feat: add AsyncStreamDeck::from_sync to wrap an already-opened StreamDeck

Allows opening a device via the synchronous API on a caller-chosen thread
and then handing it to the async wrapper. This matters on macOS, where
hidapi's IOHIDManager is bound to the run loop of the thread that created
the HidApi: enumerate/open must happen on that thread, but the existing
AsyncStreamDeck::connect runs them via block_in_place on whatever tokio
worker is current, which can crash (EXC_BREAKPOINT in CoreFoundation)
when the device set changes, e.g. after sleep/wake.

With from_sync, an application can own the HidApi on a dedicated thread,
open devices there with StreamDeck::connect, and still use the async API
for everything else.

Author: kingb

src/asynchronous.rs

@@ -46,6 +46,17 @@ impl AsyncStreamDeck {
             device: Arc::new(Mutex::new(device)),
         })
     }
+
+    /// Wraps an already-opened synchronous [StreamDeck] without using
+    /// [block_in_place], so the HID open call (which on macOS must run on the
+    /// thread that owns the IOHIDManager run loop) can be performed on a
+    /// dedicated thread and the result handed to the async runtime afterwards.
+    pub fn from_sync(device: StreamDeck) -> AsyncStreamDeck {
+        AsyncStreamDeck {
+            kind: device.kind(),
+            device: Arc::new(Mutex::new(device)),
+        }
+    }
 }
 
 /// Instance methods of the struct