Do bookkeeping of Ids, showing the Debug of it's source

crates/egui/src/containers/collapsing_header.rs

@@ -1,3 +1,4 @@
+use std::fmt::Debug;
 use std::hash::Hash;
 
 use crate::{
@@ -446,7 +447,7 @@ impl CollapsingHeader {
     /// Explicitly set the source of the [`Id`] of this widget, instead of using title label.
     /// This is useful if the title label is dynamic or not unique.
     #[inline]
-    pub fn id_salt(mut self, id_salt: impl Hash) -> Self {
+    pub fn id_salt(mut self, id_salt: impl Hash + Debug) -> Self {
         self.id_salt = Id::new(id_salt);
         self
     }
@@ -455,7 +456,7 @@ impl CollapsingHeader {
     /// This is useful if the title label is dynamic or not unique.
     #[deprecated = "Renamed id_salt"]
     #[inline]
-    pub fn id_source(mut self, id_salt: impl Hash) -> Self {
+    pub fn id_source(mut self, id_salt: impl Hash + Debug) -> Self {
         self.id_salt = Id::new(id_salt);
         self
     }

crates/egui/src/containers/combo_box.rs

@@ -1,4 +1,5 @@
 use epaint::Shape;
+use std::fmt::Debug;
 
 use crate::{
     epaint, style::StyleModifier, style::WidgetVisuals, vec2, Align2, Context, Id, InnerResponse,
@@ -43,7 +44,7 @@ pub struct ComboBox {
 
 impl ComboBox {
     /// Create new [`ComboBox`] with id and label
-    pub fn new(id_salt: impl std::hash::Hash, label: impl Into<WidgetText>) -> Self {
+    pub fn new(id_salt: impl std::hash::Hash + Debug, label: impl Into<WidgetText>) -> Self {
         Self {
             id_salt: Id::new(id_salt),
             label: Some(label.into()),
@@ -72,7 +73,7 @@ impl ComboBox {
     }
 
     /// Without label.
-    pub fn from_id_salt(id_salt: impl std::hash::Hash) -> Self {
+    pub fn from_id_salt(id_salt: impl std::hash::Hash + Debug) -> Self {
         Self {
             id_salt: Id::new(id_salt),
             label: Default::default(),
@@ -87,7 +88,7 @@ impl ComboBox {
 
     /// Without label.
     #[deprecated = "Renamed id_salt"]
-    pub fn from_id_source(id_salt: impl std::hash::Hash) -> Self {
+    pub fn from_id_source(id_salt: impl std::hash::Hash + Debug) -> Self {
         Self::from_id_salt(id_salt)
     }
 

crates/egui/src/containers/resize.rs

@@ -2,6 +2,7 @@ use crate::{
     pos2, vec2, Align2, Color32, Context, CursorIcon, Id, NumExt, Rect, Response, Sense, Shape, Ui,
     UiBuilder, UiKind, UiStackInfo, Vec2, Vec2b,
 };
+use std::fmt::Debug;
 
 #[derive(Clone, Copy, Debug)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
@@ -72,13 +73,13 @@ impl Resize {
     /// A source for the unique [`Id`], e.g. `.id_source("second_resize_area")` or `.id_source(loop_index)`.
     #[inline]
     #[deprecated = "Renamed id_salt"]
-    pub fn id_source(self, id_salt: impl std::hash::Hash) -> Self {
+    pub fn id_source(self, id_salt: impl std::hash::Hash + Debug) -> Self {
         self.id_salt(id_salt)
     }
 
     /// A source for the unique [`Id`], e.g. `.id_salt("second_resize_area")` or `.id_salt(loop_index)`.
     #[inline]
-    pub fn id_salt(mut self, id_salt: impl std::hash::Hash) -> Self {
+    pub fn id_salt(mut self, id_salt: impl std::hash::Hash + Debug) -> Self {
         self.id_salt = Some(Id::new(id_salt));
         self
     }

crates/egui/src/containers/scroll_area.rs

@@ -306,13 +306,13 @@ impl ScrollArea {
     /// A source for the unique [`Id`], e.g. `.id_source("second_scroll_area")` or `.id_source(loop_index)`.
     #[inline]
     #[deprecated = "Renamed id_salt"]
-    pub fn id_source(self, id_salt: impl std::hash::Hash) -> Self {
+    pub fn id_source(self, id_salt: impl crate::IdTrait) -> Self {
         self.id_salt(id_salt)
     }
 
