Add support for generation based on arguments.

src/mushroom.rs

@@ -1,6 +1,6 @@
 use serde_derive::Serialize;
 
-#[derive(clap::ValueEnum, Clone, Default, Debug, Serialize, PartialEq)]
+#[derive(clap::ValueEnum, Clone, Default, Debug, Serialize, PartialEq, FromFormField)]
 pub enum CapStyle {
     Cylinder,
     #[default]
@@ -8,20 +8,26 @@ pub enum CapStyle {
     Pointed,
 }
 
-#[derive(Debug, PartialEq)]
+#[derive(Debug, PartialEq, Clone, FromForm)]
 pub struct Mushroom {
     /// Stalk height in millimeters. Zero for default.
+    #[field(default = 66.0)]
     pub stalk_h: f32,
 
     /// Stalk diameter in millimeters. Zero for default.
+    #[field(default = 5.0)]
     pub stalk_r: f32,
 
     /// Cap height in millimeters. Zero for default.
+    #[field(default = 34.0)]
     pub cap_h: f32,
 
     /// Stalk diameter in millimeters. Zero for default.
+    #[field(default = 50.0)]
     pub cap_r: f32,
 
+    /// General shape of the cap.
+    #[field(default = CapStyle::Dome)]
     pub cap_style: CapStyle,
 }