Add a dedicated message and handler for parameters

Parameter widgets can send these messages to update parameters.

nih_plug_iced/src/lib.rs

@@ -9,9 +9,13 @@ use std::fmt::Debug;
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::Arc;
 
+use crate::widgets::ParamMessage;
+
 /// Re-export for convenience.
 pub use iced_baseview::*;
 
+pub mod widgets;
+
 /// Create an [`Editor`] instance using [iced](https://github.com/iced-rs/iced). The rough idea is
 /// that you implement [`IcedEditor`], which is roughly analogous to iced's regular [`Application`]
 /// trait except that it receives the [`GuiContext`] alongside its initialization flags so it can
@@ -42,7 +46,7 @@ pub fn create_iced_editor<E: IcedEditor>(
 pub trait IcedEditor: 'static + Send + Sync + Sized {
     /// See [`Application::Executor`]. You'll likely want to use [`crate::executor::Default`].
     type Executor: Executor;
-    /// See [`Application::Message`].
+    /// See [`Application::Message`]. You should have one variant containing a [`ParamMessage`].
     type Message: 'static + Clone + Debug + Send;
     /// See [`Application::Flags`].
     type InitializationFlags: 'static + Clone + Send + Sync;
@@ -53,7 +57,14 @@ pub trait IcedEditor: 'static + Send + Sync + Sized {
         context: Arc<dyn GuiContext>,
     ) -> (Self, Command<Self::Message>);
 
-    /// See [`Application::update`].
+    /// Return a reference to the GUI context.
+    /// [`handle_param_message()`][Self::handle_param_message()] uses this to interact with the
+    /// parameters.
+    fn context(&self) -> &dyn GuiContext;
+
+    /// See [`Application::update`]. When receiving the variant that contains a
+    /// [`widgets::ParamMessage`] you can call
+    /// [`handle_param_message()`][Self::handle_param_message()] to handle the parameter update.
     fn update(
         &mut self,
         window: &mut WindowQueue,
@@ -87,6 +98,23 @@ pub trait IcedEditor: 'static + Send + Sync + Sized {
     fn renderer_settings() -> iced_baseview::renderer::settings::Settings {
         iced_baseview::renderer::settings::Settings::default()
     }
+
+    /// Handle a parameter update using the GUI context.
+    fn handle_param_message(&self, message: ParamMessage) {
+        // We can't use the fancy ParamSetter here because this needs to be type erased
+        let context = self.context();
+        match message {
+            ParamMessage::BeginSetParameter(p) => unsafe { context.raw_begin_set_parameter(p) },
+            ParamMessage::SetParameterNormalized(p, v) => unsafe {
+                context.raw_set_parameter_normalized(p, v)
+            },
+            ParamMessage::ResetParameter(p) => unsafe {
+                let default_value = context.raw_default_normalized_param_value(p);
+                context.raw_set_parameter_normalized(p, default_value);
+            },
+            ParamMessage::EndSetParameter(p) => unsafe { context.raw_end_set_parameter(p) },
+        }
+    }
 }
 
 // TODO: Once we add resizing, we may want to be able to remember the GUI size. In that case we need

nih_plug_iced/src/widgets.rs

@@ -0,0 +1,22 @@
+//! Widgets and utilities for making widgets to integrate iced with NIH-plug.
+
+use nih_plug::param::internals::ParamPtr;
+
+/// A message to update a parameter value. Since NIH-plug manages the parameters, interacting with
+/// parameter values with iced works a little different from updating any other state. This main
+/// [`IcedEditor`][super::IcedEditor] should have a [`Message`][super::IcedEditor::Message] variant
+/// containing this `ParamMessage`. When it receives one of those messages, it can pass it through
+/// to [`self.handle_param_message()`][super::IcedEditor::handle_param_message].
+#[derive(Debug, Clone, Copy)]
+pub enum ParamMessage {
+    /// Begin an automation gesture for a parameter.
+    BeginSetParameter(ParamPtr),
+    /// Set a parameter to a new normalized value. This needs to be surrounded by a matching
+    /// `BeginSetParameter` and `EndSetParameter`.
+    SetParameterNormalized(ParamPtr, f32),
+    /// Reset a parameter to its default value. This needs to be surrounded by a matching
+    /// `BeginSetParameter` and `EndSetParameter`.
+    ResetParameter(ParamPtr),
+    /// End an automation gesture for a parameter.
+    EndSetParameter(ParamPtr),
+}

plugins/diopser/src/editor.rs

@@ -15,6 +15,7 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 use nih_plug::prelude::{Editor, GuiContext};
+use nih_plug_iced::widgets::ParamMessage;
 use nih_plug_iced::{create_iced_editor, Command, Element, IcedEditor, IcedState};
 use std::pin::Pin;
 use std::sync::Arc;
@@ -38,10 +39,14 @@ struct DiopserEditor {
     context: Arc<dyn GuiContext>,
 }
 
+#[derive(Debug, Clone, Copy)]
+enum EditorMessage {
+    ParamUpdate(ParamMessage),
+}
+
 impl IcedEditor for DiopserEditor {
     type Executor = nih_plug_iced::executor::Default;
-    // TODO:
+    type Message = EditorMessage;
-    type Message = ();
     type InitializationFlags = Pin<Arc<DiopserParams>>;
 
     fn new(
@@ -53,12 +58,19 @@ impl IcedEditor for DiopserEditor {
         (editor, Command::none())
     }
 
+    fn context(&self) -> &dyn GuiContext {
+        self.context.as_ref()
+    }
+
     fn update(
         &mut self,
-        window: &mut nih_plug_iced::WindowQueue,
+        _window: &mut nih_plug_iced::WindowQueue,
         message: Self::Message,
     ) -> Command<Self::Message> {
-        // TODO:
+        match message {
+            EditorMessage::ParamUpdate(message) => self.handle_param_message(message),
+        }
+
         Command::none()
     }