refactor: type-state builder pattern for windowing system

src/windowing/builder.rs

@@ -1,67 +1,61 @@
+use super::{
+    config::{Margins, WindowConfig},
+    WindowingSystem,
+};
+use crate::errors::Result;
 use slint_interpreter::ComponentDefinition;
 use smithay_client_toolkit::reexports::protocols_wlr::layer_shell::v1::client::{
     zwlr_layer_shell_v1::{self},
     zwlr_layer_surface_v1::{Anchor, KeyboardInteractivity},
 };
+use std::marker::PhantomData;
 
-use crate::errors::{LayerShikaError, Result};
+pub struct NeedsComponent;
+pub struct HasComponent;
 
-use super::{
-    config::{Margins, WindowConfig},
-    WindowingSystem,
-};
-
-pub struct WindowingSystemBuilder {
-    config: Option<WindowConfig>,
+pub struct WindowingSystemBuilder<State = NeedsComponent> {
+    config: WindowConfig,
+    _state: PhantomData<State>,
 }
 
-impl Default for WindowingSystemBuilder {
-    fn default() -> Self {
-        Self::new()
-    }
-}
-
-impl WindowingSystemBuilder {
+impl WindowingSystemBuilder<NeedsComponent> {
     #[inline]
     #[must_use]
-    pub const fn new() -> Self {
-        Self { config: None }
+    pub fn new(component_definition: ComponentDefinition) -> WindowingSystemBuilder<HasComponent> {
+        WindowingSystemBuilder {
+            config: WindowConfig::new(component_definition),
+            _state: PhantomData,
+        }
     }
+}
 
+impl WindowingSystemBuilder<HasComponent> {
     #[must_use]
     pub const fn with_height(mut self, height: u32) -> Self {
-        if let Some(ref mut config) = self.config {
-            config.height = height;
-        }
+        self.config.height = height;
         self
     }
 
     #[must_use]
     pub const fn with_layer(mut self, layer: zwlr_layer_shell_v1::Layer) -> Self {
-        if let Some(ref mut config) = self.config {
-            config.layer = layer;
-        }
+        self.config.layer = layer;
         self
     }
 
     #[must_use]
     pub const fn with_margin(mut self, top: i32, right: i32, bottom: i32, left: i32) -> Self {
-        if let Some(ref mut config) = self.config {
-            config.margin = Margins {
-                top,
-                right,
-                bottom,
-                left,
-            };
-        }
+        self.config.margin = Margins {
+            top,
+            right,
+            bottom,
+            left,
+        };
         self
     }
 
     #[must_use]
     pub const fn with_anchor(mut self, anchor: Anchor) -> Self {
-        if let Some(ref mut config) = self.config {
-            config.anchor = anchor;
-        }
+        self.config.anchor = anchor;
         self
     }
 
@@ -70,47 +64,30 @@ impl WindowingSystemBuilder {
         mut self,
         interactivity: KeyboardInteractivity,
     ) -> Self {
-        if let Some(ref mut config) = self.config {
-            config.keyboard_interactivity = interactivity;
-        }
+        self.config.keyboard_interactivity = interactivity;
         self
     }
 
     #[must_use]
     pub const fn with_exclusive_zone(mut self, zone: i32) -> Self {
-        if let Some(ref mut config) = self.config {
-            config.exclusive_zone = zone;
-        }
+        self.config.exclusive_zone = zone;
         self
     }
 
     #[must_use]
     pub fn with_namespace(mut self, namespace: String) -> Self {
-        if let Some(ref mut config) = self.config {
-            config.namespace = namespace;
-        }
+        self.config.namespace = namespace;
         self
     }
 
     #[must_use]
     pub const fn with_scale_factor(mut self, scale_factor: f32) -> Self {
-        if let Some(ref mut config) = self.config {
-            config.scale_factor = scale_factor;
-        }
-        self
-    }
-
-    #[must_use]
-    pub fn with_component_definition(mut self, component: ComponentDefinition) -> Self {
-        self.config = Some(WindowConfig::new(component));
+        self.config.scale_factor = scale_factor;
         self
     }
 
     #[allow(clippy::missing_errors_doc)]
     pub fn build(self) -> Result<WindowingSystem> {
-        let config = self
-            .config
-            .ok_or_else(|| LayerShikaError::InvalidInput("Slint component not set".into()))?;
-        WindowingSystem::new(config)
+        WindowingSystem::new(self.config)
     }
 }