Filter non-matching elements by default when groups is specified

Previously, non-matching elements were shown in grey (na_color) by
default when using groups. Now they are filtered out entirely, which
is the more intuitive behavior. To show non-matching elements, set
na_color explicitly (e.g., na_color="red").

This applies to shapes and points only (labels are raster-based and
cannot be filtered).

Baseline images removed for regeneration — existing groups tests will
produce different output with the new default.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: timtreis

src/spatialdata_plot/pl/basic.py

@@ -213,8 +213,8 @@ def render_shapes(
             `fill_alpha` will overwrite the value present in the cmap.
         groups : list[str] | str | None
             When using `color` and the key represents discrete labels, `groups` can be used to show only a subset of
-            them. Other values are set to NA. When ``na_color=None``, non-matching elements are filtered out entirely
-            instead of rendered invisibly (shapes and points only; labels are raster-based and cannot be filtered).
+            them. By default, non-matching elements are filtered out entirely (shapes and points only; labels are
+            raster-based and cannot be filtered). To show non-matching elements, set ``na_color`` explicitly.
             If element is None, broadcasting behaviour is attempted (use the same values for all elements).
         palette :  list[str] | str | None
             Palette for discrete annotations. List of valid color names that should be used for the categories. Must

src/spatialdata_plot/pl/render.py

@@ -272,9 +272,10 @@ def _render_shapes(
 
     values_are_categorical = color_source_vector is not None
 
-    # When groups are specified and na_color is fully transparent (na_color=None),
-    # filter out non-matching elements instead of showing them as invisible geometry.
-    if groups is not None and values_are_categorical and render_params.cmap_params.na_color.alpha == "00":
+    # When groups are specified, filter out non-matching elements by default.
+    # Only show non-matching elements if the user explicitly sets na_color.
+    _na = render_params.cmap_params.na_color
+    if groups is not None and values_are_categorical and (_na.default_color_set or _na.alpha == "00"):
         keep, color_source_vector, color_vector = _filter_groups_transparent_na(
             groups, color_source_vector, color_vector
         )
@@ -883,9 +884,10 @@ def _render_points(
     if added_color_from_table and col_for_color is not None:
         _reparse_points(sdata_filt, element, points_pd_with_color, transformation_in_cs, coordinate_system)
 
-    # When groups are specified and na_color is fully transparent (na_color=None),
-    # filter out non-matching points instead of rendering invisible geometry.
-    if groups is not None and color_source_vector is not None and render_params.cmap_params.na_color.alpha == "00":
+    # When groups are specified, filter out non-matching elements by default.
+    # Only show non-matching elements if the user explicitly sets na_color.
+    _na = render_params.cmap_params.na_color
+    if groups is not None and color_source_vector is not None and (_na.default_color_set or _na.alpha == "00"):
         keep, color_source_vector, color_vector = _filter_groups_transparent_na(
             groups, color_source_vector, color_vector
         )