Listen to display changed events

Replace RotationWatcher and DisplayFoldListener by a single
DisplayListener, which is notified whenever the display size or dpi
changes.

However, the DisplayListener mechanism is broken in the first versions
of Android 14 (it is fixed in android-14.0.0_r29 by commit [1]), so
continue to use the old mechanism specifically for Android 14 (where
DisplayListener may be broken), until we receive the first
"display changed" event (which proves that it works).

[1]: <5653c6b587%5E%21/>

Fixes #161 <https://github.com/Genymobile/scrcpy/issues/161>
Fixes #1918 <https://github.com/Genymobile/scrcpy/issues/1918>
Fixes #4152 <https://github.com/Genymobile/scrcpy/issues/4152>
Fixes #5362 comment <https://github.com/Genymobile/scrcpy/issues/5362#issuecomment-2416219316>
Refs #4469 <https://github.com/Genymobile/scrcpy/pull/4469>
PR #5415 <https://github.com/Genymobile/scrcpy/pull/5415>

Co-authored-by: Simon Chan <1330321+yume-chan@users.noreply.github.com>

server/src/main/java/com/genymobile/scrcpy/device/Size.java

@@ -52,6 +52,6 @@ public final class Size {
 
     @Override
     public String toString() {
-        return "Size{" + "width=" + width + ", height=" + height + '}';
+        return "Size{" + width + 'x' + height + '}';
     }
 }

server/src/main/java/com/genymobile/scrcpy/video/ScreenCapture.java

@@ -7,12 +7,15 @@ import com.genymobile.scrcpy.device.DisplayInfo;
 import com.genymobile.scrcpy.device.Size;
 import com.genymobile.scrcpy.util.Ln;
 import com.genymobile.scrcpy.util.LogUtils;
+import com.genymobile.scrcpy.wrappers.DisplayManager;
 import com.genymobile.scrcpy.wrappers.ServiceManager;
 import com.genymobile.scrcpy.wrappers.SurfaceControl;
 
 import android.graphics.Rect;
 import android.hardware.display.VirtualDisplay;
 import android.os.Build;
+import android.os.Handler;
+import android.os.HandlerThread;
 import android.os.IBinder;
 import android.view.IDisplayFoldListener;
 import android.view.IRotationWatcher;
@@ -29,9 +32,19 @@ public class ScreenCapture extends SurfaceCapture {
     private DisplayInfo displayInfo;
     private ScreenInfo screenInfo;
 
+    // Source display size (before resizing/crop) for the current session
+    private Size sessionDisplaySize;
+
     private IBinder display;
     private VirtualDisplay virtualDisplay;
 
+    private DisplayManager.DisplayListenerHandle displayListenerHandle;
+    private HandlerThread handlerThread;
+
+    // On Android 14, the DisplayListener may be broken (it never sends events). This is fixed in recent Android 14 upgrades, but we can't really
+    // detect it directly, so register a RotationWatcher and a DisplayFoldListener as a fallback, until we receive the first event from
+    // DisplayListener (which proves that it works).
+    private boolean displayListenerWorks; // only accessed from the display listener thread
     private IRotationWatcher rotationWatcher;
     private IDisplayFoldListener displayFoldListener;
 
@@ -45,39 +58,57 @@ public class ScreenCapture extends SurfaceCapture {
 
     @Override
     public void init() {
-        if (displayId == 0) {
+        if (Build.VERSION.SDK_INT == AndroidVersions.API_34_ANDROID_14) {
-            rotationWatcher = new IRotationWatcher.Stub() {
+            registerDisplayListenerFallbacks();
-                @Override
-                public void onRotationChanged(int rotation) {
-                    requestReset();
-                }
-            };
-            ServiceManager.getWindowManager().registerRotationWatcher(rotationWatcher, displayId);
         }
 
