Add display id parameter

Add --display command line parameter to specify a display id.

README.md

@@ -353,6 +353,21 @@ scrcpy --no-control
 scrcpy -n
 ```
 
+#### Display
+
+If several displays are available, it is possible to select the display to
+mirror:
+
+```bash
+scrcpy --display 1
+```
+
+The list of display ids can be retrieved by:
+
+```
+adb shell dumpsys display   # search "mDisplayId=" in the output
+```
+
 #### Turn screen off
 
 It is possible to turn the device screen off while mirroring on start with a

app/scrcpy.1

@@ -33,6 +33,15 @@ The values are expressed in the device natural orientation (typically, portrait
 .B \-\-max\-size
 value is computed on the cropped size.
 
+.TP
+.BI "\-\-display " id
+Specify the display id to mirror.
+
+The list of possible display ids can be listed by "adb shell dumpsys display"
+(search "mDisplayId=" in the output).
+
+Default is 0.
+
 .TP
 .B \-f, \-\-fullscreen
 Start in fullscreen.
@@ -131,13 +140,13 @@ Set a custom window title.
 .BI "\-\-window\-x " value
 Set the initial window horizontal position.
 
-Default is -1 (automatic).\n
+Default is "auto".\n
 
 .TP
 .BI "\-\-window\-y " value
 Set the initial window vertical position.
 
-Default is -1 (automatic).\n
+Default is "auto".\n
 
 .TP
 .BI "\-\-window\-width " value

app/src/cli.c

@@ -1,5 +1,6 @@
 #include "cli.h"
 
+#include <assert.h>
 #include <getopt.h>
 #include <stdint.h>
 #include <unistd.h>
@@ -35,6 +36,15 @@ scrcpy_print_usage(const char *arg0) {
         "        (typically, portrait for a phone, landscape for a tablet).\n"
         "        Any --max-size value is computed on the cropped size.\n"
         "\n"
+        "    --display id\n"
+        "        Specify the display id to mirror.\n"
+        "\n"
+        "        The list of possible display ids can be listed by:\n"
+        "            adb shell dumpsys display\n"
+        "        (search \"mDisplayId=\" in the output)\n"
+        "\n"
+        "        Default is 0.\n"
+        "\n"
         "    -f, --fullscreen\n"
         "        Start in fullscreen.\n"
         "\n"
@@ -116,11 +126,11 @@ scrcpy_print_usage(const char *arg0) {
         "\n"
         "    --window-x value\n"
         "        Set the initial window horizontal position.\n"
-        "        Default is -1 (automatic).\n"
+        "        Default is \"auto\".\n"
         "\n"
         "    --window-y value\n"
         "        Set the initial window vertical position.\n"
-        "        Default is -1 (automatic).\n"
+        "        Default is \"auto\".\n"
         "\n"
         "    --window-width value\n"
         "        Set the initial window width.\n"
@@ -302,8 +312,16 @@ parse_lock_video_orientation(const char *s, int8_t *lock_video_orientation) {
 
 static bool
 parse_window_position(const char *s, int16_t *position) {
+    // special value for "auto"
+    static_assert(WINDOW_POSITION_UNDEFINED == -0x8000, "unexpected value");
+
+    if (!strcmp(s, "auto")) {
+        *position = WINDOW_POSITION_UNDEFINED;
+        return true;
+    }
+
     long value;
-    bool ok = parse_integer_arg(s, &value, false, -1, 0x7FFF,
+    bool ok = parse_integer_arg(s, &value, false, -0x7FFF, 0x7FFF,
                                 "window position");
     if (!ok) {
         return false;
@@ -354,6 +372,18 @@ parse_port_range(const char *s, struct port_range *port_range) {
     return true;
 }
 
+static bool
+parse_display_id(const char *s, uint16_t *display_id) {
+    long value;
+    bool ok = parse_integer_arg(s, &value, false, 0, 0xFFFF, "display id");
+    if (!ok) {
+        return false;
+    }
+
+    *display_id = (uint16_t) value;
+    return true;
+}
+
 static bool
 parse_record_format(const char *optarg, enum recorder_format *format) {
     if (!strcmp(optarg, "mp4")) {
