Make `Command` implementations platform-specific

This allows us to introduce a platform-specific `Action` to both `iced_native`
and `iced_web` and remove the `Clipboard` from `Application::update` to maintain
purity.

Additionally, this should let us implement further actions to let users query
and modify the shell environment (e.g. window, clipboard, and more!)

13 files changed, 39 insertions, 95 deletions

diff --git a/examples/clock/src/main.rs b/examples/clock/src/main.rs
index 9bcc827b..b317ac00 100644
--- a/examples/clock/src/main.rs
+++ b/examples/clock/src/main.rs
@@ -1,7 +1,7 @@
 use iced::{
     canvas::{self, Cache, Canvas, Cursor, Geometry, LineCap, Path, Stroke},
-    executor, time, Application, Clipboard, Color, Command, Container, Element,
-    Length, Point, Rectangle, Settings, Subscription, Vector,
+    executor, time, Application, Color, Command, Container, Element, Length,
+    Point, Rectangle, Settings, Subscription, Vector,
 };
 
 pub fn main() -> iced::Result {
@@ -40,11 +40,7 @@ impl Application for Clock {
         String::from("Clock - Iced")
     }
 
-    fn update(
-        &mut self,
-        message: Message,
-        _clipboard: &mut Clipboard,
-    ) -> Command<Message> {
+    fn update(&mut self, message: Message) -> Command<Message> {
         match message {
             Message::Tick(local_time) => {
                 let now = local_time;
diff --git a/examples/download_progress/src/main.rs b/examples/download_progress/src/main.rs
index 6f844e66..cd024926 100644
--- a/examples/download_progress/src/main.rs
+++ b/examples/download_progress/src/main.rs
@@ -1,6 +1,6 @@
 use iced::{
-    button, executor, Align, Application, Button, Clipboard, Column, Command,
-    Container, Element, Length, ProgressBar, Settings, Subscription, Text,
+    button, executor, Align, Application, Button, Column, Command, Container,
+    Element, Length, ProgressBar, Settings, Subscription, Text,
 };
 
 mod download;
@@ -43,11 +43,7 @@ impl Application for Example {
         String::from("Download progress - Iced")
     }
 
-    fn update(
-        &mut self,
-        message: Message,
-        _clipboard: &mut Clipboard,
-    ) -> Command<Message> {
+    fn update(&mut self, message: Message) -> Command<Message> {
         match message {
             Message::Add => {
                 self.last_id = self.last_id + 1;
diff --git a/examples/events/src/main.rs b/examples/events/src/main.rs
index 446c190b..911ff425 100644
--- a/examples/events/src/main.rs
+++ b/examples/events/src/main.rs
@@ -1,7 +1,7 @@
 use iced::{
-    button, executor, Align, Application, Button, Checkbox, Clipboard, Column,
-    Command, Container, Element, HorizontalAlignment, Length, Settings,
-    Subscription, Text,
+    button, executor, Align, Application, Button, Checkbox, Column, Command,
+    Container, Element, HorizontalAlignment, Length, Settings, Subscription,
+    Text,
 };
 use iced_native::{window, Event};
 
@@ -40,11 +40,7 @@ impl Application for Events {
         String::from("Events - Iced")
     }
 
-    fn update(
-        &mut self,
-        message: Message,
-        _clipboard: &mut Clipboard,
-    ) -> Command<Message> {
+    fn update(&mut self, message: Message) -> Command<Message> {
         match message {
             Message::EventOccurred(event) if self.enabled => {
                 self.last.push(event);
diff --git a/examples/game_of_life/src/main.rs b/examples/game_of_life/src/main.rs
index c3e16e8b..2d46634f 100644
--- a/examples/game_of_life/src/main.rs
+++ b/examples/game_of_life/src/main.rs
@@ -12,8 +12,8 @@ use iced::slider::{self, Slider};
 use iced::time;
 use iced::window;
 use iced::{
-    Align, Application, Checkbox, Clipboard, Column, Command, Container,
-    Element, Length, Row, Settings, Subscription, Text,
+    Align, Application, Checkbox, Column, Command, Container, Element, Length,
+    Row, Settings, Subscription, Text,
 };
 use preset::Preset;
 use std::time::{Duration, Instant};
@@ -71,11 +71,7 @@ impl Application for GameOfLife {
         String::from("Game of Life - Iced")
     }
 
