Improve #[var] docs

Author: Bromeon

godot-macros/src/class/data_models/field_export.rs

@@ -548,6 +548,7 @@ impl ExportType {
         }
     }
 
+    /// Returns a `PropertyUsageFlags` identifier if this export type has a _usage_.
     pub fn to_export_usage(&self) -> Option<Ident> {
         match self {
             Self::Storage => Some(ident("STORAGE")),

godot-macros/src/lib.rs

@@ -139,9 +139,9 @@ use crate::util::{bail, ident, KvParser};
 /// (fields annotated with `@export`). In the gdext API, these two concepts are represented with `#[var]` and `#[export]` attributes respectively,
 /// which in turn are backed by the [`Var`](../register/property/trait.Var.html) and [`Export`](../register/property/trait.Export.html) traits.
 ///
-/// ## Property registration
+/// ## Register properties with `#[var]`
 ///
-/// To create a property, you can use the `#[var]` annotation:
+/// To create a property, you can use the `#[var]` annotation, which supports types implementing [`Var`](../register/property/trait.Var.html).
 ///
 /// ```
 /// # use godot::prelude::*;
@@ -207,9 +207,18 @@ use crate::util::{bail, ident, KvParser};
 /// }
 /// ```
 ///
-/// ## Property exports
+/// You can additionally provide low-level configuration of a property with the keys `hint`, `hint_string` and `usage_flags`.
+/// This is typically not necessary, but exists for full flexibility. These keys can be combined, but the combination must be
+/// meaningful in Godot, and godot-rust should generally cover known useful combinations in higher-level APIs.
 ///
-/// For exporting properties to the editor, you can use the `#[export]` attribute:
+/// - `#[var(hint = ENUM)]` denoting a constant from [`PropertyHint`](../global/struct.PropertyHint.html),
+/// - `#[var(hint_string = "one,two")]` providing a hint string for the property, which is interpreted by Godot depending on hint and context.
+/// - `#[var(usage_flags = [EDITOR, READ_ONLY])]` providing a list of [`PropertyUsageFlags`](../global/struct.PropertyUsageFlags.html).
+///
+/// ## Export properties with `#[export]`
+///
+/// To export properties to the editor, you can use the `#[export]` attribute, which supports types implementing
+/// [`Export`](../register/property/trait.Export.html):
 ///
 /// ```
 /// # use godot::prelude::*;