@@ -398,6 +428,7 @@ guess_record_format(const char *filename) {
 #define OPT_WINDOW_BORDERLESS      1011
 #define OPT_MAX_FPS                1012
 #define OPT_LOCK_VIDEO_ORIENTATION 1013
+#define OPT_DISPLAY_ID             1014
 
 bool
 scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
@@ -405,6 +436,7 @@ scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
         {"always-on-top",          no_argument,       NULL, OPT_ALWAYS_ON_TOP},
         {"bit-rate",               required_argument, NULL, 'b'},
         {"crop",                   required_argument, NULL, OPT_CROP},
+        {"display",                required_argument, NULL, OPT_DISPLAY_ID},
         {"fullscreen",             no_argument,       NULL, 'f'},
         {"help",                   no_argument,       NULL, 'h'},
         {"lock-video-orientation", required_argument, NULL,
@@ -453,6 +485,11 @@ scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
             case OPT_CROP:
                 opts->crop = optarg;
                 break;
+            case OPT_DISPLAY_ID:
+                if (!parse_display_id(optarg, &opts->display_id)) {
+                    return false;
+                }
+                break;
             case 'f':
                 opts->fullscreen = true;
                 break;

app/src/scrcpy.c

@@ -286,6 +286,7 @@ scrcpy(const struct scrcpy_options *options) {
         .max_fps = options->max_fps,
         .lock_video_orientation = options->lock_video_orientation,
         .control = options->control,
+        .display_id = options->display_id,
     };
     if (!server_start(&server, options->serial, &params)) {
         return false;

app/src/scrcpy.h

@@ -21,10 +21,11 @@ struct scrcpy_options {
     uint32_t bit_rate;
     uint16_t max_fps;
     int8_t lock_video_orientation;
-    int16_t window_x;
-    int16_t window_y;
+    int16_t window_x; // WINDOW_POSITION_UNDEFINED for "auto"
+    int16_t window_y; // WINDOW_POSITION_UNDEFINED for "auto"
     uint16_t window_width;
     uint16_t window_height;
+    uint16_t display_id;
     bool show_touches;
     bool fullscreen;
     bool always_on_top;
@@ -51,10 +52,11 @@ struct scrcpy_options {
     .bit_rate = DEFAULT_BIT_RATE, \
     .max_fps = 0, \
     .lock_video_orientation = DEFAULT_LOCK_VIDEO_ORIENTATION, \
-    .window_x = -1, \
-    .window_y = -1, \
+    .window_x = WINDOW_POSITION_UNDEFINED, \
+    .window_y = WINDOW_POSITION_UNDEFINED, \
     .window_width = 0, \
     .window_height = 0, \
+    .display_id = 0, \
     .show_touches = false, \
     .fullscreen = false, \
     .always_on_top = false, \

app/src/screen.c

@@ -186,8 +186,10 @@ screen_init_rendering(struct screen *screen, const char *window_title,
         window_flags |= SDL_WINDOW_BORDERLESS;
     }
 
-    int x = window_x != -1 ? window_x : (int) SDL_WINDOWPOS_UNDEFINED;
-    int y = window_y != -1 ? window_y : (int) SDL_WINDOWPOS_UNDEFINED;
+    int x = window_x != WINDOW_POSITION_UNDEFINED
+          ? window_x : (int) SDL_WINDOWPOS_UNDEFINED;
+    int y = window_y != WINDOW_POSITION_UNDEFINED
+          ? window_y : (int) SDL_WINDOWPOS_UNDEFINED;
     screen->window = SDL_CreateWindow(window_title, x, y,
                                       window_size.width, window_size.height,
                                       window_flags);

app/src/screen.h

@@ -8,6 +8,8 @@
 #include "config.h"
 #include "common.h"
 
+#define WINDOW_POSITION_UNDEFINED (-0x8000)
+
 struct video_buffer;
 
 struct screen {
@@ -53,6 +55,7 @@ void
 screen_init(struct screen *screen);
 
 // initialize screen, create window, renderer and texture (window is hidden)
+// window_x and window_y accept WINDOW_POSITION_UNDEFINED
 bool
 screen_init_rendering(struct screen *screen, const char *window_title,
                       struct size frame_size, bool always_on_top,