-    fn update(
-        &mut self,
-        message: Message,
-        _clipboard: &mut Clipboard,
-    ) -> Command<Message> {
+    fn update(&mut self, message: Message) -> Command<Message> {
         match message {
             Message::Grid(message, version) => {
                 if version == self.version {
diff --git a/examples/integration_opengl/src/controls.rs b/examples/integration_opengl/src/controls.rs
index 13b7fbc2..ddc6827c 100644
--- a/examples/integration_opengl/src/controls.rs
+++ b/examples/integration_opengl/src/controls.rs
@@ -1,7 +1,7 @@
 use iced_glow::Renderer;
 use iced_glutin::{
-    slider, Align, Clipboard, Color, Column, Command, Element, Length, Program,
-    Row, Slider, Text,
+    slider, Align, Color, Column, Command, Element, Length, Program, Row,
+    Slider, Text,
 };
 
 pub struct Controls {
@@ -30,13 +30,8 @@ impl Controls {
 impl Program for Controls {
     type Renderer = Renderer;
     type Message = Message;
-    type Clipboard = Clipboard;
 
-    fn update(
-        &mut self,
-        message: Message,
-        _clipboard: &mut Clipboard,
-    ) -> Command<Message> {
+    fn update(&mut self, message: Message) -> Command<Message> {
         match message {
             Message::BackgroundColorChanged(color) => {
                 self.background_color = color;
diff --git a/examples/integration_wgpu/src/controls.rs b/examples/integration_wgpu/src/controls.rs
index 36ee9b7e..824f9f53 100644
--- a/examples/integration_wgpu/src/controls.rs
+++ b/examples/integration_wgpu/src/controls.rs
@@ -1,7 +1,7 @@
 use iced_wgpu::Renderer;
 use iced_winit::{
-    slider, Align, Clipboard, Color, Column, Command, Element, Length, Program,
-    Row, Slider, Text,
+    slider, Align, Color, Column, Command, Element, Length, Program, Row,
+    Slider, Text,
 };
 
 pub struct Controls {
@@ -30,13 +30,8 @@ impl Controls {
 impl Program for Controls {
     type Renderer = Renderer;
     type Message = Message;
-    type Clipboard = Clipboard;
 
-    fn update(
-        &mut self,
-        message: Message,
-        _clipboard: &mut Clipboard,
-    ) -> Command<Message> {
+    fn update(&mut self, message: Message) -> Command<Message> {
         match message {
             Message::BackgroundColorChanged(color) => {
                 self.background_color = color;
diff --git a/examples/menu/src/main.rs b/examples/menu/src/main.rs
index 7403713c..810afa00 100644
--- a/examples/menu/src/main.rs
+++ b/examples/menu/src/main.rs
@@ -1,7 +1,6 @@
 use iced::menu::{self, Menu};
 use iced::{
-    executor, Application, Clipboard, Command, Container, Element, Length,
-    Settings, Text,
+    executor, Application, Command, Container, Element, Length, Settings, Text,
 };
 use iced_native::keyboard::{Hotkey, KeyCode, Modifiers};
 
@@ -92,11 +91,7 @@ impl Application for App {
         ])
     }
 
-    fn update(
-        &mut self,
-        message: Message,
-        _clipboard: &mut Clipboard,
-    ) -> Command<Message> {
+    fn update(&mut self, message: Message) -> Command<Message> {
         match message {
             Message::MenuActivated(entry) => self.selected = Some(entry),
         }
diff --git a/examples/pane_grid/src/main.rs b/examples/pane_grid/src/main.rs
index 3bd8aa25..5a134756 100644
--- a/examples/pane_grid/src/main.rs
+++ b/examples/pane_grid/src/main.rs
@@ -1,8 +1,7 @@
 use iced::{
     button, executor, keyboard, pane_grid, scrollable, Align, Application,
-    Button, Clipboard, Color, Column, Command, Container, Element,
-    HorizontalAlignment, Length, PaneGrid, Row, Scrollable, Settings,
-    Subscription, Text,
+    Button, Color, Column, Command, Container, Element, HorizontalAlignment,
+    Length, PaneGrid, Row, Scrollable, Settings, Subscription, Text,
 };
 use iced_native::{event, subscription, Event};
 
@@ -51,11 +50,7 @@ impl Application for Example {
         String::from("Pane grid - Iced")
     }
 
-    fn update(
-        &mut self,
-        message: Message,
-        _clipboard: &mut Clipboard,
-    ) -> Command<Message> {
+    fn update(&mut self, message: Message) -> Command<Message> {
         match message {
             Message::Split(axis, pane) => {
                 let result = self.panes.split(
diff --git a/examples/pokedex/src/main.rs b/examples/pokedex/src/main.rs
index da1d5d5d..fdf667cc 100644
--- a/examples/pokedex/src/main.rs
+++ b/examples/pokedex/src/main.rs
@@ -1,6 +1,6 @@
 use iced::{
-    button, futures, image, Align, Application, Button, Clipboard, Column,
-    Command, Container, Element, Length, Row, Settings, Text,
+    button, futures, image, Align, Application, Button, Column, Command,
+    Container, Element, Length, Row, Settings, Text,
 };
 
 pub fn main() -> iced::Result {
@@ -48,11 +48,7 @@ impl Application for Pokedex {
         format!("{} - Pokédex", subtitle)
     }
 
