Add selection subtracting for node graph

Author: wade-cheng

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

@@ -969,7 +969,7 @@ impl<'a> MessageHandler<NodeGraphMessage, NodeGraphMessageContext<'a>> for NodeG
 				}
 
 				// Clicked on the graph background so we box select
-				if !shift_click {
+				if !shift_click && !alt_click {
 					responses.add(NodeGraphMessage::SelectedNodesSet { nodes: Vec::new() })
 				}
 				self.box_selection_start = Some((node_graph_point, false));
@@ -1926,12 +1926,13 @@ impl<'a> MessageHandler<NodeGraphMessage, NodeGraphMessageContext<'a>> for NodeG
 						.transform_point2(ipp.mouse.position);
 
 					let shift = ipp.keyboard.get(Key::Shift as usize);
+					let alt = ipp.keyboard.get(Key::Alt as usize);
 					let Some(selected_nodes) = network_interface.selected_nodes_in_nested_network(selection_network_path) else {
 						log::error!("Could not get selected nodes in UpdateBoxSelection");
 						return;
 					};
 					let previous_selection = selected_nodes.selected_nodes_ref().iter().cloned().collect::<HashSet<_>>();
-					let mut nodes = if shift {
+					let mut nodes = if shift || alt {
 						selected_nodes.selected_nodes_ref().iter().cloned().collect::<HashSet<_>>()
 					} else {
 						HashSet::new()
@@ -1944,7 +1945,11 @@ impl<'a> MessageHandler<NodeGraphMessage, NodeGraphMessageContext<'a>> for NodeG
 						};
 						let quad = Quad::from_box([box_selection_start, box_selection_end_graph]);
 						if click_targets.node_click_target.intersect_path(|| quad.to_lines(), DAffine2::IDENTITY) {
-							nodes.insert(node_id);
+							if alt {
+								nodes.remove(&node_id);
+							} else {
+								nodes.insert(node_id);
+							}
 						}
 					}
 					if nodes != previous_selection {
@@ -2739,7 +2744,11 @@ impl NodeGraphMessageHandler {
 		let mut hint_data = HintData(vec![
 			HintGroup(vec![HintInfo::mouse(MouseMotion::Rmb, "Add Node")]),
 			HintGroup(vec![HintInfo::mouse(MouseMotion::Lmb, "Select Node"), HintInfo::keys([Key::Shift], "Extend").prepend_plus()]),
-			HintGroup(vec![HintInfo::mouse(MouseMotion::LmbDrag, "Select Area"), HintInfo::keys([Key::Shift], "Extend").prepend_plus()]),
+			HintGroup(vec![
+				HintInfo::mouse(MouseMotion::LmbDrag, "Select Area"),
+				HintInfo::keys([Key::Shift], "Extend").prepend_plus(),
+				HintInfo::keys([Key::Alt], "Subtract").prepend_plus(),
+			]),
 		]);
 		if self.has_selection {
 			hint_data.0.extend([