Enable/disable scrollbar auto-hide based on OS setting

crates/editor/src/editor.rs

@@ -239,6 +239,9 @@ pub enum Direction {
     Next,
 }
 
+#[derive(Default)]
+struct ScrollbarAutoHide(bool);
+
 pub fn init(cx: &mut MutableAppContext) {
     cx.add_action(Editor::new_file);
     cx.add_action(|this: &mut Editor, action: &Scroll, cx| this.set_scroll_position(action.0, cx));
@@ -327,6 +330,10 @@ pub fn init(cx: &mut MutableAppContext) {
     cx.add_async_action(Editor::confirm_rename);
     cx.add_async_action(Editor::find_all_references);
 
+    cx.set_global(ScrollbarAutoHide(
+        cx.platform().should_auto_hide_scrollbars(),
+    ));
+
     hover_popover::init(cx);
     link_go_to_definition::init(cx);
     mouse_context_menu::init(cx);
@@ -5949,6 +5956,7 @@ impl Editor {
             cx.notify();
         }
 
+        if cx.default_global::<ScrollbarAutoHide>().0 {
             self.hide_scrollbar_task = Some(cx.spawn_weak(|this, mut cx| async move {
                 Timer::after(SCROLLBAR_SHOW_INTERVAL).await;
                 if let Some(this) = this.upgrade(&cx) {
@@ -5958,6 +5966,9 @@ impl Editor {
                     });
                 }
             }));
+        } else {
+            self.hide_scrollbar_task = None;
+        }
     }
 
     fn on_buffer_changed(&mut self, _: ModelHandle<MultiBuffer>, cx: &mut ViewContext<Self>) {

crates/gpui/src/platform.rs

@@ -63,6 +63,7 @@ pub trait Platform: Send + Sync {
     fn delete_credentials(&self, url: &str) -> Result<()>;
 
     fn set_cursor_style(&self, style: CursorStyle);
+    fn should_auto_hide_scrollbars(&self) -> bool;
 
     fn local_timezone(&self) -> UtcOffset;
 

crates/gpui/src/platform/mac/platform.rs

@@ -699,6 +699,16 @@ impl platform::Platform for MacPlatform {
         }
     }
 
+    fn should_auto_hide_scrollbars(&self) -> bool {
+        #[allow(non_upper_case_globals)]
+        const NSScrollerStyleOverlay: NSInteger = 1;
+
+        unsafe {
+            let style: NSInteger = msg_send![class!(NSScroller), preferredScrollerStyle];
+            style == NSScrollerStyleOverlay
+        }
+    }
+
     fn local_timezone(&self) -> UtcOffset {
         unsafe {
             let local_timezone: id = msg_send![class!(NSTimeZone), localTimeZone];

crates/gpui/src/platform/test.rs

@@ -177,6 +177,10 @@ impl super::Platform for Platform {
         *self.cursor.lock() = style;
     }
 
+    fn should_auto_hide_scrollbars(&self) -> bool {
+        false
+    }
+
     fn local_timezone(&self) -> UtcOffset {
         UtcOffset::UTC
     }