app/src/server.c

@@ -234,10 +234,12 @@ execute_server(struct server *server, const struct server_params *params) {
     char bit_rate_string[11];
     char max_fps_string[6];
     char lock_video_orientation_string[3];
+    char display_id_string[6];
     sprintf(max_size_string, "%"PRIu16, params->max_size);
     sprintf(bit_rate_string, "%"PRIu32, params->bit_rate);
     sprintf(max_fps_string, "%"PRIu16, params->max_fps);
     sprintf(lock_video_orientation_string, "%"PRIi8, params->lock_video_orientation);
+    sprintf(display_id_string, "%"PRIu16, params->display_id);
     const char *const cmd[] = {
         "shell",
         "CLASSPATH=" DEVICE_SERVER_PATH,
@@ -264,6 +266,7 @@ execute_server(struct server *server, const struct server_params *params) {
         params->crop ? params->crop : "-",
         "true", // always send frame meta (packet boundaries + timestamp)
         params->control ? "true" : "false",
+        display_id_string,
     };
 #ifdef SERVER_DEBUGGER
     LOGI("Server debugger waiting for a client on device port "

app/src/server.h

@@ -44,6 +44,7 @@ struct server_params {
     uint16_t max_fps;
     int8_t lock_video_orientation;
     bool control;
+    uint16_t display_id;
 };
 
 // init default values

config/checkstyle/checkstyle.xml

@@ -129,11 +129,6 @@ page at http://checkstyle.sourceforge.net/config.html -->
     </module>
     <module name="IllegalInstantiation" />
     <module name="InnerAssignment" />
-    <module name="MagicNumber">
-      <property name="severity" value="info" />
-      <property name="ignoreHashCodeMethod" value="true" />
-      <property name="ignoreAnnotation" value="true" />
-    </module>
     <module name="MissingSwitchDefault" />
     <module name="SimplifyBooleanExpression" />
     <module name="SimplifyBooleanReturn" />

server/src/main/java/com/genymobile/scrcpy/ControlMessageReader.java

@@ -8,11 +8,10 @@ import java.nio.charset.StandardCharsets;
 
 public class ControlMessageReader {
 
-    private static final int INJECT_KEYCODE_PAYLOAD_LENGTH = 9;
-    private static final int INJECT_MOUSE_EVENT_PAYLOAD_LENGTH = 17;
-    private static final int INJECT_TOUCH_EVENT_PAYLOAD_LENGTH = 21;
-    private static final int INJECT_SCROLL_EVENT_PAYLOAD_LENGTH = 20;
-    private static final int SET_SCREEN_POWER_MODE_PAYLOAD_LENGTH = 1;
+    static final int INJECT_KEYCODE_PAYLOAD_LENGTH = 9;
+    static final int INJECT_TOUCH_EVENT_PAYLOAD_LENGTH = 27;
+    static final int INJECT_SCROLL_EVENT_PAYLOAD_LENGTH = 20;
+    static final int SET_SCREEN_POWER_MODE_PAYLOAD_LENGTH = 1;
 
     public static final int TEXT_MAX_LENGTH = 300;
     public static final int CLIPBOARD_TEXT_MAX_LENGTH = 4093;
@@ -122,7 +121,6 @@ public class ControlMessageReader {
         return ControlMessage.createInjectText(text);
     }
 
-    @SuppressWarnings("checkstyle:MagicNumber")
     private ControlMessage parseInjectTouchEvent() {
         if (buffer.remaining() < INJECT_TOUCH_EVENT_PAYLOAD_LENGTH) {
             return null;
@@ -172,12 +170,10 @@ public class ControlMessageReader {
         return new Position(x, y, screenWidth, screenHeight);
     }
 
-    @SuppressWarnings("checkstyle:MagicNumber")
     private static int toUnsigned(short value) {
         return value & 0xffff;
     }
 
-    @SuppressWarnings("checkstyle:MagicNumber")
     private static int toUnsigned(byte value) {
         return value & 0xff;
     }

server/src/main/java/com/genymobile/scrcpy/Controller.java

@@ -47,7 +47,6 @@ public class Controller {
         }
     }
 
-    @SuppressWarnings("checkstyle:MagicNumber")
     public void control() throws IOException {
         // on start, power on the device
         if (!device.isScreenOn()) {
@@ -76,19 +75,29 @@ public class Controller {
         ControlMessage msg = connection.receiveControlMessage();
