Adds doc comment for disabled button

Makes disabled button behavior consistent in web

examples/tour/src/main.rs

@@ -70,13 +70,15 @@ impl Sandbox for Tour {
 
         controls = controls.push(Space::with_width(Length::Fill));
 
-        if steps.can_continue() {
-            controls = controls.push(
-                button(next_button, "Next")
-                    .on_press(Message::NextPressed)
-                    .style(style::Button::Primary),
-            );
-        }
+        let mut button = button(next_button, "Next");
+        button = if steps.can_continue() {
+            button
+                .style(style::Button::Primary)
+                .on_press(Message::NextPressed)
+        } else {
+            button.style(style::Button::Disabled)
+        };
+        controls = controls.push(button);
 
         let content: Element<_> = Column::new()
             .max_width(540)
@@ -790,6 +792,7 @@ mod style {
     pub enum Button {
         Primary,
         Secondary,
+        Disabled,
     }
 
     impl button::StyleSheet for Button {
@@ -797,7 +800,8 @@ mod style {
             button::Style {
                 background: Some(Background::Color(match self {
                     Button::Primary => Color::from_rgb(0.11, 0.42, 0.87),
-                    Button::Secondary => Color::from_rgb(0.5, 0.5, 0.5),
+                    Button::Secondary => Color::from_rgb(0.055, 0.21, 0.435),
+                    Button::Disabled => Color::from_rgb(0.5, 0.5, 0.5),
                 })),
                 border_radius: 12.0,
                 shadow_offset: Vector::new(1.0, 1.0),

native/src/widget/button.rs

@@ -29,6 +29,13 @@ use std::hash::Hash;
 /// let button = Button::new(&mut state, Text::new("Press me!"))
 ///     .on_press(Message::ButtonPressed);
 /// ```
+///
+/// Buttons can be disabled by not having an on_press.
+///
+/// ```
+/// let mut state = button::State::new();
+/// let disabled_button = Button::new(&mut state, Text::new("I'm disabled!"));
+/// ```
 #[allow(missing_debug_implementations)]
 pub struct Button<'a, Message, Renderer: self::Renderer> {
     state: &'a mut State,
@@ -97,6 +104,7 @@ where
     }
 
     /// Sets the message that will be produced when the [`Button`] is pressed.
+    /// If on_press isn't set, button will be disabled.
     pub fn on_press(mut self, msg: Message) -> Self {
         self.on_press = Some(msg);
         self

web/src/widget/button.rs

@@ -20,6 +20,14 @@ use dodrio::bumpalo;
 /// let button = Button::new(&mut state, Text::new("Press me!"))
 ///     .on_press(Message::ButtonPressed);
 /// ```
+///
+/// Buttons can be disabled by not having an on_press.
+///
+/// ```
+/// let mut state = button::State::new();
+/// let disabled_button = Button::new(&mut state, Text::new("I'm disabled!"));
+/// ```
+
 #[allow(missing_debug_implementations)]
 pub struct Button<'a, Message> {
     content: Element<'a, Message>,
@@ -90,6 +98,7 @@ impl<'a, Message> Button<'a, Message> {
     }
 
     /// Sets the message that will be produced when the [`Button`] is pressed.
+    /// If on_press isn't set, button will be disabled.
     pub fn on_press(mut self, msg: Message) -> Self {
         self.on_press = Some(msg);
         self
@@ -153,6 +162,8 @@ where
             node = node.on("click", move |_root, _vdom, _event| {
                 event_bus.publish(on_press.clone());
             });
+        } else {
+            node = node.attr("disabled", "");
         }
 
         node.finish()