WIP: refactor Id system with StrongId

egui/src/containers/area.rs

@@ -32,7 +32,7 @@ impl State {
 /// This forms the base of the `Window` container.
 #[derive(Clone, Copy, Debug)]
 pub struct Area {
-    id: Id,
+    strong_id: StrongId,
     movable: bool,
     interactable: bool,
     order: Order,
@@ -41,9 +41,9 @@ pub struct Area {
 }
 
 impl Area {
-    pub fn new(id_source: impl Hash) -> Self {
+    pub fn new(strong_id_source: impl Hash) -> Self {
         Self {
-            id: Id::new(id_source),
+            strong_id: StrongId::new(strong_id_source),
             movable: true,
             interactable: true,
             order: Order::Middle,
@@ -53,7 +53,7 @@ impl Area {
     }
 
     pub fn layer(&self) -> LayerId {
-        LayerId::new(self.order, self.id)
+        LayerId::new(self.order, self.strong_id)
     }
 
     /// moveable by dragging the area?
@@ -105,7 +105,7 @@ pub(crate) struct Prepared {
 impl Area {
     pub(crate) fn begin(self, ctx: &Arc<Context>) -> Prepared {
         let Area {
-            id,
+            strong_id,
             movable,
             order,
             interactable,
@@ -113,9 +113,9 @@ impl Area {
             fixed_pos,
         } = self;
 
-        let layer_id = LayerId::new(order, id);
+        let layer_id = LayerId::new(order, strong_id);
 
-        let state = ctx.memory().areas.get(id).cloned();
+        let state = ctx.memory().areas.get(strong_id).cloned();
         let mut state = state.unwrap_or_else(|| State {
             pos: default_pos.unwrap_or_else(|| automatic_area_position(ctx)),
             size: Vec2::zero(),

egui/src/containers/panel.rs

@@ -3,6 +3,7 @@
 //! the only places where you can put you widgets.
 
 use crate::*;
+use std::hash::Hash;
 use std::sync::Arc;
 
 // ----------------------------------------------------------------------------
@@ -11,14 +12,17 @@ use std::sync::Arc;
 ///
 /// Panels should be added before adding any `Window`s.
 pub struct SidePanel {
-    id: Id,
+    strong_id: Id,
     max_width: f32,
 }
 
 impl SidePanel {
     /// The given `max_width` is a soft maximum (as always), and the actual panel may be smaller or larger.
-    pub fn left(id: Id, max_width: f32) -> Self {
-        Self { id, max_width }
+    pub fn left(strong_id_source: impl Hash, max_width: f32) -> Self {
+        Self {
+            strong_id: StrongId::new(strong_id_source),
+            max_width,
+        }
     }
 }
 
@@ -28,7 +32,10 @@ impl SidePanel {
         ctx: &Arc<Context>,
         add_contents: impl FnOnce(&mut Ui) -> R,
     ) -> (R, Response) {
-        let Self { id, max_width } = self;
+        let Self {
+            strong_id,
+            max_width,
+        } = self;
 
         let mut panel_rect = ctx.available_rect();
         panel_rect.max.x = panel_rect.max.x.at_most(panel_rect.min.x + max_width);
@@ -36,7 +43,7 @@ impl SidePanel {
         let layer_id = LayerId::background();
 
         let clip_rect = ctx.input().screen_rect();
-        let mut panel_ui = Ui::new(ctx.clone(), layer_id, id, panel_rect, clip_rect);
+        let mut panel_ui = Ui::new(ctx.clone(), layer_id, strong_id, panel_rect, clip_rect);
 
         let frame = Frame::panel(&ctx.style());
         let r = frame.show(&mut panel_ui, |ui| {
@@ -59,16 +66,16 @@ impl SidePanel {
 ///
 /// Panels should be added before adding any `Window`s.
 pub struct TopPanel {
-    id: Id,
+    strong_id: StrongId,
     max_height: Option<f32>,
 }
 
 impl TopPanel {
     /// Default height is that of `interact_size.y` (i.e. a button),
     /// but the panel will expand as needed.
-    pub fn top(id: Id) -> Self {
+    pub fn top(strong_id_source: impl Hash) -> Self {
         Self {
-            id,
+            strong_id: StrongId::new(strong_id_source),
             max_height: None,
         }
     }
@@ -80,7 +87,10 @@ impl TopPanel {
         ctx: &Arc<Context>,
         add_contents: impl FnOnce(&mut Ui) -> R,
     ) -> (R, Response) {
-        let Self { id, max_height } = self;
+        let Self {
+            strong_id,
+            max_height,
+        } = self;
         let max_height = max_height.unwrap_or_else(|| ctx.style().spacing.interact_size.y);
 
