Make Id a proper newtype

emigui/src/emigui.rs

@@ -45,7 +45,7 @@ impl Emigui {
             ctx: self.ctx.clone(),
             layer: Layer::Background,
             style: self.ctx.style(),
-            id: Default::default(),
+            id: Id::whole_screen(),
             dir: layout::Direction::Vertical,
             align: layout::Align::Center,
             cursor: Default::default(),

emigui/src/id.rs

@@ -0,0 +1,29 @@
+use std::{collections::hash_map::DefaultHasher, hash::Hash};
+
+#[derive(Clone, Copy, Debug, Hash, Eq, PartialEq)]
+pub struct Id(u64);
+
+impl Id {
+    pub fn whole_screen() -> Self {
+        Self(0)
+    }
+
+    pub fn popup() -> Self {
+        Self(1)
+    }
+
+    pub fn new<H: Hash>(source: &H) -> Id {
+        use std::hash::Hasher;
+        let mut hasher = DefaultHasher::new();
+        source.hash(&mut hasher);
+        Id(hasher.finish())
+    }
+
+    pub fn with<H: Hash>(self, child: &H) -> Id {
+        use std::hash::Hasher;
+        let mut hasher = DefaultHasher::new();
+        hasher.write_u64(self.0);
+        child.hash(&mut hasher);
+        Id(hasher.finish())
+    }
+}

emigui/src/layout.rs

@@ -1,4 +1,4 @@
-use std::{hash::Hash, sync::Arc};
+use std::sync::Arc;
 
 use crate::{widgets::*, *};
 
@@ -80,18 +80,6 @@ impl Default for Align {
 
 // ----------------------------------------------------------------------------
 
-// TODO: newtype
-pub type Id = u64;
-
-pub fn make_id<H: Hash>(source: &H) -> Id {
-    use std::hash::Hasher;
-    let mut hasher = std::collections::hash_map::DefaultHasher::new();
-    source.hash(&mut hasher);
-    hasher.finish()
-}
-
-// ----------------------------------------------------------------------------
-
 /// Show a pop-over window
 pub fn show_popup<F>(ctx: &Arc<Context>, window_pos: Vec2, add_contents: F)
 where
@@ -107,7 +95,7 @@ where
         ctx: ctx.clone(),
         layer,
         style,
-        id: Default::default(),
+        id: Id::popup(),
         dir: Direction::Vertical,
         align: Align::Min,
         cursor: window_pos + window_padding,

emigui/src/lib.rs

@@ -12,6 +12,7 @@ mod emigui;
 pub mod example_app;
 mod font;
 mod fonts;
+mod id;
 mod layers;
 mod layout;
 pub mod math;
@@ -29,8 +30,9 @@ pub use {
     color::Color,
     context::Context,
     fonts::{FontDefinitions, Fonts, TextStyle},
+    id::Id,
     layers::*,
-    layout::{Align, Id},
+    layout::Align,
     math::*,
     memory::Memory,
     mesher::{Mesh, Vertex},

emigui/src/region.rs

@@ -359,21 +359,11 @@ impl Region {
     }
 
     pub fn make_child_id<H: Hash>(&self, child_id: &H) -> Id {
-        use std::hash::Hasher;
-        let mut hasher = std::collections::hash_map::DefaultHasher::new();
-        hasher.write_u64(self.id);
-        child_id.hash(&mut hasher);
-        hasher.finish()
+        self.id.with(child_id)
     }
 
     pub fn combined_id(&self, child_id: Option<Id>) -> Option<Id> {
-        child_id.map(|child_id| {
-            use std::hash::Hasher;
-            let mut hasher = std::collections::hash_map::DefaultHasher::new();
-            hasher.write_u64(self.id);
-            child_id.hash(&mut hasher);
-            hasher.finish()
-        })
+        child_id.map(|child_id| self.id.with(&child_id))
     }
 
     // Helper function

emigui/src/widgets.rs

@@ -1,7 +1,7 @@
 #![allow(clippy::new_without_default_derive)]
 
 use crate::{
-    layout::{make_id, Direction, GuiResponse},
+    layout::{Direction, GuiResponse},
     *,
 };
 
@@ -351,7 +351,7 @@ impl<'a> Widget for Slider<'a> {
             let text_color = self.text_color;
             let value = (self.get_set_value)(None);
             let full_text = format!("{}: {:.*}", text, self.precision, value);
-            let id = Some(self.id.unwrap_or_else(|| make_id(text)));
+            let id = Some(self.id.unwrap_or_else(|| Id::new(text)));
             let mut naked = self;
             naked.id = id;
             naked.text = None;
@@ -379,7 +379,10 @@ impl<'a> Widget for Slider<'a> {
             let min = self.min;
             let max = self.max;
             debug_assert!(min <= max);
-            let id = region.combined_id(Some(self.id.unwrap_or(42))); // TODO: slider ID
+            let id = region.combined_id(Some(
+                self.id
+                    .expect("Sliders must have a text label or an explicit id"),
+            ));
             let interact = region.reserve_space(
                 Vec2 {
                     x: region.available_space.x,

emigui/src/window.rs

@@ -1,10 +1,6 @@
 use std::sync::Arc;
 
-use crate::{
-    layout::{make_id, Direction},
-    widgets::Label,
-    *,
-};
+use crate::{layout::Direction, widgets::Label, *};
 
 #[derive(Clone, Copy, Debug)]
 pub struct WindowState {
@@ -28,7 +24,7 @@ impl Window {
     where
         F: FnOnce(&mut Region),
     {
-        let id = make_id(&self.title);
+        let id = Id::new(&self.title);
 
         let mut state = ctx.memory.lock().get_or_create_window(
             id,
@@ -48,7 +44,7 @@ impl Window {
             ctx: ctx.clone(),
             layer,
             style,
-            id: Default::default(),
+            id,
             dir: Direction::Vertical,
             align: Align::Min,
             cursor: state.rect.min() + window_padding,