Make mouse click extend selection in select mode (helix-editor#5436)

* Make mouse click extend selection in select mode

* chore: better readability with `Option::take()`

helix-term/src/ui/editor.rs

@@ -1088,6 +1088,15 @@ impl EditorView {
                     if modifiers == KeyModifiers::ALT {
                         let selection = doc.selection(view_id).clone();
                         doc.set_selection(view_id, selection.push(Range::point(pos)));
+                    } else if editor.mode == Mode::Select {
+                        // Discards non-primary selections for consistent UX with normal mode
+                        let primary = doc.selection(view_id).primary().put_cursor(
+                            doc.text().slice(..),
+                            pos,
+                            true,
+                        );
+                        editor.mouse_down_range = Some(primary);
+                        doc.set_selection(view_id, Selection::single(primary.anchor, primary.head));
                     } else {
                         doc.set_selection(view_id, Selection::point(pos));
                     }
@@ -1171,19 +1180,26 @@ impl EditorView {
 
                 let (view, doc) = current!(cxt.editor);
 
-                if doc
-                    .selection(view.id)
-                    .primary()
-                    .slice(doc.text().slice(..))
-                    .len_chars()
-                    <= 1
-                {
-                    return EventResult::Ignored(None);
-                }
-
-                commands::MappableCommand::yank_main_selection_to_primary_clipboard.execute(cxt);
+                let should_yank = match cxt.editor.mouse_down_range.take() {
+                    Some(down_range) => doc.selection(view.id).primary() != down_range,
+                    None => {
+                        // This should not happen under normal cases. We fall back to the original
+                        // behavior of yanking on non-single-char selections.
+                        doc.selection(view.id)
+                            .primary()
+                            .slice(doc.text().slice(..))
+                            .len_chars()
+                            > 1
+                    }
+                };
 
-                EventResult::Consumed(None)
+                if should_yank {
+                    commands::MappableCommand::yank_main_selection_to_primary_clipboard
+                        .execute(cxt);
+                    EventResult::Consumed(None)
+                } else {
+                    EventResult::Ignored(None)
+                }
             }
 
             MouseEventKind::Up(MouseButton::Right) => {

helix-view/src/editor.rs

@@ -45,7 +45,7 @@ pub use helix_core::diagnostic::Severity;
 use helix_core::{
     auto_pairs::AutoPairs,
     syntax::{self, AutoPairConfig, IndentationHeuristic, LanguageServerFeature, SoftWrap},
-    Change, LineEnding, Position, Selection, NATIVE_LINE_ENDING,
+    Change, LineEnding, Position, Range, Selection, NATIVE_LINE_ENDING,
 };
 use helix_dap as dap;
 use helix_lsp::lsp;
@@ -967,6 +967,8 @@ pub struct Editor {
     /// times during rendering and should not be set by other functions.
     pub cursor_cache: Cell<Option<Option<Position>>>,
     pub handlers: Handlers,
+
+    pub mouse_down_range: Option<Range>,
 }
 
 pub type Motion = Box<dyn Fn(&mut Editor)>;
@@ -1083,6 +1085,7 @@ impl Editor {
             needs_redraw: false,
             cursor_cache: Cell::new(None),
             handlers,
+            mouse_down_range: None,
         }
     }
 
@@ -1981,7 +1984,7 @@ impl Editor {
 
     /// Switches the editor into normal mode.
     pub fn enter_normal_mode(&mut self) {
-        use helix_core::{graphemes, Range};
+        use helix_core::graphemes;
 
         if self.mode == Mode::Normal {
             return;