         let mut panel_rect = ctx.available_rect();
@@ -89,7 +99,7 @@ impl TopPanel {
         let layer_id = LayerId::background();
 
         let clip_rect = ctx.input().screen_rect();
-        let mut panel_ui = Ui::new(ctx.clone(), layer_id, id, panel_rect, clip_rect);
+        let mut panel_ui = Ui::new(ctx.clone(), layer_id, strong_id, panel_rect, clip_rect);
 
         let frame = Frame::panel(&ctx.style());
         let r = frame.show(&mut panel_ui, |ui| {
@@ -127,10 +137,10 @@ impl CentralPanel {
         let panel_rect = ctx.available_rect();
 
         let layer_id = LayerId::background();
-        let id = Id::new("central_panel");
+        let strong_id = Id::new("central_panel");
 
         let clip_rect = ctx.input().screen_rect();
-        let mut panel_ui = Ui::new(ctx.clone(), layer_id, id, panel_rect, clip_rect);
+        let mut panel_ui = Ui::new(ctx.clone(), layer_id, strong_id, panel_rect, clip_rect);
 
         let frame = Frame::background(&ctx.style());
         let r = frame.show(&mut panel_ui, |ui| add_contents(ui));

egui/src/id.rs

@@ -40,14 +40,14 @@ impl Id {
         Self(1)
     }
 
-    pub fn new(source: impl Hash) -> Id {
+    pub fn new(source: impl Hash) -> Self {
         use std::hash::Hasher;
         let mut hasher = ahash::AHasher::default();
         source.hash(&mut hasher);
         Id(hasher.finish())
     }
 
-    pub fn with(self, child: impl Hash) -> Id {
+    pub fn with(self, child: impl Hash) -> Self {
         use std::hash::Hasher;
         let mut hasher = ahash::AHasher::default();
         hasher.write_u64(self.0);
@@ -59,3 +59,49 @@ impl Id {
         format!("{:04X}", self.0 as u16)
     }
 }
+
+// ----------------------------------------------------------------------------
+
+/// This is an identifier that must be unique over long time.
+/// Used for storing state, like window position, scroll amount, etc.
+#[derive(Clone, Copy, Debug, Hash, Eq, PartialEq)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+pub struct StrongId(u64);
+
+impl StrongId {
+    pub fn background() -> Self {
+        Self(0)
+    }
+
+    pub fn tooltip() -> Self {
+        Self(1)
+    }
+
+    pub fn new(source: impl Hash) -> Self {
+        use std::hash::Hasher;
+        let mut hasher = ahash::AHasher::default();
+        source.hash(&mut hasher);
+        Id(hasher.finish())
+    }
+
+    pub fn with(self, child: impl Hash) -> Self {
+        use std::hash::Hasher;
+        let mut hasher = ahash::AHasher::default();
+        hasher.write_u64(self.0);
+        child.hash(&mut hasher);
+        Id(hasher.finish())
+    }
+
+    pub(crate) fn short_debug_format(&self) -> String {
+        format!("{:04X}", self.0 as u16)
+    }
+}
+
+// ----------------------------------------------------------------------------
+
+/// Ok to weaken a `StrongId`
+impl From<StrongId> for Id {
+    fn from(strong: StrongId) -> Self {
+        Id(strong.0)
+    }
+}

egui/src/memory.rs

@@ -1,14 +1,6 @@
 use std::collections::{HashMap, HashSet};
 
-use crate::{
-    area,
-    cache::Cache,
-    collapsing_header, menu,
-    paint::color::{Hsva, Srgba},
-    resize, scroll_area,
-    widgets::text_edit,
-    window, Id, LayerId, Pos2, Rect,
-};
+use crate::{cache::Cache, color::Hsva, *};
 
 /// The data that Egui persists between frames.
 ///
@@ -24,11 +16,11 @@ pub struct Memory {
     pub(crate) interaction: Interaction,
 
