Add visual feedback for select_register command

Resolves issue helix-editor#1585 by adding a status message when a register is
selected, similar to the message produced when recording a macro.
Additionally, an indicator appears on the right.

helix-term/src/commands.rs

@@ -4701,6 +4701,7 @@ fn select_register(cx: &mut Context) {
         if let Some(ch) = event.char() {
             cx.editor.autoinfo = None;
             cx.editor.selected_register = Some(ch);
+            cx.editor.set_status(format!("Selected register [{}]", ch));
         }
     })
 }

helix-term/src/ui/editor.rs

@@ -1447,13 +1447,18 @@ impl Component for EditorView {
                 disp.push_str(&key.key_sequence_format());
             }
             let style = cx.editor.theme.get("ui.text");
-            let macro_width = if cx.editor.macro_recording.is_some() {
+
+            let macro_active = cx.editor.macro_recording.is_some();
+            let register_active = cx.editor.selected_register.is_some();
+            let macro_reg_width = if macro_active && register_active {
+                7
+            } else if macro_active ^ register_active {
                 3
             } else {
                 0
             };
             surface.set_string(
-                area.x + area.width.saturating_sub(key_width + macro_width),
+                area.x + area.width.saturating_sub(key_width + macro_reg_width),
                 area.y + area.height.saturating_sub(1),
                 disp.get(disp.len().saturating_sub(key_width as usize)..)
                     .unwrap_or(&disp),
@@ -1471,6 +1476,18 @@ impl Component for EditorView {
                     style,
                 );
             }
+            if let Some(reg) = cx.editor.selected_register {
+                let disp = format!("[{}]", reg);
+                let style = style
+                    .fg(helix_view::graphics::Color::Cyan)
+                    .add_modifier(Modifier::BOLD);
+                surface.set_string(
+                    area.x + area.width.saturating_sub(macro_reg_width),
+                    area.y + area.height.saturating_sub(1),
+                    &disp,
+                    style,
+                );
+            }
         }
 
         if let Some(completion) = self.completion.as_mut() {