Make Arc<ViziaState> persistable

This allows the plugin instance's size and scale to be remembered.

Cargo.lock

@@ -2445,6 +2445,7 @@ dependencies = [
  "crossbeam",
  "nih_plug",
  "nih_plug_assets",
+ "serde",
  "vizia",
 ]
 

nih_plug_vizia/Cargo.toml

@@ -13,6 +13,8 @@ nih_plug_assets = { git = "https://github.com/robbert-vdh/nih_plug_assets.git" }
 
 baseview = { git = "https://github.com/robbert-vdh/baseview.git", branch = "feature/resize" }
 crossbeam = "0.8"
+# To make the state persistable
+serde = { version = "1.0", features = ["derive"] }
 # This fork contains changed for better keyboard modifier handling and DPI
 # scaling, window scaling, and a lot more fixes and improvements
 vizia = { git = "https://github.com/robbert-vdh/vizia.git", branch = "patched", default_features = false, features = ["baseview", "clipboard", "x11"] }

nih_plug_vizia/src/lib.rs

@@ -5,7 +5,9 @@
 
 use baseview::{WindowHandle, WindowScalePolicy};
 use crossbeam::atomic::AtomicCell;
+use nih_plug::param::internals::PersistentField;
 use nih_plug::prelude::{Editor, GuiContext, ParentWindowHandle};
+use serde::{Deserialize, Serialize};
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::Arc;
 use vizia::prelude::*;
@@ -70,21 +72,36 @@ where
     }))
 }
 
-/// State for a `nih_plug_vizia` editor. The scale factor can be manipulated at runtime by changing
+/// State for an `nih_plug_vizia` editor. The scale factor can be manipulated at runtime by changing
 /// `cx.user_scale_factor`.
-///
-/// # TODO
-///
-/// Make this serializable so it can be persisted.
+#[derive(Serialize, Deserialize)]
 pub struct ViziaState {
     /// The window's size in logical pixels before applying `scale_factor`.
+    #[serde(with = "nih_plug::param::internals::serialize_atomic_cell")]
     size: AtomicCell<(u32, u32)>,
     /// A scale factor that should be applied to `size` separate from from any system HiDPI scaling.
     /// This can be used to allow GUIs to be scaled uniformly.
+    #[serde(with = "nih_plug::param::internals::serialize_atomic_cell")]
     scale_factor: AtomicCell<f64>,
+    /// Whether the editor's window is currently open.
+    #[serde(skip)]
     open: AtomicBool,
 }
 
+impl<'a> PersistentField<'a, ViziaState> for Arc<ViziaState> {
+    fn set(&self, new_value: ViziaState) {
+        self.size.store(new_value.size.load());
+        self.scale_factor.store(new_value.scale_factor.load());
+    }
+
+    fn map<F, R>(&self, f: F) -> R
+    where
+        F: Fn(&ViziaState) -> R,
+    {
+        f(self)
+    }
+}
+
 impl ViziaState {
     /// Initialize the GUI's state. This value can be passed to [`create_vizia_editor()`]. The
     /// window size is in logical pixels, so before it is multiplied by the DPI scaling factor.

src/param/internals.rs

@@ -10,6 +10,29 @@ pub use serde_json::from_str as deserialize_field;
 /// Re-export for use in the [`Params`] proc-macro.
 pub use serde_json::to_string as serialize_field;
 
+/// Can be used with the `#[serde(with = "nih_plug::param::internals::serialize_atomic_cell")]`
+/// attribute to serialize `AtomicCell<T>`s.
+pub mod serialize_atomic_cell {
+    use crossbeam::atomic::AtomicCell;
+    use serde::{Deserialize, Deserializer, Serialize, Serializer};
+
+    pub fn serialize<S, T>(cell: &AtomicCell<T>, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+        T: Serialize + Copy,
+    {
+        cell.load().serialize(serializer)
+    }
+
+    pub fn deserialize<'de, D, T>(deserializer: D) -> Result<AtomicCell<T>, D::Error>
+    where
+        D: Deserializer<'de>,
+        T: Deserialize<'de> + Copy,
+    {
+        T::deserialize(deserializer).map(AtomicCell::new)
+    }
+}
+
 /// Describes a struct containing parameters and other persistent fields.
 ///
 /// This trait can be derived on a struct containing [`FloatParam`][super::FloatParam] and other