Add get_scale_factor task to window module

runtime/src/window.rs

@@ -63,6 +63,9 @@ pub enum Action {
     /// Get the current logical coordinates of the window.
     GetPosition(Id, oneshot::Sender<Option<Point>>),
 
+    /// Get the current scale factor (DPI) of the window.
+    GetScaleFactor(Id, oneshot::Sender<f32>),
+
     /// Move the window to the given logical coordinates.
     ///
     /// Unsupported on Wayland.
@@ -292,6 +295,13 @@ pub fn get_position(id: Id) -> Task<Option<Point>> {
     })
 }
 
+/// Gets the scale factor of the window with the given [`Id`].
+pub fn get_scale_factor(id: Id) -> Task<f32> {
+    task::oneshot(move |channel| {
+        crate::Action::Window(Action::GetScaleFactor(id, channel))
+    })
+}
+
 /// Moves the window to the given logical coordinates.
 pub fn move_to<T>(id: Id, position: Point) -> Task<T> {
     task::effect(crate::Action::Window(Action::Move(id, position)))

winit/src/program.rs

@@ -1291,7 +1291,7 @@ fn run_action<P, C>(
                 }
             }
             window::Action::GetPosition(id, channel) => {
-                if let Some(window) = window_manager.get_mut(id) {
+                if let Some(window) = window_manager.get(id) {
                     let position = window
                         .raw
                         .inner_position()
@@ -1306,6 +1306,13 @@ fn run_action<P, C>(
                     let _ = channel.send(position);
                 }
             }
+            window::Action::GetScaleFactor(id, channel) => {
+                if let Some(window) = window_manager.get_mut(id) {
+                    let scale_factor = window.raw.scale_factor();
+
+                    let _ = channel.send(scale_factor as f32);
+                }
+            }
             window::Action::Move(id, position) => {
                 if let Some(window) = window_manager.get_mut(id) {
                     window.raw.set_outer_position(

winit/src/program/window_manager.rs

@@ -80,6 +80,10 @@ where
         self.entries.iter_mut().map(|(k, v)| (*k, v))
     }
 
+    pub fn get(&self, id: Id) -> Option<&Window<P, C>> {
+        self.entries.get(&id)
+    }
+
     pub fn get_mut(&mut self, id: Id) -> Option<&mut Window<P, C>> {
         self.entries.get_mut(&id)
     }