Wait SET_CLIPBOARD ack before Ctrl+v via HID

To allow seamless copy-paste, on Ctrl+v, a SET_CLIPBOARD request is
performed before injecting Ctrl+v.

But when HID keyboard is enabled, the Ctrl+v injection is not sent on
the same channel as the clipboard request, so they are not serialized,
and may occur in any order. If Ctrl+v happens to be injected before the
new clipboard content is set, then the old content is pasted instead,
which is incorrect.

To minimize the probability of occurrence of the wrong order, a delay of
2 milliseconds was added before injecting Ctrl+v. Then 5ms. But even
with 5ms, the wrong behavior sometimes happens.

To handle it properly, add an acknowledgement mechanism, so that Ctrl+v
is injected over AOA only after the SET_CLIPBOARD request has been
performed and acknowledged by the server.

Refs e4163321f0
Refs 45b0f8123a

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

app/src/receiver.c

@@ -7,12 +7,16 @@
 #include "util/log.h"
 
 bool
-receiver_init(struct receiver *receiver, sc_socket control_socket) {
+receiver_init(struct receiver *receiver, sc_socket control_socket,
+              struct sc_acksync *acksync) {
     bool ok = sc_mutex_init(&receiver->mutex);
     if (!ok) {
         return false;
     }
+
     receiver->control_socket = control_socket;
+    receiver->acksync = acksync;
+
     return true;
 }
 
@@ -22,7 +26,7 @@ receiver_destroy(struct receiver *receiver) {
 }
 
 static void
-process_msg(struct device_msg *msg) {
+process_msg(struct receiver *receiver, struct device_msg *msg) {
     switch (msg->type) {
         case DEVICE_MSG_TYPE_CLIPBOARD: {
             char *current = SDL_GetClipboardText();
@@ -38,13 +42,16 @@ process_msg(struct device_msg *msg) {
             break;
         }
         case DEVICE_MSG_TYPE_ACK_CLIPBOARD:
-            // TODO
+            assert(receiver->acksync);
+            LOGD("Ack device clipboard sequence=%" PRIu64_,
+                 msg->ack_clipboard.sequence);
+            sc_acksync_ack(receiver->acksync, msg->ack_clipboard.sequence);
             break;
     }
 }
 
 static ssize_t
-process_msgs(const unsigned char *buf, size_t len) {
+process_msgs(struct receiver *receiver, const unsigned char *buf, size_t len) {
     size_t head = 0;
     for (;;) {
         struct device_msg msg;
@@ -56,7 +63,7 @@ process_msgs(const unsigned char *buf, size_t len) {
             return head;
         }
 
-        process_msg(&msg);
+        process_msg(receiver, &msg);
         device_msg_destroy(&msg);
 
         head += r;
@@ -84,7 +91,7 @@ run_receiver(void *data) {
         }
 
         head += r;
-        ssize_t consumed = process_msgs(buf, head);
+        ssize_t consumed = process_msgs(receiver, buf, head);
         if (consumed == -1) {
             // an error occurred
             break;