Massively reorganize and clean up the whole Rust codebase (#478)

* Massively reorganize and clean up the whole Rust codebase

* Additional changes during code review

editor/src/document/overlays_message_handler.rs

@@ -0,0 +1,40 @@
+use super::layer_panel::LayerMetadata;
+use crate::input::InputPreprocessorMessageHandler;
+use crate::message_prelude::*;
+
+use graphene::document::Document;
+use graphene::document::Document as GrapheneDocument;
+use graphene::layers::style::ViewMode;
+
+#[derive(Debug, Clone, Default)]
+pub struct OverlaysMessageHandler {
+	pub overlays_graphene_document: GrapheneDocument,
+}
+
+impl MessageHandler<OverlaysMessage, (&mut LayerMetadata, &Document, &InputPreprocessorMessageHandler)> for OverlaysMessageHandler {
+	#[remain::check]
+	fn process_action(&mut self, message: OverlaysMessage, _data: (&mut LayerMetadata, &Document, &InputPreprocessorMessageHandler), responses: &mut VecDeque<Message>) {
+		// let (layer_metadata, document, ipp) = data;
+		use OverlaysMessage::*;
+		#[remain::sorted]
+		match message {
+			ClearAllOverlays => todo!(),
+			DispatchOperation(operation) => match self.overlays_graphene_document.handle_operation(&operation) {
+				Ok(_) => (),
+				Err(e) => log::error!("OverlaysError: {:?}", e),
+			},
+		}
+
+		// Render overlays
+		responses.push_back(
+			FrontendMessage::UpdateDocumentOverlays {
+				svg: self.overlays_graphene_document.render_root(ViewMode::Normal),
+			}
+			.into(),
+		);
+	}
+
+	fn actions(&self) -> ActionList {
+		actions!(OverlaysMessageDiscriminant; ClearAllOverlays)
+	}
+}