     // states of various types of widgets
-    pub(crate) collapsing_headers: HashMap<Id, collapsing_header::State>,
+    pub(crate) collapsing_headers: HashMap<StrongId, collapsing_header::State>,
     #[cfg_attr(feature = "serde", serde(skip))]
-    pub(crate) menu_bar: HashMap<Id, menu::BarState>,
-    pub(crate) resize: HashMap<Id, resize::State>,
-    pub(crate) scroll_areas: HashMap<Id, scroll_area::State>,
+    pub(crate) menu_bar: HashMap<StrongId, menu::BarState>,
+    pub(crate) resize: HashMap<StrongId, resize::State>,
+    pub(crate) scroll_areas: HashMap<StrongId, scroll_area::State>,
     pub(crate) text_edit: HashMap<Id, text_edit::State>,
 
     #[cfg_attr(feature = "serde", serde(skip))]
@@ -197,7 +189,7 @@ impl Memory {
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 #[cfg_attr(feature = "serde", serde(default))]
 pub struct Areas {
-    areas: HashMap<Id, area::State>,
+    areas: HashMap<StrongId, area::State>,
     /// Top is last
     order: Vec<LayerId>,
     visible_last_frame: HashSet<LayerId>,

egui/src/ui.rs

@@ -7,12 +7,11 @@ use crate::{color::*, containers::*, layout::*, mutex::MutexGuard, paint::*, wid
 /// Represents a region of the screen
 /// with a type of layout (horizontal or vertical).
 pub struct Ui {
-    /// ID of this ui.
-    /// Generated based on id of parent ui together with
-    /// another source of child identity (e.g. window title).
-    /// Acts like a namespace for child uis.
-    /// Hopefully unique.
-    id: Id,
+    /// Used to seed more StrongId:s.
+    strong_id: StrongId,
+
+    /// For automatic Id generation.
+    auto_id: Id,
 
     painter: Painter,
 
@@ -49,11 +48,6 @@ pub struct Ui {
     /// If something has already been added, this will point ot style.spacing.item_spacing beyond the latest child.
     /// The cursor can thus be style.spacing.item_spacing pixels outside of the min_rect.
     cursor: Pos2, // TODO: move into Layout?
-
-    /// How many children has been added to us?
-    /// This is only used to create a unique interact ID for some widgets
-    /// that work as long as no other widgets are added/removed while interacting.
-    child_count: usize,
 }
 
 impl Ui {
@@ -63,7 +57,7 @@ impl Ui {
     pub fn new(
         ctx: Arc<Context>,
         layer_id: LayerId,
-        id: Id,
+        strong_id: StrongId,
         max_rect: Rect,
         clip_rect: Rect,
     ) -> Self {
@@ -73,14 +67,14 @@ impl Ui {
         let min_size = Vec2::zero(); // TODO: From Style
         let min_rect = layout.rect_from_cursor_size(cursor, min_size);
         Ui {
-            id,
+            strong_id,
+            auto_id: strong_id.with("auto"),
             painter: Painter::new(ctx, layer_id, clip_rect),
             min_rect,
             max_rect,
             style,
             layout,
             cursor,
-            child_count: 0,
         }
     }
 
@@ -366,7 +360,7 @@ impl Ui {
 /// # `Id` creation
 impl Ui {
     /// Use this to generate widget ids for widgets that have persistent state in `Memory`.
-    pub fn make_persistent_id<IdSource>(&self, id_source: IdSource) -> Id
+    pub fn make_persistent_id<IdSource>(&self, id_source: IdSource) -> StrongId
     where
         IdSource: Hash + std::fmt::Debug,
     {
@@ -379,15 +373,22 @@ impl Ui {
     /// Call AFTER allocating new space for your widget.
     // TODO: return from `allocate_space` ?
     pub fn make_position_id(&self) -> Id {
-        self.id.with(self.child_count)
+        let id = self.id.with(self.child_count);
+        // self.ctx().register_unique_id(id, self.cursor, "position"); // NO: position may change until we interact
+        id
     }
 }
 
 /// # Interaction
 impl Ui {
-    pub fn interact(&self, rect: Rect, id: Id, sense: Sense) -> Response {
-        self.ctx()
-            .interact(self.layer_id(), self.clip_rect(), rect, Some(id), sense)
+    pub fn interact(&self, rect: Rect, id: impl Into<Id>, sense: Sense) -> Response {
+        self.ctx().interact(
+            self.layer_id(),
+            self.clip_rect(),
+            rect,
+            Some(id.into()),
+            sense,
+        )
     }
 
     pub fn interact_hover(&self, rect: Rect) -> Response {