feat: add display UI with splash screen, dashboard, and RSSI sparkline

Implement full SSD1306 OLED display support:
- Splash screen on boot (1.5s) with project name, version, board
- Dashboard showing radio state, config, counters, RSSI/SNR
- RSSI history sparkline (64-sample ring buffer, 2px-wide bars)
- DisplayOn/DisplayOff host commands routed via dedicated channel
- Pure render functions against generic DrawTarget (no hardware coupling)
- Display on/off control bypasses radio task entirely

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/darling/examples/automatic_bounds.rs

@@ -0,0 +1,73 @@
+use darling::{FromDeriveInput, FromMeta};
+
+#[derive(FromMeta, PartialEq, Eq, Debug)]
+enum Volume {
+    Whisper,
+    Talk,
+    Shout,
+}
+
+/// A more complex example showing the ability to skip at a field or struct
+/// level while still tracking which type parameters need to be bounded.
+/// This can be seen by expanding this example using `cargo expand`.
+#[derive(FromMeta)]
+#[allow(dead_code)]
+enum Emphasis<T> {
+    Constant(Volume),
+    Variable(darling::util::PathList),
+    #[darling(skip)]
+    PerPhoneme(Option<T>),
+    Strided {
+        #[darling(skip)]
+        step: Vec<T>,
+        #[darling(multiple)]
+        volume: Vec<Volume>,
+    },
+}
+
+#[derive(FromDeriveInput)]
+#[darling(attributes(speak))]
+struct SpeakingOptions<T, U> {
+    max_volume: U,
+    #[darling(skip, default)]
+    additional_data: Vec<T>,
+}
+
+#[derive(Default)]
+struct Phoneme {
+    #[allow(dead_code)]
+    first: String,
+}
+
+// This is probably the holy grail for `darling`'s own internal use-case:
+// Auto-apply `Default` bound to skipped *field* types in `where` clause.
+impl<T, U> Default for SpeakingOptions<T, U>
+where
+    Vec<T>: Default,
+    U: Default,
+{
+    fn default() -> Self {
+        Self {
+            max_volume: Default::default(),
+            additional_data: Default::default(),
+        }
+    }
+}
+
+fn main() {
+    let derive_input = syn::parse_str(
+        r#"
+        #[derive(Speak)]
+        #[speak(max_volume = "shout")]
+        enum HtmlElement {
+            Div(String)
+        }
+    "#,
+    )
+    .unwrap();
+
+    let parsed: SpeakingOptions<Phoneme, Volume> =
+        FromDeriveInput::from_derive_input(&derive_input).unwrap();
+    assert_eq!(parsed.max_volume, Volume::Shout);
+    assert_eq!(parsed.additional_data.len(), 0);
+}

