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>

app/data/bash-completion/scrcpy

@@ -20,7 +20,6 @@ _scrcpy() {
         --crop=
         -d --select-usb
         --disable-screensaver
-        --display-buffer=
         --display-id=
         --display-orientation=
         -e --select-tcpip
@@ -90,6 +89,7 @@ _scrcpy() {
         --v4l2-sink=
         -v --version
         -V --verbosity=
+        --video-buffer=
         --video-codec=
         --video-codec-options=
         --video-encoder=
@@ -191,7 +191,6 @@ _scrcpy() {
         |--camera-size \
         |--crop \
         |--display-id \
-        |--display-buffer \
         |--max-fps \
         |-m|--max-size \
         |-p|--port \
@@ -201,6 +200,7 @@ _scrcpy() {
         |--tunnel-port \
         |--v4l2-buffer \
         |--v4l2-sink \
+        |--video-buffer \
         |--video-codec-options \
         |--video-encoder \
         |--tcpip \

app/data/zsh-completion/_scrcpy

@@ -27,7 +27,6 @@ arguments=(
     '--crop=[\[width\:height\:x\:y\] Crop the device screen on the server]'
     {-d,--select-usb}'[Use USB device]'
     '--disable-screensaver[Disable screensaver while scrcpy is running]'
-    '--display-buffer=[Add a buffering delay \(in milliseconds\) before displaying]'
     '--display-id=[Specify the display id to mirror]'
     '--display-orientation=[Set the initial display orientation]:orientation values:(0 90 180 270 flip0 flip90 flip180 flip270)'
     {-e,--select-tcpip}'[Use TCP/IP device]'
@@ -92,6 +91,7 @@ arguments=(
     '--v4l2-sink=[\[\/dev\/videoN\] Output to v4l2loopback device]'
     {-v,--version}'[Print the version of scrcpy]'
     {-V,--verbosity=}'[Set the log level]:verbosity:(verbose debug info warn error)'
+    '--video-buffer=[Add a buffering delay \(in milliseconds\) before displaying video frames]'
     '--video-codec=[Select the video codec]:codec:(h264 h265 av1)'
     '--video-codec-options=[Set a list of comma-separated key\:type=value options for the device video encoder]'
     '--video-encoder=[Use a specific MediaCodec video encoder]'

app/scrcpy.1

@@ -139,12 +139,6 @@ Also see \fB\-e\fR (\fB\-\-select\-tcpip\fR).
 .BI "\-\-disable\-screensaver"
 Disable screensaver while scrcpy is running.
 
-.TP
-.BI "\-\-display\-buffer " ms
-Add a buffering delay (in milliseconds) before displaying. This increases latency to compensate for jitter.
-
-Default is 0 (no buffering).
-
 .TP
 .BI "\-\-display\-id " id
 Specify the device display id to mirror.
@@ -560,7 +554,15 @@ It requires to lock the video orientation (see \fB\-\-lock\-video\-orientation\f
 .BI "\-\-v4l2-buffer " ms
 Add a buffering delay (in milliseconds) before pushing frames. This increases latency to compensate for jitter.
 
-This option is similar to \fB\-\-display\-buffer\fR, but specific to V4L2 sink.
+This option is similar to \fB\-\-video\-buffer\fR, but specific to V4L2 sink.
+
+Default is 0 (no buffering).
+
+.TP
+.BI "\-\-video\-buffer " ms
+Add a buffering delay (in milliseconds) before displaying video frames.
+
+This increases latency to compensate for jitter.
 
