🐛 Ensure masking polygon lines are CCW

CHANGELOG.md

@@ -13,6 +13,8 @@ All notable changes to this library are documented in this file.
 
 ### Bug Fixes
 
+- Ensure geometries going into masking helper are CCW, to mask outside of.
+
 ## **1.21.0** (6 Sep 2024)
 
 ### API Changes

src/pyiem/plot/util.py

@@ -756,7 +756,9 @@ def mask_outside_geom(gp, geom):
         geom = MultiPolygon([geom])
     trans = Transformer.from_crs(LATLON, gp.crs, always_xy=True)
     for geo in geom.geoms:
-        ccw = np.asarray(geo.exterior.coords)[::-1]
+        ccw = np.asarray(geo.exterior.coords)
+        if not geo.exterior.is_ccw:
+            ccw = ccw[::-1]
         points = trans.transform(ccw[:, 0], ccw[:, 1])
         # pylint: disable=unsubscriptable-object
         ar = np.column_stack([*points])[:-1]

tests/plot/test_geoplot.py

@@ -239,6 +239,28 @@ def test_fema_region6():
     return mp.fig
 
 
+@pytest.mark.mpl_image_compare(tolerance=PAIN)
+def test_fema_region_pcolormesh():
+    """Test problem found in production."""
+    mp = MapPlot(
+        figsize=(8, 6),
+        nocaption=True,
+        fema_region=7,
+        sector="fema_region",
+        title="FEMA Region 7",
+        nostates=True,
+    )
+    lons = np.arange(-100, -80, 0.25)
+    lats = np.arange(40, 50, 0.25)
+    vals = np.linspace(0, 1, lats.shape[0] * lons.shape[0]).reshape(
+        [lats.shape[0], lons.shape[0]]
+    )
+    lons, lats = np.meshgrid(lons, lats)
+    res = mp.pcolormesh(lons, lats, vals, np.arange(0, 1, 0.1))
+    res.set_rasterized(True)
+    return mp.fig
+
+
 @pytest.mark.mpl_image_compare(tolerance=PAIN)
 def test_nashville():
     """Test that Benton County, TNC005 does not show for OHX."""