     /// A source for the unique [`Id`], e.g. `.id_salt("second_scroll_area")` or `.id_salt(loop_index)`.
     #[inline]
-    pub fn id_salt(mut self, id_salt: impl std::hash::Hash) -> Self {
+    pub fn id_salt(mut self, id_salt: impl crate::IdTrait) -> Self {
         self.id_salt = Some(Id::new(id_salt));
         self
     }

crates/egui/src/grid.rs

@@ -1,4 +1,5 @@
 use emath::GuiRounding as _;
+use std::fmt::Debug;
 
 use crate::{
     vec2, Align2, Color32, Context, Id, InnerResponse, NumExt, Painter, Rect, Region, Style, Ui,
@@ -322,7 +323,7 @@ pub struct Grid {
 
 impl Grid {
     /// Create a new [`Grid`] with a locally unique identifier.
-    pub fn new(id_salt: impl std::hash::Hash) -> Self {
+    pub fn new(id_salt: impl std::hash::Hash + Debug) -> Self {
         Self {
             id_salt: Id::new(id_salt),
             num_columns: None,

crates/egui/src/id.rs

@@ -1,6 +1,11 @@
 // TODO(emilk): have separate types `PositionId` and `UniqueId`. ?
 
+use ahash::HashMap;
+use epaint::mutex::{Mutex, RwLock};
+use std::any::TypeId;
+use std::hash::Hasher;
 use std::num::NonZeroU64;
+use std::sync::LazyLock;
 
 /// egui tracks widgets frame-to-frame using [`Id`]s.
 ///
@@ -33,8 +38,22 @@ use std::num::NonZeroU64;
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 pub struct Id(NonZeroU64);
 
+enum IdSource {
+    Id(Id),
+    Other(String),
+}
+
+static ID_MAP: LazyLock<RwLock<HashMap<Id, (IdSource, Option<Id>)>>> = LazyLock::new(|| {
+    let mut map = HashMap::default();
+    map.insert(Id::NULL, (IdSource::Other("Id::NULL".to_owned()), None));
+    RwLock::new(map)
+});
+
 impl nohash_hasher::IsEnabled for Id {}
 
+pub trait IdTrait: std::hash::Hash + std::fmt::Debug {}
+impl<T: std::hash::Hash + std::fmt::Debug> IdTrait for T {}
+
 impl Id {
     /// A special [`Id`], in particular as a key to [`crate::Memory::data`]
     /// for when there is no particular widget to attach the data.
@@ -52,18 +71,84 @@ impl Id {
         }
     }
 
+    /// Checks if [`T`] is a [`Id`].
+    ///
+    /// If it is, it returns `IdSource::Id`, otherwise it returns `IdSource::Other`.
+    fn get_source<T: IdTrait>(t: T) -> IdSource {
+        /// Ugly hack to try to determine if T is an Id or not.
+        struct FakeHasher {
+            val: Option<u64>,
+            first: bool,
+        }
+
+        impl Hasher for FakeHasher {
+            fn finish(&self) -> u64 {
+                unreachable!()
+            }
+
+            fn write(&mut self, bytes: &[u8]) {
+                self.first = false;
+            }
+
+            fn write_u64(&mut self, i: u64) {
+                if self.first {
+                    self.val = Some(i);
+                    self.first = false;
+                } else {
+                    self.val = None;
+                }
+            }
+        }
+
+        let mut hasher = FakeHasher {
+            val: None,
+            first: true,
+        };
+
+        t.hash(&mut hasher);
+
+        let maybe_source_id = hasher.val.map(Id::from_hash);
+
+        // Ideally we would just implement IdTriat for Id with specialization, but that's not
+        // a thing yet :( So we check if the hash is already in the map, if so, the source must be
+        // an Id.
+        if let Some(maybe_source_id) = maybe_source_id {
+            if ID_MAP.read().contains_key(&maybe_source_id) {
+                IdSource::Id(maybe_source_id)
+            } else {
+                IdSource::Other(format!("{:?}", t))
+            }
+        } else {
+            IdSource::Other(format!("{:?}", t))
+        }
+    }
+
     /// Generate a new [`Id`] by hashing some source (e.g. a string or integer).
-    pub fn new(source: impl std::hash::Hash) -> Self {
-        Self::from_hash(ahash::RandomState::with_seeds(1, 2, 3, 4).hash_one(source))
+    pub fn new<T: IdTrait>(source: T) -> Self {
+        let id = Self::from_hash(ahash::RandomState::with_seeds(1, 2, 3, 4).hash_one(&source));
+
+        if !ID_MAP.read().contains_key(&id) {
+            let source = Self::get_source(source);
+            ID_MAP.write().insert(id, (source, None));
+        }
+
+        id
     }
 
