Introduce specific types for each palette::Extended field

We will have more control over color calculations for each semantic purpose this way.

examples/game_of_life/src/main.rs

@@ -12,8 +12,8 @@ use iced::theme::{self, Theme};
 use iced::time;
 use iced::window;
 use iced::{
-    Alignment, Application, Checkbox, Column, Command, Container, Element,
-    Length, Row, Settings, Subscription, Text,
+    Alignment, Application, Checkbox, Column, Command, Element, Length, Row,
+    Settings, Subscription, Text,
 };
 use preset::Preset;
 use std::time::{Duration, Instant};
@@ -143,20 +143,19 @@ impl Application for GameOfLife {
             self.grid.preset(),
         );
 
-        let content = Column::new()
+        Column::new()
             .push(
                 self.grid
                     .view()
                     .map(move |message| Message::Grid(message, version)),
             )
-            .push(controls);
-
-        Container::new(content)
-            .width(Length::Fill)
-            .height(Length::Fill)
-            .style(style::Container)
+            .push(controls)
             .into()
     }
+
+    fn theme(&self) -> Theme {
+        Theme::Dark
+    }
 }
 
 mod grid {

examples/game_of_life/src/style.rs

@@ -1,4 +1,4 @@
-use iced::{container, pick_list, Background, Color};
+use iced::{pick_list, Color};
 
 const BACKGROUND: Color = Color::from_rgb(
     0x2F as f32 / 255.0,
@@ -6,20 +6,6 @@ const BACKGROUND: Color = Color::from_rgb(
     0x36 as f32 / 255.0,
 );
 
-pub struct Container;
-
-impl container::StyleSheet for Container {
-    fn style(&self) -> container::Style {
-        container::Style {
-            background: Some(Background::Color(Color::from_rgb8(
-                0x36, 0x39, 0x3F,
-            ))),
-            text_color: Some(Color::WHITE),
-            ..container::Style::default()
-        }
-    }
-}
-
 pub struct PickList;
 
 impl pick_list::StyleSheet for PickList {