         switch (msg.getType()) {
             case ControlMessage.TYPE_INJECT_KEYCODE:
-                injectKeycode(msg.getAction(), msg.getKeycode(), msg.getMetaState());
+                if (device.supportsInputEvents()) {
+                    injectKeycode(msg.getAction(), msg.getKeycode(), msg.getMetaState());
+                }
                 break;
             case ControlMessage.TYPE_INJECT_TEXT:
-                injectText(msg.getText());
+                if (device.supportsInputEvents()) {
+                    injectText(msg.getText());
+                }
                 break;
             case ControlMessage.TYPE_INJECT_TOUCH_EVENT:
-                injectTouch(msg.getAction(), msg.getPointerId(), msg.getPosition(), msg.getPressure(), msg.getButtons());
+                if (device.supportsInputEvents()) {
+                    injectTouch(msg.getAction(), msg.getPointerId(), msg.getPosition(), msg.getPressure(), msg.getButtons());
+                }
                 break;
             case ControlMessage.TYPE_INJECT_SCROLL_EVENT:
-                injectScroll(msg.getPosition(), msg.getHScroll(), msg.getVScroll());
+                if (device.supportsInputEvents()) {
+                    injectScroll(msg.getPosition(), msg.getHScroll(), msg.getVScroll());
+                }
                 break;
             case ControlMessage.TYPE_BACK_OR_SCREEN_ON:
-                pressBackOrTurnScreenOn();
+                if (device.supportsInputEvents()) {
+                    pressBackOrTurnScreenOn();
+                }
                 break;
             case ControlMessage.TYPE_EXPAND_NOTIFICATION_PANEL:
                 device.expandNotificationPanel();
@@ -104,7 +113,9 @@ public class Controller {
                 device.setClipboardText(msg.getText());
                 break;
             case ControlMessage.TYPE_SET_SCREEN_POWER_MODE:
-                device.setScreenPowerMode(msg.getAction());
+                if (device.supportsInputEvents()) {
+                    device.setScreenPowerMode(msg.getAction());
+                }
                 break;
             case ControlMessage.TYPE_ROTATE_DEVICE:
                 device.rotateDevice();

server/src/main/java/com/genymobile/scrcpy/DesktopConnection.java

@@ -84,7 +84,6 @@ public final class DesktopConnection implements Closeable {
         controlSocket.close();
     }
 
-    @SuppressWarnings("checkstyle:MagicNumber")
     private void send(String deviceName, int width, int height) throws IOException {
         byte[] buffer = new byte[DEVICE_NAME_FIELD_LENGTH + 4];
 

server/src/main/java/com/genymobile/scrcpy/Device.java

@@ -1,5 +1,6 @@
 package com.genymobile.scrcpy;
 
+import com.genymobile.scrcpy.wrappers.InputManager;
 import com.genymobile.scrcpy.wrappers.ServiceManager;
 import com.genymobile.scrcpy.wrappers.SurfaceControl;
 import com.genymobile.scrcpy.wrappers.WindowManager;
@@ -25,9 +26,35 @@ public final class Device {
     private ScreenInfo screenInfo;
     private RotationListener rotationListener;
 
+    /**
+     * Logical display identifier
+     */
+    private final int displayId;
+
+    /**
+     * The surface flinger layer stack associated with this logical display
+     */
+    private final int layerStack;
+
+    /**
+     * The FLAG_PRESENTATION from the DisplayInfo
+     */
+    private final boolean isPresentationDisplay;
+
     public Device(Options options) {
-        DisplayInfo displayInfo = serviceManager.getDisplayManager().getDisplayInfo();
+        displayId = options.getDisplayId();
+        DisplayInfo displayInfo = serviceManager.getDisplayManager().getDisplayInfo(displayId);
+        if (displayInfo == null) {
+            int[] displayIds = serviceManager.getDisplayManager().getDisplayIds();