-        if (Build.VERSION.SDK_INT >= AndroidVersions.API_29_ANDROID_10) {
+        handlerThread = new HandlerThread("DisplayListener");
-            displayFoldListener = new IDisplayFoldListener.Stub() {
+        handlerThread.start();
-
+        Handler handler = new Handler(handlerThread.getLooper());
-                private boolean first = true;
+        displayListenerHandle = ServiceManager.getDisplayManager().registerDisplayListener(displayId -> {
-
+            if (Ln.isEnabled(Ln.Level.VERBOSE)) {
-                @Override
+                Ln.v("ScreenCapture: onDisplayChanged(" + displayId + ")");
-                public void onDisplayFoldChanged(int displayId, boolean folded) {
+            }
-                    if (first) {
+            if (Build.VERSION.SDK_INT == AndroidVersions.API_34_ANDROID_14) {
-                        // An event is posted on registration to signal the initial state. Ignore it to avoid restarting encoding.
+                if (!displayListenerWorks) {
-                        first = false;
+                    // On the first display listener event, we know it works, we can unregister the fallbacks
-                        return;
+                    displayListenerWorks = true;
-                    }
+                    unregisterDisplayListenerFallbacks();
-
-                    if (ScreenCapture.this.displayId != displayId) {
-                        // Ignore events related to other display ids
-                        return;
-                    }
-
-                    requestReset();
                 }
-            };
+            }
-            ServiceManager.getWindowManager().registerDisplayFoldListener(displayFoldListener);
+            if (this.displayId == displayId) {
-        }
+                DisplayInfo di = ServiceManager.getDisplayManager().getDisplayInfo(displayId);
+                if (di == null) {
+                    Ln.w("DisplayInfo for " + displayId + " cannot be retrieved");
+                    // We can't compare with the current size, so reset unconditionally
+                    if (Ln.isEnabled(Ln.Level.VERBOSE)) {
+                        Ln.v("ScreenCapture: requestReset(): " + getSessionDisplaySize() + " -> (unknown)");
+                    }
+                    setSessionDisplaySize(null);
+                    requestReset();
+                } else {
+                    Size size = di.getSize();
+
+                    // The field is hidden on purpose, to read it with synchronization
+                    @SuppressWarnings("checkstyle:HiddenField")
+                    Size sessionDisplaySize = getSessionDisplaySize(); // synchronized
+
+                    // .equals() also works if sessionDisplaySize == null
+                    if (!size.equals(sessionDisplaySize)) {
+                        // Reset only if the size is different
+                        if (Ln.isEnabled(Ln.Level.VERBOSE)) {
+                            Ln.v("ScreenCapture: requestReset(): " + sessionDisplaySize + " -> " + size);
+                        }
+                        // Set the new size immediately, so that a future onDisplayChanged() event called before the asynchronous prepare()
+                        // considers that the current size is the requested size (to avoid a duplicate requestReset())
+                        setSessionDisplaySize(size);
+                        requestReset();
+                    } else if (Ln.isEnabled(Ln.Level.VERBOSE)) {
+                        Ln.v("ScreenCapture: Size not changed (" + size + "): do not requestReset()");
+                    }
+                }
+            }
+        }, handler);
     }
 
     @Override
@@ -92,6 +123,7 @@ public class ScreenCapture extends SurfaceCapture {
             Ln.w("Display doesn't have FLAG_SUPPORTS_PROTECTED_BUFFERS flag, mirroring can be restricted");
         }
 
+        setSessionDisplaySize(displayInfo.getSize());
         screenInfo = ScreenInfo.computeScreenInfo(displayInfo.getRotation(), displayInfo.getSize(), crop, maxSize, lockVideoOrientation);
     }
 
@@ -146,12 +178,19 @@ public class ScreenCapture extends SurfaceCapture {
 
     @Override
     public void release() {
-        if (rotationWatcher != null) {
+        if (Build.VERSION.SDK_INT == AndroidVersions.API_34_ANDROID_14) {
-            ServiceManager.getWindowManager().unregisterRotationWatcher(rotationWatcher);
+            unregisterDisplayListenerFallbacks();
         }
-        if (Build.VERSION.SDK_INT >= AndroidVersions.API_29_ANDROID_10) {
+
-            ServiceManager.getWindowManager().unregisterDisplayFoldListener(displayFoldListener);
+        handlerThread.quitSafely();
+        handlerThread = null;
+
+        // displayListenerHandle may be null if registration failed
+        if (displayListenerHandle != null) {
+            ServiceManager.getDisplayManager().unregisterDisplayListener(displayListenerHandle);
+            displayListenerHandle = null;
         }
+
         if (display != null) {
             SurfaceControl.destroyDisplay(display);
             display = null;
@@ -191,4 +230,67 @@ public class ScreenCapture extends SurfaceCapture {
             SurfaceControl.closeTransaction();
         }
     }
+
+    private synchronized Size getSessionDisplaySize() {
+        return sessionDisplaySize;
+    }
+
+    private synchronized void setSessionDisplaySize(Size sessionDisplaySize) {
+        this.sessionDisplaySize = sessionDisplaySize;
+    }
+
+    private void registerDisplayListenerFallbacks() {
+        if (displayId == 0) {
+            rotationWatcher = new IRotationWatcher.Stub() {
+                @Override
+                public void onRotationChanged(int rotation) {
+                    if (Ln.isEnabled(Ln.Level.VERBOSE)) {
+                        Ln.v("ScreenCapture: onRotationChanged(" + rotation + ")");
+                    }
+                    requestReset();
+                }
+            };
+            ServiceManager.getWindowManager().registerRotationWatcher(rotationWatcher, displayId);
+        }
+
+        // Build.VERSION.SDK_INT >= AndroidVersions.API_29_ANDROID_10 (but implied by == API_34_ANDROID 14)
+        displayFoldListener = new IDisplayFoldListener.Stub() {
+
+            private boolean first = true;
+
+            @Override
+            public void onDisplayFoldChanged(int displayId, boolean folded) {
+                if (first) {
+                    // An event is posted on registration to signal the initial state. Ignore it to avoid restarting encoding.
+                    first = false;
+                    return;
+                }
+
+                if (Ln.isEnabled(Ln.Level.VERBOSE)) {
+                    Ln.v("ScreenCapture: onDisplayFoldChanged(" + displayId + ", " + folded + ")");
+                }
+
+                if (ScreenCapture.this.displayId != displayId) {
+                    // Ignore events related to other display ids
+                    return;
+                }
+                requestReset();
+            }
+        };
+        ServiceManager.getWindowManager().registerDisplayFoldListener(displayFoldListener);
+    }
+
+    private void unregisterDisplayListenerFallbacks() {
+        synchronized (this) {
+            if (rotationWatcher != null) {
+                ServiceManager.getWindowManager().unregisterRotationWatcher(rotationWatcher);
+                rotationWatcher = null;
+            }
+            if (displayFoldListener != null) {
+                // Build.VERSION.SDK_INT >= AndroidVersions.API_29_ANDROID_10 (but implied by == API_34_ANDROID 14)
+                ServiceManager.getWindowManager().unregisterDisplayFoldListener(displayFoldListener);
+                displayFoldListener = null;
+            }
+        }
+    }
 }

