fix and slightly refactor

ultraplot/axes/plot.py

@@ -9,8 +9,7 @@
 import re
 import sys
 from numbers import Integral, Number
-from typing import Any
-from collections.abc import Iterable
+from typing import Any, Iterable
 
 import matplotlib.artist as martist
 import matplotlib.axes as maxes
@@ -1388,12 +1387,70 @@ def _add_auto_labels(
         formatter = constructor.Formatter(
             formatter, precision=precision, **formatter_kw
         )  # noqa: E501
-        if isinstance(obj, mcontour.ContourSet):
-            self._add_contour_labels(obj, cobj, formatter, **labels_kw)
-        elif isinstance(obj, mcollections.Collection):
-            self._add_collection_labels(obj, formatter, **labels_kw)
-        else:
-            raise RuntimeError(f"Not possible to add labels to object {obj!r}.")
+        match obj:
+            case mcontour.ContourSet():
+                self._add_contour_labels(obj, cobj, formatter, **labels_kw)
+            case mcollections.QuadMesh():
+                self._add_quadmesh_labels(obj, formatter, **labels_kw)
+            case mcollections.Collection():
+                self._add_collection_labels(obj, formatter, **labels_kw)
+            case _:
+                raise RuntimeError(f"Not possible to add labels to object {obj!r}.")
+
+
+    def _add_quadmesh_labels(
+        self,
+        obj,
+        fmt,
+        *,
+        c=None,
+        color=None,
+        colors=None,
+        size=None,
+        fontsize=None,
+        **kwargs,
+    ):
+        """
+        Add labels to QuadMesh cells with support for shade-dependent text colors.
+        Values are inferred from the unnormalized mesh cell color.
+        """
+        # Parse input args
+        obj.update_scalarmappable()
+        color = _not_none(c=c, color=color, colors=colors)
+        fontsize = _not_none(size=size, fontsize=fontsize, default=rc["font.smallsize"])
+        kwargs.setdefault("ha", "center")
+        kwargs.setdefault("va", "center")
+
+        # Get the mesh data
+        array = obj.get_array()
+        coords = obj.get_coordinates()  # This gives vertices (11x11x2)
+
+        # Calculate cell centers by averaging the four corners of each cell
+        x_centers = (coords[:-1, :-1, 0] + coords[1:, 1:, 0]) / 2
+        y_centers = (coords[:-1, :-1, 1] + coords[1:, 1:, 1]) / 2
+
+        # Apply colors and create labels
+        labs = []
+        for i, ((x, y), value) in enumerate(zip(zip(x_centers.flat, y_centers.flat), array.flat)):
+            # Skip masked or invalid values
+            if value is ma.masked or not np.isfinite(value):
+                continue
+
+            # Handle discrete normalization if present
+            if isinstance(obj.norm, pcolors.DiscreteNorm):
+                value = obj.norm._norm.inverse(obj.norm(value))
+
+            # Determine text color based on background
+            icolor = color
+            if color is None:
+                _, _, lum = utils.to_xyz(obj.cmap(obj.norm(value)), "hcl")
+                icolor = "w" if lum < 50 else "k"
+
+            # Create text label
+            lab = self.text(x, y, fmt(value), color=icolor, size=fontsize, **kwargs)
+            labs.append(lab)
+
+        return labs
 
     def _add_collection_labels(
         self,
@@ -1444,7 +1501,6 @@ def _add_collection_labels(
             y = (bbox.ymin + bbox.ymax) / 2
             lab = self.text(x, y, fmt(value), color=icolor, size=fontsize, **kwargs)
             labs.append(lab)
-
         obj.set_edgecolors(edgecolors)
         return labs
 
@@ -2487,16 +2543,18 @@ def _parse_cycle(
                 resolved_cycle = None
             case True:
                 resolved_cycle = constructor.Cycle(rc["axes.prop_cycle"])
-            case constructor.Cycle():
-                resolved_cycle = constructor.Cycle(cycle)
             case str() if cycle.lower() == "none":
                 resolved_cycle = None
-            case str() | int() | Iterable():
+            case str() | int():
                 resolved_cycle = constructor.Cycle(cycle, **cycle_kw)
+            case constructor.Cycle():
+                resolved_cycle = constructor.Cycle(cycle)
             case _:
                 resolved_cycle = None
 
-        # Ignore cycle for single-column plotting unless cycle is different
+        # Ignore cycle for single-column plotting
+        resolved_cycle = None if ncycle == 1 else resolved_cycle
+
         if resolved_cycle and resolved_cycle != self._active_cycle:
             self.set_prop_cycle(resolved_cycle)