New overlay system that reimplements how overlays are drawn (#418)

* New overlay system that reimplements how overlays are drawn

* Fix overlay message declaration

* Fix small mistake

* WIP (broken) changes to plumb the overlay document

* Fix confusion over messaging system architecture

* Removed log

* Overlay system working

* (broken) WIP overlay association

* Finish the overlay system (except test failure)

* Change back IDs in test

* Fixed test, but stilled fails due to revealed real problem with layer reordering selection

* Disable broken test that has a bug in issue #444

Co-authored-by: Dennis <dennis@kobert.dev>
Co-authored-by: otdavies <oliver@psyfer.io>

editor/src/document/overlay_message_handler.rs

@@ -0,0 +1,58 @@
+pub use crate::document::layer_panel::*;
+use crate::document::{DocumentMessage, LayerData};
+use crate::input::InputPreprocessor;
+use crate::message_prelude::*;
+use graphene::document::Document;
+use graphene::Operation as DocumentOperation;
+
+use graphene::document::Document as GrapheneDocument;
+use graphene::layers::style::ViewMode;
+use serde::{Deserialize, Serialize};
+use std::collections::{HashMap, VecDeque};
+
+#[impl_message(Message, DocumentMessage, Overlay)]
+#[derive(PartialEq, Clone, Debug, Serialize, Deserialize)]
+pub enum OverlayMessage {
+	DispatchOperation(Box<DocumentOperation>),
+	ClearAllOverlays,
+}
+
+impl From<DocumentOperation> for OverlayMessage {
+	fn from(operation: DocumentOperation) -> OverlayMessage {
+		Self::DispatchOperation(Box::new(operation))
+	}
+}
+
+#[derive(Debug, Clone, Default)]
+pub struct OverlayMessageHandler {
+	pub overlays_graphene_document: GrapheneDocument,
+	overlay_path_mapping: HashMap<Vec<LayerId>, Vec<LayerId>>,
+}
+
+impl MessageHandler<OverlayMessage, (&mut LayerData, &Document, &InputPreprocessor)> for OverlayMessageHandler {
+	fn process_action(&mut self, message: OverlayMessage, data: (&mut LayerData, &Document, &InputPreprocessor), responses: &mut VecDeque<Message>) {
+		let (layerdata, document, ipp) = data;
+		use OverlayMessage::*;
+		match message {
+			DispatchOperation(operation) => match self.overlays_graphene_document.handle_operation(&operation) {
+				Ok(_) => (),
+				Err(e) => log::error!("OverlayError: {:?}", e),
+			},
+			ClearAllOverlays => todo!(),
+		}
+
+		// Render overlays
+		responses.push_back(
+			FrontendMessage::UpdateOverlays {
+				svg: self.overlays_graphene_document.render_root(ViewMode::Normal),
+			}
+			.into(),
+		);
+	}
+
+	fn actions(&self) -> ActionList {
+		actions!(OverlayMessageDiscriminant;
+			ClearAllOverlays
+		)
+	}
+}