Add Alt+drag layer duplication to the Layers panel (#4216)

* Add Alt+drag layer duplication to the Layers panel

* Code review

editor/src/messages/portfolio/document/document_message.rs

@@ -60,6 +60,10 @@ pub enum DocumentMessage {
 		context: OverlayContext,
 	},
 	DuplicateSelectedLayers,
+	DuplicateSelectedLayersTo {
+		parent: LayerNodeIdentifier,
+		insert_index: usize,
+	},
 	EnterNestedNetwork {
 		node_id: NodeId,
 	},

editor/src/messages/portfolio/document/document_message_handler.rs

@@ -449,37 +449,88 @@ impl MessageHandler<DocumentMessage, DocumentMessageContext<'_>> for DocumentMes
 					DocumentMessageHandler::get_calculated_insert_index(self.metadata(), &SelectedNodes(vec![layer.to_node()]), parent)
 				});
 
-				for layer in layers.into_iter().rev() {
-					let Some(parent) = layer.parent(self.metadata()) else { continue };
+				for original_layer in layers.into_iter().rev() {
+					let Some(parent) = original_layer.parent(self.metadata()) else { continue };
+					let insert_index = DocumentMessageHandler::get_calculated_insert_index(self.metadata(), &SelectedNodes(vec![original_layer.to_node()]), parent);
 
-					// Copy the layer
-					let mut copy_ids = HashMap::new();
-					let node_id = layer.to_node();
-					copy_ids.insert(node_id, NodeId(0));
-
-					self.network_interface
-						.upstream_flow_back_from_nodes(vec![layer.to_node()], &[], FlowType::LayerChildrenUpstreamFlow)
-						.enumerate()
-						.for_each(|(index, node_id)| {
-							copy_ids.insert(node_id, NodeId((index + 1) as u64));
-						});
-
-					let nodes = self.network_interface.copy_nodes(&copy_ids, &[]).collect::<Vec<(NodeId, NodeTemplate)>>();
-
-					let insert_index = DocumentMessageHandler::get_calculated_insert_index(self.metadata(), &SelectedNodes(vec![layer.to_node()]), parent);
-
-					let new_ids: HashMap<_, _> = nodes.iter().map(|(id, _)| (*id, NodeId::new())).collect();
-
-					let layer_id = *new_ids.get(&NodeId(0)).expect("Node Id 0 should be a layer");
-					let layer = LayerNodeIdentifier::new_unchecked(layer_id);
-					new_dragging.push(layer);
-					responses.add(NodeGraphMessage::AddNodes { nodes, new_ids });
-					responses.add(NodeGraphMessage::MoveLayerToStack { layer, parent, insert_index });
+					let Some(new_layer) = self.duplicate_layer(original_layer, responses) else { continue };
+					new_dragging.push(new_layer);
+					responses.add(NodeGraphMessage::MoveLayerToStack {
+						layer: new_layer,
+						parent,
+						insert_index,
+					});
 				}
 				let nodes = new_dragging.iter().map(|layer| layer.to_node()).collect();
 				responses.add(NodeGraphMessage::SelectedNodesSet { nodes });
 				responses.add(NodeGraphMessage::RunDocumentGraph);
 			}
+			DocumentMessage::DuplicateSelectedLayersTo { parent, insert_index } => {
+				if !self.selection_network_path.is_empty() {
+					log::error!("Duplicating selected layers is only supported for the document network");
+					return;
+				}
+
+				// Mirror the placement constraints enforced when moving layers so a copy can't land somewhere a move couldn't
+				let any_artboards = self
+					.network_interface
+					.selected_nodes()
+					.selected_layers(self.metadata())
+					.any(|layer| self.network_interface.is_artboard(&layer.to_node(), &self.selection_network_path));
+				if any_artboards && parent != LayerNodeIdentifier::ROOT_PARENT {
+					return;
+				}
+
+				let selected_any_non_artboards = self
+					.network_interface
+					.selected_nodes()
+					.selected_layers(self.metadata())
+					.any(|layer| !self.network_interface.is_artboard(&layer.to_node(), &self.selection_network_path));
+				let top_level_artboards = LayerNodeIdentifier::ROOT_PARENT
+					.children(self.metadata())
+					.any(|layer| self.network_interface.is_artboard(&layer.to_node(), &self.selection_network_path));
+				if selected_any_non_artboards && parent == LayerNodeIdentifier::ROOT_PARENT && top_level_artboards {
+					return;
+				}
+
+				let layers_to_duplicate = self.network_interface.shallowest_unique_layers_sorted(&self.selection_network_path);
+				if layers_to_duplicate.is_empty() {
+					return;
+				}
+
+				responses.add(DocumentMessage::AddTransaction);
+
+				let mut new_layers = Vec::new();
+				for layer in layers_to_duplicate {
+					let Some(new_layer) = self.duplicate_layer(layer, responses) else { continue };
+
+					// Insert each copy one slot below the previous so the duplicates keep their original top-to-bottom order
+					let placement_index = insert_index + new_layers.len();
+					new_layers.push(new_layer);
+					responses.add(NodeGraphMessage::MoveLayerToStack {
+						layer: new_layer,
+						parent,
+						insert_index: placement_index,
+					});
+
+					// Compensate the local transform so a copy dropped into a differently-transformed parent stays put in world space
+					if layer.parent(self.metadata()) != Some(parent) {
+						let layer_world_transform = self.network_interface.document_metadata().transform_to_viewport(layer);
+						let undo_parent_transform = self.network_interface.document_metadata().transform_to_viewport(parent).inverse();
+
+						responses.add(GraphOperationMessage::TransformSet {
+							layer: new_layer,
+							transform: undo_parent_transform * layer_world_transform,
+							transform_in: TransformIn::Local,
+							skip_rerender: false,
+						});
+					}
+				}
+
+				let nodes = new_layers.iter().map(|layer| layer.to_node()).collect();
+				responses.add(NodeGraphMessage::SelectedNodesSet { nodes });
+				responses.add(NodeGraphMessage::RunDocumentGraph);
+			}
 			DocumentMessage::EnterNestedNetwork { node_id } => {
 				self.breadcrumb_network_path.push(node_id);
 				self.selection_network_path.clone_from(&self.breadcrumb_network_path);
@@ -2218,6 +2269,30 @@ impl DocumentMessageHandler {
 			.unwrap_or(0)
 	}
 