+            throw new InvalidDisplayIdException(displayId, displayIds);
+        }
+
+        int displayInfoFlags = displayInfo.getFlags();
+
         screenInfo = ScreenInfo.computeScreenInfo(displayInfo, options.getCrop(), options.getMaxSize(), options.getLockedVideoOrientation());
+        layerStack = displayInfo.getLayerStack();
+        isPresentationDisplay = (displayInfoFlags & DisplayInfo.FLAG_PRESENTATION) != 0;
+
         registerRotationWatcher(new IRotationWatcher.Stub() {
             @Override
             public void onRotationChanged(int rotation) throws RemoteException {
@@ -41,12 +68,24 @@ public final class Device {
                 }
             }
         });
+
+        if ((displayInfoFlags & DisplayInfo.FLAG_SUPPORTS_PROTECTED_BUFFERS) == 0) {
+            Ln.w("Display doesn't have FLAG_SUPPORTS_PROTECTED_BUFFERS flag, mirroring can be restricted");
+        }
+
+        if (!supportsInputEvents()) {
+            Ln.w("Input events are not supported for displays with FLAG_PRESENTATION enabled for devices with API lower than 29");
+        }
     }
 
     public synchronized ScreenInfo getScreenInfo() {
         return screenInfo;
     }
 
+    public int getLayerStack() {
+        return layerStack;
+    }
+
     public Point getPhysicalPoint(Position position) {
         // it hides the field on purpose, to read it with a lock
         @SuppressWarnings("checkstyle:HiddenField")
@@ -76,7 +115,22 @@ public final class Device {
         return Build.MODEL;
     }
 
+    public boolean supportsInputEvents() {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
+            return true;
+        }
+        return !isPresentationDisplay;
+    }
+
     public boolean injectInputEvent(InputEvent inputEvent, int mode) {
+        if (!supportsInputEvents()) {
+            throw new AssertionError("Could not inject input event if !supportsInputEvents()");
+        }
+
+        if (displayId != 0 && !InputManager.setDisplayId(inputEvent, displayId)) {
+            return false;
+        }
+
         return serviceManager.getInputManager().injectInputEvent(inputEvent, mode);
     }
 

server/src/main/java/com/genymobile/scrcpy/DeviceMessageWriter.java

@@ -13,7 +13,6 @@ public class DeviceMessageWriter {
     private final byte[] rawBuffer = new byte[MAX_EVENT_SIZE];
     private final ByteBuffer buffer = ByteBuffer.wrap(rawBuffer);
 
-    @SuppressWarnings("checkstyle:MagicNumber")
     public void writeTo(DeviceMessage msg, OutputStream output) throws IOException {
         buffer.clear();
         buffer.put((byte) DeviceMessage.TYPE_CLIPBOARD);

server/src/main/java/com/genymobile/scrcpy/DisplayInfo.java

@@ -1,12 +1,25 @@
 package com.genymobile.scrcpy;
 
 public final class DisplayInfo {
+    private final int displayId;
     private final Size size;
     private final int rotation;
+    private final int layerStack;
+    private final int flags;
 
-    public DisplayInfo(Size size, int rotation) {
+    public static final int FLAG_SUPPORTS_PROTECTED_BUFFERS = 0x00000001;
+    public static final int FLAG_PRESENTATION = 0x00000008;
+
+    public DisplayInfo(int displayId, Size size, int rotation, int layerStack, int flags) {
+        this.displayId = displayId;
         this.size = size;
         this.rotation = rotation;
+        this.layerStack = layerStack;
+        this.flags = flags;
+    }
+
+    public int getDisplayId() {
+        return displayId;
     }
 
     public Size getSize() {
@@ -16,5 +29,13 @@ public final class DisplayInfo {
     public int getRotation() {
         return rotation;
     }
+
+    public int getLayerStack() {
+        return layerStack;
+    }
+
+    public int getFlags() {
+        return flags;
+    }
 }
 

server/src/main/java/com/genymobile/scrcpy/InvalidDisplayIdException.java

@@ -0,0 +1,21 @@
