Reduce history system's excessive memory usage from storing copies of images each step (#845)

* Limit saved undo history

* Do not commit path every mouse move event

* Reference count images in history system instead of cloning the image data

* Increase history storage step limit to 100

Co-authored-by: Keavon Chambers <keavon@keavon.com>

graphene/src/layers/base64_serde.rs

@@ -2,20 +2,21 @@
 
 use serde::{Deserialize, Deserializer, Serializer};
 
-pub fn as_base64<T, S>(key: &T, serializer: S) -> Result<S::Ok, S::Error>
+pub fn as_base64<S>(key: &std::rc::Rc<Vec<u8>>, serializer: S) -> Result<S::Ok, S::Error>
 where
-	T: AsRef<[u8]>,
 	S: Serializer,
 {
-	serializer.serialize_str(&base64::encode(key.as_ref()))
+	serializer.serialize_str(&base64::encode(key.as_slice()))
 }
 
-pub fn from_base64<'a, D>(deserializer: D) -> Result<Vec<u8>, D::Error>
+pub fn from_base64<'a, D>(deserializer: D) -> Result<std::rc::Rc<Vec<u8>>, D::Error>
 where
 	D: Deserializer<'a>,
 {
 	use serde::de::Error;
+
 	String::deserialize(deserializer)
-		.and_then(|string| base64::decode(&string).map_err(|err| Error::custom(err.to_string())))
+		.and_then(|string| base64::decode(string).map_err(|err| Error::custom(err.to_string())))
+		.map(std::rc::Rc::new)
 		.map_err(serde::de::Error::custom)
 }

graphene/src/layers/image_layer.rs

@@ -14,7 +14,7 @@ use std::fmt::Write;
 pub struct ImageLayer {
 	pub mime: String,
 	#[serde(serialize_with = "base64_serde::as_base64", deserialize_with = "base64_serde::from_base64")]
-	pub image_data: Vec<u8>,
+	pub image_data: std::rc::Rc<Vec<u8>>,
 	// TODO: Have the browser dispose of this blob URL when this is dropped (like when the layer is deleted)
 	#[serde(skip)]
 	pub blob_url: Option<String>,
@@ -75,7 +75,7 @@ impl LayerData for ImageLayer {
 }
 
 impl ImageLayer {
-	pub fn new(mime: String, image_data: Vec<u8>) -> Self {
+	pub fn new(mime: String, image_data: std::rc::Rc<Vec<u8>>) -> Self {
 		Self {
 			mime,
 			image_data,

graphene/src/layers/imaginate_layer.rs

@@ -53,7 +53,7 @@ pub enum ImaginateStatus {
 #[derive(Debug, Clone, Eq, PartialEq, Deserialize, Serialize)]
 pub struct ImaginateImageData {
 	#[serde(serialize_with = "base64_serde::as_base64", deserialize_with = "base64_serde::from_base64")]
-	pub image_data: Vec<u8>,
+	pub image_data: std::rc::Rc<Vec<u8>>,
 }
 
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]

graphene/src/layers/nodegraph_layer.rs

@@ -29,7 +29,7 @@ pub struct NodeGraphFrameLayer {
 #[derive(Debug, Clone, Eq, PartialEq, Deserialize, Serialize)]
 pub struct ImageData {
 	#[serde(serialize_with = "base64_serde::as_base64", deserialize_with = "base64_serde::from_base64")]
-	pub image_data: Vec<u8>,
+	pub image_data: std::rc::Rc<Vec<u8>>,
 }
 
 impl LayerData for NodeGraphFrameLayer {