vendor/darling/examples/consume_fields.rs

@@ -0,0 +1,175 @@
+// The use of fields in debug print commands does not count as "used",
+// which causes the fields to trigger an unwanted dead code warning.
+#![allow(dead_code)]
+
+//! This example shows how to do struct and field parsing using darling.
+
+use darling::{ast, FromDeriveInput, FromField, FromMeta};
+use proc_macro2::TokenStream;
+use quote::{quote, ToTokens};
+use syn::parse_str;
+
+/// A speaking volume. Deriving `FromMeta` will cause this to be usable
+/// as a string value for a meta-item key.
+#[derive(Debug, Clone, Copy, FromMeta)]
+#[darling(default)]
+enum Volume {
+    Normal,
+    Whisper,
+    Shout,
+}
+
+impl Default for Volume {
+    fn default() -> Self {
+        Volume::Normal
+    }
+}
+
+/// Support parsing from a full derive input. Unlike FromMeta, this isn't
+/// composable; each darling-dependent crate should have its own struct to handle
+/// when its trait is derived.
+#[derive(Debug, FromDeriveInput)]
+// This line says that we want to process all attributes declared with `my_trait`,
+// and that darling should panic if this receiver is given an enum.
+#[darling(attributes(my_trait), supports(struct_any))]
+struct MyInputReceiver {
+    /// The struct ident.
+    ident: syn::Ident,
+
+    /// The type's generics. You'll need these any time your trait is expected
+    /// to work with types that declare generics.
+    generics: syn::Generics,
+
+    /// Receives the body of the struct or enum. We don't care about
+    /// struct fields because we previously told darling we only accept structs.
+    data: ast::Data<(), MyFieldReceiver>,
+
+    /// The Input Receiver demands a volume, so use `Volume::Normal` if the
+    /// caller doesn't provide one.
+    #[darling(default)]
+    volume: Volume,
+}
+
+impl ToTokens for MyInputReceiver {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let MyInputReceiver {
+            ref ident,
+            ref generics,
+            ref data,
+            volume,
+        } = *self;
+
+        let (imp, ty, wher) = generics.split_for_impl();
+        let fields = data
+            .as_ref()
+            .take_struct()
+            .expect("Should never be enum")
+            .fields;
+
+        // Generate the format string which shows each field and its name
+        let fmt_string = fields
+            .iter()
+            .enumerate()
+            .map(|(i, f)| {
+                // We have to preformat the ident in this case so we can fall back
+                // to the field index for unnamed fields. It's not easy to read,
+                // unfortunately.
+                format!(
+                    "{} = {{}}",
+                    f.ident
+                        .as_ref()
+                        .map(|v| format!("{}", v))
+                        .unwrap_or_else(|| format!("{}", i))
+                )
+            })
+            .collect::<Vec<_>>()
+            .join(", ");
+
+        // Generate the actual values to fill the format string.
+        let field_list = fields
+            .into_iter()
+            .enumerate()
+            .map(|(i, f)| {
+                let field_volume = f.volume.unwrap_or(volume);
+
+                // This works with named or indexed fields, so we'll fall back to the index so we can
+                // write the output as a key-value pair.
+                let field_ident = f.ident
+                    .as_ref()
+                    .map(|v| quote!(#v))
+                    .unwrap_or_else(|| {
+                        let i = syn::Index::from(i);
+                        quote!(#i)
+                    });
+
+                match field_volume {
+                    Volume::Normal => quote!(self.#field_ident),
+                    Volume::Shout => {
+                        quote!(::std::string::ToString::to_string(&self.#field_ident).to_uppercase())
+                    }
+                    Volume::Whisper => {
+                        quote!(::std::string::ToString::to_string(&self.#field_ident).to_lowercase())
+                    }
+                }
+            })
+            .collect::<Vec<_>>();
+
+        tokens.extend(quote! {
+            impl #imp Speak for #ident #ty #wher {
+                fn speak(&self, writer: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+                    write!(writer, #fmt_string, #(#field_list),*)
+                }
+            }
+        });
+    }
+}
+
+#[derive(Debug, FromField)]
+#[darling(attributes(my_trait))]
+struct MyFieldReceiver {
+    /// Get the ident of the field. For fields in tuple or newtype structs or
+    /// enum bodies, this can be `None`.
+    ident: Option<syn::Ident>,
+
+    /// This magic field name pulls the type from the input.
+    ty: syn::Type,
+
+    /// We declare this as an `Option` so that during tokenization we can write
+    /// `field.volume.unwrap_or(derive_input.volume)` to facilitate field-level
+    /// overrides of struct-level settings.
+    ///
+    /// Because this field is an `Option`, we don't need to include `#[darling(default)]`
+    volume: Option<Volume>,
+}
+
+fn main() {
+    let input = r#"#[derive(MyTrait)]
+#[my_trait(volume = "shout")]
+pub struct Foo {
+    #[my_trait(volume = "whisper")]
+    bar: bool,
+
+    baz: i64,
+}"#;
+
+    let parsed = parse_str(input).unwrap();
+    let receiver = MyInputReceiver::from_derive_input(&parsed).unwrap();
+    let tokens = quote!(#receiver);
+
+    println!(
+        r#"
+INPUT:
+
+{}
+
+PARSED AS:
+
+{:?}
+
+EMITS:
+
+{}
+    "#,
+        input, receiver, tokens
+    );
+}