 Default is 0 (no buffering).
 

app/src/cli.c

@@ -50,6 +50,7 @@ enum {
     OPT_POWER_OFF_ON_CLOSE,
     OPT_V4L2_SINK,
     OPT_DISPLAY_BUFFER,
+    OPT_VIDEO_BUFFER,
     OPT_V4L2_BUFFER,
     OPT_TUNNEL_HOST,
     OPT_TUNNEL_PORT,
@@ -321,12 +322,10 @@ static const struct sc_option options[] = {
         .argdesc = "id",
     },
     {
+        // deprecated
         .longopt_id = OPT_DISPLAY_BUFFER,
         .longopt = "display-buffer",
         .argdesc = "ms",
-        .text = "Add a buffering delay (in milliseconds) before displaying. "
-                "This increases latency to compensate for jitter.\n"
-                "Default is 0 (no buffering).",
     },
     {
         .longopt_id = OPT_DISPLAY_ID,
@@ -898,11 +897,20 @@ static const struct sc_option options[] = {
         .argdesc = "ms",
         .text = "Add a buffering delay (in milliseconds) before pushing "
                 "frames. This increases latency to compensate for jitter.\n"
-                "This option is similar to --display-buffer, but specific to "
+                "This option is similar to --video-buffer, but specific to "
                 "V4L2 sink.\n"
                 "Default is 0 (no buffering).\n"
                 "This option is only available on Linux.",
     },
+    {
+        .longopt_id = OPT_VIDEO_BUFFER,
+        .longopt = "video-buffer",
+        .argdesc = "ms",
+        .text = "Add a buffering delay (in milliseconds) before displaying "
+                "video frames.\n"
+                "This increases latency to compensate for jitter.\n"
+                "Default is 0 (no buffering).",
+    },
     {
         .longopt_id = OPT_VIDEO_CODEC,
         .longopt = "video-codec",
@@ -2549,7 +2557,11 @@ parse_args_with_getopt(struct scrcpy_cli_args *args, int argc, char *argv[],
                 opts->power_off_on_close = true;
                 break;
             case OPT_DISPLAY_BUFFER:
-                if (!parse_buffering_time(optarg, &opts->display_buffer)) {
+                LOGW("--display-buffer is deprecated, use --video-buffer "
+                     "instead.");
+                // fall through
+            case OPT_VIDEO_BUFFER:
+                if (!parse_buffering_time(optarg, &opts->video_buffer)) {
                     return false;
                 }
                 break;

app/src/options.c

@@ -58,7 +58,7 @@ const struct scrcpy_options scrcpy_options_default = {
     .window_width = 0,
     .window_height = 0,
     .display_id = 0,
-    .display_buffer = 0,
+    .video_buffer = 0,
     .audio_buffer = -1, // depends on the audio format,
     .audio_output_buffer = SC_TICK_FROM_MS(5),
     .time_limit = 0,

app/src/options.h

@@ -261,7 +261,7 @@ struct scrcpy_options {
     uint16_t window_width;
     uint16_t window_height;
     uint32_t display_id;
-    sc_tick display_buffer;
+    sc_tick video_buffer;
     sc_tick audio_buffer;
     sc_tick audio_output_buffer;
     sc_tick time_limit;

app/src/scrcpy.c

@@ -53,7 +53,7 @@ struct scrcpy {
     struct sc_decoder video_decoder;
     struct sc_decoder audio_decoder;
     struct sc_recorder recorder;
-    struct sc_delay_buffer display_buffer;
+    struct sc_delay_buffer video_buffer;
 #ifdef HAVE_V4L2
     struct sc_v4l2_sink v4l2_sink;
     struct sc_delay_buffer v4l2_buffer;
@@ -815,11 +815,11 @@ aoa_complete:
 
         if (options->video_playback) {
             struct sc_frame_source *src = &s->video_decoder.frame_source;
-            if (options->display_buffer) {
-                sc_delay_buffer_init(&s->display_buffer,
-                                     options->display_buffer, true);
-                sc_frame_source_add_sink(src, &s->display_buffer.frame_sink);
-                src = &s->display_buffer.frame_source;
+            if (options->video_buffer) {
+                sc_delay_buffer_init(&s->video_buffer,
+                                     options->video_buffer, true);
+                sc_frame_source_add_sink(src, &s->video_buffer.frame_sink);
+                src = &s->video_buffer.frame_source;
             }
 
             sc_frame_source_add_sink(src, &s->screen.frame_sink);

doc/audio.md

@@ -170,7 +170,7 @@ latency (for both [video](video.md#buffering) and audio) might be preferable to
 avoid glitches and smooth the playback:
 
 ```
-scrcpy --display-buffer=200 --audio-buffer=200
+scrcpy --video-buffer=200 --audio-buffer=200
 ```
 