     /// Generate a new [`Id`] by hashing the parent [`Id`] and the given argument.
-    pub fn with(self, child: impl std::hash::Hash) -> Self {
+    pub fn with(self, child: impl std::hash::Hash + std::fmt::Debug) -> Self {
         use std::hash::{BuildHasher, Hasher};
         let mut hasher = ahash::RandomState::with_seeds(1, 2, 3, 4).build_hasher();
         hasher.write_u64(self.0.get());
-        child.hash(&mut hasher);
-        Self::from_hash(hasher.finish())
+        (&child).hash(&mut hasher);
+        let id = Self::from_hash(hasher.finish());
+
+        if !ID_MAP.read().contains_key(&id) {
+            let source = Self::get_source(child);
+            ID_MAP.write().insert(id, (source, Some(self)));
+        }
+
+        id
     }
 
     /// Short and readable summary
@@ -87,7 +172,24 @@ impl Id {
 
 impl std::fmt::Debug for Id {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "{:04X}", self.value() as u16)
+        write!(f, "{:04X}", self.value() as u16)?;
+        let lock = ID_MAP.read();
+        if let Some((source, parent)) = lock.get(self) {
+            match source {
+                IdSource::Id(source_id) => {
+                    write!(f, "({:?})", source_id)?;
+                }
+                IdSource::Other(label) => {
+                    write!(f, " ({})", label)?;
+                }
+            }
+            if let Some(parent) = parent {
+                // Let's hope there are no cycles!
+                write!(f, " <- {:?}", parent)?;
+            }
+        }
+
+        Ok(())
     }
 }
 

crates/egui/src/interaction.rs

@@ -70,7 +70,7 @@ impl InteractionSnapshot {
 
         fn id_ui<'a>(ui: &mut crate::Ui, widgets: impl IntoIterator<Item = &'a Id>) {
             for id in widgets {
-                ui.label(id.short_debug_format());
+                ui.label(format!("{:?}", id));
             }
         }
 

crates/egui/src/lib.rs

@@ -492,7 +492,7 @@ pub use self::{
     drag_and_drop::DragAndDrop,
     epaint::text::TextWrapMode,
     grid::Grid,
-    id::{Id, IdMap},
+    id::{Id, IdMap, IdTrait},
     input_state::{InputState, MultiTouchInfo, PointerState},
     layers::{LayerId, Order},
     layout::*,

crates/egui/src/ui.rs

@@ -1,10 +1,6 @@
 #![warn(missing_docs)] // Let's keep `Ui` well-documented.
 #![allow(clippy::use_self)]
 
-use emath::GuiRounding as _;
-use epaint::mutex::RwLock;
-use std::{any::Any, hash::Hash, sync::Arc};
-
 use crate::close_tag::ClosableTag;
 use crate::containers::menu;
 #[cfg(debug_assertions)]
@@ -30,6 +26,10 @@ use crate::{
     Style, TextStyle, TextWrapMode, UiBuilder, UiKind, UiStack, UiStackInfo, Vec2, WidgetRect,
     WidgetText,
 };
+use emath::GuiRounding as _;
+use epaint::mutex::RwLock;
+use std::fmt::Debug;
+use std::{any::Any, hash::Hash, sync::Arc};
 // ----------------------------------------------------------------------------
 
