Add crop feature

Add an option to crop the screen on the server. This allows to mirror
only part of the device screen.

README.md

@@ -294,6 +294,12 @@ screen is smaller, or cannot decode such a high definition):
 scrcpy -m 1024
 ```
 
+The device screen may be cropped to mirror only part of the screen:
+
+```bash
+scrcpy -c 1224:1440:0:0   # 1224x1440 at offset (0,0)
+```
+
 If several devices are listed in `adb devices`, you must specify the _serial_:
 
 ```bash

app/src/main.c

@@ -10,6 +10,7 @@
 
 struct args {
     const char *serial;
+    const char *crop;
     SDL_bool help;
     SDL_bool version;
     SDL_bool show_touches;
@@ -29,6 +30,12 @@ static void usage(const char *arg0) {
         "        Unit suffixes are supported: 'K' (x1000) and 'M' (x1000000).\n"
         "        Default is %d.\n"
         "\n"
+        "    -c, --crop width:height:x:y\n"
+        "        Crop the device screen on the server.\n"
+        "        The values are expressed in the device natural orientation\n"
+        "        (typically, portrait for a phone, landscape for a tablet).\n"
+        "        Any --max-size value is computed on the cropped size.\n"
+        "\n"
         "    -h, --help\n"
         "        Print this help.\n"
         "\n"
@@ -192,6 +199,7 @@ static SDL_bool parse_port(char *optarg, Uint16 *port) {
 static SDL_bool parse_args(struct args *args, int argc, char *argv[]) {
     static const struct option long_options[] = {
         {"bit-rate",     required_argument, NULL, 'b'},
+        {"crop",         required_argument, NULL, 'c'},
         {"help",         no_argument,       NULL, 'h'},
         {"max-size",     required_argument, NULL, 'm'},
         {"port",         required_argument, NULL, 'p'},
@@ -201,13 +209,16 @@ static SDL_bool parse_args(struct args *args, int argc, char *argv[]) {
         {NULL,           0,                 NULL, 0  },
     };
     int c;
-    while ((c = getopt_long(argc, argv, "b:hm:p:s:tv", long_options, NULL)) != -1) {
+    while ((c = getopt_long(argc, argv, "b:c:hm:p:s:tv", long_options, NULL)) != -1) {
         switch (c) {
             case 'b':
                 if (!parse_bit_rate(optarg, &args->bit_rate)) {
                     return SDL_FALSE;
                 }
                 break;
+            case 'c':
+                args->crop = optarg;
+                break;
             case 'h':
                 args->help = SDL_TRUE;
                 break;
@@ -253,6 +264,7 @@ int main(int argc, char *argv[]) {
 #endif
     struct args args = {
         .serial = NULL,
+        .crop = NULL,
         .help = SDL_FALSE,
         .version = SDL_FALSE,
         .show_touches = SDL_FALSE,
@@ -288,6 +300,7 @@ int main(int argc, char *argv[]) {
 
     struct scrcpy_options options = {
         .serial = args.serial,
+        .crop = args.crop,
         .port = args.port,
         .max_size = args.max_size,
         .bit_rate = args.bit_rate,

app/src/scrcpy.c

@@ -126,7 +126,7 @@ static void wait_show_touches(process_t process) {
 
 SDL_bool scrcpy(const struct scrcpy_options *options) {
     if (!server_start(&server, options->serial, options->port,
-                      options->max_size, options->bit_rate)) {
+                      options->max_size, options->bit_rate, options->crop)) {
         return SDL_FALSE;
     }
 

app/src/scrcpy.h

@@ -5,6 +5,7 @@
 
 struct scrcpy_options {
     const char *serial;
+    const char *crop;
     Uint16 port;
     Uint16 max_size;
     Uint32 bit_rate;

app/src/server.c

@@ -77,7 +77,8 @@ static SDL_bool disable_tunnel(struct server *server) {
 }
 
 static process_t execute_server(const char *serial,
-                                Uint16 max_size, Uint32 bit_rate, SDL_bool tunnel_forward) {
+                                Uint16 max_size, Uint32 bit_rate,
+                                const char *crop, SDL_bool tunnel_forward) {
     char max_size_string[6];
     char bit_rate_string[11];
     sprintf(max_size_string, "%"PRIu16, max_size);
@@ -91,6 +92,7 @@ static process_t execute_server(const char *serial,
         max_size_string,
         bit_rate_string,
         tunnel_forward ? "true" : "false",
+        crop ? crop : "",
     };
     return adb_execute(serial, cmd, sizeof(cmd) / sizeof(cmd[0]));
 }
@@ -147,7 +149,7 @@ void server_init(struct server *server) {
 }
 
