Port 'Contex Menu' demo to Rust (#32)

demos/Context Menu/code.rs

@@ -0,0 +1,30 @@
+use crate::workbench;
+use gtk::gdk;
+use gtk::gio;
+use gtk::glib;
+use gtk::prelude::*;
+
+pub fn main() {
+    let box_menu_parent: gtk::Box = workbench::builder().object("box_menu_parent").unwrap();
+    let label_emoji: gtk::Label = workbench::builder().object("label_emoji").unwrap();
+    let gesture_click: gtk::GestureClick = workbench::builder().object("gesture_click").unwrap();
+    let popover_menu: gtk::PopoverMenu = workbench::builder().object("popover_menu").unwrap();
+
+    gesture_click.connect_pressed(move |_gesture, _n_press, x, y| {
+        let position = gdk::Rectangle::new(x as i32, y as i32, 0, 0);
+        popover_menu.set_pointing_to(Some(&position));
+        popover_menu.popup();
+    });
+
+    let mood_group = gio::SimpleActionGroup::new();
+    box_menu_parent.insert_action_group("mood", Some(&mood_group));
+
+    let emoji_action = gio::SimpleAction::new("emoji", Some(&glib::VariantType::new("s").unwrap()));
+
+    emoji_action.connect_activate(
+        glib::clone!(@weak label_emoji => move |_action, parameter| {
+            label_emoji.set_label(parameter.unwrap().get::<String>().unwrap().as_str());
+        }),
+    );
+    mood_group.add_action(&emoji_action);
+}