editor: Current line highlight options (#11710)

None:

<img width="717" alt="none"
src="https://github.com/zed-industries/zed/assets/2101250/b2a741db-c64a-4275-a612-5a0d15c9cab7">

Gutter:

<img width="715" alt="gutter"
src="https://github.com/zed-industries/zed/assets/2101250/f7a68a6e-6eba-41b4-9042-5a5fe2ee21a4">

Line:

<img width="717" alt="line"
src="https://github.com/zed-industries/zed/assets/2101250/117f5b00-abd7-425b-8047-1a6fab8293a7">

All:

<img width="715" alt="all"
src="https://github.com/zed-industries/zed/assets/2101250/ebccc0da-0fa0-44e5-903c-cc49d975db76">

This PR adds the `current_line_highlight` setting that defines how to
highlight the current line in the editor:

- `none`: Don't highlight the current line.
- `gutter`: Highlight the gutter area only.
- `line`: Highlight the editor area only.
- `all` (default): Highlight the whole line.

The options have been borrowed from VSCode.

Fixes #5222
Part of #4382

Release Notes:

- Added the `current_line_highlight` setting that defines how to
highlight the current line in the editor (#5222).

crates/editor/src/editor.rs

@@ -53,6 +53,7 @@ use convert_case::{Case, Casing};
 use debounced_delay::DebouncedDelay;
 pub use display_map::DisplayPoint;
 use display_map::*;
+use editor_settings::CurrentLineHighlight;
 pub use editor_settings::EditorSettings;
 use element::LineWithInvisibles;
 pub use element::{
@@ -465,6 +466,7 @@ pub struct Editor {
     pending_rename: Option<RenameState>,
     searchable: bool,
     cursor_shape: CursorShape,
+    current_line_highlight: CurrentLineHighlight,
     collapse_matches: bool,
     autoindent_mode: Option<AutoindentMode>,
     workspace: Option<(WeakView<Workspace>, WorkspaceId)>,
@@ -519,6 +521,7 @@ pub struct EditorSnapshot {
     is_focused: bool,
     scroll_anchor: ScrollAnchor,
     ongoing_scroll: OngoingScroll,
+    current_line_highlight: CurrentLineHighlight,
 }
 
 const GIT_BLAME_GUTTER_WIDTH_CHARS: f32 = 53.;
@@ -1636,6 +1639,7 @@ impl Editor {
             pending_rename: Default::default(),
             searchable: true,
             cursor_shape: Default::default(),
+            current_line_highlight: EditorSettings::get_global(cx).current_line_highlight,
             autoindent_mode: Some(AutoindentMode::EachLine),
             collapse_matches: false,
             workspace: None,
@@ -1850,6 +1854,7 @@ impl Editor {
             ongoing_scroll: self.scroll_manager.ongoing_scroll(),
             placeholder_text: self.placeholder_text.clone(),
             is_focused: self.focus_handle.is_focused(cx),
+            current_line_highlight: self.current_line_highlight,
         }
     }
 
@@ -1938,6 +1943,15 @@ impl Editor {
         cx.notify();
     }
 
+    pub fn set_current_line_highlight(
+        &mut self,
+        current_line_highlight: CurrentLineHighlight,
+        cx: &mut ViewContext<Self>,
+    ) {
+        self.current_line_highlight = current_line_highlight;
+        cx.notify();
+    }
+
     pub fn set_collapse_matches(&mut self, collapse_matches: bool) {
         self.collapse_matches = collapse_matches;
     }
@@ -10283,6 +10297,7 @@ impl Editor {
         let editor_settings = EditorSettings::get_global(cx);
         self.scroll_manager.vertical_scroll_margin = editor_settings.vertical_scroll_margin;
         self.show_breadcrumbs = editor_settings.toolbar.breadcrumbs;
+        self.current_line_highlight = editor_settings.current_line_highlight;
 
         if self.mode == EditorMode::Full {
             let inline_blame_enabled = ProjectSettings::get_global(cx).git.inline_blame_enabled();