Make the device acknowledge device clipboard

If the client provided a sequence number on SET_CLIPBOARD request, make
the device send back an acknowledgement once the clipboard is set.

PR #2814 <https://github.com/Genymobile/scrcpy/pull/2814>

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

@@ -18,6 +18,8 @@ public final class ControlMessage {
     public static final int TYPE_SET_SCREEN_POWER_MODE = 10;
     public static final int TYPE_ROTATE_DEVICE = 11;
 
+    public static final long SEQUENCE_INVALID = 0;
+
     private int type;
     private String text;
     private int metaState; // KeyEvent.META_*

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

@@ -120,7 +120,12 @@ public class Controller {
                 }
                 break;
             case ControlMessage.TYPE_SET_CLIPBOARD:
+                long sequence = msg.getSequence();
                 setClipboard(msg.getText(), msg.getPaste());
+                if (sequence != ControlMessage.SEQUENCE_INVALID) {
+                    // Acknowledgement requested
+                    sender.pushAckClipboard(sequence);
+                }
                 break;
             case ControlMessage.TYPE_SET_SCREEN_POWER_MODE:
                 if (device.supportsInputEvents()) {

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

@@ -5,6 +5,8 @@ public final class DeviceMessage {
     public static final int TYPE_CLIPBOARD = 0;
     public static final int TYPE_ACK_CLIPBOARD = 1;
 
+    public static final long SEQUENCE_INVALID = ControlMessage.SEQUENCE_INVALID;
+
     private int type;
     private String text;
     private long sequence;

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

@@ -8,6 +8,8 @@ public final class DeviceMessageSender {
 
     private String clipboardText;
 
+    private long ack;
+
     public DeviceMessageSender(DesktopConnection connection) {
         this.connection = connection;
     }
@@ -17,18 +19,34 @@ public final class DeviceMessageSender {
         notify();
     }
 
+    public synchronized void pushAckClipboard(long sequence) {
+        ack = sequence;
+        notify();
+    }
+
     public void loop() throws IOException, InterruptedException {
         while (true) {
             String text;
+            long sequence;
             synchronized (this) {
-                while (clipboardText == null) {
+                while (ack == DeviceMessage.SEQUENCE_INVALID && clipboardText == null) {
                     wait();
                 }
                 text = clipboardText;
                 clipboardText = null;
+
+                sequence = ack;
+                ack = DeviceMessage.SEQUENCE_INVALID;
+            }
+
+            if (sequence != DeviceMessage.SEQUENCE_INVALID) {
+                DeviceMessage event = DeviceMessage.createAckClipboard(sequence);
+                connection.sendDeviceMessage(event);
+            }
+            if (text != null) {
+                DeviceMessage event = DeviceMessage.createClipboard(text);
+                connection.sendDeviceMessage(event);
             }
-            DeviceMessage event = DeviceMessage.createClipboard(text);
-            connection.sendDeviceMessage(event);
         }
     }
 }