> None:
     assert not hasattr(processed, "close")
 
 
+def test_layer_mapped_view_detaches_and_maps_shapes_and_labels() -> None:
+    import masque
+
+    child = Pattern()
+    source_pattern = Pattern(ports={'P': Port((1, 2), 0, ptype='wire')})
+    source_pattern.polygon('A', vertices=[[0, 0], [1, 0], [0, 1]])
+    source_pattern.polygon('B', vertices=[[2, 0], [3, 0], [2, 1]])
+    source_pattern.label('TEXT', string='port', offset=(1, 2))
+    source_pattern.ref('child')
+    source_pattern.annotations['note'] = ['unchanged']
+    source = Library({'child': child, 'top': source_pattern})
+    mapped = LayerMappedView(
+        source,
+        lambda layer: {'A': 'DRAW', 'B': 'DRAW', 'TEXT': 'LABEL'}.get(layer, layer),
+        )
+
+    mapped_top = mapped['top']
+
+    assert mapped_top is not source_pattern
+    assert set(mapped_top.shapes) == {'DRAW'}
+    assert len(mapped_top.shapes['DRAW']) == 2
+    assert set(mapped_top.labels) == {'LABEL'}
+    assert set(mapped_top.ports) == {'P'}
+    assert set(mapped_top.refs) == {'child'}
+    assert mapped_top.annotations == {'note': ['unchanged']}
+    assert set(source_pattern.shapes) == {'A', 'B'}
+    assert set(source_pattern.labels) == {'TEXT'}
+    assert mapped.child_graph() == source.child_graph()
+    assert mapped.source_order() == source.source_order()
+    assert masque.LayerMappedView is LayerMappedView
+    assert masque.PortLoadView is PortLoadView
+    assert not hasattr(masque, 'PortsLibraryView')
+    assert not hasattr(masque.library, 'PortsLibraryView')
+
+
+def test_layer_mapped_view_materialization_and_copy_through() -> None:
+    pattern = Pattern()
+    pattern.polygon('A', vertices=[[0, 0], [1, 0], [0, 1]])
+    source = Library({'top': pattern})
+    mapped = LayerMappedView(source, lambda _layer: 'B')
+    passthrough = LayerMappedView(source, lambda _layer: 'B', copy_through=True)
+
+    assert mapped.source_cell('top') is None
+    assert passthrough.source_cell('top') == (source, 'top')
+    transient = passthrough.materialize('top', persist=False)
+    assert set(transient.shapes) == {'B'}
+    assert passthrough.source_cell('top') == (source, 'top')
+
+    persistent = passthrough['top']
+    assert passthrough['top'] is persistent
+    assert passthrough.source_cell('top') is None
+    assert set(persistent.shapes) == {'B'}
+
+
+def test_layer_mapped_view_composes_with_ports_and_overlay() -> None:
+    pattern = Pattern()
+    pattern.polygon('A', vertices=[[0, 0], [1, 0], [0, 1]])
+    source = Library({'top': pattern})
+    ports = PortLoadView(source, ports={'top': {'P': Port((1, 2), 0)}})
+    mapped = LayerMappedView(ports, lambda _layer: 'B')
+    overlay = OverlayLibrary()
+    overlay.add_source(mapped)
+
+    top = overlay['top']
+
+    assert set(top.shapes) == {'B'}
+    assert set(top.ports) == {'P'}
+    assert mapped.borrowed_sources() == (ports,)
+    assert not pattern.ports
+
+
 def test_library_subtree() -> None:
     lib = Library()
     lib["a"] = Pattern()
@@ -655,7 +729,7 @@ def test_library_materialization_and_borrowing_capabilities() -> None:
 
     overlay = OverlayLibrary()
     overlay.add_source(lazy)
-    ports = PortsLibraryView(overlay)
+    ports = PortLoadView(overlay)
     subtree = ports.subtree("top")
 
     assert isinstance(overlay, IMaterializable)
@@ -676,7 +750,7 @@ def test_library_materialization_and_borrowing_capabilities() -> None:
 def test_borrowed_source_cell_tracks_persistent_materialization() -> None:
     source = Library({"top": Pattern()})
     source.library_info = {"name": "not-forwarded"}      # type: ignore[attr-defined]
-    processed = PortsLibraryView(source)
+    processed = PortLoadView(source)
 
     assert processed.source_cell("top") == (source, "top")
     assert not hasattr(processed, "library_info")