 /// This is what you use to place widgets.
@@ -226,7 +226,7 @@ impl Ui {
         &mut self,
         max_rect: Rect,
         layout: Layout,
-        id_salt: impl Hash,
+        id_salt: impl Hash + Debug,
         ui_stack_info: Option<UiStackInfo>,
     ) -> Self {
         self.new_child(
@@ -1036,7 +1036,7 @@ impl Ui {
     /// Use this to generate widget ids for widgets that have persistent state in [`Memory`].
     pub fn make_persistent_id<IdSource>(&self, id_salt: IdSource) -> Id
     where
-        IdSource: Hash,
+        IdSource: Hash + Debug,
     {
         self.id.with(&id_salt)
     }
@@ -1049,7 +1049,7 @@ impl Ui {
     /// Same as `ui.next_auto_id().with(id_salt)`
     pub fn auto_id_with<IdSource>(&self, id_salt: IdSource) -> Id
     where
-        IdSource: Hash,
+        IdSource: Hash + Debug,
     {
         Id::new(self.next_auto_id_salt).with(id_salt)
     }
@@ -2373,7 +2373,7 @@ impl Ui {
     /// ```
     pub fn push_id<R>(
         &mut self,
-        id_salt: impl Hash,
+        id_salt: impl Hash + Debug,
         add_contents: impl FnOnce(&mut Ui) -> R,
     ) -> InnerResponse<R> {
         self.scope_dyn(UiBuilder::new().id_salt(id_salt), Box::new(add_contents))
@@ -2473,7 +2473,7 @@ impl Ui {
     #[inline]
     pub fn indent<R>(
         &mut self,
-        id_salt: impl Hash,
+        id_salt: impl Hash + Debug,
         add_contents: impl FnOnce(&mut Ui) -> R,
     ) -> InnerResponse<R> {
         self.indent_dyn(id_salt, Box::new(add_contents))
@@ -2481,7 +2481,7 @@ impl Ui {
 
     fn indent_dyn<'c, R>(
         &mut self,
-        id_salt: impl Hash,
+        id_salt: impl Hash + Debug,
         add_contents: Box<dyn FnOnce(&mut Ui) -> R + 'c>,
     ) -> InnerResponse<R> {
         assert!(

crates/egui/src/ui_builder.rs

@@ -1,9 +1,9 @@
-use std::{hash::Hash, sync::Arc};
-
 use crate::close_tag::ClosableTag;
 #[allow(unused_imports)] // Used for doclinks
 use crate::Ui;
 use crate::{Id, LayerId, Layout, Rect, Sense, Style, UiStackInfo};
+use std::fmt::Debug;
+use std::{hash::Hash, sync::Arc};
 
 /// Build a [`Ui`] as the child of another [`Ui`].
 ///
@@ -37,7 +37,7 @@ impl UiBuilder {
     /// You should give each [`Ui`] an `id_salt` that is unique
     /// within the parent, or give it none at all.
     #[inline]
-    pub fn id_salt(mut self, id_salt: impl Hash) -> Self {
+    pub fn id_salt(mut self, id_salt: impl Hash + Debug) -> Self {
         self.id_salt = Some(Id::new(id_salt));
         self
     }

crates/egui/src/viewport.rs

@@ -131,7 +131,7 @@ impl ViewportId {
     pub const ROOT: Self = Self(Id::NULL);
 
     #[inline]
-    pub fn from_hash_of(source: impl std::hash::Hash) -> Self {
+    pub fn from_hash_of(source: impl crate::IdTrait) -> Self {
         Self(Id::new(source))
     }
 }

crates/egui/src/widgets/text_edit/builder.rs

@@ -166,13 +166,13 @@ impl<'t> TextEdit<'t> {
 
     /// A source for the unique [`Id`], e.g. `.id_source("second_text_edit_field")` or `.id_source(loop_index)`.
     #[inline]
-    pub fn id_source(self, id_salt: impl std::hash::Hash) -> Self {
+    pub fn id_source(self, id_salt: impl crate::IdTrait) -> Self {
         self.id_salt(id_salt)
     }
 
     /// A source for the unique [`Id`], e.g. `.id_salt("second_text_edit_field")` or `.id_salt(loop_index)`.
     #[inline]
-    pub fn id_salt(mut self, id_salt: impl std::hash::Hash) -> Self {
+    pub fn id_salt(mut self, id_salt: impl crate::IdTrait) -> Self {
         self.id_salt = Some(Id::new(id_salt));
         self
     }

crates/egui_extras/src/table.rs

@@ -275,7 +275,7 @@ impl<'a> TableBuilder<'a> {
     /// This is required if you have multiple tables in the same [`Ui`].
     #[inline]
     #[deprecated = "Renamed id_salt"]
-    pub fn id_source(self, id_salt: impl std::hash::Hash) -> Self {
+    pub fn id_source(self, id_salt: impl egui::IdTrait) -> Self {
         self.id_salt(id_salt)
     }
 
@@ -283,7 +283,7 @@ impl<'a> TableBuilder<'a> {
     ///
     /// This is required if you have multiple tables in the same [`Ui`].
     #[inline]
-    pub fn id_salt(mut self, id_salt: impl std::hash::Hash) -> Self {
+    pub fn id_salt(mut self, id_salt: impl egui::IdTrait) -> Self {
         self.id_salt = Id::new(id_salt);
         self
     }