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/keyboard_inject.c

@@ -189,11 +189,11 @@ convert_input_key(const SDL_KeyboardEvent *from, struct control_msg *to,
 static void
 sc_key_processor_process_key(struct sc_key_processor *kp,
                              const SDL_KeyboardEvent *event,
-                             bool device_clipboard_set) {
+                             uint64_t ack_to_wait) {
     // The device clipboard synchronization and the key event messages are
     // serialized, there is nothing special to do to ensure that the clipboard
     // is set before injecting Ctrl+v.
-    (void) device_clipboard_set;
+    (void) ack_to_wait;
 
     struct sc_keyboard_inject *ki = DOWNCAST(kp);
 
@@ -256,5 +256,7 @@ sc_keyboard_inject_init(struct sc_keyboard_inject *ki,
         .process_text = sc_key_processor_process_text,
     };
 
+    // Key injection and clipboard synchronization are serialized
+    ki->key_processor.async_paste = false;
     ki->key_processor.ops = &ops;
 }