vendor/darling/examples/expr_with.rs

@@ -0,0 +1,26 @@
+use darling::{util::parse_expr, FromDeriveInput, FromMeta};
+use syn::{parse_quote, Expr};
+
+#[derive(FromDeriveInput)]
+#[darling(attributes(demo))]
+pub struct Receiver {
+    #[darling(with = parse_expr::preserve_str_literal, map = Some)]
+    example1: Option<Expr>,
+    #[darling(
+        // A closure can be used in lieu of a path.
+        with = |m| Ok(String::from_meta(m)?.to_uppercase()),
+        default
+    )]
+    example2: String,
+}
+
+fn main() {
+    let input = Receiver::from_derive_input(&parse_quote! {
+        #[demo(example1 = test::path, example2 = "hello")]
+        struct Example;
+    })
+    .unwrap();
+
+    assert_eq!(input.example1, Some(parse_quote!(test::path)));
+    assert_eq!(input.example2, "HELLO".to_string());
+}

vendor/darling/examples/fallible_read.rs

@@ -0,0 +1,85 @@
+//! This example demonstrates techniques for performing custom error handling
+//! in a derive-input receiver.
+//!
+//! 1. Using `darling::Result` as a carrier to preserve the error for later display
+//! 1. Using `Result<T, syn::Meta>` to attempt a recovery in imperative code
+//! 1. Using the `map` darling meta-item to post-process a field before returning
+//! 1. Using the `and_then` darling meta-item to post-process the receiver before returning
+
+use darling::{FromDeriveInput, FromMeta};
+use syn::parse_str;
+
+#[derive(Debug, FromDeriveInput)]
+#[darling(attributes(my_trait), and_then = MyInputReceiver::autocorrect)]
+pub struct MyInputReceiver {
+    /// This field must be present and a string or else parsing will panic.
+    #[darling(map = MyInputReceiver::make_string_shouty)]
+    name: String,
+
+    /// If this field fails to parse, the struct can still be built; the field
+    /// will contain the error. The consuming struct can then decide if this
+    /// blocks code generation. If so, panic or fail in `and_then`.
+    frequency: darling::Result<i64>,
+
+    /// If this field fails to parse, the struct can still be built; the field
+    /// will contain an `Err` with the original `syn::Meta`. This can be used
+    /// for alternate parsing attempts before panicking.
+    amplitude: Result<u64, syn::Meta>,
+}
+
+impl MyInputReceiver {
+    /// This function will be called by `darling` _after_ it's finished parsing the
+    /// `name` field but before initializing `name` with the resulting value. It's
+    /// a good place for transforms that are easiest to express on already-built
+    /// types.
+    fn make_string_shouty(s: String) -> String {
+        s.to_uppercase()
+    }
+
+    /// This function will be called by `darling` _after_ it's finished parsing the
+    /// input but before returning to the caller. This is a good place to initialize
+    /// skipped fields or to perform corrections that don't lend themselves to being
+    /// done elsewhere.
+    fn autocorrect(self) -> darling::Result<Self> {
+        let Self {
+            name,
+            frequency,
+            amplitude,
+        } = self;
+
+        // Amplitude doesn't have a sign, so if we received a negative number then
+        // we'll go ahead and make it positive.
+        let amplitude = match amplitude {
+            Ok(amp) => amp,
+            Err(mi) => (i64::from_meta(&mi)?).unsigned_abs(),
+        };
+
+        Ok(Self {
+            name,
+            frequency,
+            amplitude: Ok(amplitude),
+        })
+    }
+}
+
+fn main() {
+    let input = r#"#[derive(MyTrait)]
+#[my_trait(name="Jon", amplitude = "-1", frequency = 1)]
+pub struct Foo;"#;
+
+    let parsed = parse_str(input).unwrap();
+    let receiver = MyInputReceiver::from_derive_input(&parsed).unwrap();
+
+    println!(
+        r#"
+INPUT:
+
+{}
+
+PARSED AS:
+
+{:?}
+    "#,
+        input, receiver
+    );
+}