 SDL_bool server_start(struct server *server, const char *serial, Uint16 local_port,
-                      Uint16 max_size, Uint32 bit_rate) {
+                      Uint16 max_size, Uint32 bit_rate, const char *crop) {
     server->local_port = local_port;
 
     if (serial) {
@@ -188,7 +190,8 @@ SDL_bool server_start(struct server *server, const char *serial, Uint16 local_po
     }
 
     // server will connect to our server socket
-    server->process = execute_server(serial, max_size, bit_rate, server->tunnel_forward);
+    server->process = execute_server(serial, max_size, bit_rate, crop,
+                                     server->tunnel_forward);
     if (server->process == PROCESS_NONE) {
         if (!server->tunnel_forward) {
             close_socket(&server->server_socket);

app/src/server.h

@@ -31,7 +31,7 @@ void server_init(struct server *server);
 
 // push, enable tunnel et start the server
 SDL_bool server_start(struct server *server, const char *serial, Uint16 local_port,
-                      Uint16 max_size, Uint32 bit_rate);
+                      Uint16 max_size, Uint32 bit_rate, const char *crop);
 
 // block until the communication with the server is established
 socket_t server_connect_to(struct server *server);

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

@@ -3,6 +3,7 @@ package com.genymobile.scrcpy;
 import com.genymobile.scrcpy.wrappers.ServiceManager;
 
 import android.graphics.Point;
+import android.graphics.Rect;
 import android.os.Build;
 import android.os.RemoteException;
 import android.view.IRotationWatcher;
@@ -20,7 +21,7 @@ public final class Device {
     private RotationListener rotationListener;
 
     public Device(Options options) {
-        screenInfo = computeScreenInfo(options.getMaxSize());
+        screenInfo = computeScreenInfo(options.getCrop(), options.getMaxSize());
         registerRotationWatcher(new IRotationWatcher.Stub() {
             @Override
             public void onRotationChanged(int rotation) throws RemoteException {
@@ -40,23 +41,40 @@ public final class Device {
         return screenInfo;
     }
 
-    private ScreenInfo computeScreenInfo(int maxSize) {
+    private ScreenInfo computeScreenInfo(Rect crop, int maxSize) {
         DisplayInfo displayInfo = serviceManager.getDisplayManager().getDisplayInfo();
         boolean rotated = (displayInfo.getRotation() & 1) != 0;
         Size deviceSize = displayInfo.getSize();
-        Size videoSize = computeVideoSize(deviceSize, maxSize);
+        Rect contentRect = new Rect(0, 0, deviceSize.getWidth(), deviceSize.getHeight());
-        return new ScreenInfo(deviceSize, videoSize, rotated);
+        if (crop != null) {
+            if (rotated) {
+                // the crop (provided by the user) is expressed in the natural orientation
+                crop = flipRect(crop);
+            }
+            if (!contentRect.intersect(crop)) {
+                // intersect() changes contentRect so that it is intersected with crop
+                Ln.w("Crop rectangle (" + formatCrop(crop) + ") does not intersect device screen (" + formatCrop(deviceSize.toRect()) + ")");
+                contentRect = new Rect(); // empty
+            }
+        }
+
+        Size videoSize = computeVideoSize(contentRect.width(), contentRect.height(), maxSize);
+        return new ScreenInfo(contentRect, videoSize, rotated);
+    }
+
+    private static String formatCrop(Rect rect) {
+        return rect.width() + ":" + rect.height() + ":" + rect.left + ":" + rect.top;
     }
 
     @SuppressWarnings("checkstyle:MagicNumber")
-    private static Size computeVideoSize(Size inputSize, int maxSize) {
+    private static Size computeVideoSize(int w, int h, int maxSize) {
         // Compute the video size and the padding of the content inside this video.
         // Principle:
         // - scale down the great side of the screen to maxSize (if necessary);
         // - scale down the other side so that the aspect ratio is preserved;
         // - round this value to the nearest multiple of 8 (H.264 only accepts multiples of 8)
-        int w = inputSize.getWidth() & ~7; // in case it's not a multiple of 8
+        w &= ~7; // in case it's not a multiple of 8
-        int h = inputSize.getHeight() & ~7;
+        h &= ~7;
         if (maxSize > 0) {
             if (BuildConfig.DEBUG && maxSize % 8 != 0) {
                 throw new AssertionError("Max size must be a multiple of 8");
@@ -87,10 +105,10 @@ public final class Device {
             // the device may have been rotated since the event was generated, so ignore the event
             return null;
         }
-        Size deviceSize = screenInfo.getDeviceSize();
+        Rect contentRect = screenInfo.getContentRect();
         Point point = position.getPoint();
-        int scaledX = point.x * deviceSize.getWidth() / videoSize.getWidth();
+        int scaledX = contentRect.left + point.x * contentRect.width() / videoSize.getWidth();
-        int scaledY = point.y * deviceSize.getHeight() / videoSize.getHeight();
+        int scaledY = contentRect.top + point.y * contentRect.height() / videoSize.getHeight();
         return new Point(scaledX, scaledY);
     }
 
