Enable mouse scrolling in TabViews (#363)

* Forward events from a TabView to the selected Tab

* Forward mouse events to the front screen instead of the focused screen

src/ui/layout.rs

@@ -247,8 +247,7 @@ impl View for Layout {
             }
 
             if position.y < self.last_size.y.saturating_sub(2 + cmdline_height) {
-                if let Some(ref id) = self.focus {
-                    let screen = self.views.get_mut(id).unwrap();
+                if let Some(screen) = self.get_current_screen_mut() {
                     screen.view.on_event(event);
                 }
             } else if position.y < self.last_size.y - cmdline_height {

src/ui/tabview.rs

@@ -2,6 +2,7 @@ use std::cmp::{max, min};
 use std::collections::HashMap;
 
 use cursive::align::HAlign;
+use cursive::event::{Event, EventResult};
 use cursive::theme::{ColorStyle, ColorType, PaletteColor};
 use cursive::traits::View;
 use cursive::{Cursive, Printer, Vec2};
@@ -100,6 +101,14 @@ impl View for TabView {
             tab.view.layout(Vec2::new(size.x, size.y - 1));
         }
     }
+
+    fn on_event(&mut self, event: Event) -> EventResult {
+        if let Some(tab) = self.tabs.get_mut(self.selected) {
+            tab.view.on_event(event)
+        } else {
+            EventResult::Ignored
+        }
+    }
 }
 
 impl ViewExt for TabView {