Remove scaling of highlight width, fix showing shapes for uneven coor…

…dinates (#6629)

# References and relevant issues

This PR is created as result of debug
#6627 (comment)
As 0.4.19 branch has fewer problems than #6628 is created for 0.4.19. 

# Description

Fix logic for selecting of visible shapes based on idea from #2289. It
is lucky that we do not hit this earlier.

Removes scaling of width of markers border (this is same like in #6628)

To improve readability, this update `ShapesVisual` to have named
subvisuals.

napari/_vispy/layers/shapes.py

@@ -9,6 +9,8 @@
 
 
 class VispyShapesLayer(VispyBaseLayer):
+    node: ShapesVisual
+
     def __init__(self, layer) -> None:
         node = ShapesVisual()
         super().__init__(layer, node)
@@ -20,8 +22,8 @@ def __init__(self, layer) -> None:
         self.layer.text.events.connect(self._on_text_change)
 
         # TODO: move to overlays
-        self.node._subvisuals[3].symbol = 'square'
-        self.node._subvisuals[3].scaling = False
+        self.node.highlight_vertices.symbol = 'square'
+        self.node.highlight_vertices.scaling = False
 
         self.reset()
         self._on_data_change()
@@ -48,7 +50,7 @@ def _on_data_change(self):
         ):
             vertices = np.pad(vertices, ((0, 0), (0, 1)), mode='constant')
 
-        self.node._subvisuals[0].set_data(
+        self.node.shape_faces.set_data(
             vertices=vertices, faces=faces, face_colors=colors
         )
 
@@ -68,7 +70,7 @@ def _on_highlight_change(self):
             vertices = np.zeros((3, self.layer._slice_input.ndisplay))
             faces = np.array([[0, 1, 2]])
 
-        self.node._subvisuals[1].set_data(
+        self.node.shape_highlights.set_data(
             vertices=vertices,
             faces=faces,
             color=self.layer._highlight_color,
@@ -84,16 +86,15 @@ def _on_highlight_change(self):
             _,
         ) = self.layer._compute_vertices_and_box()
 
-        # use last dimension of scale like (thickness cannot be anisotropic)
-        width = settings.appearance.highlight_thickness / self.layer.scale[-1]
+        width = settings.appearance.highlight_thickness
 
         if vertices is None or len(vertices) == 0:
             vertices = np.zeros((1, self.layer._slice_input.ndisplay))
             size = 0
         else:
             size = self.layer._vertex_size
 
-        self.node._subvisuals[3].set_data(
+        self.node.highlight_vertices.set_data(
             vertices,
             size=size,
             face_color=face_color,
@@ -105,7 +106,7 @@ def _on_highlight_change(self):
             pos = np.zeros((1, self.layer._slice_input.ndisplay))
             width = 0
 
-        self.node._subvisuals[2].set_data(
+        self.node.highlight_lines.set_data(
             pos=pos, color=edge_color, width=width
         )
 
@@ -123,8 +124,7 @@ def _update_text(self, *, update_node=True):
 
     def _get_text_node(self):
         """Function to get the text node from the Compound visual"""
-        text_node = self.node._subvisuals[-1]
-        return text_node
+        return self.node.text
 
     def _on_text_change(self, event=None):
         if event is not None:

napari/_vispy/visuals/shapes.py

@@ -18,3 +18,28 @@ class ShapesVisual(ClippingPlanesMixin, Compound):
 
     def __init__(self) -> None:
         super().__init__([Mesh(), Mesh(), Line(), Markers(), Text()])
+
+    @property
+    def shape_faces(self) -> Mesh:
+        """Mesh for shape faces"""
+        return self._subvisuals[0]
+
+    @property
+    def shape_highlights(self) -> Mesh:
+        """Mesh for shape highlights"""
+        return self._subvisuals[1]
+
+    @property
+    def highlight_lines(self) -> Line:
+        """Lines for shape highlights"""
+        return self._subvisuals[2]
+
+    @property
+    def highlight_vertices(self) -> Markers:
+        """Vertices for shape highlights"""
+        return self._subvisuals[3]
+
+    @property
+    def text(self) -> Text:
+        """Text labels"""
+        return self._subvisuals[4]

napari/layers/shapes/_shape_list.py

@@ -271,7 +271,9 @@ def _update_displayed(self):
         # Slice key must exactly match mins and maxs of shape as then the
         # shape is entirely contained within the current slice.
         if len(self.shapes) > 0:
-            self._displayed = np.all(self.slice_keys == slice_key, axis=(1, 2))
+            self._displayed = np.all(
+                np.abs(self.slice_keys - slice_key) < 0.5, axis=(1, 2)
+            )
         else:
             self._displayed = np.array([])
         disp_indices = np.where(self._displayed)[0]