pass mask group into ApplyMaskStencil as rasterization groundwork

Author: krVatsal

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

@@ -1189,10 +1189,11 @@ impl MessageHandler<DocumentMessage, DocumentMessageContext<'_>> for DocumentMes
 					}
 				} else {
 					// Apply the mask group to the target layers
-					if self.mask_group_id.is_some() {
+					if let Some(mask_group_id) = self.mask_group_id {
 						responses.add(DocumentMessage::AddTransaction);
 						responses.add(GraphOperationMessage::ApplyMaskStencil {
 							layers: self.mask_target_layers.clone(),
+							mask_group: LayerNodeIdentifier::new_unchecked(mask_group_id),
 						});
 						responses.add(DocumentMessage::EndTransaction);
 					}

editor/src/messages/portfolio/document/graph_operation/graph_operation_message.rs

@@ -128,5 +128,6 @@ pub enum GraphOperationMessage {
 	},
 	ApplyMaskStencil {
 		layers: Vec<LayerNodeIdentifier>,
+		mask_group: LayerNodeIdentifier,
 	},
 }

editor/src/messages/portfolio/document/graph_operation/graph_operation_message_handler.rs

@@ -439,7 +439,10 @@ impl MessageHandler<GraphOperationMessage, GraphOperationMessageContext<'_>> for
 				// (skipped automatically when identity, so file-open with content at origin creates no Transform node).
 				modify_inputs.transform_set(placement_transform, TransformIn::Local, false);
 			}
-			GraphOperationMessage::ApplyMaskStencil { layers } => {
+			GraphOperationMessage::ApplyMaskStencil { layers, mask_group } => {
+				let _ = mask_group;
+
+				// TODO: Rasterize `mask_group` into a stencil image and apply that stencil to each target layer.
 				// For each target layer, toggle clip mode so the existing clip infrastructure is engaged.
 				for layer in layers {
 					responses.add(GraphOperationMessage::ClipModeToggle { layer });