feat: add diff view component

crates/core/src/scroll_area.rs

@@ -1,3 +1,4 @@
+use std::sync::Arc;
 use std::time::Duration;
 use std::time::Instant;
 
@@ -54,9 +55,9 @@ struct AutohideState {
 }
 
 impl Autohide {
-    pub(crate) fn new(window: &mut Window, cx: &mut App) -> Self {
+    pub(crate) fn new(key: ElementId, window: &mut Window, cx: &mut App) -> Self {
         let view = window.current_view();
-        let state = window.use_keyed_state("scrollbar-autohide", cx, |_, _| AutohideState {
+        let state = window.use_keyed_state(key, cx, |_, _| AutohideState {
             last_activity: None,
             hide_task: None,
         });
@@ -195,6 +196,11 @@ impl ScrollArea {
     }
 }
 
+/// Names keyed state under the scrollbar's own id.
+pub fn scrollbar_state_key(name: &'static str, id: &ElementId) -> ElementId {
+    ElementId::NamedChild(Arc::new(id.clone()), SharedString::from(name))
+}
+
 /// Pure thumb geometry for an overlay scrollbar.
 pub(crate) fn thumb_geometry(
     viewport: Pixels,
@@ -247,11 +253,12 @@ impl RenderOnce for ScrollArea {
                 ScrollbarVisibility::Always => false,
                 ScrollbarVisibility::Autohide => true,
             };
+            let id = self.id.clone();
             wrapper.extend(std::iter::once(
                 canvas(|_, _, _| {}, {
                     let handle = handle.clone();
                     move |_, _, window, cx| {
-                        paint_scrollbar(&handle, autohide, window, cx);
+                        paint_scrollbar(&handle, &id, autohide, window, cx);
                     }
                 })
                 .absolute()
@@ -265,7 +272,13 @@ impl RenderOnce for ScrollArea {
 }
 
 /// Paints the overlay scrollbar thumb.
-fn paint_scrollbar(handle: &ScrollHandle, autohide: bool, window: &mut Window, cx: &mut App) {
+fn paint_scrollbar(
+    handle: &ScrollHandle,
+    key: &ElementId,
+    autohide: bool,
+    window: &mut Window,
+    cx: &mut App,
+) {
     let theme = cx.theme();
     let view = window.current_view();
 
@@ -281,8 +294,9 @@ fn paint_scrollbar(handle: &ScrollHandle, autohide: bool, window: &mut Window, c
         return;
     }
 
-    let autohide_state = autohide.then(|| Autohide::new(window, cx));
-    let drag = window.use_keyed_state("scrollbar-thumb-drag", cx, |_, _| {
+    let autohide_state =
+        autohide.then(|| Autohide::new(scrollbar_state_key("autohide", key), window, cx));
+    let drag = window.use_keyed_state(scrollbar_state_key("thumb-drag", key), cx, |_, _| {
         Option::<(Pixels, Pixels)>::None
     });
     let dragging = drag.read(cx).is_some();

crates/core/src/scrollbar.rs

@@ -1,23 +1,15 @@
-//! Overlay scrollbars for scroll surfaces, including gpui's virtualized
-//! `uniform_list` and `list`. Render the scrollbar as a later child of a
-//! `.relative()` container around the scrolled surface:
-//!
-//! ```
-//! div().relative()
-//!     .child(uniform_list(...).track_scroll(&handle))
-//!     .child(Scrollbar::vertical(handle))
-//! ```
+//! Overlay scrollbars for scroll surfaces.
 
 use std::rc::Rc;
 
 use gpui::{
-    App, Bounds, DispatchPhase, IntoElement, ListState, MouseButton, MouseDownEvent,
+    App, Bounds, DispatchPhase, ElementId, IntoElement, ListState, MouseButton, MouseDownEvent,
     MouseMoveEvent, MouseUpEvent, Pixels, Point, RenderOnce, ScrollEvent, ScrollHandle,
     Styled as _, UniformListScrollHandle, Window, canvas, fill, point,
 };
 use gpui_native_theme::ActiveTheme as _;
 
-use crate::scroll_area::{Autohide, thumb_geometry, thumb_style};
+use crate::scroll_area::{Autohide, scrollbar_state_key, thumb_geometry, thumb_style};
 
 /// Re-exported so callers only need the scrollbar module.
 pub use crate::scroll_area::ScrollbarVisibility;
@@ -130,12 +122,13 @@ impl Axis {
     }
 }
 
-/// An overlay scrollbar; the caller renders it over the scrolled surface.
+/// An overlay scrollbar, the caller renders it over the scrolled surface.
 #[derive(IntoElement)]
 pub struct Scrollbar {
     axis: Axis,
     handle: Rc<dyn ScrollbarHandle>,
     visibility: ScrollbarVisibility,
+    key: ElementId,
 }
 
 impl Scrollbar {
@@ -148,6 +141,7 @@ impl Scrollbar {
             axis: Axis::Vertical,
             handle: Rc::new(handle),
             visibility: ScrollbarVisibility::default(),
+            key: ElementId::Name("scrollbar".into()),
         }
     }
 
@@ -160,6 +154,7 @@ impl Scrollbar {
             axis: Axis::Horizontal,
             handle: Rc::new(handle),
             visibility: ScrollbarVisibility::default(),
+            key: ElementId::Name("scrollbar".into()),
         }
     }
 
@@ -168,6 +163,12 @@ impl Scrollbar {
         self.visibility = visibility;
         self
     }
+
+    /// Names this scrollbar's state.
+    pub fn key(mut self, key: impl Into<ElementId>) -> Self {
+        self.key = key.into();
+        self
+    }
 }
 
 impl RenderOnce for Scrollbar {
@@ -176,7 +177,8 @@ impl RenderOnce for Scrollbar {
             let handle = self.handle;
             let axis = self.axis;
             let visibility = self.visibility;
-            move |_, _, window, cx| paint_scrollbar(&handle, axis, visibility, window, cx)
+            let key = self.key;
+            move |_, _, window, cx| paint_scrollbar(&handle, axis, visibility, &key, window, cx)
         })
         .absolute()
         .inset_0()
@@ -190,6 +192,7 @@ fn paint_scrollbar(
     handle: &Rc<dyn ScrollbarHandle>,
     axis: Axis,
     visibility: ScrollbarVisibility,
+    key: &ElementId,
     window: &mut Window,
     cx: &mut App,
 ) {
@@ -214,7 +217,9 @@ fn paint_scrollbar(
         ScrollbarVisibility::Always => false,
         ScrollbarVisibility::Autohide => true,
     };
-    let autohide_state = autohide.then(|| Autohide::new(window, cx));
+
+    let autohide_state =
+        autohide.then(|| Autohide::new(scrollbar_state_key("autohide", key), window, cx));
 
     let track_length = viewport_along - inset * 2.0;
 
@@ -262,7 +267,9 @@ fn paint_scrollbar(
         }
     };
 
-    let drag = window.use_keyed_state("scrollbar-thumb-drag", cx, |_, _| Drag::None);
+    let drag = window.use_keyed_state(scrollbar_state_key("thumb-drag", key), cx, |_, _| {
+        Drag::None
+    });
     let dragging = drag.read(cx).is_some();
 
     let alpha = match &autohide_state {