+package com.genymobile.scrcpy;
+
+public class InvalidDisplayIdException extends RuntimeException {
+
+    private final int displayId;
+    private final int[] availableDisplayIds;
+
+    public InvalidDisplayIdException(int displayId, int[] availableDisplayIds) {
+        super("There is no display having id " + displayId);
+        this.displayId = displayId;
+        this.availableDisplayIds = availableDisplayIds;
+    }
+
+    public int getDisplayId() {
+        return displayId;
+    }
+
+    public int[] getAvailableDisplayIds() {
+        return availableDisplayIds;
+    }
+}

server/src/main/java/com/genymobile/scrcpy/Options.java

@@ -11,6 +11,7 @@ public class Options {
     private Rect crop;
     private boolean sendFrameMeta; // send PTS so that the client may record properly
     private boolean control;
+    private int displayId;
 
     public int getMaxSize() {
         return maxSize;
@@ -75,4 +76,12 @@ public class Options {
     public void setControl(boolean control) {
         this.control = control;
     }
+
+    public int getDisplayId() {
+        return displayId;
+    }
+
+    public void setDisplayId(int displayId) {
+        this.displayId = displayId;
+    }
 }

server/src/main/java/com/genymobile/scrcpy/ScreenEncoder.java

@@ -71,10 +71,12 @@ public class ScreenEncoder implements Device.RotationListener {
                 // does not include the locked video orientation
                 Rect unlockedVideoRect = screenInfo.getUnlockedVideoSize().toRect();
                 int videoRotation = screenInfo.getVideoRotation();
+                int layerStack = device.getLayerStack();
+
                 setSize(format, videoRect.width(), videoRect.height());
                 configure(codec, format);
                 Surface surface = codec.createInputSurface();
-                setDisplaySurface(display, surface, videoRotation, contentRect, unlockedVideoRect);
+                setDisplaySurface(display, surface, videoRotation, contentRect, unlockedVideoRect, layerStack);
                 codec.start();
                 try {
                     alive = encode(codec, fd);
@@ -145,7 +147,6 @@ public class ScreenEncoder implements Device.RotationListener {
         return MediaCodec.createEncoderByType("video/avc");
     }
 
-    @SuppressWarnings("checkstyle:MagicNumber")
     private static MediaFormat createFormat(int bitRate, int maxFps, int iFrameInterval) {
         MediaFormat format = new MediaFormat();
         format.setString(MediaFormat.KEY_MIME, "video/avc");
@@ -178,12 +179,12 @@ public class ScreenEncoder implements Device.RotationListener {
         format.setInteger(MediaFormat.KEY_HEIGHT, height);
     }
 
-    private static void setDisplaySurface(IBinder display, Surface surface, int orientation, Rect deviceRect, Rect displayRect) {
+    private static void setDisplaySurface(IBinder display, Surface surface, int orientation, Rect deviceRect, Rect displayRect, int layerStack) {
         SurfaceControl.openTransaction();
         try {
             SurfaceControl.setDisplaySurface(display, surface);
             SurfaceControl.setDisplayProjection(display, orientation, deviceRect, displayRect);
-            SurfaceControl.setDisplayLayerStack(display, 0);
+            SurfaceControl.setDisplayLayerStack(display, layerStack);
         } finally {
             SurfaceControl.closeTransaction();
         }

server/src/main/java/com/genymobile/scrcpy/ScreenInfo.java

@@ -104,7 +104,6 @@ public final class ScreenInfo {
         return rect.width() + ":" + rect.height() + ":" + rect.left + ":" + rect.top;
     }
 
-    @SuppressWarnings("checkstyle:MagicNumber")
     private static Size computeVideoSize(int w, int h, int maxSize) {
         // Compute the video size and the padding of the content inside this video.
