chore: reduce component overhead (#3)

Reviewed-on: reya/gpui-native-kit#3

crates/data/src/tabs.rs

@@ -32,6 +32,8 @@ pub enum TabsVariant {
 
 /// One tab of a [`Tabs`] strip.
 pub struct Tab {
+    /// The stable identity for element state; must survive reordering.
+    key: ElementId,
     label: SharedString,
     icon: Option<IconRole>,
     lead: Option<AnyElement>,
@@ -42,12 +44,14 @@ pub struct Tab {
 }
 
 impl Tab {
-    /// Creates a tab with this label.
-    pub fn new<L>(label: L) -> Self
+    /// Creates a tab shown as `label`, identified by `key`.
+    pub fn new<K, L>(key: K, label: L) -> Self
     where
+        K: Into<ElementId>,
         L: Into<SharedString>,
     {
         Self {
+            key: key.into(),
             label: label.into(),
             icon: None,
             lead: None,
@@ -210,7 +214,6 @@ impl RenderOnce for Tabs {
                     cx,
                     tab,
                     index,
-                    self.selected == index,
                     self.selected,
                     self.variant,
                     &self.on_change,
@@ -268,7 +271,6 @@ fn render_tab(
     cx: &App,
     tab: Tab,
     index: usize,
-    selected: bool,
     selected_index: usize,
     variant: TabsVariant,
     on_change: &Option<ChangeHandler>,
@@ -276,6 +278,7 @@ fn render_tab(
     focus: &gpui::FocusHandle,
 ) -> AnyElement {
     let mut tab = tab;
+    let selected = index == selected_index;
 
     let theme = cx.theme();
     let metrics = theme.sizes.resolve(Size::default());
@@ -301,10 +304,11 @@ fn render_tab(
     };
 
     let mut strip_tab = div()
-        .id(("tab", index))
+        .id((tab.key.clone(), "tab"))
         .debug_selector({
-            let id = format!("{tabs_id}-tab-{}", tab.label);
-            move || id
+            let tabs_id = tabs_id.clone();
+            let label = tab.label.clone();
+            move || format!("{tabs_id}-tab-{}", label)
         })
         .flex()
         .items_center()
@@ -364,7 +368,7 @@ fn render_tab(
 
     if tab.busy && !tab.disabled {
         strip_tab = strip_tab.child(
-            Spinner::new(("tab-busy", index))
+            Spinner::new((tab.key.clone(), "tab-busy"))
                 .small()
                 .accessibility_label("Loading"),
         );
@@ -401,14 +405,15 @@ fn render_tab_close(
     index: usize,
     on_close: &Option<CloseHandler>,
 ) -> AnyElement {
-    Button::new(("tab-close", index))
+    Button::new((tab.key.clone(), "tab-close"))
         .icon(IconRole::Close)
         .variant(ButtonVariant::Ghost)
         .small()
         .tab_stop(false)
         .debug_selector({
-            let id = format!("{tabs_id}-close-{}", tab.label);
-            move || id.clone()
+            let tabs_id = tabs_id.clone();
+            let label = tab.label.clone();
+            move || format!("{tabs_id}-close-{}", label)
         })
         .tooltip(Tooltip::text("Close"))
         .accessibility_label(SharedString::from(format!("Close {}", tab.label)))