+	/// Copies `layer` together with its full upstream node chain, queueing the new nodes with freshly minted IDs.
+	/// Returns the new layer's identifier; the caller places it into the stack with a `MoveLayerToStack` response.
+	fn duplicate_layer(&mut self, layer: LayerNodeIdentifier, responses: &mut VecDeque<Message>) -> Option<LayerNodeIdentifier> {
+		let mut copy_ids = HashMap::new();
+		copy_ids.insert(layer.to_node(), NodeId(0));
+		self.network_interface
+			.upstream_flow_back_from_nodes(vec![layer.to_node()], &[], FlowType::LayerChildrenUpstreamFlow)
+			.enumerate()
+			.for_each(|(index, node_id)| {
+				copy_ids.insert(node_id, NodeId((index + 1) as u64));
+			});
+
+		let nodes = self.network_interface.copy_nodes(&copy_ids, &[]).collect::<Vec<(NodeId, NodeTemplate)>>();
+		let new_ids: HashMap<_, _> = nodes.iter().map(|(id, _)| (*id, NodeId::new())).collect();
+
+		let Some(&new_layer_id) = new_ids.get(&NodeId(0)) else {
+			log::error!("Could not duplicate layer because its root node copy is missing");
+			return None;
+		};
+		responses.add(NodeGraphMessage::AddNodes { nodes, new_ids });
+
+		Some(LayerNodeIdentifier::new_unchecked(new_layer_id))
+	}
+
 	pub fn group_layers(
 		responses: &mut VecDeque<Message>,
 		insert_index: usize,

frontend/src/components/panels/Layers.svelte

@@ -349,6 +349,7 @@
 			if (distance > DRAG_THRESHOLD) {
 				internalDragState.active = true;
 				dragInPanel = true;
+				layerToClipUponClick = undefined;
 
 				const layer = internalDragState.listing.entry;
 				if (!$nodeGraph.selected.includes(layer.id)) {
@@ -381,7 +382,7 @@
 		}
 	}
 
-	function draggingPointerUp() {
+	function draggingPointerUp(e: PointerEvent) {
 		if (internalDragState?.active && dragDropTarget) {
 			// Ensure the dragged layer is part of the selection, matching the move-in-tree behavior
 			if (!$nodeGraph.selected.includes(internalDragState.layerId)) selectLayer(internalDragState.listing, false, false);
@@ -393,9 +394,12 @@
 		} else if (internalDragState?.active && draggingData) {
 			const { select, insertParentId, insertIndex } = draggingData;
 
-			// Commit the move
+			// Ensure the dragged layer is part of the selection before committing
 			select?.();
-			editor.moveLayerInTree(insertParentId, insertIndex);
+
+			// Holding Alt drops a duplicate of the selection at the target instead of moving the originals
+			if (e.altKey) editor.duplicateLayerInTree(insertParentId, insertIndex);
+			else editor.moveLayerInTree(insertParentId, insertIndex);
 
 			// Prevent the subsequent click event from processing
 			justFinishedDrag = true;

frontend/wrapper/src/editor_wrapper.rs

@@ -756,6 +756,18 @@ impl EditorWrapper {
 		self.dispatch(message);
 	}
 
+	/// Duplicate the selected layers, placing the copies within the given folder at the given index.
+	/// If the folder is `None`, they are inserted into the document root.
+	/// If the insert index is `None`, they are inserted at the start of the folder.
+	#[wasm_bindgen(js_name = duplicateLayerInTree)]
+	pub fn duplicate_layer_in_tree(&self, insert_parent_id: Option<u64>, insert_index: Option<usize>) {
+		let message = DocumentMessage::DuplicateSelectedLayersTo {
+			parent: insert_parent_id.map(NodeId).map(LayerNodeIdentifier::new_unchecked).unwrap_or_default(),
+			insert_index: insert_index.unwrap_or_default(),
+		};
+		self.dispatch(message);
+	}
+
 	/// Set the name for the layer
 	#[wasm_bindgen(js_name = setLayerName)]
 	pub fn set_layer_name(&self, id: u64, name: String) {