Show active buffer's language on the right in the status bar

crates/language_selector/src/active_buffer_language.rs

@@ -0,0 +1,86 @@
+use editor::Editor;
+use gpui::{
+    elements::*, CursorStyle, Entity, MouseButton, RenderContext, Subscription, View, ViewContext,
+    ViewHandle,
+};
+use settings::Settings;
+use std::sync::Arc;
+use workspace::{item::ItemHandle, StatusItemView};
+
+pub struct ActiveBufferLanguage {
+    active_language: Option<Arc<str>>,
+    _observe_active_editor: Option<Subscription>,
+}
+
+impl Default for ActiveBufferLanguage {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl ActiveBufferLanguage {
+    pub fn new() -> Self {
+        Self {
+            active_language: None,
+            _observe_active_editor: None,
+        }
+    }
+
+    fn update_language(&mut self, editor: ViewHandle<Editor>, cx: &mut ViewContext<Self>) {
+        let editor = editor.read(cx);
+        self.active_language.take();
+        if let Some((_, buffer, _)) = editor.active_excerpt(cx) {
+            if let Some(language) = buffer.read(cx).language() {
+                self.active_language = Some(language.name());
+            }
+        }
+
+        cx.notify();
+    }
+}
+
+impl Entity for ActiveBufferLanguage {
+    type Event = ();
+}
+
+impl View for ActiveBufferLanguage {
+    fn ui_name() -> &'static str {
+        "ActiveBufferLanguage"
+    }
+
+    fn render(&mut self, cx: &mut RenderContext<Self>) -> ElementBox {
+        if let Some(active_language) = self.active_language.as_ref() {
+            MouseEventHandler::<Self>::new(0, cx, |state, cx| {
+                let theme = &cx.global::<Settings>().theme.workspace.status_bar;
+                let style = theme.active_language.style_for(state, false);
+                Label::new(active_language.to_string(), style.text.clone())
+                    .contained()
+                    .with_style(style.container)
+                    .boxed()
+            })
+            .with_cursor_style(CursorStyle::PointingHand)
+            .on_click(MouseButton::Left, |_, cx| cx.dispatch_action(crate::Toggle))
+            .boxed()
+        } else {
+            Empty::new().boxed()
+        }
+    }
+}
+
+impl StatusItemView for ActiveBufferLanguage {
+    fn set_active_pane_item(
+        &mut self,
+        active_pane_item: Option<&dyn ItemHandle>,
+        cx: &mut ViewContext<Self>,
+    ) {
+        if let Some(editor) = active_pane_item.and_then(|item| item.act_as::<Editor>(cx)) {
+            self._observe_active_editor = Some(cx.observe(&editor, Self::update_language));
+            self.update_language(editor, cx);
+        } else {
+            self.active_language = None;
+            self._observe_active_editor = None;
+        }
+
+        cx.notify();
+    }
+}

crates/language_selector/src/language_selector.rs

@@ -1,5 +1,6 @@
-use std::sync::Arc;
+mod active_buffer_language;
 
+pub use active_buffer_language::ActiveBufferLanguage;
 use editor::Editor;
 use fuzzy::{match_strings, StringMatch, StringMatchCandidate};
 use gpui::{
@@ -10,6 +11,7 @@ use language::{Buffer, LanguageRegistry};
 use picker::{Picker, PickerDelegate};
 use project::Project;
 use settings::Settings;
+use std::sync::Arc;
 use workspace::{AppState, Workspace};
 
 actions!(language_selector, [Toggle]);