theme: Add theme_name to get current active theme name. (#1190)

And fix theme menu selected item in example when theme mode changed.

crates/story/src/themes.rs

@@ -6,7 +6,7 @@ use gpui::{
 use gpui_component::{
     button::{Button, ButtonVariants},
     popup_menu::PopupMenuExt,
-    IconName, Sizable, Theme, ThemeRegistry,
+    ActiveTheme, IconName, Sizable, Theme, ThemeRegistry,
 };
 use serde::{Deserialize, Serialize};
 
@@ -38,6 +38,11 @@ pub fn init(cx: &mut App) {
     }) {
         tracing::error!("Failed to watch themes directory: {}", err);
     }
+
+    cx.observe_global::<Theme>(|cx| {
+        AppState::global_mut(cx).theme_name = Some(cx.theme().theme_name().into());
+    })
+    .detach();
 }
 
 #[derive(Action, Clone, PartialEq)]

crates/ui/src/theme/mod.rs

@@ -101,6 +101,15 @@ impl Theme {
         self.mode.is_dark()
     }
 
+    /// Returns the current theme name.
+    pub fn theme_name(&self) -> &SharedString {
+        if self.is_dark() {
+            &self.dark_theme.name
+        } else {
+            &self.light_theme.name
+        }
+    }
+
     // /// Sets the theme to default light.
     // pub fn set_default_light(&mut self) {
     //     self.light_theme = ThemeColor::light();