server/src/main/java/com/genymobile/scrcpy/wrappers/DisplayManager.java

@@ -11,17 +11,40 @@ import android.annotation.SuppressLint;
 import android.annotation.TargetApi;
 import android.content.Context;
 import android.hardware.display.VirtualDisplay;
+import android.os.Handler;
 import android.view.Display;
 import android.view.Surface;
 
 import java.lang.reflect.Constructor;
 import java.lang.reflect.Field;
 import java.lang.reflect.Method;
+import java.lang.reflect.Proxy;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
 @SuppressLint("PrivateApi,DiscouragedPrivateApi")
 public final class DisplayManager {
+
+    // android.hardware.display.DisplayManager.EVENT_FLAG_DISPLAY_CHANGED
+    public static final long EVENT_FLAG_DISPLAY_CHANGED = 1L << 2;
+
+    public interface DisplayListener {
+        /**
+         * Called whenever the properties of a logical {@link android.view.Display},
+         * such as size and density, have changed.
+         *
+         * @param displayId The id of the logical display that changed.
+         */
+        void onDisplayChanged(int displayId);
+    }
+
+    public static final class DisplayListenerHandle {
+        private final Object displayListenerProxy;
+        private DisplayListenerHandle(Object displayListenerProxy) {
+            this.displayListenerProxy = displayListenerProxy;
+        }
+    }
+
     private final Object manager; // instance of hidden class android.hardware.display.DisplayManagerGlobal
     private Method createVirtualDisplayMethod;
     private Method requestDisplayPowerMethod;
@@ -158,4 +181,50 @@ public final class DisplayManager {
             return false;
         }
     }
+
+    public DisplayListenerHandle registerDisplayListener(DisplayListener listener, Handler handler) {
+        try {
+            Class<?> displayListenerClass = Class.forName("android.hardware.display.DisplayManager$DisplayListener");
+            Object displayListenerProxy = Proxy.newProxyInstance(
+                    ClassLoader.getSystemClassLoader(),
+                    new Class[] {displayListenerClass},
+                    (proxy, method, args) -> {
+                        if ("onDisplayChanged".equals(method.getName())) {
+                            listener.onDisplayChanged((int) args[0]);
+                        }
+                        return null;
+                    });
+            try {
+                manager.getClass()
+                        .getMethod("registerDisplayListener", displayListenerClass, Handler.class, long.class, String.class)
+                        .invoke(manager, displayListenerProxy, handler, EVENT_FLAG_DISPLAY_CHANGED, FakeContext.PACKAGE_NAME);
+            } catch (NoSuchMethodException e) {
+                try {
+                    manager.getClass()
+                            .getMethod("registerDisplayListener", displayListenerClass, Handler.class, long.class)
+                            .invoke(manager, displayListenerProxy, handler, EVENT_FLAG_DISPLAY_CHANGED);
+                } catch (NoSuchMethodException e2) {
+                    manager.getClass()
+                            .getMethod("registerDisplayListener", displayListenerClass, Handler.class)
+                            .invoke(manager, displayListenerProxy, handler);
+                }
+            }
+
+            return new DisplayListenerHandle(displayListenerProxy);
+        } catch (Exception e) {
+            // Rotation and screen size won't be updated, not a fatal error
+            Ln.e("Could not register display listener", e);
+        }
+
+        return null;
+    }
+
+    public void unregisterDisplayListener(DisplayListenerHandle listener) {
+        try {
+            Class<?> displayListenerClass = Class.forName("android.hardware.display.DisplayManager$DisplayListener");
+            manager.getClass().getMethod("unregisterDisplayListener", displayListenerClass).invoke(manager, listener.displayListenerProxy);
+        } catch (Exception e) {
+            Ln.e("Could not unregister display listener", e);
+        }
+    }
 }