-    fn update(
-        &mut self,
-        message: Message,
-        _clipboard: &mut Clipboard,
-    ) -> Command<Message> {
+    fn update(&mut self, message: Message) -> Command<Message> {
         match message {
             Message::PokemonFound(Ok(pokemon)) => {
                 *self = Pokedex::Loaded {
diff --git a/examples/solar_system/src/main.rs b/examples/solar_system/src/main.rs
index 8f844828..c8f74978 100644
--- a/examples/solar_system/src/main.rs
+++ b/examples/solar_system/src/main.rs
@@ -8,8 +8,8 @@
 //! [1]: https://developer.mozilla.org/en-US/docs/Web/API/Canvas_API/Tutorial/Basic_animations#An_animated_solar_system
 use iced::{
     canvas::{self, Cursor, Path, Stroke},
-    executor, time, window, Application, Canvas, Clipboard, Color, Command,
-    Element, Length, Point, Rectangle, Settings, Size, Subscription, Vector,
+    executor, time, window, Application, Canvas, Color, Command, Element,
+    Length, Point, Rectangle, Settings, Size, Subscription, Vector,
 };
 
 use std::time::Instant;
@@ -48,11 +48,7 @@ impl Application for SolarSystem {
         String::from("Solar system - Iced")
     }
 
-    fn update(
-        &mut self,
-        message: Message,
-        _clipboard: &mut Clipboard,
-    ) -> Command<Message> {
+    fn update(&mut self, message: Message) -> Command<Message> {
         match message {
             Message::Tick(instant) => {
                 self.state.update(instant);
diff --git a/examples/stopwatch/src/main.rs b/examples/stopwatch/src/main.rs
index 51972e01..983cf3e6 100644
--- a/examples/stopwatch/src/main.rs
+++ b/examples/stopwatch/src/main.rs
@@ -1,6 +1,6 @@
 use iced::{
-    button, executor, time, Align, Application, Button, Clipboard, Column,
-    Command, Container, Element, HorizontalAlignment, Length, Row, Settings,
+    button, executor, time, Align, Application, Button, Column, Command,
+    Container, Element, HorizontalAlignment, Length, Row, Settings,
     Subscription, Text,
 };
 use std::time::{Duration, Instant};
@@ -49,11 +49,7 @@ impl Application for Stopwatch {
         String::from("Stopwatch - Iced")
     }
 
-    fn update(
-        &mut self,
-        message: Message,
-        _clipboard: &mut Clipboard,
-    ) -> Command<Message> {
+    fn update(&mut self, message: Message) -> Command<Message> {
         match message {
             Message::Toggle => match self.state {
                 State::Idle => {
diff --git a/examples/todos/src/main.rs b/examples/todos/src/main.rs
index 97415475..7a8ecc1a 100644
--- a/examples/todos/src/main.rs
+++ b/examples/todos/src/main.rs
@@ -1,7 +1,7 @@
 use iced::{
     button, scrollable, text_input, Align, Application, Button, Checkbox,
-    Clipboard, Column, Command, Container, Element, Font, HorizontalAlignment,
-    Length, Row, Scrollable, Settings, Text, TextInput,
+    Column, Command, Container, Element, Font, HorizontalAlignment, Length,
+    Row, Scrollable, Settings, Text, TextInput,
 };
 use serde::{Deserialize, Serialize};
 
@@ -58,11 +58,7 @@ impl Application for Todos {
         format!("Todos{} - Iced", if dirty { "*" } else { "" })
     }
 
-    fn update(
-        &mut self,
-        message: Message,
-        _clipboard: &mut Clipboard,
-    ) -> Command<Message> {
+    fn update(&mut self, message: Message) -> Command<Message> {
         match self {
             Todos::Loading => {
                 match message {
diff --git a/examples/url_handler/src/main.rs b/examples/url_handler/src/main.rs
index f14e5227..ee2d249a 100644
--- a/examples/url_handler/src/main.rs
+++ b/examples/url_handler/src/main.rs
@@ -1,6 +1,6 @@
 use iced::{
-    executor, Application, Clipboard, Command, Container, Element, Length,
-    Settings, Subscription, Text,
+    executor, Application, Command, Container, Element, Length, Settings,
+    Subscription, Text,
 };
 use iced_native::{
     event::{MacOS, PlatformSpecific},
@@ -34,11 +34,7 @@ impl Application for App {
         String::from("Url - Iced")
     }
 
-    fn update(
-        &mut self,
-        message: Message,
-        _clipboard: &mut Clipboard,
-    ) -> Command<Message> {
+    fn update(&mut self, message: Message) -> Command<Message> {
         match message {
             Message::EventOccurred(event) => {
                 if let Event::PlatformSpecific(PlatformSpecific::MacOS(