Fix a single layer twice selected hiding the properties (#2911)

* Fix a single layer twice selected hiding the properties

* Comment that the same node appears several times

---------

Co-authored-by: Keavon Chambers <keavon@keavon.com>

Author: 0HyperCube

editor/src/messages/portfolio/document/node_graph/node_graph_message_handler.rs

@@ -2265,6 +2265,12 @@ impl NodeGraphMessageHandler {
 			}
 		}
 
+		// The same layer/node may appear several times. Sort and dedup them for a stable ordering.
+		layers.sort();
+		layers.dedup();
+		nodes.sort();
+		nodes.dedup();
+
 		// Next, we decide what to display based on the number of layers and nodes selected
 		match *layers.as_slice() {
 			// If no layers are selected, show properties for all selected nodes

editor/src/messages/portfolio/document/utility_types/nodes.rs

@@ -61,6 +61,7 @@ pub struct LayerPanelEntry {
 	pub clippable: bool,
 }
 
+/// IMPORTANT: the same node may appear multiple times.
 #[derive(Debug, Clone, Default, serde::Serialize, serde::Deserialize, PartialEq, Eq, specta::Type)]
 pub struct SelectedNodes(pub Vec<NodeId>);
 
@@ -129,6 +130,7 @@ impl SelectedNodes {
 		self.selected_layers(metadata).any(|selected| selected == layer)
 	}
 
+	/// IMPORTANT: the same node may appear multiple times.
 	pub fn selected_nodes(&self) -> impl Iterator<Item = &NodeId> + '_ {
 		self.0.iter()
 	}