Handle down/up actions for BACK or POWER ON

Pressing right-click generates either BACK or POWER ON, depending on the
current screen state.

Forward DOWN and UP events separately to the device, to generate key
events accordingly.

Ref #1062 <https://github.com/Genymobile/scrcpy/issues/1062>

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

@@ -85,6 +85,13 @@ public final class ControlMessage {
         return msg;
     }
 
+    public static ControlMessage createBackOrScreenOn(int action) {
+        ControlMessage msg = new ControlMessage();
+        msg.type = TYPE_BACK_OR_SCREEN_ON;
+        msg.action = action;
+        return msg;
+    }
+
     public static ControlMessage createEmpty(int type) {
         ControlMessage msg = new ControlMessage();
         msg.type = type;

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

@@ -13,6 +13,7 @@ public class ControlMessageReader {
     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;
+    private static final int BACK_OR_SCREEN_ON_PAYLOAD_LENGTH = 1;
 
     public static final int TEXT_MAX_LENGTH = 300;
     public static final int CLIPBOARD_TEXT_MAX_LENGTH = 4093;
@@ -73,6 +74,8 @@ public class ControlMessageReader {
                 msg = parseSetScreenPowerMode();
                 break;
             case ControlMessage.TYPE_BACK_OR_SCREEN_ON:
+                msg = parseBackOrScreenOn();
+                break;
             case ControlMessage.TYPE_EXPAND_NOTIFICATION_PANEL:
             case ControlMessage.TYPE_COLLAPSE_NOTIFICATION_PANEL:
             case ControlMessage.TYPE_GET_CLIPBOARD:
@@ -164,6 +167,14 @@ public class ControlMessageReader {
         return ControlMessage.createSetScreenPowerMode(mode);
     }
 
+    private ControlMessage parseBackOrScreenOn() {
+        if (buffer.remaining() < BACK_OR_SCREEN_ON_PAYLOAD_LENGTH) {
+            return null;
+        }
+        int action = toUnsigned(buffer.get());
+        return ControlMessage.createBackOrScreenOn(action);
+    }
+
     private static Position readPosition(ByteBuffer buffer) {
         int x = buffer.getInt();
         int y = buffer.getInt();

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

@@ -26,6 +26,9 @@ public class Controller {
     private final MotionEvent.PointerProperties[] pointerProperties = new MotionEvent.PointerProperties[PointersState.MAX_POINTERS];
     private final MotionEvent.PointerCoords[] pointerCoords = new MotionEvent.PointerCoords[PointersState.MAX_POINTERS];
 
+    private boolean backPressed;
+    private boolean powerPressed;
+
     public Controller(Device device, DesktopConnection connection) {
         this.device = device;
         this.connection = connection;
@@ -88,7 +91,7 @@ public class Controller {
                 injectScroll(msg.getPosition(), msg.getHScroll(), msg.getVScroll());
                 break;
             case ControlMessage.TYPE_BACK_OR_SCREEN_ON:
-                pressBackOrTurnScreenOn();
+                pressBackOrTurnScreenOn(msg.getAction());
                 break;
             case ControlMessage.TYPE_EXPAND_NOTIFICATION_PANEL:
                 device.expandNotificationPanel();
@@ -223,8 +226,33 @@ public class Controller {
         return device.injectInputEvent(event, InputManager.INJECT_INPUT_EVENT_MODE_ASYNC);
     }
 
-    private boolean pressBackOrTurnScreenOn() {
-        int keycode = device.isScreenOn() ? KeyEvent.KEYCODE_BACK : KeyEvent.KEYCODE_POWER;
-        return injectKeycode(keycode);
+    private boolean pressBackOrTurnScreenOn(int action) {
+        int keycode = -1;
+        if (action == KeyEvent.ACTION_UP) {
+            // if BACK or POWER were pressed, this action is the corresponding release event (regardless of the screen state)
+            if (backPressed) {
+                keycode = KeyEvent.KEYCODE_BACK;
+                backPressed = false;
+            } else if (powerPressed) {
+                keycode = KeyEvent.KEYCODE_POWER;
+                powerPressed = false;
+            }
+        }
+
+        if (keycode == -1) {
+            keycode = device.isScreenOn() ? KeyEvent.KEYCODE_BACK : KeyEvent.KEYCODE_POWER;
+        }
+
+        if (action == KeyEvent.ACTION_DOWN) {
+            if (keycode == KeyEvent.KEYCODE_BACK) {
+                backPressed = true;
+                powerPressed = false;
+            } else {
+                backPressed = false;
+                powerPressed = true;
+            }
+        }
+
+        return injectKeyEvent(action, keycode, 0, 0);
     }
 }

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

@@ -145,6 +145,7 @@ public class ControlMessageReaderTest {
         ByteArrayOutputStream bos = new ByteArrayOutputStream();
         DataOutputStream dos = new DataOutputStream(bos);
         dos.writeByte(ControlMessage.TYPE_BACK_OR_SCREEN_ON);
+        dos.writeByte(KeyEvent.ACTION_UP);
 
         byte[] packet = bos.toByteArray();
 
@@ -152,6 +153,7 @@ public class ControlMessageReaderTest {
         ControlMessage event = reader.next();
 
         Assert.assertEquals(ControlMessage.TYPE_BACK_OR_SCREEN_ON, event.getType());
+        Assert.assertEquals(KeyEvent.ACTION_UP, event.getAction());
     }
 
     @Test