refactor: id-keyed popover/context-menu API (cce-ui Phase 6bc slice 2)

register_popover takes &mut; active_popovers holds WidgetIds resolved
through ui_context.tree; context_menu::mouse_input takes the ctx.

 src/main.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/main.rs b/src/main.rs
index 4f26121..79ecdfe 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -911,7 +911,7 @@ impl Application for TypefaceApp {
         // spawn an empty popup surface (no render_popovers override here).
         self.ui_context.clear_popovers();
         if self.selected_family.is_some() && self.style_dropdown.popover_rect().is_some() {
-            self.ui_context.register_popover(&self.style_dropdown);
+            self.ui_context.register_popover(&mut self.style_dropdown);
         }
 
         let base_low = cce_ui::colors::page_low_color();