Fixes for multiple shape layers

plugin/napari_lattice/shape_selector.py

@@ -5,14 +5,16 @@
 from magicgui.widgets import Select
 from napari.layers import Shapes
 from napari.components.layerlist import LayerList
+from collections import defaultdict
+from contextlib import contextmanager
 
 from plugin.napari_lattice.utils import get_viewer
 
 if TYPE_CHECKING:
     from napari.utils.events.event import Event
     from numpy.typing import NDArray
 
-@dataclass
+@dataclass(frozen=True, eq=True)
 class Shape:
     """
     Holds data about a single shape within a Shapes layer
@@ -21,16 +23,32 @@ class Shape:
     index: int
 
     def __str__(self) -> str:
-        return f"{self.layer.name} {self.index}"
+        return f"{self.layer.name}: Shape {self.index}"
 
     def get_array(self) -> NDArray:
         return self.layer.data[self.index]
 
 @magicclass
 class ShapeSelector:
+
+    _blocked: bool
+
     def __init__(self, *args, **kwargs) -> None:
         # Needed to handle extra kwargs
-        pass
+        self._blocked = False
+
+    @contextmanager
+    def _block(self):
+        """
+        Context manager that prevents event handlers recursively calling each other.
+        Yields a boolean, which means functions should proceed if `True`, or return immediately if `False`
+        """
+        if self._blocked:
+            yield False
+        else:
+            self._blocked = True
+            yield True
+            self._blocked = False
 
     def _get_shape_choices(self, widget: Select | None = None) -> Iterator[Tuple[str, Shape]]:
         """
@@ -48,11 +66,16 @@ def _on_selection_change(self, event: Event) -> None:
         Triggered when the user clicks on one or more shapes.
         The widget is then updated to synchronise
         """
-        source: Shapes = event.source
-        selection: list[Shape] = []
-        for index in source.selected_data:
-            selection.append(Shape(layer=source, index=index))
-        self.shapes.value = selection
+        # Prevent recursion
+        with self._block() as execute:
+            if not execute:
+                return
+
+            source: Shapes = event.source
+            selection: list[Shape] = []
+            for index in source.selected_data:
+                selection.append(Shape(layer=source, index=index))
+            self.shapes.value = selection
 
     def _connect_shapes(self, shapes: Shapes) -> None:
         """
@@ -104,18 +127,20 @@ def _widget_changed(self, values: list) -> None:
         Triggered when the plugin widget is changed.
         We then synchronise the Napari shape selection with it.
         """
-        layers: set[Shapes] = set()
-        indices: set[int] = set()
-        value: Shape
-
-        for value in values:
-            layers.add(value.layer)
-            indices.add(value.index)
-
-        if len(layers) > 1:
-            raise Exception("Shapes from multiple layers selected. This shouldn't be possible")
-
-        if layers:
-            layer = layers.pop()
-            layer.selected_data = indices
-            layer.refresh()
+        with self._block() as execute:
+            if not execute:
+                return
+            layers: dict[Shapes, list[int]] = {layer: [] for layer in get_viewer().layers if isinstance(layer, Shapes)}
+            value: Shape
+
+            # Find the current selection for each layer
+            for value in values:
+                layers[value.layer].append(value.index)
+
+            # For each layer, set the appropriate selection (this can't be done incrementally)
+            for layer, shapes in layers.items():
+                layer.selected_data = shapes
+
+            # Re-calculate the selections for all Shapes layers (since some have been deselected)
+            for layer in layers.keys():
+                    layer.refresh()