Make Arc<IcedState> persistable

Cargo.lock

@@ -2435,6 +2435,7 @@ dependencies = [
  "iced_baseview",
  "nih_plug",
  "nih_plug_assets",
+ "serde",
 ]
 
 [[package]]

nih_plug_iced/Cargo.toml

@@ -62,3 +62,5 @@ crossbeam = "0.8"
 # Upstream doesn't work with the current iced version, this branch also contains
 # additional features
 iced_baseview = { git = "https://github.com/robbert-vdh/iced_baseview.git", branch = "feature/update-baseview", default_features = false }
+# To make the state persistable
+serde = { version = "1.0", features = ["derive"] }

nih_plug_iced/src/lib.rs

@@ -92,7 +92,9 @@
 use baseview::{WindowOpenOptions, WindowScalePolicy};
 use crossbeam::atomic::AtomicCell;
 use crossbeam::channel;
+use nih_plug::param::internals::PersistentField;
 use nih_plug::prelude::{Editor, GuiContext, ParentWindowHandle};
+use serde::{Deserialize, Serialize};
 use std::fmt::Debug;
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::Arc;
@@ -229,13 +231,30 @@ pub trait IcedEditor: 'static + Send + Sync + Sized {
     }
 }
 
-// TODO: Once we add resizing, we may want to be able to remember the GUI size. In that case we need
+/// State for an `nih_plug_iced` editor.
-//       to make this serializable (only restoring the size of course) so it can be persisted.
+#[derive(Serialize, Deserialize)]
 pub struct IcedState {
+    /// The window's size in logical pixels before applying `scale_factor`.
+    #[serde(with = "nih_plug::param::internals::serialize_atomic_cell")]
     size: AtomicCell<(u32, u32)>,
+    /// Whether the editor's window is currently open.
+    #[serde(skip)]
     open: AtomicBool,
 }
 
+impl<'a> PersistentField<'a, IcedState> for Arc<IcedState> {
+    fn set(&self, new_value: IcedState) {
+        self.size.store(new_value.size.load());
+    }
+
+    fn map<F, R>(&self, f: F) -> R
+    where
+        F: Fn(&IcedState) -> R,
+    {
+        f(self)
+    }
+}
+
 impl IcedState {
     /// Initialize the GUI's state. This value can be passed to [`create_iced_editor()`]. The window
     /// size is in logical pixels, so before it is multiplied by the DPI scaling factor.