vendor/darling/examples/from_word_and_expr.rs

@@ -0,0 +1,58 @@
+use darling::{ast::Data, util::Flag, FromDeriveInput, FromMeta};
+use darling_macro::FromField;
+
+#[derive(Default, FromMeta)]
+#[darling(from_word = || Ok(Default::default()), from_expr = |expr| Ok(ErrorPolicy::from(expr)))]
+struct ErrorPolicy {
+    warn: Flag,
+    value: Option<syn::Expr>,
+}
+
+impl From<&'_ syn::Expr> for ErrorPolicy {
+    fn from(expr: &'_ syn::Expr) -> Self {
+        ErrorPolicy {
+            warn: Flag::default(),
+            value: Some(expr.clone()),
+        }
+    }
+}
+
+#[derive(FromField)]
+#[darling(attributes(toml))]
+struct Field {
+    default: Option<ErrorPolicy>,
+    recover: Option<ErrorPolicy>,
+}
+
+#[derive(FromDeriveInput)]
+#[darling(attributes(toml))]
+struct TomlConfig {
+    data: Data<(), Field>,
+}
+
+fn main() {
+    let input = TomlConfig::from_derive_input(&syn::parse_quote! {
+        struct Config {
+            #[toml(default, recover(warn))]
+            field1: String,
+            #[toml(default = String::new())]
+            field2: String,
+        }
+    })
+    .unwrap();
+
+    assert!(input.data.is_struct());
+    let fields = input.data.take_struct().expect("input is struct").fields;
+    assert!(fields[0].default.is_some());
+    assert!(fields[0]
+        .recover
+        .as_ref()
+        .map(|r| r.warn.is_present())
+        .unwrap_or(false));
+    assert!(fields[1]
+        .default
+        .as_ref()
+        .map(|d| d.value.is_some())
+        .unwrap_or(false));
+    assert!(fields[1].recover.is_none());
+}

vendor/darling/examples/heterogeneous_enum_and_word.rs

@@ -0,0 +1,79 @@
+//! This example demonstrates:
+//!
+//! - The behavior of a derived `FromMeta` implementation for heterogeneous enums
+//!   (i.e. enums that include a mix of unit, newtype and struct variants).
+//! - Using `#[darling(word)]` to specify a unit variant to use when a receiver field
+//!   is specified without a value (i.e. a unit variant to use for deriving the
+//!   `FromMeta::from_word` method).
+//! - Using `#[darling(default)]` on a receiver field to fall back to `Default::default()`
+//!   for the enum's value when the receiver field is not specified by the caller.
+
+use darling::{Error, FromDeriveInput, FromMeta};
+use syn::parse_quote;
+
+/// A playback volume.
+#[derive(Debug, FromMeta, PartialEq, Eq)]
+enum Volume {
+    Normal,
+    #[darling(word)]
+    Low,
+    High,
+    #[darling(rename = "dB")]
+    Decibels(u8),
+}
+
+impl Default for Volume {
+    fn default() -> Self {
+        Volume::Normal
+    }
+}
+
+#[derive(Debug, FromDeriveInput)]
+#[darling(attributes(play))]
+struct PlayReceiver {
+    #[darling(default)]
+    volume: Volume,
+}
+
+fn main() {
+    // `Default::default()` is used when `volume` is not specified.
+    let missing_volume = PlayReceiver::from_derive_input(&parse_quote! {
+        #[play]
+        struct Player;
+    })
+    .unwrap();
+    assert_eq!(Volume::Normal, missing_volume.volume);
+
+    // `#[darling(word)]` unit variant is used when `volume` is specified as a word with no value.
+    let empty_volume = PlayReceiver::from_derive_input(&parse_quote! {
+        #[play(volume)]
+        struct Player;
+    })
+    .unwrap();
+    assert_eq!(Volume::Low, empty_volume.volume);
+
+    // Specified `volume` value is used when provided.
+    let unit_variant_volume = PlayReceiver::from_derive_input(&parse_quote! {
+        #[play(volume(high))]
+        struct Player;
+    })
+    .unwrap();
+    assert_eq!(Volume::High, unit_variant_volume.volume);
+    let newtype_volume = PlayReceiver::from_derive_input(&parse_quote! {
+        #[play(volume(dB = 100))]
+        struct Player;
+    })
+    .unwrap();
+    assert_eq!(Volume::Decibels(100), newtype_volume.volume);
+
+    // Multiple `volume` values result in an error.
+    let err = PlayReceiver::from_derive_input(&parse_quote! {
+        #[play(volume(low, dB = 20))]
+        struct Player;
+    })
+    .unwrap_err();
+    assert_eq!(
+        err.to_string(),
+        Error::too_many_items(1).at("volume").to_string()
+    );
+}

