Fix observer removal and Android scale factor tracking

dpi/src/lib.rs

@@ -134,7 +134,7 @@ pub struct LogicalUnit<P>(pub P);
 impl<P> LogicalUnit<P> {
     /// Represents a maximum logical unit that is equal to [`f64::MAX`].
     pub const MAX: LogicalUnit<f64> = LogicalUnit::new(f64::MAX);
-    /// Represents a minimum logical unit of [`f64::MAX`].
+    /// Represents a minimum logical unit of [`f64::MIN`].
     pub const MIN: LogicalUnit<f64> = LogicalUnit::new(f64::MIN);
     /// Represents a logical unit of `0_f64`.
     pub const ZERO: LogicalUnit<f64> = LogicalUnit::new(0.0);
@@ -228,7 +228,7 @@ pub struct PhysicalUnit<P>(pub P);
 impl<P> PhysicalUnit<P> {
     /// Represents a maximum physical unit that is equal to [`f64::MAX`].
     pub const MAX: LogicalUnit<f64> = LogicalUnit::new(f64::MAX);
-    /// Represents a minimum physical unit of [`f64::MAX`].
+    /// Represents a minimum physical unit of [`f64::MIN`].
     pub const MIN: LogicalUnit<f64> = LogicalUnit::new(f64::MIN);
     /// Represents a physical unit of `0_f64`.
     pub const ZERO: LogicalUnit<f64> = LogicalUnit::new(0.0);
@@ -322,7 +322,7 @@ pub enum PixelUnit {
 impl PixelUnit {
     /// Represents a maximum logical unit that is equal to [`f64::MAX`].
     pub const MAX: PixelUnit = PixelUnit::Logical(LogicalUnit::new(f64::MAX));
-    /// Represents a minimum logical unit of [`f64::MAX`].
+    /// Represents a minimum logical unit of [`f64::MIN`].
     pub const MIN: PixelUnit = PixelUnit::Logical(LogicalUnit::new(f64::MIN));
     /// Represents a logical unit of `0_f64`.
     pub const ZERO: PixelUnit = PixelUnit::Logical(LogicalUnit::new(0.0));

winit-android/src/event_loop.rs

@@ -110,6 +110,7 @@ pub struct EventLoop {
     primary_pointer: Option<FingerId>,
     ignore_volume_keys: bool,
     combining_accent: Option<char>,
+    scale_factor: f64,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
@@ -143,6 +144,7 @@ impl EventLoop {
         let event_loop_proxy = Arc::new(EventLoopProxy::new(android_app.create_waker()));
 
         let redraw_flag = SharedFlag::new();
+        let scale_factor = scale_factor(android_app);
 
         Ok(Self {
             android_app: android_app.clone(),
@@ -161,6 +163,7 @@ impl EventLoop {
             cause: StartCause::Init,
             ignore_volume_keys: attributes.ignore_volume_keys,
             combining_accent: None,
+            scale_factor,
         })
     }
 
@@ -207,9 +210,9 @@ impl EventLoop {
                     app.window_event(&self.window_target, GLOBAL_WINDOW, event);
                 },
                 MainEvent::ConfigChanged { .. } => {
-                    let old_scale_factor = scale_factor(&self.android_app);
                     let scale_factor = scale_factor(&self.android_app);
-                    if (scale_factor - old_scale_factor).abs() < f64::EPSILON {
+                    if (scale_factor - self.scale_factor).abs() > f64::EPSILON {
+                        self.scale_factor = scale_factor;
                         let new_surface_size = Arc::new(Mutex::new(screen_size(&self.android_app)));
                         let event = event::WindowEvent::ScaleFactorChanged {
                             surface_size_writer: SurfaceSizeWriter::new(Arc::downgrade(

winit-common/src/core_foundation/main_run_loop.rs

@@ -131,6 +131,6 @@ impl MainRunLoop {
     /// This is also done automatically when the [`MainRunLoopObserver`] is dropped.
     pub fn remove_observer(&self, observer: &MainRunLoopObserver, mode: &CFRunLoopMode) {
         // Same as in `add_observer`, accessing the main loop's observer is fine.
-        self.main_run_loop.add_observer(Some(&observer.observer), Some(mode));
+        self.main_run_loop.remove_observer(Some(&observer.observer), Some(mode));
     }
 }

winit/src/changelog/unreleased.md

@@ -98,6 +98,8 @@ changelog entry.
 
 ### Fixed
 
+- On Android, only emit `ScaleFactorChanged` when the scale factor actually
+  changes.
 - On Windows, fix a freeze that occurs when the keyboard layout is switched by
   tools such as Punto Switcher. The `WM_INPUTLANGCHANGE` message is now handled
   to refresh the cached keyboard layout, while still deferring to