@@ -113,4 +131,8 @@ public final class Device {
     public synchronized void setRotationListener(RotationListener rotationListener) {
         this.rotationListener = rotationListener;
     }
+
+    static Rect flipRect(Rect crop) {
+        return new Rect(crop.top, crop.left, crop.bottom, crop.right);
+    }
 }

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

@@ -1,9 +1,12 @@
 package com.genymobile.scrcpy;
 
+import android.graphics.Rect;
+
 public class Options {
     private int maxSize;
     private int bitRate;
     private boolean tunnelForward;
+    private Rect crop;
 
     public int getMaxSize() {
         return maxSize;
@@ -28,4 +31,12 @@ public class Options {
     public void setTunnelForward(boolean tunnelForward) {
         this.tunnelForward = tunnelForward;
     }
+
+    public Rect getCrop() {
+        return crop;
+    }
+
+    public void setCrop(Rect crop) {
+        this.crop = crop;
+    }
 }

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

@@ -56,12 +56,12 @@ public class ScreenEncoder implements Device.RotationListener {
             do {
                 MediaCodec codec = createCodec();
                 IBinder display = createDisplay();
-                Rect deviceRect = device.getScreenInfo().getDeviceSize().toRect();
+                Rect contentRect = device.getScreenInfo().getContentRect();
                 Rect videoRect = device.getScreenInfo().getVideoSize().toRect();
                 setSize(format, videoRect.width(), videoRect.height());
                 configure(codec, format);
                 Surface surface = codec.createInputSurface();
-                setDisplaySurface(display, surface, deviceRect, videoRect);
+                setDisplaySurface(display, surface, contentRect, videoRect);
                 codec.start();
                 try {
                     alive = encode(codec, outputStream);

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

@@ -1,18 +1,20 @@
 package com.genymobile.scrcpy;
 
+import android.graphics.Rect;
+
 public final class ScreenInfo {
-    private final Size deviceSize;
+    private final Rect contentRect; // device size, possibly cropped
     private final Size videoSize;
     private final boolean rotated;
 
-    public ScreenInfo(Size deviceSize, Size videoSize, boolean rotated) {
+    public ScreenInfo(Rect contentRect, Size videoSize, boolean rotated) {
-        this.deviceSize = deviceSize;
+        this.contentRect = contentRect;
         this.videoSize = videoSize;
         this.rotated = rotated;
     }
 
-    public Size getDeviceSize() {
+    public Rect getContentRect() {
-        return deviceSize;
+        return contentRect;
     }
 
     public Size getVideoSize() {
@@ -24,6 +26,6 @@ public final class ScreenInfo {
         if (rotated == newRotated) {
             return this;
         }
-        return new ScreenInfo(deviceSize.rotate(), videoSize.rotate(), newRotated);
+        return new ScreenInfo(Device.flipRect(contentRect), videoSize.rotate(), newRotated);
     }
 }

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

@@ -1,5 +1,7 @@
 package com.genymobile.scrcpy;
 
+import android.graphics.Rect;
+
 import java.io.IOException;
 
 public final class Server {
@@ -63,9 +65,31 @@ public final class Server {
         boolean tunnelForward = Boolean.parseBoolean(args[2]);
         options.setTunnelForward(tunnelForward);
 
+        if (args.length < 4) {
+            return options;
+        }
+        Rect crop = parseCrop(args[3]);
+        options.setCrop(crop);
+
         return options;
     }
 
+    private static Rect parseCrop(String crop) {
+        if (crop.isEmpty()) {
+            return null;
+        }
+        // input format: "width:height:x:y"
+        String[] tokens = crop.split(":");
+        if (tokens.length != 4) {
+            throw new IllegalArgumentException("Crop must contains 4 values separated by colons: \"" + crop + "\"");
+        }
+        int width = Integer.parseInt(tokens[0]);
+        int height = Integer.parseInt(tokens[1]);
+        int x = Integer.parseInt(tokens[2]);
+        int y = Integer.parseInt(tokens[3]);
+        return new Rect(x, y, x + width, y + height);
+    }
+
     public static void main(String... args) throws Exception {
         Thread.setDefaultUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {
             @Override