vendor/darling/examples/shorthand_or_long_field.rs

@@ -0,0 +1,79 @@
+//! Example showing potentially-nested meta item parsing with `darling::util::Override`.
+//!
+//! Based on https://stackoverflow.com/q/68046070/86381 by https://github.com/peterjoel
+
+// The use of fields in debug print commands does not count as "used",
+// which causes the fields to trigger an unwanted dead code warning.
+#![allow(dead_code)]
+
+use std::borrow::Cow;
+
+use darling::{util::Override, FromDeriveInput, FromMeta};
+use syn::{Ident, Path};
+
+#[derive(Debug, FromDeriveInput)]
+#[darling(attributes(myderive))]
+struct MyDeriveInput {
+    ident: Ident,
+    /// We can infer the right "table" behavior for this derive, but we want the caller to be
+    /// explicit that they're expecting the inference behavior to avoid cluttering some hypothetical
+    /// database. Therefore this field is required, but can take word form or key-value form.
+    ///
+    /// To make this field optional, we could add `#[darling(default)]`, or we could
+    /// wrap it in `Option` if the presence or absence of the word makes a difference.
+    table: Override<Table>,
+}
+
+impl MyDeriveInput {
+    fn table(&self) -> Cow<'_, Table> {
+        match &self.table {
+            Override::Explicit(value) => Cow::Borrowed(value),
+            Override::Inherit => Cow::Owned(Table {
+                name: self.ident.to_string(),
+                value: None,
+            }),
+        }
+    }
+}
+
+#[derive(Debug, Clone, FromMeta)]
+struct Table {
+    name: String,
+    value: Option<Path>,
+}
+
+fn from_str(s: &str) -> darling::Result<MyDeriveInput> {
+    FromDeriveInput::from_derive_input(&syn::parse_str(s)?)
+}
+
+fn main() {
+    let missing = from_str(
+        r#"
+        #[derive(MyTrait)]
+        struct Foo(u64);
+    "#,
+    )
+    .unwrap_err();
+
+    let short_form = from_str(
+        r#"
+        #[derive(MyTrait)]
+        #[myderive(table)]
+        struct Foo(u64);
+    "#,
+    )
+    .unwrap();
+
+    let long_form = from_str(
+        r#"
+        #[derive(MyTrait)]
+        #[myderive(table(name = "Custom"))]
+        struct Foo(u64);
+    "#,
+    )
+    .unwrap();
+
+    println!("Error when missing: {}", missing);
+    println!("Short form: {:?}", short_form.table());
+    println!("Long form: {:?}", long_form.table());
+}

vendor/darling/examples/supports_struct.rs

@@ -0,0 +1,61 @@
+// The use of fields in debug print commands does not count as "used",
+// which causes the fields to trigger an unwanted dead code warning.
+#![allow(dead_code)]
+
+use darling::{ast, util, FromDeriveInput, FromField};
+use syn::{Ident, Type};
+
+#[derive(Debug, FromField)]
+#[darling(attributes(lorem))]
+pub struct LoremField {
+    ident: Option<Ident>,
+    ty: Type,
+    #[darling(default)]
+    skip: bool,
+}
+
+#[derive(Debug, FromDeriveInput)]
+#[darling(attributes(lorem), supports(struct_named))]
+pub struct Lorem {
+    ident: Ident,
+    data: ast::Data<util::Ignored, LoremField>,
+}
+
+fn main() {
+    let good_input = r#"#[derive(Lorem)]
+pub struct Foo {
+    #[lorem(skip)]
+    bar: bool,
+
+    baz: i64,
+}"#;
+
+    let bad_input = r#"#[derive(Lorem)]
+    pub struct BadFoo(String, u32);"#;
+
+    let parsed = syn::parse_str(good_input).unwrap();
+    let receiver = Lorem::from_derive_input(&parsed).unwrap();
+    let wrong_shape_parsed = syn::parse_str(bad_input).unwrap();
+    let wrong_shape = Lorem::from_derive_input(&wrong_shape_parsed).expect_err("Shape was wrong");
+
+    println!(
+        r#"
+INPUT:
+
+{}
+
+PARSED AS:
+
+{:?}
+
+BAD INPUT:
+
+{}
+
+PRODUCED ERROR:
+
+{}
+    "#,
+        good_input, receiver, bad_input, wrong_shape
+    );
+}