solitaire_engine/src/safe_area.rs

@@ -84,7 +84,8 @@ impl Plugin for SafeAreaInsetsPlugin {
         #[cfg(target_os = "android")]
         app.init_resource::<android::SafeAreaPollTries>()
             .add_systems(Update, android::refresh_insets)
-            .add_systems(Update, android::rearm_on_resumed);
+            .add_systems(Update, android::rearm_on_resumed)
+            .add_systems(Update, android::refresh_surface_size);
     }
 }
 
@@ -225,6 +226,7 @@ fn on_app_resumed(
 mod android {
     use super::{AppLifecycle, SafeAreaInsets};
     use bevy::prelude::*;
+    use bevy::window::WindowResized;
 
     /// Tracks how many frames `refresh_insets` has polled.  Stored as a
     /// `Resource` (not `Local`) so that `rearm_on_resumed` can reset it to 0
@@ -299,11 +301,108 @@ mod android {
     ) {
         for event in lifecycle.read() {
             if matches!(event, AppLifecycle::WillResume) {
+                // Evidence line for #130: winit's Android backend has open
+                // TODOs around forwarding resume notifications, so whether
+                // this ever fires on a given device is an open question.
+                info!("safe_area: AppLifecycle::WillResume received; re-arming inset poll");
                 poll.0 = 0;
             }
         }
     }
 
+    /// Polls the decor view's size via JNI and forces a relayout when it
+    /// disagrees with Bevy's cached `Window` resolution (#130).
+    ///
+    /// winit's Android backend does not forward content-rect changes that
+    /// happen while the app is backgrounded (fold/unfold on foldables), so
+    /// after a fold cycle Bevy can keep rendering and laying out for the
+    /// previous screen's dimensions. Unlike `refresh_insets` this poller
+    /// never settles: it cannot rely on `AppLifecycle::WillResume` to re-arm
+    /// it, because that event is itself delivered through the same unreliable
+    /// lifecycle plumbing. A JNI round-trip every `POLL_INTERVAL_FRAMES`
+    /// frames is cheap.
+    ///
+    /// On a mismatch it:
+    /// 1. writes the real size into `window.resolution` so the renderer
+    ///    reconfigures the surface and systems reading `window.width()` see
+    ///    the truth,
+    /// 2. emits a synthetic `WindowResized` (logical pixels) so
+    ///    `on_window_resized` in `table_plugin` recomputes the board layout,
+    /// 3. re-arms the inset poller, because a screen change almost always
+    ///    moves the system bars too — covering the "re-poll never fires"
+    ///    hole left open in #116.
+    pub(super) fn refresh_surface_size(
+        mut frame: Local<u32>,
+        mut windows: Query<(Entity, &mut Window)>,
+        mut resize_events: MessageWriter<WindowResized>,
+        mut poll: ResMut<SafeAreaPollTries>,
+    ) {
+        const POLL_INTERVAL_FRAMES: u32 = 30; // ~0.5 s @ 60 fps
+
+        *frame += 1;
+        if !frame.is_multiple_of(POLL_INTERVAL_FRAMES) {
+            return;
+        }
+        let Some((entity, mut window)) = windows.iter_mut().next() else {
+            return;
+        };
+
+        let (decor_w, decor_h) = match query_decor_size() {
+            Ok(size) => size,
+            Err(e) => {
+                // One-time note; the bridge simply isn't up yet during the
+                // first frames of a launch.
+                if *frame == POLL_INTERVAL_FRAMES {
+                    warn!("safe_area: decor size query failed (will retry): {e}");
+                }
+                return;
+            }
+        };
+        if decor_w == 0 || decor_h == 0 {
+            return; // decor view not laid out yet
+        }
+
+        // Reads go through `Deref` and do not trip change detection; only
+        // mutate `window` once a mismatch is confirmed.
+        let cached_w = window.resolution.physical_width();
+        let cached_h = window.resolution.physical_height();
+        if decor_w == cached_w && decor_h == cached_h {
+            return;
+        }
+
+        info!(
+            "safe_area: decor view is {decor_w}x{decor_h} but cached resolution is \
+             {cached_w}x{cached_h}; forcing relayout (fold/unfold missed by winit?)"
+        );
+        window.resolution.set_physical_resolution(decor_w, decor_h);
+        let scale = window.scale_factor();
+        resize_events.write(WindowResized {
+            window: entity,
+            width: decor_w as f32 / scale,
+            height: decor_h as f32 / scale,
+        });
+        poll.0 = 0;
+    }
+
+    /// Physical pixel size of the activity's decor view — the ground truth
+    /// for the surface we are actually being displayed on, independent of
+    /// whatever winit last told Bevy.
+    fn query_decor_size() -> Result<(u32, u32), String> {
+        use solitaire_data::android_jni;
+
+        android_jni::with_activity_env(|env, activity| {
+            let window = env
+                .call_method(activity, "getWindow", "()Landroid/view/Window;", &[])?
+                .l()?;
+            let decor = env
+                .call_method(&window, "getDecorView", "()Landroid/view/View;", &[])?
+                .l()?;
+            let w = env.call_method(&decor, "getWidth", "()I", &[])?.i()?;
+            let h = env.call_method(&decor, "getHeight", "()I", &[])?.i()?;
+            Ok((w.max(0) as u32, h.max(0) as u32))
+        })
+    }
+
     fn query_insets() -> Result<SafeAreaInsets, String> {
         use solitaire_data::android_jni;