 It is also possible to configure another audio buffer (the audio output buffer),

doc/develop.md

@@ -21,9 +21,9 @@ the client and on the server.
 If video is enabled, then the server sends a raw video stream (H.264 by default)
 of the device screen, with some additional headers for each packet. The client
 decodes the video frames, and displays them as soon as possible, without
-buffering (unless `--display-buffer=delay` is specified) to minimize latency.
-The client is not aware of the device rotation (which is handled by the server),
-it just knows the dimensions of the video frames it receives.
+buffering (unless `--video-buffer=delay` is specified) to minimize latency. The
+client is not aware of the device rotation (which is handled by the server), it
+just knows the dimensions of the video frames it receives.
 
 Similarly, if audio is enabled, then the server sends a raw audio stream (OPUS
 by default) of the device audio output (or the microphone if

doc/video.md

@@ -189,15 +189,15 @@ The configuration is available independently for the display,
 [v4l2 sinks](video.md#video4linux) and [audio](audio.md#buffering) playback.
 
 ```bash
-scrcpy --display-buffer=50   # add 50ms buffering for display
-scrcpy --v4l2-buffer=300     # add 300ms buffering for v4l2 sink
+scrcpy --video-buffer=50     # add 50ms buffering for video playback
 scrcpy --audio-buffer=200    # set 200ms buffering for audio playback
+scrcpy --v4l2-buffer=300     # add 300ms buffering for v4l2 sink
 ```
 
 They can be applied simultaneously:
 
 ```bash
-scrcpy --display-buffer=50 --v4l2-buffer=300
+scrcpy --video-buffer=50 --v4l2-buffer=300
 ```
 
 

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) {
-            rotationWatcher = new IRotationWatcher.Stub() {
-                @Override
-                public void onRotationChanged(int rotation) {
-                    requestReset();
-                }
-            };
-            ServiceManager.getWindowManager().registerRotationWatcher(rotationWatcher, displayId);
+        if (Build.VERSION.SDK_INT == AndroidVersions.API_34_ANDROID_14) {
+            registerDisplayListenerFallbacks();
         }
 
-        if (Build.VERSION.SDK_INT >= AndroidVersions.API_29_ANDROID_10) {
-            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 (ScreenCapture.this.displayId != displayId) {
-                        // Ignore events related to other display ids
-                        return;
-                    }
-
-                    requestReset();
+        handlerThread = new HandlerThread("DisplayListener");
+        handlerThread.start();
+        Handler handler = new Handler(handlerThread.getLooper());
+        displayListenerHandle = ServiceManager.getDisplayManager().registerDisplayListener(displayId -> {
+            if (Ln.isEnabled(Ln.Level.VERBOSE)) {
+                Ln.v("ScreenCapture: onDisplayChanged(" + displayId + ")");
+            }
+            if (Build.VERSION.SDK_INT == AndroidVersions.API_34_ANDROID_14) {
+                if (!displayListenerWorks) {
+                    // On the first display listener event, we know it works, we can unregister the fallbacks
+                    displayListenerWorks = true;
+                    unregisterDisplayListenerFallbacks();
                 }
-            };
-            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) {
-            ServiceManager.getWindowManager().unregisterRotationWatcher(rotationWatcher);
+        if (Build.VERSION.SDK_INT == AndroidVersions.API_34_ANDROID_14) {
+            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/video/SurfaceEncoder.java

@@ -72,6 +72,7 @@ public class SurfaceEncoder implements AsyncProcessor {
             boolean headerWritten = false;
 
             do {
+                capture.consumeReset(); // If a capture reset was requested, it is implicitly fulfilled
                 capture.prepare();
                 Size size = capture.getSize();
                 if (!headerWritten) {

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);
+        }
+    }
 }