Introduce a status bar and add the cursor position to it

Co-Authored-By: Nathan Sobo <nathan@zed.dev>
Co-Authored-By: Max Brunsfeld <max@zed.dev>

crates/workspace/src/status_bar.rs

@@ -0,0 +1,127 @@
+use crate::{ItemViewHandle, Pane, Settings};
+use gpui::{
+    elements::*, ElementBox, Entity, MutableAppContext, RenderContext, Subscription, View,
+    ViewContext, ViewHandle,
+};
+use postage::watch;
+
+pub trait StatusItemView: View {
+    fn set_active_pane_item(
+        &mut self,
+        active_pane_item: Option<&dyn crate::ItemViewHandle>,
+        cx: &mut ViewContext<Self>,
+    );
+}
+
+trait StatusItemViewHandle {
+    fn id(&self) -> usize;
+    fn set_active_pane_item(
+        &self,
+        active_pane_item: Option<&dyn ItemViewHandle>,
+        cx: &mut MutableAppContext,
+    );
+}
+
+pub struct StatusBar {
+    left_items: Vec<Box<dyn StatusItemViewHandle>>,
+    right_items: Vec<Box<dyn StatusItemViewHandle>>,
+    active_pane: ViewHandle<Pane>,
+    _observe_active_pane: Subscription,
+    settings: watch::Receiver<Settings>,
+}
+
+impl Entity for StatusBar {
+    type Event = ();
+}
+
+impl View for StatusBar {
+    fn ui_name() -> &'static str {
+        "StatusBar"
+    }
+
+    fn render(&mut self, _: &mut RenderContext<Self>) -> ElementBox {
+        let theme = &self.settings.borrow().theme.workspace.status_bar;
+        Flex::row()
+            .with_children(
+                self.left_items
+                    .iter()
+                    .map(|i| ChildView::new(i.id()).aligned().boxed()),
+            )
+            .with_child(Empty::new().expanded(1.).boxed())
+            .with_children(
+                self.right_items
+                    .iter()
+                    .map(|i| ChildView::new(i.id()).aligned().boxed()),
+            )
+            .contained()
+            .with_style(theme.container)
+            .constrained()
+            .with_height(theme.height)
+            .boxed()
+    }
+}
+
+impl StatusBar {
+    pub fn new(
+        active_pane: &ViewHandle<Pane>,
+        settings: watch::Receiver<Settings>,
+        cx: &mut ViewContext<Self>,
+    ) -> Self {
+        let mut this = Self {
+            left_items: Default::default(),
+            right_items: Default::default(),
+            active_pane: active_pane.clone(),
+            _observe_active_pane: cx
+                .observe(active_pane, |this, _, cx| this.update_active_pane_item(cx)),
+            settings,
+        };
+        this.update_active_pane_item(cx);
+        this
+    }
+
+    pub fn add_left_item<T>(&mut self, item: ViewHandle<T>, cx: &mut ViewContext<Self>)
+    where
+        T: 'static + StatusItemView,
+    {
+        self.left_items.push(Box::new(item));
+        cx.notify();
+    }
+
+    pub fn add_right_item<T>(&mut self, item: ViewHandle<T>, cx: &mut ViewContext<Self>)
+    where
+        T: 'static + StatusItemView,
+    {
+        self.right_items.push(Box::new(item));
+        cx.notify();
+    }
+
+    pub fn set_active_pane(&mut self, active_pane: &ViewHandle<Pane>, cx: &mut ViewContext<Self>) {
+        self.active_pane = active_pane.clone();
+        self._observe_active_pane =
+            cx.observe(active_pane, |this, _, cx| this.update_active_pane_item(cx));
+        self.update_active_pane_item(cx);
+    }
+
+    fn update_active_pane_item(&mut self, cx: &mut ViewContext<Self>) {
+        let active_pane_item = self.active_pane.read(cx).active_item();
+        for item in self.left_items.iter().chain(&self.right_items) {
+            item.set_active_pane_item(active_pane_item.as_deref(), cx);
+        }
+    }
+}
+
+impl<T: StatusItemView> StatusItemViewHandle for ViewHandle<T> {
+    fn id(&self) -> usize {
+        self.id()
+    }
+
+    fn set_active_pane_item(
+        &self,
+        active_pane_item: Option<&dyn ItemViewHandle>,
+        cx: &mut MutableAppContext,
+    ) {
+        self.update(cx, |this, cx| {
+            this.set_active_pane_item(active_pane_item, cx)
+        });
+    }
+}