Implement 'Extended Clipboard' support

This enable UTF-8 encoded clipboard sharing.

Re: #121

app/src/main/cpp/native-vnc.cpp

@@ -126,15 +126,23 @@ static void onBell(rfbClient *client) {
     env->CallVoidMethod(obj, mid);
 }
 
-static void onGotXCutText(rfbClient *client, const char *text, int len) {
+static void onGotXCutText(rfbClient *client, const char *text, int len, bool is_utf8) {
     auto obj = getManagedClient(client);
     auto env = context.getEnv();
     auto cls = context.managedCls;
 
-    jmethodID mid = env->GetMethodID(cls, "cbGotXCutText", "([B)V");
+    jmethodID mid = env->GetMethodID(cls, "cbGotXCutText", "([BZ)V");
     jbyteArray bytes = env->NewByteArray(len);
     env->SetByteArrayRegion(bytes, 0, len, reinterpret_cast<const jbyte *>(text));
-    env->CallVoidMethod(obj, mid, bytes);
+    env->CallVoidMethod(obj, mid, bytes, is_utf8);
+}
+
+static void onGotXCutTextLatin1(rfbClient *client, const char *text, int len) {
+    onGotXCutText(client, text, len, false);
+}
+
+static void onGotXCutTextUTF8(rfbClient *client, const char *text, int len) {
+    onGotXCutText(client, text, len, true);
 }
 
 static rfbBool onHandleCursorPos(rfbClient *client, int x, int y) {
@@ -231,7 +239,8 @@ static void setCallbacks(rfbClient *client) {
     client->GetPassword = onGetPassword;
     client->GetCredential = onGetCredential;
     client->Bell = onBell;
-    client->GotXCutText = onGotXCutText;
+    client->GotXCutText = onGotXCutTextLatin1;
+    client->GotXCutTextUTF8 = onGotXCutTextUTF8;
     client->HandleCursorPos = onHandleCursorPos;
     client->FinishedFrameBufferUpdate = onFinishedFrameBufferUpdate;
     client->MallocFrameBuffer = onMallocFrameBuffer;
@@ -377,12 +386,16 @@ Java_com_gaurav_avnc_vnc_VncClient_nativeSendPointerEvent(JNIEnv *env, jobject t
 
 extern "C"
 JNIEXPORT jboolean JNICALL
-Java_com_gaurav_avnc_vnc_VncClient_nativeSendCutText(JNIEnv *env, jobject thiz, jlong client_ptr, jbyteArray bytes) {
+Java_com_gaurav_avnc_vnc_VncClient_nativeSendCutText(JNIEnv *env, jobject thiz, jlong client_ptr, jbyteArray bytes,
+                                                     jboolean is_utf8) {
+    auto client = (rfbClient *) client_ptr;
     auto textBuffer = env->GetByteArrayElements(bytes, nullptr);
     auto textLen = env->GetArrayLength(bytes);
     auto textChars = reinterpret_cast<char *>(textBuffer);
 
-    rfbBool result = SendClientCutText((rfbClient *) client_ptr, textChars, textLen);
+    rfbBool result = is_utf8
+                     ? SendClientCutTextUTF8(client, textChars, textLen)
+                     : SendClientCutText(client, textChars, textLen);
 
     env->ReleaseByteArrayElements(bytes, textBuffer, JNI_ABORT);
     return (jboolean) result;

app/src/main/java/com/gaurav/avnc/vnc/VncClient.kt

@@ -183,7 +183,8 @@ class VncClient(private val observer: Observer) {
      * Sends text to remote desktop's clipboard.
      */
     fun sendCutText(text: String) = executeSend {
-        nativeSendCutText(nativePtr, text.toByteArray(StandardCharsets.ISO_8859_1))
+        if (!nativeSendCutText(nativePtr, text.toByteArray(StandardCharsets.UTF_8), true))
+            nativeSendCutText(nativePtr, text.toByteArray(StandardCharsets.ISO_8859_1), false)
     }
 
     /**
@@ -227,7 +228,7 @@ class VncClient(private val observer: Observer) {
     private external fun nativeProcessServerMessage(clientPtr: Long, uSecTimeout: Int): Boolean
     private external fun nativeSendKeyEvent(clientPtr: Long, keySym: Int, xtCode: Int, isDown: Boolean): Boolean
     private external fun nativeSendPointerEvent(clientPtr: Long, x: Int, y: Int, mask: Int): Boolean
-    private external fun nativeSendCutText(clientPtr: Long, bytes: ByteArray): Boolean
+    private external fun nativeSendCutText(clientPtr: Long, bytes: ByteArray, isUTF8: Boolean): Boolean
     private external fun nativeRefreshFrameBuffer(clientPtr: Long): Boolean
     private external fun nativeGetDesktopName(clientPtr: Long): String
     private external fun nativeGetWidth(clientPtr: Long): Int
@@ -245,8 +246,10 @@ class VncClient(private val observer: Observer) {
     private fun cbGetCredential() = observer.onCredentialRequired()
 
     @Keep
-    private fun cbGotXCutText(bytes: ByteArray) {
-        observer.onGotXCutText(StandardCharsets.ISO_8859_1.decode(ByteBuffer.wrap(bytes)).toString())
+    private fun cbGotXCutText(bytes: ByteArray, isUTF8: Boolean) {
+        (if (isUTF8) StandardCharsets.UTF_8 else StandardCharsets.ISO_8859_1).let {
+            observer.onGotXCutText(it.decode(ByteBuffer.wrap(bytes)).toString())
+        }
     }
 
     @Keep