feat: Add window drag support from winit

Exposes access to the winit window's window_drag method as an action.

native/src/window/action.rs

@@ -5,6 +5,12 @@ use std::fmt;
 
 /// An operation to be performed on some window.
 pub enum Action<T> {
+    /// Moves the window with the left mouse button until the button is
+    /// released.
+    ///
+    /// There’s no guarantee that this will work unless the left mouse
+    /// button was pressed immediately before this function is called.
+    Drag,
     /// Resize the window.
     Resize {
         /// The new logical width of the window
@@ -37,6 +43,7 @@ impl<T> Action<T> {
         T: 'static,
     {
         match self {
+            Self::Drag => Action::Drag,
             Self::Resize { width, height } => Action::Resize { width, height },
             Self::Move { x, y } => Action::Move { x, y },
             Self::SetMode(mode) => Action::SetMode(mode),
@@ -48,6 +55,7 @@ impl<T> Action<T> {
 impl<T> fmt::Debug for Action<T> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
+            Self::Drag => write!(f, "Action::Drag"),
             Self::Resize { width, height } => write!(
                 f,
                 "Action::Resize {{ widget: {}, height: {} }}",

winit/src/application.rs

@@ -615,6 +615,9 @@ pub fn run_command<A, E>(
                 }
             },
             command::Action::Window(action) => match action {
+                window::Action::Drag => {
+                    let _res = window.drag_window();
+                }
                 window::Action::Resize { width, height } => {
                     window.set_inner_size(winit::dpi::LogicalSize {
                         width,

winit/src/window.rs

@@ -4,6 +4,11 @@ use iced_native::window;
 
 pub use window::{Event, Mode};
 
+/// Begins dragging the window while the left mouse button is held.
+pub fn drag<Message>() -> Command<Message> {
+    Command::single(command::Action::Window(window::Action::Drag))
+}
+
 /// Resizes the window to the given logical dimensions.
 pub fn resize<Message>(width: u32, height: u32) -> Command<Message> {
     Command::single(command::Action::Window(window::Action::Resize {