Editor tab bar settings (#7356)

This PR is another step to tabless editing (#6424, #4963). It adds
support for tab bar settings that allow the user to change its placement
or to hide completely.

Configuraton:

```json
"tab_bar": {
  "show": true
}
```

Placemnet options are "top", "bottom" and "no".

This PR intentionally doesn't affect tab bars of other panes (Terminal
for instance) to keep code changes small. I guess we'll do the rest in
separate PRs.

Release Notes:

- Added support for configuring the editor tab bar (part of #6424,
#4963).

---------

Co-authored-by: Mikayla <mikayla@zed.dev>

crates/workspace/src/item.rs

@@ -69,7 +69,7 @@ impl ClosePosition {
 pub struct ItemSettingsContent {
     /// Whether to show the Git file status on a tab item.
     ///
-    /// Default: true
+    /// Default: false
     git_status: Option<bool>,
     /// Position of the close button in a tab.
     ///

crates/workspace/src/pane.rs

@@ -203,6 +203,7 @@ pub struct Pane {
     custom_drop_handle:
         Option<Arc<dyn Fn(&mut Pane, &dyn Any, &mut ViewContext<Pane>) -> ControlFlow<(), ()>>>,
     can_split: bool,
+    should_display_tab_bar: Rc<dyn Fn(&ViewContext<Pane>) -> bool>,
     render_tab_bar_buttons: Rc<dyn Fn(&mut Pane, &mut ViewContext<Pane>) -> AnyElement>,
     _subscriptions: Vec<Subscription>,
     tab_bar_scroll_handle: ScrollHandle,
@@ -312,6 +313,7 @@ impl Pane {
             can_drop_predicate,
             custom_drop_handle: None,
             can_split: true,
+            should_display_tab_bar: Rc::new(|cx| TabBarSettings::get_global(cx).show),
             render_tab_bar_buttons: Rc::new(move |pane, cx| {
                 // Ideally we would return a vec of elements here to pass directly to the [TabBar]'s
                 // `end_slot`, but due to needing a view here that isn't possible.
@@ -468,6 +470,13 @@ impl Pane {
         &self.activation_history
     }
 
+    pub fn set_should_display_tab_bar<F>(&mut self, should_display_tab_bar: F)
+    where
+        F: 'static + Fn(&ViewContext<Pane>) -> bool,
+    {
+        self.should_display_tab_bar = Rc::new(should_display_tab_bar);
+    }
+
     pub fn set_can_split(&mut self, can_split: bool, cx: &mut ViewContext<Self>) {
         self.can_split = can_split;
         cx.notify();
@@ -1963,6 +1972,9 @@ impl Render for Pane {
             key_context.add("EmptyPane");
         }
 
+        let should_display_tab_bar = self.should_display_tab_bar.clone();
+        let display_tab_bar = should_display_tab_bar(cx);
+
         v_flex()
             .key_context(key_context)
             .track_focus(&self.focus_handle)
@@ -2061,7 +2073,7 @@ impl Render for Pane {
                     }
                 }),
             )
-            .when(self.active_item().is_some(), |pane| {
+            .when(self.active_item().is_some() && display_tab_bar, |pane| {
                 pane.child(self.render_tab_bar(cx))
             })
             .child({

crates/workspace/src/workspace_settings.rs

@@ -60,11 +60,16 @@ pub struct WorkspaceSettingsContent {
 
 #[derive(Deserialize)]
 pub struct TabBarSettings {
+    pub show: bool,
     pub show_nav_history_buttons: bool,
 }
 
 #[derive(Clone, Default, Serialize, Deserialize, JsonSchema)]
 pub struct TabBarSettingsContent {
+    /// Whether or not to show the tab bar in the editor.
+    ///
+    /// Default: top
+    pub show: Option<bool>,
     /// Whether or not to show the navigation history buttons in the tab bar.
     ///
     /// Default: true