Support disabling angle brackets in SelectView popup button

Allow a SelectView to be configured as "raw" (using the same terminology
as Button) to omit the angle brackets around the current item label.

cursive-core/src/views/select_view.rs

@@ -72,6 +72,8 @@ pub struct SelectView<T = String> {
 
     // `true` if we show a one-line view, with popup on selection.
     popup: bool,
+    // `true` if we skip the angle brackets around the popup button
+    raw: bool,
 
     // We need the last offset to place the popup window
     // We "cache" it during the draw, so we need interior mutability.
@@ -102,6 +104,7 @@ impl<T: 'static + Send + Sync> SelectView<T> {
             on_submit: None,
             align: Align::top_left(),
             popup: false,
+            raw: false,
             autojump: false,
             last_offset: Mutex::new(Vec2::zero()),
             last_size: Vec2::zero(),
@@ -167,6 +170,19 @@ impl<T: 'static + Send + Sync> SelectView<T> {
         self.last_required_size = None;
     }
 
+    /// Disable drawing angle brackets around the popup button.
+    ///
+    /// Chainable variant.
+    #[must_use]
+    pub fn raw(self) -> Self {
+        self.with(|s| s.set_raw(true))
+    }
+
+    /// Disable drawing angle brackets around the popup button.
+    pub fn set_raw(&mut self, raw: bool) {
+        self.raw = raw;
+    }
+
     /// Sets a callback to be used when an item is selected.
     #[crate::callback_helpers]
     pub fn set_on_select<F>(&mut self, cb: F)
@@ -944,9 +960,11 @@ impl<T: 'static + Send + Sync> View for SelectView<T> {
             printer.with_style(style, |printer| {
                 // Prepare the entire background
                 printer.print_hline((1, 0), x, " ");
-                // Draw the borders
-                printer.print((0, 0), "<");
-                printer.print((x, 0), ">");
+                if !self.raw {
+                    // Draw the borders
+                    printer.print((0, 0), "<");
+                    printer.print((x, 0), ">");
+                }
 
                 if let Some(label) = self.items.get(focus).map(|item| &item.label) {
                     // And center the text?
@@ -1006,7 +1024,8 @@ impl<T: 'static + Send + Sync> View for SelectView<T> {
             .max()
             .unwrap_or(1);
         let size = if self.popup {
-            Vec2::new(w + 2, 1)
+            let extra = if self.raw { 0 } else { 2 };
+            Vec2::new(w + extra, 1)
         } else {
             let h = self.items.len();