linux: Primary clipboard (#10534)

Implements copying from and pasting to the primary selection.

Release Notes:

- N/A

crates/editor/src/editor.rs

@@ -1828,6 +1828,29 @@ impl Editor {
         old_cursor_position: &Anchor,
         cx: &mut ViewContext<Self>,
     ) {
+        // Copy selections to primary selection buffer
+        #[cfg(target_os = "linux")]
+        if local {
+            let selections = self.selections.all::<usize>(cx);
+            let buffer_handle = self.buffer.read(cx).read(cx);
+
+            let mut text = String::new();
+            for (index, selection) in selections.iter().enumerate() {
+                let text_for_selection = buffer_handle
+                    .text_for_range(selection.start..selection.end)
+                    .collect::<String>();
+
+                text.push_str(&text_for_selection);
+                if index != selections.len() - 1 {
+                    text.push('\n');
+                }
+            }
+
+            if !text.is_empty() {
+                cx.write_to_primary(ClipboardItem::new(text));
+            }
+        }
+
         if self.focus_handle.is_focused(cx) && self.leader_peer_id.is_none() {
             self.buffer.update(cx, |buffer, cx| {
                 buffer.set_active_selections(

crates/editor/src/element.rs

@@ -502,6 +502,34 @@ impl EditorElement {
         cx.stop_propagation();
     }
 
+    fn mouse_middle_down(
+        editor: &mut Editor,
+        event: &MouseDownEvent,
+        position_map: &PositionMap,
+        text_hitbox: &Hitbox,
+        cx: &mut ViewContext<Editor>,
+    ) {
+        if !text_hitbox.is_hovered(cx) || editor.read_only(cx) {
+            return;
+        }
+
+        if let Some(item) = cx.read_from_primary() {
+            let point_for_position =
+                position_map.point_for_position(text_hitbox.bounds, event.position);
+            let position = point_for_position.previous_valid;
+
+            editor.select(
+                SelectPhase::Begin {
+                    position,
+                    add: false,
+                    click_count: 1,
+                },
+                cx,
+            );
+            editor.insert(item.text(), cx);
+        }
+    }
+
     fn mouse_up(
         editor: &mut Editor,
         event: &MouseUpEvent,
@@ -2903,6 +2931,9 @@ impl EditorElement {
                         MouseButton::Right => editor.update(cx, |editor, cx| {
                             Self::mouse_right_down(editor, event, &position_map, &text_hitbox, cx);
                         }),
+                        MouseButton::Middle => editor.update(cx, |editor, cx| {
+                            Self::mouse_middle_down(editor, event, &position_map, &text_hitbox, cx);
+                        }),
                         _ => {}
                     };
                 }