         // Principle:

server/src/main/java/com/genymobile/scrcpy/Server.java

@@ -16,6 +16,7 @@ public final class Server {
     }
 
     private static void scrcpy(Options options) throws IOException {
+        Ln.i("Device: " + Build.MANUFACTURER + " " + Build.MODEL + " (Android " + Build.VERSION.RELEASE + ")");
         final Device device = new Device(options);
         boolean tunnelForward = options.isTunnelForward();
         try (DesktopConnection connection = DesktopConnection.open(device, tunnelForward)) {
@@ -68,7 +69,6 @@ public final class Server {
         }).start();
     }
 
-    @SuppressWarnings("checkstyle:MagicNumber")
     private static Options createOptions(String... args) {
         if (args.length < 1) {
             throw new IllegalArgumentException("Missing client version");
@@ -80,8 +80,8 @@ public final class Server {
                     "The server version (" + BuildConfig.VERSION_NAME + ") does not match the client " + "(" + clientVersion + ")");
         }
 
-        if (args.length != 9) {
-            throw new IllegalArgumentException("Expecting 9 parameters");
+        if (args.length != 10) {
+            throw new IllegalArgumentException("Expecting 10 parameters");
         }
 
         Options options = new Options();
@@ -111,10 +111,12 @@ public final class Server {
         boolean control = Boolean.parseBoolean(args[8]);
         options.setControl(control);
 
+        int displayId = Integer.parseInt(args[9]);
+        options.setDisplayId(displayId);
+
         return options;
     }
 
-    @SuppressWarnings("checkstyle:MagicNumber")
     private static Rect parseCrop(String crop) {
         if ("-".equals(crop)) {
             return null;
@@ -139,7 +141,6 @@ public final class Server {
         }
     }
 
-    @SuppressWarnings("checkstyle:MagicNumber")
     private static void suggestFix(Throwable e) {
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
             if (e instanceof MediaCodec.CodecException) {
@@ -151,6 +152,16 @@ public final class Server {
                 }
             }
         }
+        if (e instanceof InvalidDisplayIdException) {
+            InvalidDisplayIdException idie = (InvalidDisplayIdException) e;
+            int[] displayIds = idie.getAvailableDisplayIds();
+            if (displayIds != null && displayIds.length > 0) {
+                Ln.e("Try to use one of the available display ids:");
+                for (int id : displayIds) {
+                    Ln.e("    scrcpy --display " + id);
+                }
+            }
+        }
     }
 
     public static void main(String... args) throws Exception {

server/src/main/java/com/genymobile/scrcpy/StringUtils.java

@@ -5,7 +5,6 @@ public final class StringUtils {
         // not instantiable
     }
 
-    @SuppressWarnings("checkstyle:MagicNumber")
     public static int getUtf8TruncationIndex(byte[] utf8, int maxLength) {
         int len = utf8.length;
         if (len <= maxLength) {

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

@@ -12,15 +12,28 @@ public final class DisplayManager {
         this.manager = manager;
     }
 
-    public DisplayInfo getDisplayInfo() {
+    public DisplayInfo getDisplayInfo(int displayId) {
         try {
-            Object displayInfo = manager.getClass().getMethod("getDisplayInfo", int.class).invoke(manager, 0);
+            Object displayInfo = manager.getClass().getMethod("getDisplayInfo", int.class).invoke(manager, displayId);
+            if (displayInfo == null) {
+                return null;
+            }
             Class<?> cls = displayInfo.getClass();
             // width and height already take the rotation into account
             int width = cls.getDeclaredField("logicalWidth").getInt(displayInfo);
             int height = cls.getDeclaredField("logicalHeight").getInt(displayInfo);
             int rotation = cls.getDeclaredField("rotation").getInt(displayInfo);
-            return new DisplayInfo(new Size(width, height), rotation);
+            int layerStack = cls.getDeclaredField("layerStack").getInt(displayInfo);
+            int flags = cls.getDeclaredField("flags").getInt(displayInfo);
