T13b Trees: Tree, TreeNode, TreeSelect, Outline, Disclosure (review pending: codex 401)

src/primitives/disclosure.rs

@@ -0,0 +1,65 @@
+use std::f32::consts::FRAC_PI_2;
+
+use gpui::{
+    Animation, AnimationExt, App, ElementId, Hsla, IntoElement, RenderOnce, Window, radians,
+};
+
+use super::{Icon, IconName};
+use crate::{
+    motion,
+    theme::{ActiveTheme, IconSize},
+};
+
+/// A chevron that points right when shut and down when open, turning on each change and still on first paint.
+#[derive(IntoElement)]
+pub struct Disclosure {
+    id: ElementId,
+    open: bool,
+    size: IconSize,
+    color: Option<Hsla>,
+}
+
+impl Disclosure {
+    pub fn new(id: impl Into<ElementId>, open: bool) -> Self {
+        Self {
+            id: id.into(),
+            open,
+            size: IconSize::Xs,
+            color: None,
+        }
+    }
+
+    pub fn size(mut self, size: IconSize) -> Self {
+        self.size = size;
+        self
+    }
+
+    /// Its color; the subtle foreground unless set.
+    pub fn color(mut self, color: Hsla) -> Self {
+        self.color = Some(color);
+        self
+    }
+}
+
+impl RenderOnce for Disclosure {
+    fn render(self, window: &mut Window, cx: &mut App) -> impl IntoElement {
+        let open = self.open;
+        let turns = motion::changes((self.id.clone(), "turns"), open, window, cx);
+        let color = self.color.unwrap_or(cx.theme().colors.fg_subtle);
+        let turn = |share: f32| radians(share * FRAC_PI_2);
+        let icon = Icon::new(IconName::ChevronRight)
+            .size(self.size)
+            .color(color);
+        if turns == 0 {
+            return icon
+                .rotate(turn(if open { 1.0 } else { 0.0 }))
+                .into_any_element();
+        }
+        icon.with_animation(
+            (self.id, format!("turn-{turns}")),
+            Animation::new(motion::duration(motion::FAST, cx)).with_easing(motion::ease_out_cubic),
+            move |icon, t| icon.rotate(turn(if open { t } else { 1.0 - t })),
+        )
+        .into_any_element()
+    }
+}

src/primitives/mod.rs

@@ -1,4 +1,5 @@
 mod backdrop;
+mod disclosure;
 mod divider;
 mod focus;
 mod ghost;
@@ -10,6 +11,7 @@ mod severity;
 mod tooltip;
 
 pub use backdrop::{Backdrop, Place};
+pub use disclosure::Disclosure;
 pub use divider::Divider;
 pub use focus::{FocusNext, FocusPrev, FocusRing, FocusScope};
 pub(crate) use focus::{Takeover, give_back, tab_stop, take_focus};