[vis] Fix automatic colors for connected point clouds

phi/vis/_matplotlib/_matplotlib_plots.py

@@ -185,7 +185,7 @@ def _get_range(bounds: Box, index: int):
 
 def _next_line_color(axes: Axes, kind: str = None, get_index=False):
     kind = ['patches', 'lines', 'collections', 'containers'] if kind is None else kind.split(',')
-    next_index = max([len(getattr(axes, a)) for a in kind])
+    next_index = max([len(getattr(axes, k)) for k in kind])
     if get_index:
         return next_index
     return _default_color(next_index)
@@ -573,6 +573,7 @@ def plot(self, data: Field, figure, subplot, space: Box, min_val: float, max_val
 
     @staticmethod
     def _plot_points(axis: Axes, data: Field, dims: tuple, vector: Shape, color: Tensor, alpha: Tensor, err: Tensor, min_val, max_val, label):
+        connected = spatial(data.points)
         if isinstance(data.sampled_elements, GeometryStack):
             for idx in data.sampled_elements.object_dims.meshgrid():
                 PointCloud2D._plot_points(axis, data[idx], dims, vector, color[idx], alpha[idx], err[idx], min_val, max_val, label)
@@ -581,10 +582,13 @@ def _plot_points(axis: Axes, data: Field, dims: tuple, vector: Shape, color: Ten
         x, y = reshaped_numpy(data.points.vector[dims], [vector, non_channel(data)])
         if (color == None).all:
             if not math.is_finite(data.values).any:
-                mpl_colors = [_next_line_color(axis)] * non_channel(data).volume
+                mpl_colors = [_next_line_color(axis, 'lines' if connected else 'collections')] * non_channel(data).volume
             else:
                 values = reshaped_numpy(data.values, [non_channel(data)])
-                mpl_colors = add_color_bar(axis, values, min_val, max_val)
+                if np.any(values != values[0]):
+                    mpl_colors = add_color_bar(axis, values, min_val, max_val)
+                else:
+                    mpl_colors = [_next_line_color(axis, 'lines' if connected else 'collections')] * non_channel(data).volume
         else:
             mpl_colors = matplotlib_colors(color, non_channel(data), default=0)
         alphas = reshaped_numpy(alpha, [non_channel(data)])
@@ -635,13 +639,13 @@ def _plot_points(axis: Axes, data: Field, dims: tuple, vector: Shape, color: Ten
                 rad = reshaped_numpy(data.geometry.bounding_radius(), [data.shape.non_channel])
                 shapes = [plt.Circle((xi, yi), radius=ri, linewidth=0, alpha=a, facecolor=ci) for xi, yi, ri, ci, a in zip(x, y, rad, mpl_colors, alphas)]
                 axis.add_collection(matplotlib.collections.PatchCollection(shapes, match_original=True))
-        if spatial(data.points):  # Connect by line
+        if connected:  # Connect by line
             for i, idx in enumerate(instance(data).meshgrid()):
                 for sp_dim in spatial(data):
                     other_sp = spatial(data).without(sp_dim)
                     xs, ys = reshaped_numpy(data[idx].points.vector[dims], [vector, sp_dim, other_sp])
                     if (color == None).all:
-                        col = _next_line_color(axis)
+                        col = _next_line_color(axis, 'lines' if connected else 'collections')
                     else:
                         col = _plt_col(color)
                     alpha_f = float(alpha[idx].max)