+            return new DisplayInfo(displayId, new Size(width, height), rotation, layerStack, flags);
+        } catch (Exception e) {
+            throw new AssertionError(e);
+        }
+    }
+
+    public int[] getDisplayIds() {
+        try {
+            return (int[]) manager.getClass().getMethod("getDisplayIds").invoke(manager);
         } catch (Exception e) {
             throw new AssertionError(e);
         }

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

@@ -17,6 +17,8 @@ public final class InputManager {
     private final IInterface manager;
     private Method injectInputEventMethod;
 
+    private static Method setDisplayIdMethod;
+
     public InputManager(IInterface manager) {
         this.manager = manager;
     }
@@ -37,4 +39,23 @@ public final class InputManager {
             return false;
         }
     }
+
+    private static Method getSetDisplayIdMethod() throws NoSuchMethodException {
+        if (setDisplayIdMethod == null) {
+            setDisplayIdMethod = InputEvent.class.getMethod("setDisplayId", int.class);
+        }
+        return setDisplayIdMethod;
+    }
+
+    public static boolean setDisplayId(InputEvent inputEvent, int displayId) {
+        try {
+            Method method = getSetDisplayIdMethod();
+            method.invoke(inputEvent, displayId);
+            return true;
+        } catch (InvocationTargetException | IllegalAccessException | NoSuchMethodException e) {
+            // just a warning, it might happen on old devices
+            Ln.w("Cannot associate a display id to the input event");
+            return false;
+        }
+    }
 }

server/src/test/java/com/genymobile/scrcpy/ControlMessageReaderTest.java

@@ -28,6 +28,9 @@ public class ControlMessageReaderTest {
         dos.writeInt(KeyEvent.META_CTRL_ON);
         byte[] packet = bos.toByteArray();
 
+        // The message type (1 byte) does not count
+        Assert.assertEquals(ControlMessageReader.INJECT_KEYCODE_PAYLOAD_LENGTH, packet.length - 1);
+
         reader.readFrom(new ByteArrayInputStream(packet));
         ControlMessage event = reader.next();
 
@@ -77,7 +80,6 @@ public class ControlMessageReaderTest {
     }
 
     @Test
-    @SuppressWarnings("checkstyle:MagicNumber")
     public void testParseTouchEvent() throws IOException {
         ControlMessageReader reader = new ControlMessageReader();
 
@@ -95,6 +97,9 @@ public class ControlMessageReaderTest {
 
         byte[] packet = bos.toByteArray();
 
+        // The message type (1 byte) does not count
+        Assert.assertEquals(ControlMessageReader.INJECT_TOUCH_EVENT_PAYLOAD_LENGTH, packet.length - 1);
+
         reader.readFrom(new ByteArrayInputStream(packet));
         ControlMessage event = reader.next();
 
@@ -110,7 +115,6 @@ public class ControlMessageReaderTest {
     }
 
     @Test
-    @SuppressWarnings("checkstyle:MagicNumber")
     public void testParseScrollEvent() throws IOException {
         ControlMessageReader reader = new ControlMessageReader();
 
@@ -126,6 +130,9 @@ public class ControlMessageReaderTest {
 
         byte[] packet = bos.toByteArray();
 
+        // The message type (1 byte) does not count
+        Assert.assertEquals(ControlMessageReader.INJECT_SCROLL_EVENT_PAYLOAD_LENGTH, packet.length - 1);
+
         reader.readFrom(new ByteArrayInputStream(packet));
         ControlMessage event = reader.next();
 
@@ -233,6 +240,9 @@ public class ControlMessageReaderTest {
 
         byte[] packet = bos.toByteArray();
 
+        // The message type (1 byte) does not count
+        Assert.assertEquals(ControlMessageReader.SET_SCREEN_POWER_MODE_PAYLOAD_LENGTH, packet.length - 1);
+
         reader.readFrom(new ByteArrayInputStream(packet));
         ControlMessage event = reader.next();
 

server/src/test/java/com/genymobile/scrcpy/StringUtilsTest.java

@@ -8,7 +8,6 @@ import java.nio.charset.StandardCharsets;
 public class StringUtilsTest {
 
     @Test
-    @SuppressWarnings("checkstyle:MagicNumber")
     public void testUtf8Truncate() {
         String s = "aÉbÔc";
         byte[] utf8 = s.getBytes(StandardCharsets.UTF_8);