Show breadcrumbs in the toolbar

crates/breadcrumbs/Cargo.toml

@@ -0,0 +1,21 @@
+[package]
+name = "breadcrumbs"
+version = "0.1.0"
+edition = "2021"
+
+[lib]
+path = "src/breadcrumbs.rs"
+doctest = false
+
+[dependencies]
+collections = { path = "../collections" }
+editor = { path = "../editor" }
+gpui = { path = "../gpui" }
+language = { path = "../language" }
+theme = { path = "../theme" }
+workspace = { path = "../workspace" }
+
+[dev-dependencies]
+editor = { path = "../editor", features = ["test-support"] }
+gpui = { path = "../gpui", features = ["test-support"] }
+workspace = { path = "../workspace", features = ["test-support"] }

crates/breadcrumbs/src/breadcrumbs.rs

@@ -0,0 +1,99 @@
+use editor::{Anchor, Editor};
+use gpui::{
+    elements::*, AppContext, Entity, RenderContext, Subscription, View, ViewContext, ViewHandle,
+};
+use language::{BufferSnapshot, OutlineItem};
+use std::borrow::Cow;
+use theme::SyntaxTheme;
+use workspace::{ItemHandle, Settings, ToolbarItemView};
+
+pub struct Breadcrumbs {
+    editor: Option<ViewHandle<Editor>>,
+    editor_subscription: Option<Subscription>,
+}
+
+impl Breadcrumbs {
+    pub fn new() -> Self {
+        Self {
+            editor: Default::default(),
+            editor_subscription: Default::default(),
+        }
+    }
+
+    fn active_symbols(
+        &self,
+        theme: &SyntaxTheme,
+        cx: &AppContext,
+    ) -> Option<(BufferSnapshot, Vec<OutlineItem<Anchor>>)> {
+        let editor = self.editor.as_ref()?.read(cx);
+        let cursor = editor.newest_anchor_selection().head();
+        let (buffer, symbols) = editor
+            .buffer()
+            .read(cx)
+            .read(cx)
+            .symbols_containing(cursor, Some(theme))?;
+        if buffer.path().is_none() && symbols.is_empty() {
+            None
+        } else {
+            Some((buffer, symbols))
+        }
+    }
+}
+
+impl Entity for Breadcrumbs {
+    type Event = ();
+}
+
+impl View for Breadcrumbs {
+    fn ui_name() -> &'static str {
+        "Breadcrumbs"
+    }
+
+    fn render(&mut self, cx: &mut RenderContext<Self>) -> ElementBox {
+        let theme = cx.global::<Settings>().theme.clone();
+        let (buffer, symbols) =
+            if let Some((buffer, symbols)) = self.active_symbols(&theme.editor.syntax, cx) {
+                (buffer, symbols)
+            } else {
+                return Empty::new().boxed();
+            };
+
+        let filename = if let Some(path) = buffer.path() {
+            path.to_string_lossy()
+        } else {
+            Cow::Borrowed("untitled")
+        };
+
+        Flex::row()
+            .with_child(Label::new(filename.to_string(), theme.breadcrumbs.text.clone()).boxed())
+            .with_children(symbols.into_iter().flat_map(|symbol| {
+                [
+                    Label::new(" > ".to_string(), theme.breadcrumbs.text.clone()).boxed(),
+                    Text::new(symbol.text, theme.breadcrumbs.text.clone())
+                        .with_highlights(symbol.highlight_ranges)
+                        .boxed(),
+                ]
+            }))
+            .boxed()
+    }
+}
+
+impl ToolbarItemView for Breadcrumbs {
+    fn set_active_pane_item(
+        &mut self,
+        active_pane_item: Option<&dyn ItemHandle>,
+        cx: &mut ViewContext<Self>,
+    ) {
+        self.editor_subscription = None;
+        self.editor = None;
+        if let Some(editor) = active_pane_item.and_then(|i| i.act_as::<Editor>(cx)) {
+            self.editor_subscription = Some(cx.subscribe(&editor, |_, _, event, cx| match event {
+                editor::Event::BufferEdited => cx.notify(),
+                editor::Event::SelectionsChanged { local } if *local => cx.notify(),
+                _ => {}
+            }));
+            self.editor = Some(editor);
+        }
+        cx.notify();
+    }
+}