fix(python): extend CF_RULE struct layout to match fm_cf_rule_t

The Python wheel drives formulon_capi.wasm through wasmtime using a
hand-mirrored byte layout of the C ABI structs. CF_RULE in
packages/python/formulon/_structs.py was defined before fm_cf_rule_t
gained ColorScale/DataBar/IconSet fields, leaving the Python struct at
88 bytes against the real 168-byte C struct. alloc_struct(LIB,
S.CF_RULE) therefore allocated a WASM-linear-memory buffer 80 bytes too
small for what fm_sheet_cf_add_rule/fm_sheet_cf_get_at actually
read/write, corrupting the round-tripped type field (and potentially
nearby WASM heap state) and failing
test_cf_add_get_evaluate_clear ("0 != 1").

- Add CFVO_BLOB and CF_COLOR_BLOB opaque blob primitives, following the
  existing VALUE_BLOB precedent, for the by-value-embedded fm_cfvo_t
  and fm_cf_color_t sub-structs
- Generalize Struct.unpack()'s opaque-blob skip from the hardcoded
  "blob16" check to "kind not in _FMT" so future blob kinds don't need
  another hardcoded name
- Extend CF_RULE's field list with every field fm_cf_rule_t gained:
  color_scale_thresholds/colors/count, data_bar_engaged,
  data_bar_min/max (CFVO_BLOB), data_bar_fill (CF_COLOR_BLOB),
  data_bar_show_value, data_bar_min/max_length_pct, icon_set_engaged,
  icon_set_name, icon_set_thresholds, icon_set_threshold_count,
  icon_set_reverse, icon_set_show_value, icon_set_percent, in the
  declared order of src/c_api/formulon_c.h. Struct's existing
  alignment-rounding reproduces the C compiler's inter-field padding
  automatically; total size now correctly computes to 168 bytes
- Update the stale EXPECTED_SIZES["CF_RULE"] drift guard in
  packages/python/tests/test_surface.py from 88 to 168

Testing:
- make python-test: 52/52 pass, including
  test_cf_add_get_evaluate_clear and test_struct_sizes
- make python-wheel followed by installing the built wheel into a
  fresh venv and running the test suite against it (the same path
  release.yml's smoke test step runs): 52/52 pass
- Native ctest -LE "SLOW|LOAD|BENCH": 14929/14929 pass, confirming no
  native regression from this Python-only change

Author: libraz

packages/python/formulon/_structs.py

@@ -37,6 +37,14 @@
 # decoded by :meth:`Struct.unpack`; callers read it via Value._from_wasm
 # against ``ptr + offset``.
 VALUE_BLOB = ("blob16", 16, 8)
+# Opaque 12-byte, 4-aligned blob: an inline ``fm_cfvo_t`` (``uint8_t type;
+# uint8_t _pad[3]; int32_t gte; const char* value;``). Not decoded by
+# :meth:`Struct.unpack`; callers who need the sub-fields read them at
+# ``ptr + offset`` with their own struct.unpack_from calls.
+CFVO_BLOB = ("blob_cfvo", 12, 4)
+# Opaque 4-byte, 1-aligned blob: an inline ``fm_cf_color_t`` (four
+# ``uint8_t`` channels). Not decoded by :meth:`Struct.unpack`.
+CF_COLOR_BLOB = ("blob_cf_color", 4, 1)
 
 _FMT = {
     "ptr": "<I",
@@ -77,13 +85,14 @@ def pack(self, lib, ptr: int, values: Dict[str, object]) -> None:
     def unpack(self, lib, ptr: int) -> Dict[str, int]:
         """Read every scalar field from ``[ptr, ptr+size)`` into a dict.
 
-        Opaque ``blob16`` fields (inline ``fm_value_t``) are skipped; read
-        them separately via ``Value._from_wasm(ptr + self.offsets[name][1])``.
+        Opaque blob fields (any ``kind`` not in ``_FMT``, e.g. an inline
+        ``fm_value_t`` or ``fm_cfvo_t``) are skipped; callers decode those
+        separately against ``ptr + self.offsets[name][1]``.
         """
         raw = lib.read_bytes(ptr, self.size)
         out: Dict[str, int] = {}
         for fname, (kind, off) in self.offsets.items():
-            if kind == "blob16":
+            if kind not in _FMT:
                 continue
             out[fname] = struct.unpack_from(_FMT[kind], raw, off)[0]
         return out
@@ -248,6 +257,23 @@ def alloc_struct(lib, layout: Struct) -> int:
         ("std_dev", F64),
         ("text", PTR),
         ("time_period_engaged", I32),
+        ("color_scale_thresholds", PTR),
+        ("color_scale_colors", PTR),
+        ("color_scale_count", U32),
+        ("data_bar_engaged", I32),
+        ("data_bar_min", CFVO_BLOB),
+        ("data_bar_max", CFVO_BLOB),
+        ("data_bar_fill", CF_COLOR_BLOB),
+        ("data_bar_show_value", I32),
+        ("data_bar_min_length_pct", U8),
+        ("data_bar_max_length_pct", U8),
+        ("icon_set_engaged", I32),
+        ("icon_set_name", U8),
+        ("icon_set_thresholds", PTR),
+        ("icon_set_threshold_count", U32),
+        ("icon_set_reverse", I32),
+        ("icon_set_show_value", I32),
+        ("icon_set_percent", I32),
     ],
 )
 

packages/python/tests/test_surface.py

@@ -45,7 +45,7 @@ class StructLayoutTests(unittest.TestCase):
         "SHEET_PROTECTION": 88,
         "VIEWPORT": 20,
         "CF_MATCH": 72,
-        "CF_RULE": 88,
+        "CF_RULE": 168,
         "PIVOT_CELL": 40,
         "PIVOT_FIELD_SPEC": 20,
         "PIVOT_DATA_FIELD_SPEC": 28,